Options for treating PSP include:
- Supplemental oxygen and observation
- Chest tube or catheter thoracostomy
- Simple aspiration
Supplemental oxygen and observation is generally the strategy used in clinically stable patients with a first episode of PSP that is small and without severe symptoms. The rationale for supplemental oxygen in this population is based upon experience and data from animal models which report that the rate of resorption of air from the pleural space is increased up to six-fold if humidified 100% oxygen is administered.9
Since patients with PSP have no underlying lung disease, when the pneumothorax is small, oxygenation is generally within normal limits or low normal. Thus, oxygen is administered to promote the resorption of air (mostly nitrogen) from the pleural space. However, the optimal target fraction of inspired oxygen (FiO2) or peripheral oxygen saturation (SpO2) is unclear. Many experts will deliver high FiO2 (e.g., 100% oxygen via a nonrebreather mask) targeting a SpO2 of 100% while others administer lower FiO2 (e.g., 6 to 10 L via nasal cannulae) to target an SpO2 >96%. A FiO2 >6 L is generally administered to target a SpO2 >96%.
High flow oxygen via nasal cannulae (HFNC) should not be used since a small amount of positive pressure is delivered to the upper airway and could theoretically worsen the pneumothorax. For similar reasons, noninvasive positive pressure should also be avoided.
Observation while on supplemental oxygen should last about six hours, after which a CXR should be performed. If the CXR demonstrates no progression or an improvement in pneumothorax size, reliable patients with ready access to emergency medical services can be discharged home off oxygen with instructions to return if symptoms worsen. For patients requiring admission, oxygen should be continued as long as the patient is in the hospital and has a pneumothorax. Regardless of the patient’s disposition, a repeat CXR is typically performed 12 to 48 hours later.
If the pneumothorax is resolved, patients should be followed up in an outpatient setting within two to four weeks with a repeat CXR and be given instructions to be evaluated in an acute care setting should symptoms recur. If the pneumothorax fails to improve or worsens, then the pleural air should be removed via catheter or chest tube thoracostomy, although some clinicians repeat the aspiration. Choosing among these is at the discretion of the clinician. If the CXR demonstrates the worsening of the pneumothorax, the patient should have a chest tube thoracostomy placed and be admitted.
Aspiration is generally performed in clinically stable patients with a large PSP in facilities with expertise. Catheter aspiration is preferred rather than needle aspiration using equipment available in most commercial thoracentesis kits since needle aspiration alone may increase the risk of perforating the visceral pleural membrane and perpetuating the pneumothorax.
Catheter aspiration is typically performed blindly, although ultrasound guidance may be used. Similar to the procedure described for thoracentesis, an 18-gauge needle with an 8 to 9 French (Fr) catheter, which is attached to a three-way stopcock, is inserted into the pleural space generally in the second intercostal space at the mid-clavicular line.
Once the clinician observes that air can be aspirated (i.e., demonstrates access to the pleural space), the catheter is threaded deeper into the pleural space, and then the needle is withdrawn. Once the catheter is in place, air is manually aspirated using a syringe (typically 60 cc syringe) attached to the stopcock. Aspiration should continue until resistance is met or 4 L of air has been removed. While BTS guidelines suggest that no more than 2.5 liters should be withdrawn, experience suggests that up to 4 L may be withdrawn. Volumes >4 L suggest that a prolonged or persistent air leak (PAL) is present and that further expansion of the lung is unlikely. Once resistance is felt during aspiration and no more air can be aspirated, this usually indicates lung re-expansion. In this situation, two equally acceptable approaches exist, which are at the discretion of the clinician.9
The stopcock should be closed, and the indwelling catheter secured to the chest wall. A CXR should be obtained four hours later. If the lung is fully expanded and symptoms have improved, the catheter can be removed. Following an additional two hours of observation, another CXR should be performed. If the lung remains expanded on this CXR, the patient can be discharged with appropriate clinical and radiographic follow up within 24 to 48 hours.9 If the lung has not expanded fully or the CXR demonstrates worsening of the pneumothorax, a chest tube thoracostomy should be placed.
The catheter can be left in place and attached to a Heimlich (i.e., one-way) valve. The patient can then be discharged with clinical and CXR follow-up within one to two days.9 If follow-up imaging demonstrates recurrence, then a chest tube or catheter thoracostomy should be placed.
A Heimlich valve allows the unidirectional flow of air away from the leak. The rubber flap in between both ends functions as the one-way valve. If there is no resistance after 4 L of air has been aspirated and/or the lung has not adequately expanded on imaging, it is assumed that there is a PAL, and a chest tube or catheter thoracostomy should be placed. Consideration should be given to a preventive measure as soon as feasible.
The preference for aspiration in patients with a first PSP rather than tube or catheter thoracostomy (small- or large-bore) is based upon evidence from observational studies, small randomized trials and meta-analyses that report efficacy rates ranging from 30% to 80% and shorter hospital stays with aspiration.9
For example, one meta-analysis of six studies (435 patients) reported that compared with tube thoracostomy, simple aspiration was associated with shorter hospital stays and a lower adverse event rate. However, aspiration was associated with lower rates of immediate success, although the success rates at one year were the same in both interventions.9 This meta-analysis is limited, however, since most of the included trials were small.
Another 2018 network meta-analysis of 29 randomized trials (4,262 patients) similarly reported that in patients with a first episode of PSP there was no difference in the recurrence rate when tube thoracostomy or aspiration was used, but aspiration was associated with fewer hospital days.9
A chest tube or catheter thoracostomy should be placed in the following subgroups of patients based upon the assumed high risk of recurrence:
- Clinically stable patients with a PSP who fail observation or aspiration
- Patients who are unstable due to a pneumothorax
- Patients with recurrent PSP
Thoracostomy is also appropriate for the following:
- Complex loculated pneumothorax (unusual in PSP)
- Concurrent hemothorax or pleural effusion necessitating drainage
- In centers without expertise for air aspiration
- In patients with bilateral or very large pneumothoraces (e.g., complete collapse)
- Severe symptoms