Exchange of oxygen and carbon dioxide in the lungs depends on effective ventilation and adequate circulation of blood through both lungs. The amount of surface areas available for diffusion greatly affects gaseous exchange. Ventilation brings oxygen into the lungs where it is released into the alveoli in exchange for the carbon dioxide, which has been deposited by the capillaries. If ventilation is not uniform throughout both lungs, the rate of oxygen replenishment is reduced, leading to hypoxia. This situation occurs in the presence of air in the pleural cavity called pneumothorax. Air in this normally closed space will disrupt the negative pressure that keeps the lung from collapsing at the end of exhalation. Under normal conditions, the thoracic cavity is a closed, airtight space. Any disruption will result in a loss of negative pressure, within the intrapleural space. Air and/or fluid collect, taking up the space within the pleural cavity that the lungs need in order to expand. The result is partial or total collapse of the lung. Conditions that disrupt the normally negative pressure within the pleural space, either because of disease, injury, surgery, or iatrogenic causes, will result in loss of negative pressure. The introduction of air into the pleural cavity can quickly lead to lung collapse. The evacuation of air or fluid or both from the pleural cavity is accomplished through a closed drainage system.
It is important to review the normal anatomy and physiology of the thorax to understand what can go wrong in the structure and function of the chest and how these problems can be treated. The thoracic cavity is divided into three compartments: one compartment for each of the lungs and the mediastinum that lies between the lungs. The ribs, sternum, and intercostal muscles protect these structures. The main muscles of the chest wall are the external and internal intercostals. Each extends from one rib to the rib below. The function of the external intercostals is to draw the ribs together and elevate the rib cage, which enlarges the thoracic cavity, while the internal intercostals decrease the dimension of the thoracic cavity. The main muscle of respiration is the diaphragm. It stretches across the bottom of the thorax, separating the thoracic cavity from the abdominal cavity.
The mediastinum contains the thymus gland, the great vessels, the thoracic duct and small lymph nodes, the heart, a branch of the phrenic nerve, and parts of the trachea and esophagus. The two membranes surrounding the lungs are the parietal pleura, which lines the chest cavity and the visceral pleura, which covers the lungs. These two membranes are lubricated so that they glide against each other. The space between these two membranes has a negative pressure and contains neither air nor fluid. Collection of either of these substances can interfere with breathing and may cause the lung to collapse. Problems in the pleural cavity include pneumothorax (air in the cavity, hemothorax (blood in the cavity), hemo-pneumothorax (both blood and air in the cavity and Atelectasis (the collapse of lung tissue). Between these two membranes is the pleural space, which is not a true space but rather contains a thin layer of serous fluid. This fluid acts as a lubricant to keep the parietal and visceral membranes in contact with each other during respiration, allowing them to slide smoothly over one another. The potential exists for a space between these two membranes; hence it is called the pleural space.
The lungs and chest wall contain elastic tissue that tends to pull in opposite directions, the lungs pulling inward and the chest wall pulling outward. Air moves in and out of the thorax based on pressure changes. When the phrenic nerve stimulates the diaphragm, it contracts and moves downward. The external intercostal muscles also move the rib cage up and out. The lung itself expands because of the movement of the diaphragm and the chest wall. The surface tension of the pleural fluid holds the pleura together, thus keeping the lungs from collapsing. As these opposing forces try to pull the parietal and visceral pleura apart, a negative pressure is created within the pleural space. This negative intrapleural pressure keeps the pleural surfaces in contact, holding the lung against the chest wall and expanding the lungs to fill the pleural compartment completely. The intrapleural pressure must remain negative at all times in order to keep the lungs fully expanded. The extent of negative intrapleural pressure depends on the phase of respiration. At rest, the intrapleural pressure is – 5 cmH2O and the intrapulmonary pressure (pressure in the alveoli) equal atmospheric pressure. During inspiration, the thoracic cavity enlarges, decreasing intrapleural pressure to – 6 to – 12 cm H2O and lowering intrapulmonary pressure 2 to 3 cm H2O less than the atmosphere, causing air to be drawn into the lungs. During expiration, the intrapleural pressure “increases” to – 4 to – 8 cm H2O and intrapulmonary pressure increases 2 to 3 cm H2O greater than the atmosphere, causing air to be passively forced out of the lungs.
Pneumothorax is the presence of air in the pleural cavity. Air in this normally closed space will disrupt the negative pressure that keeps the lungs from collapsing at the end of exhalation. The introduction of air into the pleural cavity can quickly lead to lung collapse. There are two main types of pneumothorax: closed and open. A closed pneumothorax occurs when the outer chest wall and parietal pleura remain intact, but damaged visceral pleura allows air to enter the pleural cavity from the lung, An open pneumothorax occurs when an opening in the outer chest wall allows air to enter the pleural cavity from the outside rather than (or in addition to) from the lung. This can result from damage to either the parietal pleura alone or to both pleural membranes.
Spontaneous pneumothorax is usually caused by the rupture of a small bleb (an enlarged air sac) on the lung’s surface. It most typically occurs in young tall males and may be caused by the mechanical stresses that occur at the top of a long, upright lung. It may also result from intrapulmonary disease processes that weaken the lung, making it more prone to rupture. Such diseases include emphysema, cystic fibrosis, tuberculosis, and necrotizing pneumonia.
Iatrogenic pneumothorax has two major causes. One is the use of positive pressure ventilation such as intermittent positive pressure breathing (IPPB) treatments. In patients with weakened lung tissue, the addition of positive pressure to the lung can overstretch damaged, friable lung tissue and cause rupture. High-pressure mechanical ventilation sometimes used to treat respiratory failure such as adult respiratory distress syndrome (ARDS) can also cause pneumothorax. The positive end expiratory pressure (PEEP) used to prevent alveolar collapse can cause alveolar rupture. The second major iatrogenic cause is unintentional lung perforation during invasive procedures such as thoracentesis and central venous catheter placement, especially placement through the subclavian access.
Tension pneumothorax can be caused by patients receiving positive pressure ventilation, especially with high levels of PEEP (over 15 cm H2O). Tension pneumothorax occurs when air rapidly accumulates in the pleural cavity and cannot be evacuated as quickly. Pressure builds up, which not only collapses the lung, but can also shift the mediastinum and severely impede venous return and cardiac output. A tension pneumothorax is life threatening and must be relieved promptly. Signs of tension pneumothorax in a mechanically ventilated patient include shortness of breath, decreased breath sounds on one side, hyperresounance to percussion, sudden sustained increase in the inspiratory pressure on the ventilator’s manometer (with simultaneous sounding of the high pressure alarm), a deviated trachea, and lack of movement on that side of the chest. Patients with chronic lung disease should be given positive pressure ventilation with caution.
Open pneumothorax occurs when the outer chest was has been penetrated. The most common cause is trauma – gunshot wounds, stab wounds, and crushing chest injuries. Blunt trauma to the chest wall can cause rib fractures that can, in turn, puncture the lung and cause pneumothorax by allowing air to leak out of the lung into the pleural cavity. Penetrating trauma such as gunshot or stab wounds cause open pneumothorax, commonly called sucking chest wounds. A patient’s signs and symptoms will vary greatly with the magnitude of the injury and the damage to underlying structures. The pneumothorax is often less serious than the damage to major structures such as a ruptured aorta or other vascular damage. Another type of open pneumothorax occurs with intentional chest trauma, as with thoracic surgery. The pleural cavity is disrupted as soon as the chest wall is opened.
Pneumo-mediastinum is the term given to the presence of air in the mediastinum. It can be seen as a complication of alveolar rupture near the hilus, when air dissects along the bronchovascular plane instead of directly extravasating into the pleural cavity. The diagnosis is made by X-ray since patients exhibit few signs or symptoms. It may cause some chest pain, but usually does not affect pulmonary function. In some cases, the air may dissect up into the soft tissues of the neck and may produce subcutaneous emphysema. This is easily visible on physical exam, and palpation of the affected area will reveal crepitus.
Other pleural abnormalities that may require intervention are pleural effusion and empyema. Pleural effusion is the accumulation of fluid within the pleural cavity. The presence of blood is called a hemothorax; the presence of lymph fluid, chylothorax. Clear, serous fluid can be from a number of sources. For example, a displaced central venous catheter allows IV fluids, serum, or total parenteral nutrition to be infused into the pleural space. It must be withdrawn and examined if the source is not readily apparent or the patient is experiencing respiratory distress. Empyema is a pleural effusion that involves purulent material in the pleural cavity. It is caused by pneumonia, lung abscess, and iatrogenic contamination of the pleural cavity or contamination from the original injury.
Any time the negative pressure in the pleural cavity is disrupted by the presence of air or fluid resulting in pulmonary compromise, the medical treatment is to drain the air or fluid. Fluid can be drained intermittently by thoracentesis (a needle is placed through the chest wall and fluid is withdrawn). If the fluid remains or reaccumulates, the procedure must be repeated.
Patients with continuous air or fluid leaks that compromise ventilation and gas exchange may need to have a chest tube inserted for constant drainage. The chest tube (also called a thoracotomy tube or thoracic catheter) is sterile, flexible, vinyl, silicone, latex, or medical grade plastic nonthrombogenic catheter that is approximately 20 inches (50 cm) long and varies in size. Adults usually require a 16- to 24-guage chest tube for a simple pneumothorax, whereas a 28- to 36-guage tube is used to drain liquid accumulations. Smaller chest tubes are available for children. The end, which will be in the patient’s pleural space, has a number of drainage holes to prevent tip occlusion from clots or tissue, and the distal end connects to a chest drainage system. The drainage holes can usually be detected on chest x-ray as intermittent breaks in a radiopaque line. Once the chest tube has been properly positioned and secured, the x-ray should be checked to ensure that all drainage holes are inside the chest wall.
The location of the chest tube will depend on what is being drained. If air must be drained, the tube will be placed near the apex of the lung at the second intercostals space in the mid-clavicular line, since free air in the pleural cavity will rise to the highest point possible. If fluid must be drained, the tube will be placed near the base of the lung, usually in the fourth to sixth intercostals space along the midaxillary line. This is because gravity will pull fluid down to the lung bases. In the event of a hemo pneumothorax, two chest tubes may be inserted, one anteriorly in the apex to remove air and one laterally at the base of the lung to drain fluid. When two chest tubes are used, they are frequently attached to a single chest drainage system by a Y connector. After open-heart surgery, one or two mediastinal tubes may be placed to drain blood in front of and behind the heart, positioned directly under the sternum.
The specific technique of chest tube insertion depends on the operator and the clinical conditions. Generally though, the procedure starts with administration of pain medication and local anesthesia (unless the tube must be placed under emergency conditions or is inserted at the end of a surgical procedure). For a pleural tube, the incision is made in the chest wall where the tube will be inserted, and dissection is carried out through the intercostals muscles and over the rib to the parietal pleura. The parietal pleura is punctured with a hemostat, a finger is used to create the intrapleural tract and the chest tube is guided through the opening. This method is referred to as the blunt-dissection method. The trocar method uses a pointed trocar to penetrate the thoracic cavity. The chest tube is passed through the hollow trocar, which is then removed, and the chest tube is left in place.
Once the tube is in place, it may be sutured to the chest wall to minimize the risk of dislodgement and connected to a drainage device. The insertion site can be wrapped with petrolatum gauze depending on operator preference, and an airtight dressing will cover the site. Placement should be checked by chest x-ray as soon as possible. With lung or cardiac surgery, chest tubes are placed through the chest wall before closing, and the patient is sent to the recovery room or intensive care unit with the tube in place. Again, a chest x-ray will be taken and examined to check placement.
Closed chest drainage systems use gravity and/or suction to restore negative pressure and remove air, fluid, and/or blood from the pleural space so that the collapsed lung can re-expand. Whenever a chest tube is inserted it must be connected to a one-way mechanism that allows air to escape from the pleural space while preventing air to enter from the atmosphere. This can be accomplished by using an underwater seal mechanism. Traditionally, chest drainage was accomplished with a three-bottle chest drainage system. The three-bottle system has been replaced by various disposable units that incorporate the traditional functions of the three-bottle system and integrates them into one plastic unit. Disposable chest drainage systems have a number of safety advantages over glass bottle systems as well as ease in set-up. Air or fluid can exit the pleural space as a result of gravity, but the water seal prevents it from being drawn back into the cavity.
The collection chamber is at the right side of the unit. The 6-foot tubing connects directly to the chest tube. Any fluid drainage from the chest goes into this chamber. It is usually calibrated in 1 ml increments up to 100 ml, 2 ml increments from 100 ml to 200 ml and 5 ml increments from 200 ml to 2500 ml. It has a surface that can be marked with the time and date of drainage.
The water seal chamber is the middle chamber. When this chamber is filled with fluid up to the 2 cm line, a 2 cm water seal is established. A short latex tube at the top of this chamber is either left open to air for gravity drainage or attached to a suction source. The water seal chamber should have fluid gently bubbling immediately upon insertion of the chest tube, during expiration and with coughing. In addition to maintaining the original purpose of the water seal – keeping air from entering the pleural cavity the system has a calibrated manometer in the water seal chamber to measure the amount of negative pressure referred from the pleural cavity. The water level in the water seal manometer rises as intrapleural pressure becomes more negative. The water level in the water seal should be monitored routinely to check for evaporation. Continuous bubbling in this chamber indicates a leak in the system. Fluctuations in the water level in the water-seal chamber of 5 to 10 cm, rising (during inhalation) and falling (during expiration), should be observed with spontaneous respirations. If the patient is on mechanical ventilation, the pattern of fluctuation will be just the opposite. Additionally, if suction is being applied, this must be temporarily disconnected to correctly assess for fluctuations in the water-seal chamber.
The systems have high negativity float valves in the top of the water seal chamber. This maintains the water seal in the event of high negative intrapleural pressures, as may occur with the deep breath taken before vigorous coughing, or with forced inspiration from an upper airway obstruction. High negativity can also occur if the chest tubing is stripped. High negativity is indicated by rising water in the water seal chamber. Depressing the high negativity relief valve will allow filtered air into the system, relieving negativity and allowing the water level to return to baseline in the water seal. In instances of falsely imposed high negative pressure, such as stripping chest tubes, water will continue to rise, filling the high negativity relief chamber at the top of the water seal chamber. This relief chamber will automatically vent excessive negative pressure, which will prevent respiratory compromise from accumulated negativity. Water spillover into the collection chamber is also minimized.
The systems also have positive pressure relief valves. They remain closed when suction is applied to the system, but open whenever pressure within the system becomes positive. Since the only way for air to leave the system is through the suction port, obstruction of the suction line (by rolling the bed on top of the tubing, for instance) could cause accumulation of air in the system leading to tension pneumothorax. This safety feature not present in the glass-bottle system, allows venting of the positive pressure, minimizing the risk of a tension pneumothorax.
The patient air leak meter is made up of a number of numbered columns, reading from 1 (low) to 7 (high). As air flow through the system increases, bubbling will occur toward the higher end of the scale. Decreasing flow will result in bubbling on the lower end of the scale. This feature provides an indication of air leak magnitude, allowing the clinician to monitor air leak increase or decrease as therapeutic interventions (such as adding or increasing PEEP) are made.
The suction control chamber is the chamber on the left side of the unit. The units come with two mechanisms to regulate the amount of suction transmitted to the pleural space: wet or dry suction. Wet suction regulates the amount of suction by the height of a column of water in the suction control chamber. Note, it is the height of a column of water, not the setting of the suction source that actually limits the amount of suction transmitted to the pleural cavity. A suction pressure of –20 cm H2O is commonly recommended, but lower levels may be required for infants and for patients with friable lung tissue, or if ordered by the physician.
To use wet suction, the suction control chamber is filled with sterile water to the desired height. Connect the tubing supplied with the unit to suction tubing, and then to the suction source. Adjust the source suction to produce gentle bubbling in the suction control chamber. The appearance of gentle bubbling assures you that the amount of suction set (by the height of the column of water) is the amount of suction being applied to the chest cavity; excess suction is vented through the bubbling. Increasing suction at the suction source will increase airflow through the system; it will have minimal effect on the level of suction imposed on the chest cavity.
Excessive source suction will not only cause loud bubbling (which can disturb patients and caregivers), but will also hasten evaporation of water from suction control chamber; decreasing the suction applied to the chest cavity. Self-sealing diaphragms are provided to adjust the water level in this chamber should overfilling or evaporation occurs.
The dry suction control chamber is even easier to use. Instead of regulating the level of suction with a column of water, suction is controlled by a self-compensating regulator. A dial on the side of the suction control chamber allows for the desired level of suction to be set according to the physician’s order. As with the wet unit, the short tubing supplied with the unit is connected to the suction source. The source must provide a minimum of 20 LPM of airflow. Once connected to suction, increase the level of suction until the float appears in the suction indicator window. The visual confirmation of suction pressure provides the same assurance as the gentle bubbling (patient air leak) or changes in suction pressure (surge/decrease at the suction source). With the dry suction unit, the level of suction set can be increased at any time.
Not all patients require suction. Suction may be discontinued to transport a patient; it may be discontinued 24 hours before chest tube removal. If suction is discontinued, make sure the suction tubing remains open to atmosphere to allow air to leave the drainage system unless suction is discontinued at the same time as the clamping of the chest tube.
The Nurse has eight responsibilities:
If the patient’s chest tube insertion is performed under non-emergency conditions, it might be the nurse’s responsibility to ensure that adequate analgesia is provided and sterile technique is maintained throughout the procedure. Once the tube is in place, the dressing is secured, and the patient is safe, attention will focus on the chest tube and drainage system. The chest tube will be connected to the drainage system by approximately six feet of tubing. These tubing connections must be airtight; secure them with adhesive tape so they do not come apart.
The tubing and the drainage system should be positioned below the patient’s chest at all times for gravity drainage and to prevent fluid backflow. It may be desirable to coil the long tubing and secure it to a draw sheet with a safety pin (allowing enough tubing so that the patient can move in bed comfortably) to prevent dangling loops of tubing. Check tubing connections periodically as directed by facility policy.
During the first 2 hours after insertion of the chest tube, observe the fluid every 15-minutes. Observe the drainage every hour during the first 24 hours. After that time, observe the color consistency and amount of drainage every 8 hours. The amount can be estimated by marking the drainage chamber each time it is measured. Include the amount of drainage on the intake and output record.
Documentation should include amount, color and presence of clots in the drainage. Document any abnormalities in the system and all interventions. The current respiratory status, including rate, rhythm, and breath sounds should be noted. Note the reaction of the client to the procedure as well as the amount of explanation and appropriate level of understanding and acceptance by client and family. The following is an example of documentation.
Respiratory assessment is within normal limits. No complaint of shortness of breath; no signs of increased work of breathing. Breath sounds clear and equal bilaterally, but difficult to assess due to transmitted sounds from suction on drainage system. No evidence of subcutaneous emphysema; no hyper resonance to percussion. Drainage in collection chamber 10 ml of straw-colored fluid past 2 hours. Bubbling noted in water seal chamber. Assessment of drainage system and inspection of chest tube insertion site show no leaks. Fluid level in the suction control chamber is at 20 cm with gentle bubbling present.
Clamping of chest tubes is generally not indicated, but it may be ordered prior to removing the chest tube or to locate the source of an air leak (indicated by continuous bubbling in the water-seal chamber). To clamp a chest tube, two covered or rubber-tipped Kelly clamps are attached to the tube in opposite directions near the insertion site. Once clamped, air and fluid will accumulate in the pleural space, and with no method to escape, a tension pneumothorax may result. Therefore, clamps should only be left on for less than a minute. To locate a leak, clamp the tubing at various points along its length. Once a clamp is located between the air leak and the water seal, the bubbling will stop. If the bubbling stops when the clamp is placed close to the chest, air may be escaping from the pleural space or from around the insertion site, and this should be reported. If the bubbling stops as the tubing is clamped along its length, check the connections to make sure they are airtight. If the bubbling does not stop, the chest drainage system may be defective and may need to be replaced. The chest tube may be clamped to keep air from entering the pleural space while the collection unit is being replaced, but it is safer to immerse the distal end of the tubing into a container of sterile water or normal saline to create a temporary water seal during replacement.
Assess the respiratory status. Auscultate both lungs to assess the presence or return of breath sounds. Assess color (e.g., discoloration of the fingernails or around the lips) to detect signs of hypoxia. Observe for bilateral chest expansion. Because a disruption in the drainage system can cause a pneumothorax and/or a pleural effusion, assessment must be on-going.
There are seven symptoms:
Chest tube assessment begins at the insertion site. Ensure that the dressing is intact, clean, and dry. Follow the tubing from the chest tube to the drainage system; making sure there are no kinks or leaks. Check that all tubing connections are taped securely. Make sure there are no hanging, dependent loops of tubing that could get caught on anything or, if the loops contain fluid, cause resistance to flow out of the chest. It is important to educate the patient and family about the importance of not kinking or catching the tubing on anything.
Inspect the drainage system first looking at the collection chamber. Note the level and assess the character of the drainage; is it bloody, straw-colored, or purulent? What is the rate of drainage? Next look at the water seal chamber. Is the water level correct at 2 cm? Is there bubbling? It means air is getting into the system. It could mean a leak from the lung, from somewhere in the tubing, or at the chest wall insertion site. Investigate any significant increase or decrease in the bubbling. The air leak meter provides an objective indication of magnitude of airflow through the system. If there is no bubbling, the water level should rise and fall with the patient’s respiration. During spontaneous respirations, the water level should rise during inhalation and fall during exhalation. If the patient is receiving positive pressure ventilation, the oscillation will be just the opposite. The water level should fall with inhalation and rise with exhalation. The magnitude of the oscillation will also depend on how stiff the patient’s lungs are and how much of the intrapulmonary pressure is transmitted to the pleural cavity. Positive end expiratory pressure (PEEP) may dampen the oscillations. Again, it depends on how stiff the lungs are and how much PEEP is used. Oscillations may be absent if the lung is full expanded and suction has drawn the lung up against the holes in the chest tube.
Inspect the suction control chamber. Make sure the water level is where it should be as determined by the doctor’s order or facility policy. Water can evaporate from this chamber so the level may drop; refill the chamber as necessary (turn off suction to refill). Make sure the suction source is set so you see the gentle bubbling in the suction control chamber. If suction is not being used, or the patient is being transported check to make sure the suction tubing is open to the atmosphere. The tubing should not be capped or clamped, nor should it be left connected to the suction device with the suction source turned off. The patient’s diagnosis and need for chest drainage will determine how often to repeat assessments.
Assessment for patients with mediastinal drainage will be somewhat different. In addition to a respiratory assessment, a thorough cardiac assessment is essential. Signs of cardiac tamponade reflect decreased venous return; so much fluid collects around the heart that it cannot expand to accept venous return. Subsequently, cardiac output drops severely. Jugular venous distention, increased central venous pressure (CVP), and falling blood pressure are ominous signs. As with all patients having chest drainage, dressings and tubing should be checked but with this patient the attention must be directed more toward the collection chamber, since the main purpose of mediastinal tube is to drain fluid from the mediastinum following heart surgery. It is important to monitor the rate of drainage from the mediastinum. A patient with only mediastinal tube should have no bubbling or fluctuations in the water seal chamber, since the tubes are not in contact with the pleural cavity. Bubbling usually indicates either a leak in the tubing or displacement of the chest tube. The water seal chamber should still be monitored for levels of negativity. Milking or striping of the chest tube is not done since both can create significant high negative pressures. Not only can this negativity pull the water up in the water seal chamber, but it can also put the patient at risk for mediastinal trauma and graft trauma depending on the precise location of the distal end of the chest tube within the mediastinum.
Milking and stripping is the term used to mean gentle kneading of the tubing. The tube is alternately compressed and released in short sections, which causes momentary bursts of suction within the tubing. Stripping is a much more vigorous procedure during which long segments of the tubing are compressed and released. Stripping has been shown to cause dangerously high negative pressures (up to -400 cm H2O). This can cause damage to lung tissue and disruption of suture lines and should only be used with extreme caution. Many facilities no longer permit nurses to use routine milking or stripping to remove clots.
Infection control concerns with chest tubes are varied. Gloves should be worn and hand washing should be done before and after handling the chest drainage system. The chest drainage procedure should be carried out under sterile conditions. The opening into the chest wall provides a means of access for pathogenic organisms. Cover the wound with an antiseptic ointment and sterile dressing. The water in the chest drainage system must be sterile to prevent the chance of contamination. If the tube becomes disconnected, use sterile scissors to trim off the contaminated ends and insert a sterile 5-in-1 connector.
Care must be used when collecting drainage specimens from a chest tube drainage system. Auto-transfusion-capable units have a self-sealing sampling port in the connectors on the six-foot patient tube. Fresh specimens for laboratory analysis can be withdrawn using a blunt or needle-less access device. Units not used for auto-transfusion have a self-sealing diaphragm on the back of the collection chamber that allows removal of drainage fluid safely and easily. A blunt or needle-less system can be used to withdraw fluid. Do not take a specimen from the connecting tubing. The tubing is not self-sealing, and a needle puncture could create a leak. If a hemothorax is draining through a thoracostomy tube into a collection system containing sterile normal saline the blood is available for auto transfusion.
Critical situations can occur in patients with chest tubes. In pleural cavity drainage, the major hazard is tension pneumothorax. The most likely cause is obstructed tubing between the water seal chamber and the patient. Most collection systems have a positive pressure relief valve in the water seal chamber that allows venting of excess pressure in the pleural cavity, so any blockage causing symptoms will be proximal to the valve, that is, between the patient and the drainage system. Rapid assessment and intervention is required. The physician should be notified and if the source of the obstruction cannot be found the entire drainage system may need to be replaced. The physician may need to do a needle thoracostomy to vent the pleural pressure and prevent mediastinal shift while the cause of the pneumothorax is determined.
Two critical situations likely to be encountered in patients with mediastinal tubes are either sudden hemorrhage or sudden cessation of drainage. Sudden hemorrhaging in a postoperative cardiac patient is likely caused by a ruptured suture line or blown graft. The patient can lose 1000 – 1500 ml of blood in a matter of minutes. The surgeon should be called immediately and the patient should be prepared to return to the operating room. The other problem, a sudden (not gradual) cessation of drainage can be caused by the accumulated clotted blood, which has occluded the mediastinal tube. This situation can lead to cardiac tamponade.
Another concerning situation is the disruption of the chest tube drainage system. The decision whether to clamp a chest tube when the drainage system has been knocked over and disconnected or otherwise disrupted is based on the initial assessment of the water seal chamber. If there has been no bubbling in the water seal, you can deduce there is no air leak from the lung. Therefore, the tube may be clamped for the short time it takes to reestablished drainage (either by reconnecting the tubes or by replacing the drainage system if contamination has occurred). If there has been bubbling and the assessment has determined there is an air leak from the lung, the chest tube MUST NOT BE CLAMPED. Doing so will cause air to accumulate in the pleural cavity since the air has no means of escape. This can rapidly lead to tension pneumothorax. The entry of a small amount of air into the pleural cavity is not as dangerous as the potential for tension pneumothorax if the tube is clamped.
A patient with mediastinal tubes should also be evaluated before clamping. If the patient has copious drainage, clamping the tube could lead to cardiac tamponade. If there is minimal drainage, the tube may be clamped only for the short time it takes to set up a new drainage system. Tubing clamps must be used. Standard clamps can be used after first covering them with rubber or taping the teeth to prevent damage to the chest tube.
The chest tube should not be clamped during transport or ambulation unless the drainage system becomes disrupted during patient movement. Even then, clamping the tube is only appropriate if there has been no evidence of an air leak. Clamping a tube through which there has been an air leak. Clamping a tube through which there has been an air leak can cause tension pneumothorax.
Some physicians prefer to clamp a patient’s pleural chest tube before it is removed. The patient is then monitored for respiratory distress, which may indicate reaccumulation of pneumothorax. A chest X-ray may also be taken to assess how well the patient will tolerate chest tube removal. The clamp should be removed and drainage re-established if the patient develops respiratory distress.
Exchange of oxygen and carbon dioxide in the lungs depends on effective ventilation and adequate circulation of blood through both lungs. The amount of surface area available for diffusion greatly affects gaseous exchange. Ventilation brings oxygen into the lungs where it is released into the alveoli in exchange for carbon dioxide, which has been deposited by the capillaries. If ventilation is not uniform throughout both lungs, the rate of oxygen replenishment is reduced, leading to hypoxia. This situation occurs in pneumothorax. Chest drainage systems evacuate air and or fluid and permit re-expansion of the lungs.
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