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Oxygen Management

3 Contact Hours including 3 Advanced Pharmacology Hours
Only Advanced Practice Nurses will receive credit for this course.
This peer reviewed course is applicable for the following professions:
Advanced Practice Registered Nurse (APRN), Certified Nurse Practitioner, Certified Registered Nurse Anesthetist (CRNA), Clinical Nurse Specialist (CNS), Registered Nurse Practitioner, Respiratory Therapist (RT)
This course will be updated or discontinued on or before Friday, September 20, 2024

Nationally Accredited

CEUFast, Inc. is accredited as a provider of nursing continuing professional development by the American Nurses Credentialing Center's Commission on Accreditation. ANCC Provider number #P0274.


≥92% of participants will understand the management of oxygen as an aid in several levels of respiratory failure.

Supplemental oxygen is recognized as a drug in modern medicine. Oxygen commonly treats medical conditions with poor tissue and arterial oxygenation, including hypoxemia. The most common indication for administering supplemental oxygen is acute or chronic hypoxemia. Causes include pulmonary infection, chronic obstructive pulmonary disease (COPD), congestive heart failure, pulmonary embolism, and shock. The Oxygen Management course thoroughly examines the clinical recommendations for using oxygen therapy in different disease conditions. It presents a harmonized summary of recommendations from the German S3 guideline and the British Thoracic Society Guideline in oxygen use in adults. The oxygen delivery systems and regimens will also be discussed based on available clinical research evidence.


After completing this continuing education course, the participants will be able to meet the following objectives:

  1. Describe supplemental oxygen therapy in modern medicine.
  2. Identify the monitoring requirements for oxygen therapy.
  3. Determine the appropriate prescription recommendations for oxygen therapy.
  4. Interpret the recommendations for oxygen settings in different medical cases.
  5. Compare and contrast the prevalent practice recommendations for oxygen therapy indications in special diagnoses and presentations.
  6. Describe the clinical practice points in home oxygen therapy.
  7. Explain the various options in oxygen therapy delivery.
CEUFast Inc. and the course planners for this educational activity do not have any relevant financial relationship(s) to disclose with ineligible companies whose primary business is producing, marketing, selling, re-selling, or distributing healthcare products used by or on patients.

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To earn of certificate of completion you have one of two options:
  1. Take test and pass with a score of at least 80%
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Author:    Jassin Jouria (MD)

Oxygen Supplementation as a Care Plan in Modern Medicine

In recent times, the focus of medical research and licensed procedural experiments have widely explored the possibilities of alternative care plans. These alternative care plans have been adopted as supplemental or secondary regimens to the conventional plan to broaden modern medicine's reach. These new plans have gained medical acceptance in different parts of the world. As the COVID-19 pandemic raged, studies exploring using hyperbaric oxygen as a symptom relief in chronic COVID-19 infection increased significantly. The dark moment in medical history witnessed the introduction of many alternative care plans. However, supplemental oxygen helped record unprecedented success in managing COVID-19 symptoms, especially in the elderly.

Before the COVID-19 pandemic, supplemental oxygen therapy was widely accepted in inpatient emergency services. For instance, lower respiratory tract infections, including viral pneumonia, placed a considerable health burden on the pediatric population of third world countries. In many severe cases, the clinical symptoms documented for pediatric patients battling active respiratory syncytial (a multinucleated mass of cytoplasm that is not separated into individual cells) virus infection include low blood oxygen saturation and breathing difficulty. In the United States, these severe symptoms are commonly reported in the diagnosed cases pegged at 800,000 children annually. In these cases, the need for supplemental oxygen therapy is considered a criterion for inpatient admission. In a guideline study on diagnosing, managing, and preventing respiratory tract infections, Ralson et al. (2014) recommended oxygen supplementation as a primary treatment for these conditions.

In the therapy plan for cerebral ischemia, increasing cerebral perfusion and blood oxygen perfusion is considered a focal therapy goal. Bronchodilators and nitroglycerin are deemed unpopular in modern medicine. Hyperbaric oxygen therapy has been considered a new alternative to conventional care plans for cerebral ischemia patients. So far, supplemental oxygen therapy has been considered a credible alternative in medical conditions requiring an effective cell/tissue oxygen perfusion method. Some of these conditions requiring a low-risk, high-yield oxygen perfusion plan include severe blood loss, decompression sickness, acute traumatic ischemia, bronchiolitis, carbon monoxide poisoning, and pulmonary embolism.

Recently, hyperbaric oxygen's effectiveness in treating chronic tuberculosis has been explored. Scientific theories supporting these studies hold that the affected group of neurons in the penumbra zone (the area surrounding an ischemic event such as thrombotic or embolic stroke) might be reactivated and become biologically viable after several years. Supplemental oxygen therapy may help manage neurodegenerative diseases in patients with neuropsychological and electrophysiological abnormalities.

However, despite the promising potential of supplemental oxygen therapy in human medicine, a conservative approach to implementation is recommended as available scientific evidence on oxygen therapy remains insufficient. The possible adverse effects of high-concentration oxygen doses on the cellular level and end-organs remain largely unknown. There are also concerns about the potential long-term effects of this therapy in the pediatric population. Further advanced scientific investigations are required to establish a dosing guideline, document the cellular effects, and solve the uncertainties about oxygen supplementation. Currently, the scientific summaries on oxygen supplementation therapy in inpatient hospital care include:

  • Supplemental oxygen therapy improved sensorimotor functions and enhanced P30 amplitude in the damaged hemisphere of chronic TB patients (Ravimohan et al., 2018).
  • COVID-19 patients presenting with typical signs of pulmonary impairments reported significant medical benefits in studies prescribing supplemental oxygen therapy as an asymptomatic management option (Daher et al., 2021).
  • Supplemental oxygen delivered under hyperbaric conditions increases the chances of brain tissue oxygen perfusion by ten-fold in patients with cerebral ischemia. Supplemental oxygen is also well-tolerated and considered safe under standard protocols.

Case Study

Amoke is a 45-year-old African American, crushing it hard in her career as the Chief Brand Promoter for Megatron Capital Financing. Her demanding work schedule involves around-the-clock work and travel plans. She had just returned on a trip to Lagos -a metropolis in Africa's biggest economy, Nigeria. The journey to Lagos was largely successful; however, Amoke's 3-weeks extended stay exposed her to the hydrocarbon-polluted air in Lagos.

Two days after the visit, she reportedly fainted while presenting a new brand campaign. She was rushed to a Chicago Hospital and admitted to Emergency Observation Care. On examination, Amoke's first clinical summary documented the following signs and symptoms:

  • Labored breathing
  • Chest pain on inhalation
  • Cramping pain in the trunk region
  • Mild swelling of the calf
  • Periodic gasping
  • Cold extremities and paleness

There was documented long-term drug use. No evidence of strangulation or domestic abuse. No personal or family history of asthma and no documentation of any chronic medical problems. She was reportedly healthy until that morning at the board meeting. She mentioned how her symptoms started during the last few days of her trip. Her vital signs during the first hour of admission:

  • A heart rate of 125 beats per minute
  • A blood pressure of 190/85 mmHg
  • A surface body temperature of 37.5 degrees Celsius
  • Oxygen saturation of 87%
  • A respiratory rate of 25 breaths per minute

Her increased heart rate (tachycardia) indicated altered metabolism as the body struggled for oxygenated air and proper lung perfusion. Amoke's resting respiratory rate is higher than the medical standard of 12-20/min for adults. Finally, a low oxygen saturation rate of 85% and the complaints of chest pain on inhalation suggest a problem with lung oxygenation.

The Junior Resident on duty performed a physical examination and ordered Salbutamol 5 mg stat. Ten minutes after nebulization, Amoke had shown little signs of improvement. A second Salbutamol course was also futile. Her complaints of gripping chest pain increased, and she regressed quickly, becoming unresponsive to sudden touch as her heart rate increased by 9 points.

The attending Resident halted the Salbutamol therapy, switching to a supplemental oxygen regimen. A concentrated oxygen regimen was initiated. She was also hooked to an ECG to monitor the heart's electrical activity. A nitroglycerin tab was given for the chest pain.

About 20 minutes later, the supplemental oxygen therapy significantly improved her condition. She had pupil dilation in response to light and exhibited a conscious response to gripping touch. Her ECG showed a stable pattern. Her vitals also improved significantly, with her heart rate falling to 85/min and her pulse oximetry oxygen saturation increasing to 96%. She was scheduled for a blood test and x-ray imaging for further investigations. Amoke's case is another in a long list of medical evidence suggesting the efficacy of oxygen supplementation therapy in inpatient emergency admissions.

Overview of Oxygen Supplementation in Human Medicine

Discovered independently by Carl Wilhelm Scheele and Joseph Priestly in 1776, oxygen has established a reference position in biomedical and physical science (Gottlieb et al., 2021). In physical science, oxygen is primarily recognized as an element, catalyst, and reactive agent. Beyond this recognition, biomedical science explored oxygen as a possible cheap drug for symptomatic relief in medical conditions characterized by poor blood oxygen saturation levels. Technological improvement in the development of compressed gas technology and pressure regulations solved the early problems with oxygen storage. Solving this problem also significantly improved medical investigations focused on a possible oxygen therapy plan.

Cells leverage oxygen supply to produce energy from nutrients. The lung primarily supplies oxygen to cells in humans and other similar mammals. The supply function oxygenates the blood, aids cellular metabolism, and removes carbon monoxide waste from the cells. Medical impairments unbalancing this simple exchange compromises oxygen metabolism and subsequently disrupt cellular oxygen perfusion. For instance, oxygen uptake and excretion of carbon monoxide are compromised in ventilatory insufficiency. Carbon monoxide exhibits a superior tissue perfusion rate compared to oxygen, explaining why pulmonary insufficiency compromises cellular uptake of oxygen and not the release of carbon monoxide.

The scientific basis for using high-concentration oxygen regimens in human medicine leverages the oxygen-cell exchange. Modifying this exchange impacts oxygen physiology for symptomatic relief. The common indications for the prescription of supplemental oxygen therapy include pulmonary embolism, cardiac failure, chronic obstructive pulmonary disease (COPD), pulmonary infection, septic shock, and congestive heart failure. There are also reports of the beneficial use of this therapy in cyanide poisoning, gas embolism, and burn injuries. With the exemption of pathology irreversible airway blockage causing difficulty in direct administration, there are absolutely no contraindications to supplemental oxygen therapy.

Physiology of Oxygen Metabolism and Transport

Biological oxygen binding to the blood is facilitated by heme, a transport component of the red blood cells. The level of blood saturation (binding to red blood cells) depends primarily on the partial pressure of oxygen. Under normobaric conditions, blood saturation is minimal as oxygen dissolves negligibly in the blood. CaO2 is measured in mL O2/dL blood and described as Oxygen Content. Hb represents the hemoglobin concentration measured in g/dL, and the constant value of 1.34 represents a constant - Huefner's factor. SO2 and paO2 are measured in mmHg and respectively describe oxygen saturation and oxygen partial pressure. The arterial oxygen saturation (CaO2) indicates the percentage of hemoglobin saturated with oxygen at the time of measurement. The oxygen saturation of hemoglobin (SO2) can be directly determined by measuring arterial oxygen saturation (SaO2) or by using pulse oximetry (SpO2).

The hemoglobin-oxygen exchange is captured by a blood gas analysis and described by paO2 as a critical determinant in pulmonary oxygenation. However, it is hard to measure tissue oxygenation levels with these parameters. Tissue oxygenation is better calculated considering hemoglobin levels and cardiac output as additional factors with SO2 and paO2. These parameters are not immediately available, forcing clinicians to consider hypoxemia as an oxygenation measure. In supplemental oxygen therapy plans, the relationship between arterial oxygen saturation as a factor of partial oxygen pressure is monitored throughout therapy. The linear relationship between these two is captured in the graph below.

graph of relationship between oxygen saturation and the partial pressure of oxygen

Fig 1: Relationship between oxygen saturation and the partial pressure of oxygen

Saturation levels in the tissue and the corresponding arterial oxygenation depend massively on the oxygen-hemoglobin relationship. The relationship also directly impacts oxygen transport in the biological system. Only a negligible amount of oxygen is transported in the plasma; the bulk percentage needed for tissue oxygenation and gas exchange is transported in the blood by the hemoglobin. The hemoglobin oxygen saturation is studied with the partial pressure of arterial oxygen (PaO2). The oxygen-hemoglobin dissociation curve represents this relationship.

graph shoing the oxyhemoglobin dissociation curve

Fig 2: The Oxyhemoglobin Dissociation Curve

At PaO2 values greater than 60 mmHg, the oxygen saturation rate does not respond to further changes in PaO2, and the curve becomes relatively flat. At PaO2 values below 60mmHg, the slope becomes steeper, indicating a sudden decrease in oxygen saturation levels. At this stage, tissue saturation becomes minimal, and the biological responses to insufficient oxygen appear. At this threshold, many guidelines recommend the administration of supplemental oxygen to boost tissue oxygen saturation levels.

Physiological factors directly affecting PaO2 values can displace the oxygen-hemoglobin curve to the right or the left. In hypothermic conditions, the curve assumes a leftward shift. Carbon monoxide poisoning, alkalosis, decreased levels of 2,3-diphosphglycerate (2,3-DPG), and methemoglobinemia shifted the curve leftward. A rightward shift of the oxygen-hemoglobin curve indicates impaired tissue oxygenation and unloads oxygen from the tissue. Hyperthermia, increased 2,3-diphosphglycerate (2,3-DPG) levels, hypercapnia, and acidosis are notorious triggers of a rightward shift. By monitoring the clinical severities of these factors, clinicians can determine the need for supplemental oxygen administration or termination of ongoing oxygen therapy.

Sourcing and Storing Supplemental Oxygen

Medical gas pipelines are the primary sources of supplemental oxygen in many hospitals. Proper storage requires engineering input in pressure regulations and storage space measurements. E-cylinders are considered a viable alternative for storage and transport on a smaller scale. These cylinders have a pressure of 2000 per square inch per unit, each carrying approximately 650 liters of oxygen. The sturdy design of E-cylinders allows for easy use and multiple-angle orientation during use since they are unaffected by gravity.

H-cylinder is common in hospitals operating frequent oxygen supplemental procedures with a central oxygen supply system. Unlike E-cylinders, H-cylinders can store approximately 7000 liters of oxygen at total capacity. With a set flow rate of 5 liters per minute, an E-cylinder can dispense supplemental oxygen for about 2 hours, making it the choice storage unit for anesthetic procedures and short-duration oxygen therapies.

photo of oxygen e-cylinders

Fig 3: Oxygen E-Cylinders

Flow rates are controlled using a variable-orifice flow meter. Depending on the delivery system, the operational protocol of these flowmeters might vary. A flow meter traps the compressed oxygen in the cylinders at high pressure and dispenses it at lower pressures in a uniform stream. The rate measurements are obtained at the center of a floating ball. These meters have tapered tubes with the smallest diameter at the bottom. The arrangement creates a variable annular space between the floating ball and the tube's inner wall. Flow meters are made specifically for a type of gas since the viscosity and density of each gas impact differently on the flow rate. A knob system on the flow meter allows for rate adjustment and flow monitoring.

Portable oxygen concentrators are also available for ambulatory patients and those requiring long-term oxygen therapy at home. These devices compress ambient air, concentrate it, and deliver it using a flow protocol similar to the E- and H-cylinders (Hardavella et al., 2019). Modern brand designs of portable oxygen concentrators can provide about 10 liters of oxygen per minute. They can achieve high tissue saturation rates at this flow rate in emergency conditions requiring supplemental oxygen interventions.

Recommendations on Humidification of Supplemental Oxygen

Humidified oxygen is not required in low-flow oxygen delivery and short-term high-flow oxygen administration courses (Calligaro et al., 2020). Therefore, humidified oxygen is not needed in pre-hospital settings. It is reasonable to use humidified oxygen in cases of upper respiratory discomfort due to dryness and in patients who require high-flow oxygen therapy for an extended period. Humidified oxygen can also be used in patients with an artificial airway requiring long-term oxygen management.

Clinical studies highlight the benefits of humidified oxygen in patients with viscous secretions. The British Thoracic Society guideline warns against the use of bubble bottles which allow a stream of oxygen to bubble through a container of water. These bubble bottles increase the risk of airway infections and prescribe no clinically significant benefits in patients. The decision to use humidified oxygen in the therapy course should be made individually. The attending specialist is advised to critically examine the risk and benefits of such a decision as the clinical evidence supporting humidified oxygen therapy is insufficient to recommend wide use.

Poiroux et al. (2018) published a study investigating the effects of dry versus humidified oxygen. The study, with a participant pool of 354 subjects, examined the impact of these two methods on the quality of life of patients administered oxygen therapy under intensive care. The study data could not demonstrate that non-humidified oxygen was less effective in these patients than humidified oxygen after a 6–8-hour therapy course (Poiroux et al., 2018).

Oxygen Prescriptions

In modern medicine, oxygen is classified as a drug and should be administered based on good drug-prescribing and monitoring practices. The German S3 guideline of supplemental oxygen therapy recommends the prescription of oxygen by a trained physician, specifying a target range of oxygen saturation. Each prescription should be based primarily on the patient's evaluation by a senior clinician or specially trained health care professionals. In a grouped population study of oxygen prescription in patients, Harper et al. (2021) reported the proportion of inpatients with oxygen prescription ranging from 40 to 60%.

The British Thoracic Society Guideline recommends a standard oxygen prescription document for all healthcare facilities. Alternatively, facilities can opt for a designated oxygen section on all drug prescribing documents or sections for oxygen prescription in an electronic prescribing system. Except for sudden illness or critical emergencies requiring quick interventions, a formal oxygen prescription should always be provided before an oxygen therapy course is initiated. These prescriptions should always be signed and specify the administration protocol details, including oxygen concentration, flow rate, target saturation range, and duration of administration. It is essential to ensure all nursing staff understand the aim of the therapy, including all healthcare professionals attending to the patients.

Clinicians are encouraged to disregard the old practice of specifying a fixed oxygen concentration or fraction of inspired oxygen. The method has no clear target for the therapy, making it hard for the nursing team to plan appropriately for monitoring and weaning when necessary. In emergencies, the lack of a formal oxygen prescription should not preclude the administration of supplemental oxygen. In pre-hospital cases, first responders and medical personnel should administer oxygen liberally if required to improve clinical symptoms. However, written documentation, including the duration of emergency administration, oxygen concentration, and flow rate, should be made in all instances of emergency medical interventions. Emergency oxygen administration should be based on the guidance provided on the card for patients with an oxygen alert card until blood gas measurements can be conducted.

In prescribing the delivery system, the attending specialist should consider oxygen requirements, breathing pattern, mouth opening, and risk of hypercapnia. Once therapy is initiated, the medical team should reassess the patient to detect possible signs of clinical deterioration at the early stage of treatment. It is essential in patients with no prior history of supplemental oxygen therapy. Early reassessments should also examine the risks of complications or the need for intensive care (Quinten et al., 2018). The reassessment interval should be determined by the severity of vital signs and the extent of hypoxemia. Patients who are started on oxygen therapy can be reassessed every 4 to 6 hours. The British Thoracic Society guideline recommends a 6-hour assessment interval for patients started on oxygen therapy and continuous monitoring depending on where the treatment was initiated.

Regardless of where therapy was initiated, continuous monitoring is recommended in track and trigger systems if multiple vital signs are outside the normal physiological ranges. In this case, the oxygen concentration required to achieve a target saturation range may depend primarily on the risk of a life-threatening complication or clinical deterioration (Arnolds et al., 2022). Suppose high-flow nasal cannula oxygen (HFNC) is initiated in a patient with no prior history of oxygen therapy under emergency conditions. In that case, the German S3 guideline also recommends continuous SpO2, pulse, and respiratory rate monitoring. Other vital signs, including mental state, blood pressure, and body temperature, should also be monitored (Kang et al., 2020).

Patient Assessment in Immediate Oxygen Therapy Initiation

Recommendations on initiating oxygen therapy in emergency settings prioritize recognizing the clinical symptoms of conditions in which oxygen therapy is indicated. Medical personnel are expected to be capable of recognizing the clinical signs of inadequate tissue oxygenation. The pathophysiological mechanisms resulting in low tissue oxygenation are broadly categorized into two groups. The two groups include those impairing the oxygen-hemoglobin complex system and those causing arterial hypoxemia. Recognizing these mechanisms requires careful patient evaluation. However, more than one mechanism may contribute to poor tissue oxygenation in the same patient. The pathophysiological mechanism grouped under the failure of the oxygen-hemoglobin transport system include:

  • Low hemoglobin concentration
  • Poor tissues perfusion rate
  • Hemoglobinopathies, high carboxyhemoglobin concentration, and other conditions implicated in the abnormal oxygen dissociation curve
  • Histotoxic poisoning of the intracellular enzymes, including cyanide poisoning, paraquat poisoning, and septicemia
  • In arterial hypoxemia, the pathophysiological mechanisms implicated include:
    • Right to left shunts
    • Low inspired oxygen partial pressure
    • Alveolar hypoventilation in sleep apnea, opiate poisoning, etc
    • Ventilation-perfusion mismatch in asthma, atelectatic lung zones, etc

The clinical symptoms of these pathophysiological mechanisms are nonspecific and can be challenging to recognize quickly. These symptoms include altered mental state, dyspnea, cyanosis, tachypnoea, arrhythmias, and coma. In all patients under evaluation for a possible oxygen therapy regimen, arterial oxygen saturation (SaO2) and partial oxygen pressure (PaO2) measurements are the principal indicators for initiating, prescribing, monitoring, and modifying supplemental oxygen therapy.

Arterial oxygen saturation and partial oxygen pressure can be normal in some patients presenting with clinical evidence of tissue hypoxemia caused by low cardiac output, anemia, and failure of tissues to use oxygen. In these cases, mixed venous oxygen partial pressure measured in pulmonary artery blood is considered a better index of tissue oxygenation as its value approximates to mean partial tissue pressure. The most widely used guidelines in assessing the patient for a possible immediate oxygen intervention include:

  • Assess the airway and optimize airflow using airway positioning as necessary in the patient. Head tilts, chin lifts, and left lateral tilts might be required.
  • Perform a thorough clinical assessment and documentation, including cardiovascular, respiratory, and neurological system assessments, at the beginning of every shift.
  • Check and document oxygen equipment set up and any change in patient positioning at the beginning of each shift.
  • Oxygen flow rate, patency of tubing, and humidifier settings should be checked and documented hourly.
  • Heart rate, respiratory rate, respiratory distress, and oxygen saturation -using continuous pulse oximetry, should be checked hourly and recorded on the patient's observation chart.

An updated series of evidence-based patient assessment recommendations were included in the latest update of the British Thoracic Society guideline for supplemental oxygen use in adults. Recommendations relevant to the central theme of this course include:

  • Chronically hypoxemic patients presenting a 3% or greater fall in oxygen saturation on their usual saturation range should be assessed using blood gas estimations in the hospital.
  • In patients with comorbidities, including asthma, heart failure, and other illnesses, the appropriate therapy protocol should be initiated following the standard management plans for the diseases.
  • In a pre-hospital setting or in patients under ambulatory care, oxygen saturation levels should be monitored until the patient's vitals are stable and a specialist does a full assessment. The concentration of oxygen administered should be adjusted upwards or downwards to maintain the appropriate saturation range.
  • In emergencies, administer oxygen empirically without a formal prescription to restore airflow. The lack of formal oxygen prescription should not restrict oxygen administration in a formal setting. The oxygen concentration, the flow rate, adjustment, and the patient's response should be documented.
  • Emergency service providers, first responders, and medical personnel on a rural visit should be equipped with portable pulse oximeters and oxygen cylinders and guide the use of oxygen as part of their emergency response equipment.

In acutely ill patients presenting for clinical intervention, oxygen therapy (if indicated) should be aimed at maintaining a patent airway. In patients with cardiac arrest, respiratory distress, or respiratory arrest, administer oxygen empirically. The American College of Chest Physicians and the National Heart, Lung, and Blood Institute recommended a list of conditions to classify clinical conditions requiring empirical initiation of oxygen therapy. These conditions include:

  • Cardiac and respiratory arrest
  • Hypoxemia (PAO2<7.8 kPa, SaO2<90%)
  • Hypotension (Systolic blood pressure < 100 mmHg)
  • Low cardiac output and metabolic acidosis (bicarbonate < 18 mmol/l)
  • Respiratory distress (respiratory rate > 24/min)

Guidelines on Oxygen Supplementation

The British Thoracic Society Guidelines for Oxygen Supplementation provided a harmonized protocol and evidence-based recommendations for administering supplemental oxygen. The summarized points on this guideline include:

Intended Users and Target Population

The British Thoracic Society Guidelines for Oxygen Supplementation are intended for healthcare professionals and specialists handling oxygen prescriptions in patients requiring emergency interventions. These guidelines invariably cover first responders, non-profits, and volunteers involved in the clinical management of patients requiring oxygen therapy. Regarding the target population, the British Thoracic Society Guidelines for Oxygen Supplementation addresses the use of supplemental oxygen in three broad categories. The categories cover palliative care and patients admitted under pre-hospital and hospital settings. These include:

  • Hypoxemic or critically ill patients
  • Non-hypoxemic patients requiring supplemental oxygen therapy
  • Hypoxemic patients and patients at risk of hypoxemia

With reference to evidence-based studies on oxygen therapy effectiveness, this guideline also excluded its recommendations from different populations. Patient groups and areas not covered by this guideline include:

  • Pediatrics -the current revision only applies to patients aged 16 and above
  • Patients initiating oxygen use at home for clinical and non-clinical reasons
  • Ongoing home care regimen for hypoxemic patients
  • Hyperbaric oxygen
  • Oxygen used in diving, hiking, air travel, animal experiments, and high-altitude climbing
  • Oxygen use in high-dependency units and intensive care units

Clinical Protocols for Oxygen Supplementation in Selected Clinical Conditions

Supplemental oxygen prescription and administration should be handled by trained clinicians with certification in patient assessment and symptom management. Therapy should start with documentation of respiratory rate, pulse rate, blood pressure, and body temperature and assess circulating blood volume and anemia. If patients present with a life-threatening complication, the clinician on duty is advised to seek clinical assistance from an intensive care specialist. In a pre-hospital care setting, the attending clinician should be prepared to call for an ambulance should an emergency arise.

Initial assessment and monitoring of hypoxemia and hypercapnia should include a track and trigger system. These systems provide updated real-time guidance on rapid changes in patient's vital signs. A track and trigger system might also guide therapy modification and clinical review on supplemental oxygen administration. Oxygen saturation should be tracked and monitored using pulse oximetry in all breathless patients started on supplemental oxygen. Keeping a real-time update of flow rate and volume of oxygen delivered in an observation chart is also recommended. Vital sign changes in patients at risk of hypercapnic respiratory failure should be strictly monitored.

Good Clinical Assessment Practice in Patients with Suspected Hypoxemia Cases

Curate an extensive medical history in acutely breathless patients when immediately possible. The medical history may indicate the possibility of specific acute illness conditions, including pulmonary embolism, pneumonia, heart failure, asthma, COPD, and acute exacerbation of any chronic obstructive airway conditions. Do not discontinue oxygen administration to monitor oximetry measurements on room air in patients undergoing active supplemental oxygen therapy.

Conduct and document the results of a thorough physical examination. Physical examination may provide further evidence of an ongoing impairment in normal physiology, suggesting a diagnosis of common chronic conditions in these patients. However, it is common not to get a definitive diagnosis without the results of chest radiographs. Record arterial oxygen saturation measured by pulse oximetry (SpO2). A blood gas assessment should be performed in patients with unexplained confusion and agitation, as this may indicate hypoxemia and/or hypercapnia.

Tachypnea and tachycardia have been commonly confirmed in hypoxemic patients compared to a physical finding of cyanosis. Consequently, the attending clinician is advised to monitor the patient's respiratory and heart rates carefully.

Appropriate changes should be made to any track and trigger system to allow for a lower target range in patients at risk of hypercapnic respiratory failure. These patients should score no points for saturation if they are within their target range. They should be awarded points if the saturation falls below the recommended range or increases above the target range while on active oxygen therapy. A normal SpO2 should not negate the need for continuous blood gas measurements for patients on supplemental oxygen therapy.

Emergency Admissions Requiring Oxygen Therapy in Critical Illnesses

In cardiopulmonary resuscitation, use the highest feasible inspired oxygen for pulmonary ventilation. Ensure spontaneous circulation until arterial blood oxygen saturation can be reliably monitored. At this point, monitor saturation closely and aim for a recommended saturation range of 94 - 98%. An arterial blood sample should be examined to guide modifications to active oxygen therapy. If hypercapnic respiratory failure is suspected, the target saturation range should be modified to 88 - 92%, or mechanical ventilation should be initiated.

In critical illnesses, including major trauma, sepsis, shock, and anaphylaxis, supplemental oxygen therapy should be initiated with a reservoir mask at 15 L/min. Set the primary target saturation range at 94–98%. Adopt this recommendation in patients with critical illness with a documented risk factor for hypercapnia pending blood gas measurements and specialist assessment results. Lower oxygen concentrations may help maintain the target saturation range in patients with spontaneous circulations and a reliable oximetry reading. In patients on emergency therapy for drowning, the oxygen saturation target range should be set at 94% - 98% once spontaneous circulation is established.

In cases of acute seizures due to epilepsy or other causes, high-concentration oxygen should be administered until a satisfactory oximetry measurement can be obtained. The attending clinician should aim for an oxygen saturation target range of 94–98%. Reset saturation target range to 88–92% in patients with clinical signs suggesting a high risk of hypercapnic respiratory failure.

The target saturation range should be set at 94–98% in patients with a major head injury. Initial treatment should involve high-concentration oxygen from a reservoir mask at 15 L/min pending the availability of satisfactory blood gas measurements or until the airway is secured by intubation.

In carbon monoxide poisoning, an apparently 'normal' oximetry reading may be produced by carboxyhemoglobin. The attending clinician is advised to adopt a target oxygen saturation of 100% and use a reservoir mask at 15 L/min, irrespective of the oximeter reading and PaO2.

Supplemental Oxygen Therapy in Chronic Obstructive Pulmonary Disease

Hypercapnic respiratory failure and respiratory acidosis are common complications in patients with exacerbations of COPD. These complications might develop throughout hospital admission even if the initial oxygen saturation levels were satisfactory. Strictly regulate excessive supplemental oxygen use in patients with COPD. The risk of respiratory acidosis in patients with hypercapnic respiratory failure is increased if the PaO2 is above 10.0 kPa due to previous excessive oxygen use.

If following blood gas measurements, the pH and PCO2 are normal, set the saturation target range to 94–98% unless there is a documented history of previous hypercapnic respiratory failure requiring intermittent positive pressure ventilation or the patient's usual oxygen saturation when clinically stable is below 94%. The saturation target range in these patients should be 88 - 92%. Monitor changes in PCO2 or falling pH by conducting periodic blood gas assessments.

Recheck blood gases after 30–60 min (or if there is evidence of clinical deterioration) for all patients with COPD or other risk factors for hypercapnic respiratory failure, even if the initial PCO2 measurement was normal. Bicarbonate and pH levels are important factors to consider in monitoring oxygen therapy in these patients. A raised PCO2, a pH greater or less than 7.35 ([H+] ≤45 nmol/L), and/or a high bicarbonate level greater than 28 mmol/L suggest a case of chronic hypercapnia. The target oxygen saturation for these patients is pegged at 88 - 92%. Blood gases should be repeated at 30 – 60 mins.

Non-invasive ventilation (NIV) with targeted oxygen therapy should be started if respiratory acidosis persists for more than 30 min after initial standard medical management. Consider switching stabilized patients from Venturi masks to nasal cannulas. The attending specialist should consider setting a patient-specific target range in patients using long-term home oxygen therapy for COPD. Range setting is essential in patients who would require inappropriate modification of the oxygen therapy protocols to meet the standard saturation range of 88–92%.

Supplemental Oxygen Therapy in Pregnancy

Supplemental oxygen therapy is recommended in pregnant women who suffer from major trauma, sepsis, or acute illness. Administration protocol should be similar to other seriously ill patients. The guideline recommendation for target oxygen saturation in this population is pegged at 94% - 98%. The target saturation applies to women presenting with hypoxemia as an acute pregnancy complication. During labor, supplemental oxygen can be administered to women with underlying hypoxemic conditions. The target oxygen saturation range should be set to 94% - 98% unless they are at risk of hypercapnic respiratory failure.

A left lateral lift or manual uterine displacement should be considered in pregnant women above 20 weeks of gestational age presenting with a high risk of developing associated cardiovascular compromise. Positioning on the left relieves pressure on the aorta. Positioning eliminates the risk of aortocaval compression. A full lateral positioning can also be considered.

Pregnant women above 2 weeks of gestation presenting with clinical symptoms of hypoxemia associated with altered consciousness should also be managed on a left lateral tilt. Patients requiring further respiratory or cardiovascular support will benefit from a left lateral tilt. A left lateral tilt or manual uterine displacement optimizes oxygen delivery and improves cardiac output.

Supplemental oxygen should only be initiated during labor when there is clinical evidence of maternal hypoxemia, defined as an oxygen saturation level of less than 94%. There is little evidence supporting supplemental oxygen therapy in intrauterine fetal resuscitation. There is also no clinical evidence of harm to the fetus if oxygen is initiated for an extended period in uncomplicated labor.

Supplemental Oxygen Therapy in Patients with Neurological Disorders

Urgent medical assessment and clinical intervention are required in patients at risk of respiratory failure due to neurological disorders. The initial evaluation is focused on the level of risk and a possible need for non-invasive or invasive ventilator support rather than oxygen therapy. Oxygen saturation level monitoring in these patients is done with spirometry and blood gases.

In morbidly obese patients with a body mass index (BMI) greater than 40 kg/m2, oxygen supplementation should be initiated and maintained at a target saturation range of 88 - 92%. These patients are at risk of hypoventilation even if they present with no clinical evidence of obstructive sleep apnea. Hypercapnic patients with comorbidities should be considered for NIV oxygenation (Davidson et al., 2016).

Supplemental Oxygen Therapy in Palliative Geriatric Care

In geriatric patients under palliative care, oxygen therapy care goals are designed to improve the symptoms of breathlessness significantly. The care goals are considered more complex than a mere correction of hypoxemia. Therapy should only be initiated with the early involvement of palliative care specialists and physiotherapists. A diagnosis pattern highlighting a comprehensive assessment of the possible underlying factors responsible for breathlessness should be considered first.

Low-dose opioids and a trial of a handheld fan should be considered primary interventions. These have shown clinical effectiveness in relieving breathlessness in the geriatric population. The saturation target range and selected administration method should be personalized for each patient for convenience and comfortability. A formal periodic assessment of efficacy should be made, and oxygen therapy discontinued if considered not beneficial to the patient.

Supplemental oxygen therapy in palliative care requires specialist monitoring for a low rate, possible contraindication assessment, and any ongoing adverse treatment. In this population, supplemental oxygen therapy is limited to a patient with a consistently stable SpO2 greater than 90% with a documented improved relief of breathlessness with oxygen. Oxygen therapy should be considered a second option in non-hypoxemic geriatric patients. Opioids and pharmacotherapy should be regarded as primary therapy.

Oxygen care protocol should also be determined based on the patient's life quality in palliative care. Comfortable patients with no obvious respiratory and physical distress generally do not require oxygen care, which should not influence therapy. Generally, there is no need for tracking oxygen saturation partial pressure during the last days of life in patients with distress.

As a general recommendation in these patients, oxygen therapy should not be continued in the absence of patient benefit or where its disadvantages (discomfort of masks or nasal cannula, drying of mucous membranes) outweigh any likely symptomatic benefit. A comprehensive assessment of contributing factors to therapy failure should also be carried out.

Supplemental Oxygen Therapy in Perioperative Care and Procedures Requiring Conscious Sedation

A saturation oxygen range of 94% – 98% in most surgical patients is recommended. The guideline exempts surgical patients with a high risk of hypercapnic respiratory failure. The population's saturation oxygen is lower at 88 - 92%. Despite the lack of clinical evidence from randomized studies, this guideline recommends using pulse oximetry for saturation level monitoring. The following are supplemental oxygen protocols. Hyperoxemia is not a common recommendation in this population during the perioperative and postoperative periods.

Oxygen supplementation is recommended in all surgical procedures requiring short-term or long-term conscious sedation. The guideline recommends periodic monitoring of oxygen saturation levels using pulse oximetry during the procedures and the recovery phase. The recommendation is beneficial in fiber-optic bronchoscopy and upper GI endoscopy in patients with hypercapnia, where arterial oxygen saturation (SaO2) reduction is expected.

Arterial oxygenation reduction is considered one of the major complications in many perioperative care plans. In the case of a significant decrease in arterial oxygenation characterized by a SpO2 of less than 90%, supplemental oxygen therapy should be initiated as a corrective plan. In this case, the target oxygen saturation range is pegged at 94–98% and 88–92% in those at risk of hypercapnic respiratory failure.

Patients with cardiorespiratory conditions undergoing procedures are more likely to experience hypoxemia and hypercapnia. The frequency of hypoxemia increases if patients are heavily sedated. Routine oxygen administration is not recommended in these patients as it conceals the clinical signs of respiratory failure. Blood gas measurement is required if these patients are administered supplemental oxygen for a prolonged period.

At all stages of conscious sedation, routine clinical assessment is recommended. Capnography or transcutaneous carbon dioxide levels should also be monitored to help identify clinical signs indicating respiratory depression.

The target oxygen saturation range for these patients during the recovery phase after conscious sedation is pegged at 94–98% in most patients and 88–92% in those at risk of hypercapnic respiratory failure.

Oximetry should be monitored in patients using patient-controlled analgesia for hypoxemia. The primary clinical aim of oxygen therapy in these patients is maintaining a stable oxygen saturation level.

Oxygen Therapy in Conditions Requiring Frequent Oxygen Supplementation

Stroke Management

Oxygen saturation level monitoring is clinically crucial in stroke management as it impacts disease prognosis. Saturation levels should be monitored every four hours in these patients with all episodes of hypoxemia. If hypoxemia develops post-stroke, the attending specialist should assess the patients and make a clinical review of possible causes and the best therapy approach. Oxygen should only be initiated in severe cases involving airway occlusion after securing airway integrity.

Supplemental oxygen is administered at the lowest concentration needed to achieve a target saturation range of 94–98% and 88–92% in patients at a high risk of hypercapnic respiratory failure. A high concentration of supplemental oxygen should be avoided in stroke management unless this is required to maintain normal oxygen saturation.

Oxygen administration in stroke is advised through the nasal route. The recommendation exempts patients with pathological nasal blockage, contraindications to nasal delivery, and patients in which a different delivery route shows clear clinical benefits.

As in patients with cardiorespiratory conditions, patients managed with supplemental oxygen in stroke episodes should be aligned in the best possible upright position. If patients regress into a reduced level of consciousness, this guideline recommends a recovery position with the paralyzed side lowest.

Respiratory Conditions with Low Risks of Hypercapnic Respiratory Failure

The target oxygen saturation level is 94 - 98% in pneumonia patients with a high risk of hypercapnic respiratory failure. The oxygen saturation level recommendation is the same for acute asthma attacks. In lung cancer complications, including repetitive episodes of breathlessness, set the target oxygen saturation level to 94 - 98%. If there is a coexisting diagnosis of COPD, refer to the recommendation on COPD.

In lung diseases of interstitial origin, including acute deterioration of pulmonary fibrosis, aim for an oxygen saturation target of 94 - 98%. If deterioration severity prevents proper oxygenation, raise the saturation level to the highest point possible. A target saturation level of 94-98% should be set for patients without the risk of hypercapnic respiratory failure. In patients having hospital observations without drainage, use high concentration oxygen at a 15 L/min flow rate unless there is a significant risk of hypercapnic respiratory failure.

A target oxygen saturation level of 94 - 98% should also be set in pleural effusion and 88 - 92% if the patient shows clinical signs suggesting a risk of hypercapnic respiratory failure. In pulmonary embolism, aim for a saturation level of 94 - 98% or 88 - 92% if the patient is at risk of hypercapnic respiratory failure.

Patients at Risk of Hypercapnic Respiratory Failure

In patients with known COPD, morbid obesity, cystic fibrosis, chest wall deformities or neuromuscular disorders, or fixed airflow obstruction associated with bronchiectasis or other hypercapnic respiratory failure risk factors, the recommended target oxygen saturation range is set at 88 - 92%. The British Thoracic Society recommendation emphasizes the availability of blood gas results.

Treatment should be based on the results of blood gas samples in previous episodes of acute exacerbations. A low oxygen concentration therapy should be initiated in patients with prior hypercapnic failure who presented without an alert card.

Low oxygen therapy for these patients should start at 2-3 L/min using a Venturi 24% mask. As an alternative, the attending specialist should consider a 28% Venturi mask at 4 L/min or a nasal cannula at 1-2 L/min. These patients also require a standby ambulance and emergency services. Saturation should be reduced if it passes the 92% mark and increases if it falls below the 88% mark.

Non-Respiratory Conditions

In patients with acute heart failure, raise the oxygen saturation level to 94–98% or 88–92% if a significant risk of hypercapnic respiratory failure exists. In patients with cardiogenic pulmonary edema not responding to standard treatment, continuous positive airway pressure (CPAP) should be considered. Entrained oxygen or high-flow humidified nasal oxygen may be used as an adjunct therapy in raising the oxygen saturation level. The oxygen level should be 94 - 98% or 88 - 92% if the patient is at risk of hypercapnic respiratory failure.

In anemia, aim at an oxygen saturation of 94–98% or 88–92% if the patient is at risk of hypercapnic respiratory failure. In sickle cell crisis, set the saturation level target to 94–98% or 88–92%. Oximetry measurements should be taken, and arterialized capillary blood gases should be sampled. In acute coronary syndromes and myocardial infarction, aim for an oxygen saturation target of 94–98% or 88–92% in patients at risk of hypercapnic respiratory failure.

In cluster headaches, administer supplemental oxygen at a flow rate of 12 L/min to achieve a reliably high saturation level. The guideline recommends an oxygen saturation rate of 94–98% or 88–92% in renal and metabolic disorders if the patient is at risk of hypercapnic respiratory failure.

Oxygen Supplementation as Driving Gas System for Nebulized Treatments

Oxygen supplementation can be explored as a driving gas system for administering nebulized drugs. In asthma patients, piped oxygen administered from an oxygen cylinder fitted with a high-flow regulator capable of delivering a flow rate of >6 L/min should be used as a driving gas system for nebulizers.

If the cylinder cannot match the recommended flow rate, an air-driven nebulizer fitted to an electrical compressor is a viable alternative. The nebulizer should be used with supplemental oxygen administered by a nasal cannula delivering oxygen at 2-6 L/min. The saturation rate should be monitored.

Nebulized medications should be given using an ultrasonic nebulizer or a jet nebulizer driven by compressed air. The guideline also recommends the concurrent administration of supplemental oxygen by nasal cannula to achieve an oxygen saturation rate of 88 - 92%.

The same oxygen saturation rate should also be adopted in managing patients at a high risk of hypercapnic respiratory failure before blood gas analysis results are available. In these patients, oxygen saturation levels should be closely monitored.

In patients managed on oxygen therapy, the protocol should be changed to include using supplemental oxygen. Once the nebulized treatment is completed, the previous target oxygen protocol should be reinstituted. The attending specialist should ensure hypoxemia does not occur while administering nebulized treatments.

In patients with COPD scheduled for nebulized therapy, supplemental oxygen administration should be limited to 6 minutes. The risk of hypercapnic respiratory failure is limited. A therapeutic dose of the nebulized drug is quickly delivered.

Management Protocol in Patients Suspected of Excessive Oxygen Therapy

Patients on oxygen therapy should be monitored for hypercapnic respiratory failure to prevent potential hypoxemia. If this is suspected, the oxygen assistance should be reduced to the least amount needed to preserve an oxygenation range of approximately 90%. A non-rebreather mask or 1–2 L/min via nasal cannula can be used to accomplish this. Abrupt discontinuation of oxygen may cause fatal rebound hypoxemia.

German S3 Guideline for Oxygen Therapy in Acute Care of Adults and Patients

The German S3 guidelines were developed within the Program for National Disease Management Guidelines (AWMF). As the first national guideline on supplemental oxygen therapy, the German S3 guideline directly addressed clinical concerns surrounding oxygen prescriptions and oxygen therapy in disease conditions. Target ranges of oxygen saturation levels recommended in this guideline are based on ventilation status risk of hypercapnic respiratory failure. There is also an overview of patient safety and comfort, indications requiring supplemental oxygen therapy, therapy monitoring, weaning, and other protocols covering oxygen use in inpatient admissions. The general recommendations adopted as practice points in the German S3 guideline on supplemental oxygen use include the following:

  1. Positioning is considered a fundamental factor in therapy effectiveness. In conscious hypoxemic patients, an upright positioning may improve tissue oxygen saturation levels and disease prognosis. Clinical evidence links acute respiratory failure in morbidly obese patients with supine positioning. Pregnant women should be positioned on the left side to reduce the risk of aortocaval compression.
  2. In non-hypoxemic patients, nonpharmacological options, including relaxation exercises, cooling of the face, airflow from a table fan, and walking aids, should be considered the primary therapy option in palliative care. Opioids are effective in the management of dyspnea in non-hypoxemic patients.
  3. Respiratory rate is an important vital sign to be monitored in a hypoxemic patient on oxygen therapy. Respiratory rate is used in the track and trigger system and as a prognostic score. Patients are considered clinically stable at a National Early Warning 2 (NEWS2) score greater than 5, with the vital sign predominantly in the noncritical stage.
  4. Pulse oximetry is recommended as a simple, non-invasive method of measuring the arterial oxygen saturation level in both inpatient and outpatient clinical settings. Oximetry measurements can significantly reduce the number of blood gas tests required. However, pulse oximetry is less accurate than measuring arterial blood oxygen saturation.

Supplementary Oxygen Therapy in Poisoning

Unlike the British Thoracic Society's guideline on supplemental oxygen use, the Germany S3 guideline established a relationship between hyperbaric oxygen therapy (HBO) and reduced mortality. The German S3 recommendation is focused on the use of oxygen therapy in patients with carbon monoxide poisoning. In this guideline, expert submissions support the efficacy of high-dose oxygen in achieving hemoglobin saturation and shortening the elimination half-life of carbon monoxide, despite carbon monoxide's higher affinity for hemoglobin than oxygen (Rose et al., 2017). The consensus recommendation points for the management of patients with carbon monoxide poisoning include the following:

  • Patients with acute carbon monoxide poisoning should be started on oxygen therapy until the carbon monoxide-hemoglobin complex (COHb) has reduced to normal levels at less than 3% and presenting symptoms have completely resolved. Treatment should be immediately started with the highest possible oxygen concentration irrespective of oxygen saturation (SpO2) at presentation.
  • In paraquat and bleomycin poisoning, conservative oxygen therapy is recommended. Clinical evidence suggests the initiation of supplemental oxygen only at saturation levels below 85%. The attending specialist can decide on treatment based on the patient's presenting condition.
  • Available clinical evidence suggests a possible risk of complications in managing paraquat poisoning with supplemental oxygen. The oxygen molecules reportedly bind with the paraquat, forming reactive free radicals initiating the development of pulmonary fibrosis.
  • Since oxygen administration has been associated with an increased risk of pulmonary complications in bleomycin poisoning, periodic monitoring of the essential vital signs is highly advised. Frequent monitoring is necessary since no upper limit of oxygen saturation above which the risk of complication increases has been identified.
  • Regardless of the saturation level, it is reasonable to continue supplemental oxygen therapy for carbon monoxide poisoning for up to 6 hours. These patients should be given 100% oxygen without delay; hyperbaric oxygen is an option in a severe case of carbon monoxide poisoning. High-dose oxygen can be delivered via masks, HFNC, and NIV in addition to the tube.

Supplemental Oxygen Therapy in COVID-19 and Infectious Lung Diseases

The guideline prescribes oxygen therapy in patients presenting with a history of pulmonary diseases with or without a complication of breathlessness or isolated hypoxemia. No clinical symptoms of airway restriction and shortness of breath may be present in silent hypoxemia. The guideline draws consensus recommendations from clinical studies advocating blood gas analyses (ABG) for COVID-19 patients (Tobin et al., 2020). The German S3 guideline recommendation for supplemental oxygen therapy in lung infections and COVID-19 includes the following:

  • Set up a closely monitored pulse oximetry on admission and track respiratory rate. There is clinical evidence suggesting a dynamic deterioration rate in these patients. Early warning systems, including NEWS2, can also be used. The priority should be on monitoring the vital signs.
  • Currently, there is insufficient clinical evidence supporting a target oxygen saturation level range for COVID-19 patients. The lack of evidence also makes the goals of supplemental oxygen in these patients unclear. In addition, in COVID-19 patients, hyperoxemia under oxygen therapy can cause delayed detection of respiratory failure. With close clinical monitoring in these patients, saturation levels should be increased to the highest, safest level.
  • The supplemental oxygen algorithm below should be considered in patients admitted on a viral respiratory tract infection diagnosis.

chart showing the supplemental oxygen algorithm

Fig 4. Supplemental Oxygen Algorithm

The German S3 guideline recommends wearing personal protective equipment, distancing and properly fitting the high flow oxygen therapy (HFNC) or NIV mask, and wearing month-nose protection by patients undergoing supplemental oxygen therapy to control disease spread in patients with infectious respiratory conditions. It is important since increased aerosol formations have been observed at higher oxygen flow rates via nasal cannula and face masks.

High-flow cannulas have a tighter fit, as expired air extends less than 20 cm from a patient on high-flow oxygen therapy. Venturi masks also have high air integrity, preventing the long-distance extension of expired air.

Supplementary Oxygen in Ventilated Patients

Ventilated patients in the Intensive Care Unit must be monitored closely and placed on supplemental oxygen. Although, the risk of hypercapnic respiratory failure is minimal under mechanical ventilation. However, there are increasing submissions on the harmful effects of supplemental oxygen on ventilated patients (Palmer et al., 2019). Based on study evidence from randomized trials and meta-analysis of different study groups, the recommendation for oxygen therapy in ventilated patients include the following:

  • The target arterial oxygen saturation rate recommended in ventilated patients is 92 - 96%. Oxygen should be guided by oxygen saturation measurements tracked by pulse oximetry and arterial blood gas analysis (ABG). It is recommended in pre-hospital settings.
  • Conservative oxygen therapy should be considered the primary option over liberal oxygens therapy in ventilated patients requiring supplemental oxygen. A 2017 meta-analysis provided enough evidence for this recommendation as it found that conservative oxygen therapy is associated with a lower ICU mortality rate, 28-day mortality, in-hospital mortality, and non-respiratory organ failure rate (Hirase et al., 2019).
  • In patients with severe hypoxemia on invasive ventilation, there are significant differences in the 90-day mortality index if the attending specialist opts for a conservative or liberal oxygen delivery method. The HOT-ICU trial on oxygen target ranges in ICU patients provided this clinical evidence (Schjørring et al., 2021). The attending specialist is advised to select a personalized delivery method better for the patient.

Oxygen Therapy in Cluster Headaches

In cluster headaches, oxygen should be administered at a flow rate of at least 15 L/min via a reservoir mask. Administration duration should not be less than 15 minutes. Clinical evidence supporting this recommendation also shows data indicating a high functional outcome in patients under this category (Dirkx et al., 2018).

Supplemental oxygen appears to provide more symptomatic relief for patients with cluster headaches when compared with ergotamine therapy. A clinical trial compared ergotamine therapy with oxygen administration (7 L/min experimentation) in 50 patients with cluster headaches. Around 82% of patients in the oxygen therapy group and 70% in the ergotamine group reported relief.

Supplemental oxygen therapy in cluster headaches also showed a better relief score than normal air therapy. A randomized placebo-controlled trial reported freedom from pain after 15 minutes in 78% of the participants who were administered concentrated oxygen.

Pre-hospital Oxygen Therapy

Supplemental oxygen therapy should aim at a target saturation range of 92 - 96% or 88 - 92% in patients with a high risk of hypercapnic respiratory failure (Kopsaftis et al., 2020). High-dose oxygen, defined as 100% or 15 L/min, should only be administered if pulse oximetry fails to reliably establish oxygen saturation levels in critical conditions (outpatient settings).

Randomized trials on oxygen therapy have shown a high clinical benefit when lower oxygen saturation ranges are set. COPD patients with acute symptom exacerbations have reported benefits (Sepehrvand et al., 2018). If oxygen saturation measurement is not available or not reliable, oxygen should be administered as if no pulse oximeter was available. The recommendation is only advised in critical conditions (e.g., emergency CPR), as pulse oximetry is vital in the initial stages of patient assessment before starting supplemental oxygen administration.

During CPR, the highest possible oxygen flow rate should be used as a priority, aiming principally at tissue saturation and patient resuscitation. After spontaneous circulation is restored and oxygen saturation level becomes reliable, the attending medical personnel should aim for an oxygen saturation range of 92 - 96% (Holmberg et al., 2020).

A nonmedical staff may also administer supplemental oxygen as a first-aid intervention based on the strict premise of necessity. The recommendation also advises that emergency medical service personnel be trained in oxygen therapy and administration procedures. Since blood gas analyses are unavailable in this setting, training on recognizing the clinical symptoms of hypercapnic respiratory failure is also advised.

Guidelines on Home Oxygen Therapy

Patients may be prescribed home oxygen therapy in conditions requiring long-term oxygen therapy. Feasibility studies on home oxygen therapy plans indicated the need for medical supervision and periodic patient assessment. The plan, when indicated, reduces patients' hospital admission period and significantly eliminates the risk of hospital-acquired infections. Home oxygen therapy may be advised in some chronic conditions, including cardiac impairment and COPD. Home oxygen therapy improves disease prognosis and the clinical symptoms at presentation when administered correctly with no technical errors. The different, widely-recognized protocols of home oxygen therapy include the following (Shebl et al., 2022):

  • Ambulatory Oxygen Therapy (AOT): is prescribed in physically active patients with severe resting hypoxia. All other chronic conditions resulting in severe low saturation levels and requiring long-term oxygen management can also be covered with a home delivery protocol.
  • Nocturnal Oxygen Therapy: under this delivery protocol, oxygen is administered overnight and not during the daytime. Multiple studies, including the report by Lacasse et al. (2020), have investigated the clinical potentials of long-term continuous oxygen doses administered via a concentrator.
  • Long-term Oxygen Therapy: is the most widely prescribed home oxygen delivery protocol. Supplemental oxygen is administered in patients with chronic hypoxemia. Stationary concentrators are popular with this protocol.
  • Palliative Oxygen Therapy: protocol uses oxygen to relieve the sensation of persistent refractory breathlessness in advanced disease or life-limiting illness, irrespective of underlying pathology, where all reversible causes have been or are being treated optimally.
  • Short Burst Oxygen Therapy (SBOT): protocol is indicated for the relief of breathlessness, not relieved by any other treatments. It is used intermittently at home for short periods, for example, 10–20 minutes at a time. Oxygen used in this way has traditionally been ordered for non-hypoxemic patients and used for subjective relief of dyspnea before exercise for oxygenation or after exercise for relief of dyspnea and recovery from exertion.

Long-term Oxygen Therapy (LTOT) Recommendations in Chronic Conditions:

Chronic Obstructive Pulmonary Disease

Long-term oxygen therapy should be advised in patients with stable COPD and a resting PaO2<7.3 kPa. LTOT is also indicated in COPD patients with a resting PaO2<8 kPa with clinical evidence of peripheral edema, polycythopenia (hematocrit ≥ 55%), or pulmonary hypertension. LTOT should be considered if other clinical criteria are fulfilled in patients with resting hypercapnia.

The UK MRC (Medical Research Council) domiciliary oxygen trial provided evidence on the clinical impact of LTOT in these patients. The study population included 87 hypoxemic patients with chronic bronchitis and emphysema, also presenting with a PaO2 range of 5.3 - -8. kPa. Patients were randomized to two study groups of 'no oxygen' and 'supplemental oxygen' at 15h/day with a target PaO2 of >8 kPa. Over a 5-year study period, the mortality rate in the 'no oxygen' group was more (30 out of 45 patients) than in the 'supplemental oxygen' group (19 out of 42).

COPD patients may develop nocturnal hypoxemia, decreased functional capacity, and nocturnal hypoventilation during REM sleep. LTOT has also been shown to improve the quality of REM sleep and reduce sleep latency in these patients.

Cystic Fibrosis

LTOT should be instituted in cystic fibrosis patients with a resting PaO2 less than or equal to 7.3 kPa. The recommendation should also be adopted in cystic fibrosis patients with resting PaO2<8.0 kPa, presenting clinical evidence of pulmonary hypertension, edema, or polycythopenia (hematocrit ≥ 55%).

Pulmonary Hypertension

In patients with pulmonary or idiopathic pulmonary hypertension, LTOT is recommended when the PaO2 is < 8kPa. Patients at risk of hypoxemia and presenting with pulmonary hypertension as a complication should follow this recommendation.

LTOT may improve tissue oxygen perfusion levels in these patients and reduce the risk of developing complications associated with severe hypoxemia.

Neuromuscular or Chest Wall Disorders

The British Thoracic Society guideline on supplemental oxygen therapy recommended non-invasive ventilation as the treatment of choice in patients with neuromuscular diseases or chest wall diseases causing type II respiratory failure. However, LTOT should be considered in hypoxemia patients not responding to non-invasive ventilation.

LTOT should also be considered in patients with severe restrictive diseases and those with airway diseases or obesity causing complications of hypoxemia not responding to non-invasive ventilation protocols.

Advanced Cardiac Failure

In patients with advanced cardiac failure with a resting PaO2<7.3 kPa, LTOT is recommended. LTOT is recommended for patients with a resting PaO2<8.0kPa, with a clinical presentation of peripheral edema, polycythemia (hematocrit ≥ 55%), or pulmonary hypertension on ECG or echocardiography. LTOT may improve disease prognosis, increase tissue oxygenation, and reduce the risk of hypoxemia-related clinical complications.

General Management Points for Patients on LTOT

In LTOT, patients should not be assessed solely with pulse oximetry. The attending specialist should conduct an initial assessment using arterial blood gas sampling. During periods of apparent clinical stability, two arterial blood gas assessments should be performed at least 3 weeks before LTOT can be initiated. Capillary blood gas sampling can be used to remeasure PaCO2 and pH at different oxygen flow rates for oxygen titration during this assessment. Patients should be reassessed after the oxygen titration is complete. Arterial blood gas helps to determine if the target oxygenation range has been achieved.

Patients who develop worsened hypercapnia or respiratory acidosis during an initial assessment may have comorbidity. Further clinical assessments and evaluation of physiological integrity are recommended. Suppose an unstable clinical state is confirmed if these patients experienced two repeated occasions of worsened hypercapnia or respiratory acidosis. In this case, the patient should only have domiciliary oxygen initiated with nocturnal ventilator support. The British Thoracic Society recommends the initiation of LTOT at a flow rate of 1 L/min and titrated up in 1 L/min increment until the SpO2 is greater than 90%.

Without any contraindications, the LTOT flow rate should be increased by 1 L/min during sleep in non-hypercapnic patients. Ambulatory and nocturnal oximetry may be performed to allow a more accurate flow rate. Patients in clinically stable conditions with optimal neurological and cognitive functioning may be allowed to safely initiate, control, and monitor the flow rate increments. Until the target PaO2 is achieved, flow rates may be increased at 20 min intervals during an oxygen titration. Follow-up, including the blood gases and flow rate assessment, should be scheduled for 3 months after the initiation of LTOT. After this first schedule, the next follow should be at 6 to 12 months if the initial assessment is considered satisfactory.

Nocturnal Oxygen Therapy (LTOT) Recommendations in Chronic Conditions

Cardiac Failure

Nocturnal oxygen therapy (NOT) should be considered (in conjunction with non-invasive ventilation support) in patients with clinical evidence of established ventilatory failure. Patients with cardiac failure and nocturnal hypoxemia who do not fulfill LTOT criteria should be excluded from NOT. Improved nocturnal oxygenation levels may be noticed in cardiac failure patients treated with NOT. However, there is weak study evidence of long-term clinical benefits on survival rate, sleep quality, disease prognosis, and a reduction in complication risk. NIV support is essential in patients presenting with hypercapnia as a complication of cardiac failure.

Neuromuscular Weakness

NOT with NIV support should be considered in patients with neuromuscular weakness presenting with evidence of established ventilatory failure. In patients with neuromuscular weakness affecting the respiratory muscles, NOT should not be ordered alone. Patients with neuromuscular weakness and nocturnal episodic hypoxemia need daytime blood gas measurements.

Obstructive Sleep Apnea, Obesity, Hypoventilation Syndrome, or Overlap Syndrome

NOT should not be ordered alone in patients with obstructive sleep apnea, obesity, hypoventilation syndrome, or overlap syndrome. In these patients, supplemental oxygen therapy using NOT is considered adjunctive therapy to NIV as there is only weak clinical evidence supporting home oxygen in these conditions.

Cardiac Disease and Nocturnal Desaturation

NOT should be considered in severe heart failure patients who are not eligible for LTOT and present with clinical evidence of sleep-disordered breathing leading to daytime symptoms after other causes of nocturnal desaturation have been excluded.

In these patients, NOT is initiated at a flow rate of 1 – 2 L/min, with clinical response assessed by improving daytime symptoms, including daytime sleepiness. Blood gas measurements should be conducted to exclude respiratory acidosis and worsening hypercapnia.

Equipment and Setup Protocols for Home Oxygen Therapy

Regarding the popular guidelines on home oxygen management, the equipment can be classified into three different groups.

Oxygen Source (Concentrators, Cylinders, and Liquid Oxygen)

Home oxygen cylinders used in delivering oxygen therapies are either stationary or transportable. The prescribed type depends on the patient's clinical need and mobility. Oxygen concentrators are the most commonly used device for home oxygen protocols which can be stationed in a patient's home or may be portable with the patient taking the unit outside of the house and into the workplace.

The concentrator delivers an approximately 90% oxygen-based gas mixture after filtering room air to remove nitrogen. Depending on the technology and other technical specifications, the performance of the oxygen concentrator may differ. In most brands of this device, the maximum oxygen concentration delivered is 96%. The British Thoracic Society recommendation on oxygen concentrators prescribes a flow rate of 4 L/min or less when an oxygen concentrator is used.

Oxygen Delivery (Cannula, Masks, Conservers, and Tracheal Devices)

Nasal cannulas are recommended when oxygen therapy is prescribed for 15 h/day, and there is a requirement for regulated oxygen supplementation. The cannula provides a continuous flow of entrained oxygen so that each liter per minute of oxygen flow offers an additional 4% to the inspired oxygen concentration. Oxygen-conserving devices enable cylinders to last longer and serve substantial economic benefits to the patient. With these devices, oxygen is only provided through inspiration – which helps reduce the waste of oxygen during expiration.

Additional Equipment (Humidifiers and Equipment to Carry Oxygen)

Supplementary equipment, including humidifiers, trolleys, and backpacks, is indicated to reduce the burden of care for patients and caregivers. Trolleys and other wheeled devices can improve the patient's quality of life, shorten the distance walked at home, reduce the energy expended on lifting cylinders and eliminate discomfort during exercise. Generally, supplementary devices help minimize stress and inconvenience and address technical difficulties surrounding home oxygen provision.

Complications, Contraindications, and Adverse Effects of Home Oxygen Therapies

There is a significant risk of personal injury and fire hazards associated with home oxygen therapy. Patients on LTOT should be advised of the need for smoking cessation. In major studies on the risk assessment of home oxygen therapies, lighting a cigarette constitutes the largest chunk of personal injuries in patients undergoing home oxygen therapy. Other causes of injuries in these patients include lighting a cooker, electric sparks, candles, and other open flames. Identified issues on the burden of therapy in these patients include decreased mobility, daytime inconvenience, nasal prong discomfort, and technical noise from the device setup.

Patent education should emphasize medical intervention to modify flow rates and oxygen concentration. There are increasing reports of patients and caregivers changing the therapy protocols without a medical supervision order. Since oxygen is administered as a drug in these patients, medical advice should be sought before co-administering other medicines with the therapy. In patients experiencing a sudden deterioration of vital signs and clinical symptoms, caregivers should be educated on the need to call an ambulance and alert the medical team immediately.

Supplemental Oxygen Delivery Systems

Depending on the patient's age, oxygen requirements, therapeutic goals, tolerance, and humidification needs, various oxygen delivery methods are available for both inpatient and pre-hospital settings. These delivery systems are categorized into two broad classes- low-flow delivery methods and high-flow delivery methods. The low-flow delivery methods include:

  • Simple face masks
  • Nasal prongs
  • Tracheostomy masks
  • Non-rebreather face mask
  • Isolette – (Used in neonatal intensive care units)

The high-flow delivery methods also include:

  • Ventilators
  • CPAP/BiPAP drivers
  • High flow nasal prong therapy

The masks and valve design popular with these delivery systems allows the administration of inspired supplemental oxygen of 24 - 90%. The inspired concentration and, subsequently, the oxygen saturation attained depend on the ventilation minute volume and the flow rate. The high-flow mask systems can deliver an estimated 40 L/min of oxygen sufficient to meet the saturation level target in many inpatient settings. At this rate, the systems ensure the breathing pattern does not affect the FiO2 as the delivery flow rate exceeds the physiological respiratory rate. With both the high-flow and low-flow delivery options, the most widely used masks in oxygen therapy include the following.

Rebreathing and Anesthetic Oxygen Mask

Although not commonly used, these masks provide supplemental oxygen concentrations greater than 60%. The design incorporates non-rebreathing valves and reservoir bags. The tight-fitting mask can achieve 100% oxygen if used in cardiac or respiratory arrest patients. The only contraindication for use is the oxygen toxicity risks and prolonged use in some patients.

Nasal Prongs

These delivery options are simple to use and convenient for long-term oxygen therapy use in patients. The oxygen flow rate (1-6 L/min) varies with the ventilation minute volume determines the FiO2. When the oxygen flow rate achieves a 2 L/min delivery, the oxygen in the hypopharynx of the patients amounts to a range of 25% to 30%. As with rebreathing-type masks, nasal prongs are convenient for long periods of use and can be used while eating or talking. Local irritation and dermatitis may occur in patients on long-term usage.

High-Flow Jet Mixing Masks

These are suitable for delivering low oxygen concentrations (24-35%). In patients with an unstable breathing pattern, these masks provide a ventilatory requirement unaffected by the breathing pattern. Consequently, the flow rate and oxygen concentration can be easily modified to achieve target saturation levels quickly. In patients with COPD and respiratory failure, high-flow jet mixing masks reduces the risk of carbon dioxide retention and improve the clinical symptoms of hypoxemia. With a high flow delivery, rebreathing of gas is not considered a significant problem with these masks.

Low-Flow Masks

These masks deliver oxygen moderately at a flow range of 6-10 L/min, achieving an oxygen concentration of up to 60%. They are used primarily in type 1 respiratory failure cases requiring supplemental oxygen, including pulmonary embolus and pulmonary edema. A technical disadvantage of this mask is its low flow rate, allowing the possibility of significant rebreathing as air is poorly flushed from the face mask. Low-flow masks make it difficult to achieve a low inspired oxygen concentration and prevent carbon dioxide retention.

Hyperbaric Oxygenation

Oxygen is delivered at a pressure of 300kPa, allowing a significant increase in arterial oxygenation to about 300%. Tissue oxygenation also significantly improves as tissue perfusion rate increases. However, hyperbaric oxygenation should only be used in special cases. In addition to fulfilling clinical circumstances and suitability for each patient, selecting any oxygen delivery system is also expected to comply with standard guidelines on oxygen therapy. The German S3 guideline recommendation selects nasal prongs as the primary delivery choice for low oxygen flow rates of less than 6 L/min.

Fig 5: Pros and Cons of different oxygen delivery systems

Key: FiO2 – inspired oxygen concentration, PEEP – positive end-expiratory pressure.

Nasal prongs
(FiO2 0.26-0.54)
photo of nasal prongs
  • Increased patient comfort
  • Low cost
  • Does not interfere with the oral intake
  • FiO2 limited/unreliable
  • FiO2 dependent on mouth opening and respiratory rate
Nasal cannula
(FiO2 0.2-0.4)

picture of nasal cannula
  • Low cost
  • Occupies only one nostril
  • Does not interfere with oral intake
  • Mucous membrane irritation
Simple face masks
(FiO2 0.35-0.60)

image of simple face mask
  • FiO2 independent of mouth opening
  • Low cost
  • Low patient comfort
  • Prevents eating and drinking
  • Experienced providers necessary
Venturi mask
(FiO2 0.24-0.60)

picture of venturi mask
  • Low aerosol formation
  • Reduced risk of hyperoxia and hypercapnia
  • Low patient comfort
  • Prevents eating and drinking
  • Experienced providers necessary
Face tent
(FiO2 0.35-0.50)

No image
  • Increased Patient comfort
  • High FiO2 delivery
  • FiO2 unreliable
Reservoir mask
(FiO2 0.60-0.90)

picture of reservoir mask
  • Useful in emergency situations
  • High FiO2 delivery
  • Low patient comfort
  • Prevents eating and drinking
  • Risk of hypercapnia at flows <5 L/min
High-flow cannula
(Fi02 0.3-1.0)

No image
  • High FiO2 delivery
  • Increased patient comfort
  • Accepted aerosol formation
  • Provides modest PEEP
  • Good FiO2 control
  • Higher cost
  • Closer monitoring
  • More staff effort required
Ventilation mask
(FiO2 0.3-1.0)

picture of ventilation mask
  • High FiO2 delivery
  • Low aerosol formation
  • Higher cost
  • Low patient comfort
  • More staff effort

Venturi masks should also be considered as an alternative. These masks use Bernoulli's effect, introducing oxygen through a tapered nozzle and swilling the air-oxygen mix as it enters at a high flow rate for inhalation. Unlike nasal prongs, a Venturi mask does not increase inspired oxygen concentration at higher flow rates (Pennisi et al., 2019).

High-Flow Oxygen Therapy

The concentration of oxygen administered and the flow rate of delivery are considered primary factors in the evaluation of the effectiveness of an oxygen therapy protocol. A recent study focused on nasal high-flow oxygen therapy in patients with hypoxia and reported how the effective inspiratory oxygen concentration depends on the patient's respiratory flow and breathing pattern (Schwabbauer et al., 2014). As with this study, recent studies on supplemental oxygen therapy have consistently explored high-flow oxygen therapy in conditions requiring oxygen.

In high-flow oxygen therapy, humidified oxygen is heated and delivered using specially-designed nasal cannulas capable of providing supplemental oxygen at a rate of 40-60 L/min. Modern high-flow cannulas deliver oxygen at a rate higher than the patient's physiological respiratory flow. Consequently, a defined fraction of oxygen in inspired air (FiO2) is delivered up to 1.0, independent of the patient's breathing pattern. In addition to rapidly boosting the saturation state, HFNCs also reduce the work of breathing and the risk of damage to the respiratory epithelium and respiratory discomfort. HFNCs are now widely used in intensive care units.

In a systemic review of a randomized-controlled quasi-experimental study, Marjanovic et al. (2020) compared the use of high-flow oxygen therapy versus conventional oxygen therapy in patients with acute respiratory failure admitted to the emergency department. The researchers indicated that high-flow oxygen decreased dyspnea and the respiratory rate in the study population (Marjanovic et al., 2020). In another systematic review conducted by Ou et al. (2017), study results indicated that the reintubation rate of critically ill patients was lower when high-flow oxygen was used compared with conventional oxygen delivery methods (Ou et al., 2017). High-flow oxygen also shortens hospital stays and lowers the intubation rate in immunosuppressed patients with acute pulmonary failure (Wen et al., 2019).

The German S3 guideline recommends that patients on high-flow oxygen therapy should be closely monitored and therapy discontinuation clearly defined. Patient monitoring should be done with pulse oximetry and observed for any clinical symptoms suggesting a therapy complication. In hospitalized patients with acute hypoxic pulmonary failure without hypercapnia, high-flow oxygen should be administered at a flow rate of 6 L/min via a nasal cannula or mask if the oxygen saturation level drops below 92%. Since HFNCs are not readily available outside the hospital, medical personnel and first responders should consider CPAP/NIV and reservoir masks as effective alternatives.

Practical Recommendations in Monitoring Oxygen Dispensing and Documentation (S3 and BTCS Recommendations)

Oxygen delivery, therapy monitoring, and vital sign documentation are all fundamental requirements in supplemental oxygen care (O'Donnell et al., 2019). First responders, nurses, and medical personnel dispensing oxygen in clinical conditions where it is indicated are expected to sign the drug chart at every drug round. A periodic check on the delivery system's integrity is also recommended, especially in consciously sedated patients. These checks should also document the oxygen saturation range and provide the data necessary for weaning if needed.

The British Thoracic Society guideline prescribes a 5-minute periodic check for patients started on oxygen. The recommendation also includes patients who require an increased oxygen concentration and those whose oxygen therapy has been stopped. The delivery system should be modified to normalize the saturation range in stable patients with an oxygen saturation higher than the target saturation range. The nursing staff is expected to have a real-time update on the saturation range, and flow rate of patients started on oxygen.

Blood gas measurement should be done every 30 – 60 minutes in patients with a target saturation range of 88 - 92%. The recommendation should also be adopted in patients at risk of developing hypercapnic respiratory failure but with a normal PCO2 on the initial blood gas measurement. Periodic checks in these patients should include the level of carbon dioxide. In stable patients with an oxygen saturation range normalized within the target range, blood gas measurements should not be repeated. Unless there are clear indications of clinical deterioration in signs and symptoms, blood gas measurement should not be repeated in patients with no risk of hypercapnic respiratory failure.

In stable patients responding to therapy, SPO2 and the necessary variables should be monitored at least four times daily. Saturation levels should be monitored continuously in those with an active critical illness. Level 2 or 3 care in a critical care unit or high-dependency unit should also be considered. Once clinical stability is achieved and the oxygen saturation level normalizes, therapy should be continued or modified depending on the patient's condition. In patients with a saturation level below the target range, oxygen therapy should be increased and decreased if the saturation level is above the target range.

After every episode of therapy modification, the new saturation rate, flow rate, and delivery system should be recorded on the patient's personalized observation chart after 5 minutes. However, all modifications to an ongoing therapy should be approved by a senior specialist trained in supplemental oxygen therapy. All changes must be signed on the observations chart. In cases where a reduced oxygen concentration is approved as a therapy modification in a stable patient to maintain a target saturation, repeat blood gas measurements are not required. Patients with no risk of hypercapnic respiratory failure also do not need a recurrent blood gas measurement after an increased oxygen concentration to maintain the desired saturation range. However, the attending specialists should examine why the oxygen saturation level has fallen.

Repeated blood gas measurements should be carried out in patients at risk of hypercapnic respiratory failure and placed on an oxygen protocol to achieve a target range of 88 to 92%. After every increase in oxygen therapy, these measurements should be done at 30 – 60-minute intervals. Pulse oximetry is the recommended primary mode of monitoring in patients with no risk of hypercapnic respiratory failure. Provided the patient's vitals are stable and the desired oxygen saturation range is maintained (94 – 98%), repeated blood gas measurements are not required. Adjustments to the oxygen therapy should be guided against technical faults in the delivery system. Before a medical order for a flow rate increase, the medical personnel should check all parts of the oxygen delivery systems for technical faults and errors. The recommendation should be adopted in all patients regardless of clinical circumstances. Blood gas measurements should be repeated in all patients if the oxygen saturation fails to increase following a 5-10 minute period after increasing the oxygen therapy. A review of possible clinical concerns should be considered in this case.

Weaning –Discontinuation of Oxygen Supplementation Therapy

On oxygen therapy discontinuation, the expert consensus in modern medicine states that oxygen delivery should be reduced when a patient is clinically stable, and oxygen saturation is above the target range or within the range for several hours. Oxygen therapy is effective in restoring tissue and arterial oxygenation in different clinical conditions. Study results reporting improvements in symptoms in patients on oxygen therapy support this. Documented signs of clinical stability in these patients include a normal respiratory rate and stable vital signs. During the short phase of recovery from an acute condition, some patients experience transient hypoxemia. Exercise-induced desaturation has also been reported in patients with acceptable oxygen saturations.

The German S3 guideline recommends discontinuing oxygen therapy in patients not at risk of hypercapnic respiratory failure. Patients being discontinued from oxygen should be within the target oxygenation range for several hours under a flow rate of 2 L/min. In patients at risk of hypercapnic respiratory failure, the lowest volume of oxygen administered before weaning should be 1 L/min or 0.5 L/min as necessary. A 24% Venturi mask set at 2 L/min as the lowest oxygen concentration before weaning can be considered in patients at risk of hypercapnic respiratory failure. If the target saturation range is maintained at this rate, repeat gas measurements are not required, and the patient can be eventually weaned off oxygen if stable.

The British Thoracic Society guideline recommends two consecutive observations on the target oxygen saturation level before oxygen therapy is stopped. Due to the possibility of impending clinical decline, the recommendation for the target oxygen range must be continually monitored. It may be suitable to adjust the target range after reviewing COPD patients who may have accommodated to have oxygen saturations <94% normally or in patients who may be appropriately discharged from the hospital with oxygen levels <94% but need an outpatient oxygen evaluation. Weaning off oxygen may be prescribed once the respective patient has ended the course of the initial prescription for oxygen supplementation.

Immediately after stopping oxygen therapy, the saturation should be monitored. If it is maintained at the target saturation level, a repeat check should be conducted one hour later. During this period, if the oxygen saturation and the physiological track and trigger score are considered satisfactory, the weaning process is successful, and the patient has safely completed the therapy course. In successfully weaned patients with underlying comorbidities, saturation level and vital signs should be monitored as the patient is managed for these conditions.

If the target saturation level falls after stopping oxygen therapy, the weaning attempt is deemed unsuccessful (Rostin et al., 2019). In this case, the oxygen therapy is restarted with the lowest oxygen concentration maintained in the patient before weaning. Hold steady at this concentration and observe for 5 minutes. If this concentration restores the desired saturation level, continue oxygen therapy with this protocol and attempt weaning at a later date. However, the patients must fulfill all the necessary conditions, including stable vital signs, before weaning is initiated later.

Suppose a higher oxygen concentration is required to re-establish the target saturation range. In that case, the attending specialist should conduct a thorough clinical review examining the cause of deterioration before starting a new therapy protocol. The review should check for episodic hypoxemia or transient asymptomatic desaturation. Studies have reported patients experiencing episodic hypoxemia due to minor exertion or mucus plugging after properly discontinued oxygen therapy. A new oxygen protocol may be initiated in these patients. However, a new oxygen protocol is not required in cases of transient asymptomatic desaturation.

Home oxygen may be required after hospital discharge in patients with COPD who have completed a course of oxygen therapy. The S3 German guideline recommends continuing oxygen therapy even after discharge in patients that cannot be successfully weaned off oxygen. The decision to initiate long-term oxygen therapy after discharge should not be made only based on blood gas measurements conducted during the acute illness phase. A follow-up plan should also be initiated after discharge, and patients should be educated on the need for therapy adherence.

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