Management of pneumothorax and persistent air leak—a narrative review

Introduction to pneumothorax

A pneumothorax is defined as gas within the pleural space, which occurs when air from the airway, lung, atmosphere, or, rarely, the gastrointestinal tract enters the pleural space. In the rare circumstance that a thoracic wall or neck defect allows atmospheric air to enter the pleural space, this is known as an “open pneumothorax”. When pleural air arises from inside the body, such as the airway, lung, or gastrointestinal tract, then this is known as a “closed pneumothorax”. Closed pneumothoraces are immensely more common, even among trauma patients (1). Due to this, pneumothoraces are assumed to be “closed” unless otherwise specifically referred to as “open”.

Most pneumothoraces are due to defects in the alveoli (alveolar-pleural fistula, APF) or proximal airways (bronchopleural fistula, BPF) that allow air to escape the airway/lung and enter the pleural space. Per convention, pneumothoraces are further classified as primary spontaneous, secondary spontaneous, iatrogenic, or traumatic. Correctly identifying the etiology and classification of a pneumothorax is important, for it partially determines the current management paradigm.

A pneumothorax that occurs in the absence of any culprit external factor is known as a spontaneous pneumothorax (SP). The incidence of SP is 22.2–24.0 per 100,000 in men, 6.7–9.8 per 100,000 in women, and slowly increasing with time (2-5). Further, a primary SP (PSP) occurs in the absence of known clinical lung disease (6). The annual incidence of PSP is 7.4–18 per 100,000 in men and 1.2–6 per 100,000 in women and typically occurs in patients 10–35 years of age (7-9). In contrast, a secondary SP (SSP) occurs in the setting of clinically apparent lung disease, such as emphysematous/bullous lung disease, malignancy, lung infections, cystic lung disease, granulomatous lung disease, and/or connective tissue lung disease. The annual incidence of SSP is 6.3 per 100,000 in men and 2.0 per 100,000 in women with a peak incidence in the 7^th–8^th decade of life (2,7-9). Considering the peak incidences of both PSP and SSP, SPs occur in a bimodal distribution with peaks at ~15–35 and 60+ years of age (2,3,5,7-9).

It is important to note that the classification between PSP and SSP is likely on a spectrum, where a PSP may be a harbinger of unrecognized or developing lung disease. With the increased use of computed tomography (CT) imaging, underlying lung defects are more readily apparent than previously recognized with chest radiography (CXR) alone. As such, there is controversy on how a pneumothorax in the context of simple cysts/blebs without other clinically evident lung diseases should be classified (10). Further, pleural porosity appears to play a role in many cases with or without subpleural defects; pleural porosity is when air leaks from an area of thinned visceral pleura rather than a macroscopic injury or defect (11,12). Controversy also surrounds the classification of catamenial pneumothorax, which typically occurs in the setting of thoracic endometriosis, rather than true parenchymal lung disease (13). Catamenial pneumothorax will not be further addressed in this article.

In contrast, an iatrogenic or traumatic pneumothorax occurs when an external factor creates a pleural defect allowing air to enter the pleural space. An iatrogenic pneumothorax (IP) occurs directly due to a medical intervention. A traumatic pneumothorax is due to non-iatrogenic trauma (like a penetrating or blunt thoracic injury).

Objective

Our article begins with an introduction to pneumothoraces and emphasizes the current societal guidelines and evidence-based literature for SP acute management, including PSP and SSP. The article finishes with a review of persistent pneumothorax, persistent air leak (PAL), and relevant management options—with a focus on medical and bronchoscopic modalities. Importantly, the purpose of this article is not to make recommendations for clinical practice but to summarize the current societal recommendations and most pertinent evidence. We present this article in accordance with the Narrative Review reporting checklist (available at https://amj.amegroups.com/article/view/10.21037/amj-23-168/rc).

Methods

The article is a narrative review article with the purpose of providing readers with an updated review on the topics of SP acute management and PAL management based on the current evidence and societal guidelines with particular focus on medical and bronchoscopic management options. When available, emphasis was placed on more recent and/or better-quality studies. The literature review was performed by the primary author with a search window of 1970 to July 15^th, 2023. PubMed/MEDLINE and Cochrane databases were searched. The literature search was restricted to English articles. However, if pertinent non-English articles were included in article references, then these articles were reviewed with the assistance of Google Translate™ neural machine translation services. Additional search methodology details can be seen in Table S1.

Spontaneous pneumothorax management societal guidelines

When a pneumothorax is identified, management is dependent on etiology, patient stability, pneumothorax size, pneumothorax recurrence, and whether other indications for chest tube thoracostomy exist. Significant variations in individual or institutional practice (14,15) and societal guidelines exist (16-21). In addition, several of these guidelines are outdated with numerous pertinent studies being published since their release. For instance, the American College of Chest Physicians (ACCP) SP management consensus statement was last published in 2001 and was based almost entirely on expert opinion-based surveys (16). Similarly, the Belgian Society of Pneumology (now the Belgian Respiratory Society, BeRS) (17) last published their SP management guidelines in 2005. In 2018, the Spanish Society of Thoracic Surgery (SECT) published their SP management guidelines (18) and the German Society for Thoracic Surgery, German Society for Pulmonology, the German Radiological Society, and the German Society of Internal Medicine published their S3 guidelines on SP and post-interventional pneumothorax management (19). The French Speaking Society of Respiratory Diseases (SPLF), the French Society of Emergency Medicine (SFMU), the French Intensive Care Society (SRLF), the French Society of Anesthesia & Intensive Care Medicine (SFAR), and the French Society of Thoracic and Cardiovascular Surgery (SFCTCV) published PSP management guidelines in early 2023 (20). Most recently, the British Thoracic Society (BTS) published its updated Guidelines for Pleural Disease in July 2023 (21). The European Respiratory Society published a task force statement regarding PSP management in 2015, but, importantly, its goal was to describe the evidence and practices for PSP management at that time and did not attempt to make recommendations or guidelines for clinical practice (22).

Initial therapy options for an SP include observation with or without supplemental oxygen, aspiration including needle aspiration or catheter aspiration, chest catheter thoracostomy, and/or chest tube thoracostomy. Other management considerations are the treatment setting (ambulatory vs. inpatient), size of chest catheter/tube thoracostomy, and drainage methods (1-way valve vs. water seal vs. suction system and strength of suction).

Due to the evolution of equipment, studies from different eras have variability in how the terms “chest catheter” and “chest tube” are defined and used. However, in general, the term “catheter” refers to more flexible and smaller diameter tubes (≤14 F) while a “tube” is stiffer and larger in diameter (>14 F) (23). In addition, the differences between needle aspiration, catheter aspiration, and catheter thoracostomy are also somewhat blurred. Needle aspiration and catheter aspiration refer to the one-time or intermittent manual aspiration of pleural air using a syringe attached to a needle or catheter. However, some studies that employ the term “needle aspiration” actually insert a catheter for aspiration (24,25). Whereas catheter thoracostomy refers to a catheter that is inserted into the pleural space and left in place for drainage or sealed for potential future drainage. That said, a catheter initially inserted for aspiration could be left in place and later attached to a continuous drainage system. Thus, when looking at different studies, it is important to clarify how the terms used specifically translate to the actual treatment methods employed. For simplicity and clarity, this paper will refer to one-time or intermittent aspiration, whether with a needle, angiocatheter, or small-bore catheter, as “simple aspiration”. To limit excessive granularity, the terms “chest tube insertion” or “chest tube drainage” will be generally used throughout the article to refer to chest catheter thoracostomy or chest tube thoracostomy, but it may not always refer to a tube >14 F. In fact, a meta-analysis of 11 randomized controlled trials (RCTs) and cohort studies suggests that chest catheters (≤14 F) for SPs have a similar success rate along with lower complication rate, shorter drainage duration, and shorter hospital stay compared to large-bore chest tubes (≥24 F) (26). Thus, if chest tube drainage is needed, then chest catheters or small-bore chest tubes are generally recommended unless another indication for a large-bore chest tube exists. Henceforth, the article will only detail chest catheter/tube size if referring to a specific societal recommendation or if pertinent.

The overall management of SP has also evolved with time. Older guidelines, such as the 2001 ACCP consensus statement, recommend a more aggressive approach to management (16). In comparison, modern guidelines have generally become more conservative in their approach (17-21), as most clearly demonstrated in the newest 2023 BTS guidelines. These important differences will be further detailed below.

SP assessment

Patient stability

Of utmost importance when managing a pneumothorax, is the stability of the patient. Regardless of etiology or size, an emergent intervention to evacuate intrapleural air is necessary if the patient is deemed to be unstable from a pneumothorax. Most societal guidelines utilize a clinical gestalt for patient instability. For instance, the BTS guidelines simply utilize hemodynamic stability and/or the presence of “breathlessness” as the criteria to identify a stable vs. unstable patient (21). Similarly, SPLF/SMFU/SRLF/SFAR/SFCTCV guidelines utilize “signs of immediate severity” defined as respiratory distress or hemodynamic instability as the clinical markers for an unstable patient (20). In contrast, the older 2001 ACCP consensus statement defines a stable patient as meeting all the following criteria: respiratory rate <24 breaths/min, heart rate >60 beats/min and <120 beats/min, normal blood pressure, room air O₂ saturation >90%, and patient able to speak in whole sentences between breaths (16). The ACCP statement deems a patient unstable if any of these criteria are not met. The 2018 SECT guidelines fused both the ACCP and prior 2010 BTS criteria (hemodynamic instability and/or breathlessness) to determine patient stability (16,18,27). There is no data to suggest that these strict numeric cutoffs gain any advantage or insight over a clinical gestalt of patient stability.

In an unstable patient, chest tube drainage is recommended in nearly all circumstances. This may be preceded by emergent needle decompression in some scenarios, depending on the patient’s severity of clinical instability (20). Societal guidelines also identify other high-risk features, such as bilateral pneumothorax, hemopneumothorax, or associated significant hypoxia, in which immediate chest tube drainage is likely warranted (16,17,19-21).

Lethality directly related to SP is rare. However, multiple retrospective studies have demonstrated an increase in mortality for patients ≥45 years of age (3,19) or ≥55 years of age (2) with an inpatient mortality rate as high as 16% for patients ≥90 years of age (Figure 1).

Figure 1 Mortality of inpatients with a primary diagnosis of pneumothorax (3,19).

Pneumothorax size

Pneumothorax size has become less important in modern management of SP, as there is more clinical weight placed on patient stability and symptoms. Nonetheless, discussion of pneumothorax size remains necessary since most clinical studies and guidelines still reference it. CT is the gold standard for determining pneumothorax size (28), but CT is not routinely recommended in the initial diagnostic evaluation of SP. Most commonly, a standard CXR is obtained and used to determine initial pneumothorax size. Importantly, ultrasound is also an important tool when evaluating cardiopulmonary failure or trying to identify a pneumothorax (29,30), but sizing a pneumothorax with ultrasound (31) is not nearly as well-established.

Despite the routine use of CXR, there is significant variation between societal guidelines on how small vs. large pneumothoraces are classified on CXR. The ACCP defines a large pneumothorax as ≥3 cm between the apex chest wall and pleural line (16). In comparison, the prior 2010 BTS guidelines defined a large pneumothorax as >2 cm between the lung margin and the chest wall at the level of the hilum (27). The BeRS, SECT, and SPLF/SMFU/SRLF/SFAR/SFCTCV guidelines similarly define a large pneumothorax as having lung dehiscence over the whole length of the lateral chest wall—referred to as a “complete” pneumothorax (17,18,20). The BeRS and SPLF/SMFU/SRLF/SFAR/ SFCTCV guidelines have the additional criterium of “cut-off point of 20% by Light-index” (see Table 1 footnotes) or ≥2 cm between the lung margin and the chest wall at the hilum level, respectively, to differentiate small vs. large pneumothorax. The German S3 guidelines recommend using the Collins Method for determining pneumothorax size (19), to be discussed in the next paragraph. Importantly, the newest 2023 BTS guidelines do not directly reference pneumothorax sizing in their decision-making flowchart but note that size “does dictate the safety of conducting an intervention”. Their guidelines suggest that a pneumothorax is likely to be of sufficient size for an intervention (if needed) when the pneumothorax is “≥2 cm laterally or apically” on CXR (21). See Table 1 for complete societal pneumothorax sizing recommendations.

On a standard CXR, the Collins Method strongly corresponds with CT measurements (r=0.98, P<0.0001) (28). However, the Collins Method is more complex and requires the sum of interpleural distances at the apex, upper half midpoint, and lower half midpoint. The sum of these interpleural distances is then inserted into a formula to estimate the true percentage pneumothorax size (see Figure 2). For instance, a sum of interpleural distances of 9.7 cm (~10 cm) corresponds to a 50% pneumothorax size. Interestingly, a study comparing the three different ACCP, 2010 BTS, and BeRS methodologies to determine small vs. large pneumothorax size showed poor agreement, with all three methods agreeing less than half the time (32). The methods were also more likely to underestimate the true pneumothorax size compared to the Collins Method (33). This complicates the evaluation of pneumothorax clinical studies because different sizing classification methods across different studies may not be comparing similar patient groups.

Figure 2 ACCP, 2010 BTS, and Collins pneumothorax sizing methods utilizing standard upright poster-anterior chest radiograph (16,19,21,27,28). ACCP: interpleural distance measuredly linearly from apex to cupola (A). 2010 BTS: interpleural distance measuredly linearly at the level of the hilum (Y). Of importance, the 2023 BTS guidelines no longer recommend pneumothorax sizing other than to determine sufficient safety for a procedure, if warranted. Collins: interpleural distances are measured linearly at three locations—the apex and the midpoints of the upper and lower halves of the collapsed lung. The dotted line represents the midline of the collapsed lung. These three measurements are then summed and used to estimate the true percentage of pneumothorax size, in the equation: Estimated true % pneumothorax size =4.2+[4.7×(A+B+C)]. ACCP, American College of Chest Physicians; BTS, British Thoracic Society.

Primary SP management

Overall, PSPs are generally better tolerated than SSPs. A cross-sectional study in France found that of patients with their first PSP, 83% had a respiratory rate ≤25, 99% had an SpO₂ ≥90%, 96% had a heart rate ≤120, and 98% had a mean blood pressure ≥70 mmHg; however, 40% reported dyspnea. Patients with a recurrent PSP had similar findings (34). In addition, the development of tension physiology or death from a PSP is exceedingly rare (2,6).

However, if a PSP does cause clinical instability, then hospitalization with chest tube drainage is recommended. If there is concern for tension pneumothorax, then emergent needle decompression may be considered (20). The SPLF/SMFU/SRLF/SFAR/SFCTCV guidelines explicitly mention emergent needle decompression followed by subsequent chest tube drainage (20), but most other societies do not mention needle decompression and generally recommend “immediate” chest tube drainage (16-18,20,21). In unstable patients, the ACCP and 2023 BTS guidelines recommend immediate chest tube drainage in all patients (16,21). The BeRS and SPLF/SMFU/SRLF/SFAR/SFCTCV guidelines recommend simple aspiration vs. chest tube drainage depending on the patient’s severity of clinical instability (17,20).

Modern societal guidelines have trended toward more conservative management of PSP and emphasizing patient stability and symptoms over PSP size, but the 2023 BTS guidelines are the first to (nearly) do away with SP sizing in their management algorithm. BTS recommends a conservative observational approach to all stable patients with asymptomatic/minimally symptomatic PSP, regardless of PSP size (21). This new recommendation is based on the most recent available clinical trial data, as further described in section “Evidence for SP management strategies”. An important exception is for patients who are ≥50 years of age with a smoking history. In these patients, BTS guidelines recommend that all SPs should be treated as SSPs given the high probability of underlying lung disease (21). For stable, asymptomatic/minimally symptomatic patients with their first small PSP, all other major societal guidelines agree with conservative observation (16-20).

However, societal recommendations notably diverge for stable patients with their first large asymptomatic/minimally symptomatic PSP. Proposed management strategies include conservative observation, simple aspiration, 1-way valve drainage, or chest tube drainage. The most invasive, and likely archaic, recommendation is that of the 2001 ACCP consensus statement advocating for chest thoracostomy with either a chest catheter (≤14 F) or a moderate-sized chest tube (16–22 F) attached to water seal or a 1-way valve. The ACCP also suggests admission for most patients, but reliable patients could be discharged home with a chest catheter attached to a 1-way valve (16). As the middle ground, the SECT guidelines recommend simple aspiration in most cases. If pneumothorax resolves on repeat CXR and certain patient criteria are met, then patients can be discharged with subsequent outpatient follow-up (18). The BeRS and SPLF/SMFU/SRLF/SFAR/SFCTCV guidelines similarly recommend aspiration or chest tube drainage (17,20) with the SPLF/SMFU/SRLF/SFAR/SFCTCV recommending outpatient management based on the results of the intervention and multiple patient criteria. Reaching the most conservative end of the spectrum, the 2023 BTS guidelines, again, no longer delineate small vs. large PSP, recommending conservative observation with outpatient review for all asymptomatic/minimally symptomatic PSP cases. See Table 1, Table 2, and Figure 3 for a more complete comparison of societal recommendations.

Figure 3 Spontaneous pneumothorax initial management based on review of society recommendations (16-21). *, BTS 2023 guidelines note “Pneumothorax of sufficient size to intervene depends on clinical context, but, in general, usually ≥2 cm laterally or apically on CXR, or any size on CT scan which can be safely accessed with radiological support.” SP, spontaneous pneumothorax; PSP, primary SP; SSP, secondary SP; CXR, chest radiograph; CT, computed tomography; CTD, chest tube drainage; ACCP, American College of Chest Physicians; BeRS, Belgian Respiratory Society; SECT, Spanish Society of Thoracic Surgery; SPLF, Speaking Society of Respiratory Diseases.

For patients undergoing conservative observation, the recommended timing of this outpatient follow-up differs between society guidelines (see Tables 1,2 or the respective society guidelines). Precautionary instructions should be provided on discharge, as further discussed in section “Ambulatory care vs. inpatient” (21,35,36). If a more conservative approach fails (e.g., observation, ambulatory 1-way valve, or simple aspiration), then escalation to admission and a more invasive intervention is generally recommended. This is typically chest tube drainage, but simple aspiration may be reasonable depending on the clinical scenario (17-20,25).

Secondary SP management

Due to the presence of underlying lung disease, SSPs have a higher likelihood of causing clinical instability and significant symptoms compared to PSP (2,7,27), and hypoxia is usually accentuated (19). SP (PSP and SSP combined) has a mortality incidence of ~1 per million per year, but the mortality incidence jumps to ~2–4 per million per year in patients ≥55 years of age (2). A German study similarly found that SP mortality was 0.03% for patients under 45 years of age but started to uptick at 45–50 years of age (~1%) and progressively increased with age until 16% mortality was seen in patients ≥90 years of age (3,19) (see Figure 1). These older populations are much more likely to have an SSP than PSP.

Due to the higher risk, the major societal guidelines uniformly recommend that any patient with an SSP and clinical instability, significant symptoms, or high-risk characteristics should be hospitalized and undergo immediate chest tube drainage regardless of SSP size (16-19,21). However, that is where the uniformity ends, as every society has slight variations in recommended management for stable patients with asymptomatic/minimally symptomatic SSPs.

The newest 2023 BTS guidelines represent the largest departure from prior societal guidelines. Keeping in line with its more conservative approach, BTS recommends that asymptomatic/minimally symptomatic patients with an SSP of any size be managed via conservative observation. However, in contrast to their PSP recommendations, SSPs should be observed in the inpatient setting until pneumothorax stability is well established. In stable patients with a small SSP, most prior societal guidelines similarly suggest inpatient conservative observation (16-18). Although the 2001 ACCP consensus statement suggests consideration of chest tube drainage depending on the extent of symptoms and course of pneumothorax (16). In contrast to the new 2023 BTS guidelines, all other major societal guidelines recommend that stable patients with large SSPs should be managed with chest tube drainage (16-19). See Table 1, Table 2, and Figure 3 for a more complete comparison of societal recommendations.

Evidence for SP management strategies

The societal recommendations for the management of both PSPs and SSPs remain heterogenous, but are consistently moving toward a more conservative direction. As this shift might suggest, there is a growing body of evidence demonstrating comparable results for conservative management, simple aspiration, and chest tube drainage.

Aspiration vs. chest tube drainage

In studies comparing simple aspiration versus chest tube drainage, most have demonstrated that simple aspiration has a lower likelihood of immediate success, at 54–85% for simple aspiration and 63–93% for chest tube drainage (15,24,25,37-47). One study with an unusually low chest tube drainage immediate success rate (32%) was excluded from the range (24). Interestingly, subgroup analyses have shown that a pneumothorax size >75% by Collins Method or larger aspiration of air (mean 2.52 liters) were associated with higher simple aspiration failure rates (40,45).

Despite the lower likelihood of initial success, if simple aspiration is successful, then it avoids chest tube drainage which carries more risk of complications. Further, studies have shown that patients who fail simple aspiration do as well, and possibly even better, with subsequent chest tube drainage than patients who undergo initial chest tube drainage (25,37-39,41,42,44). A 2017 Cochrane Review including 435 patients in 7 small RCTs determined there was low-to-moderate quality evidence that chest tube drainage achieved higher immediate success rates for PSPs compared to simple aspiration. However, adverse events occurred more frequently in the initial chest tube drainage group (47). Subsequent 2020 meta-analyses demonstrated similar findings of borderline improved initial success rates or no difference in success rates with chest tube drainage compared to simple aspiration (46,48). Despite an improved initial success rate, Tan et al. surprisingly identified that initial chest tube drainage was associated with a higher surgical rate than initial simple aspiration (RR 0.17, P=0.03) (46). In addition, chest tube drainage was associated with a higher hospitalization rate and longer duration of hospital stay compared to simple aspiration (46). Chest tube drainage was again associated with more adverse events than simple aspiration. There were no differences in 1-week success rate or recurrence at 3-months or 1-year (46,48).

Most recently, the larger EXPRED randomized control non-inferiority trial investigated 402 patients 18–50 years of age with “complete” PSP. These patients were randomly assigned to simple aspiration with thoracentesis cannula (up to 2 aspiration attempts) or chest tube drainage (16 or 20 F). If pneumothorax persisted after the 2^nd aspiration, then chest tube drainage was performed. Treatment success was defined as a pneumothorax smaller than 2 cm at apex 24 hours after the first-line intervention. First-line treatment failure occurred in 29% for simple aspiration and 18% for chest tube drainage (confidence interval: 0.026–0.200). Interestingly, however, only 6% of the first-line simple aspiration group went on to fail second-line chest tube drainage by 24 hours compared to 18% in the first-line chest tube drainage group failing by 24 hours. There were no differences at 7 days or with 1-year recurrence. Despite the slightly, but statistically significant, higher first-line failure rate with simple aspiration, the EXPRED authors reasoned that this difference is not clinically significant since simple aspiration was better tolerated and safer than chest tube drainage and had similar results at 7 days.

In comparison, there have been far fewer studies comparing aspiration vs. chest tube drainage for the management of SSPs. Prior studies have suggested that aspiration is less successful for SSP than PSP. For instance, Cho and Lee found that simple aspiration was successful in 83% of patients with PSP and only 47% of patients with SSP (49). However, it is important to note that this study used a 7-F catheter, and the catheter was kept inserted for a mean of 2.8 days, which is not particularly consistent with a simple aspiration protocol. Some SP studies have included SSP subgroups (24,25,41), but few SSP patients were included and produced mixed results. Interestingly, the RCT with the largest number of SSP cases (n=48) suggested that simple aspiration (16 gauge subclavian catheter = ~5 F) had a better immediate success rate for SSP than chest tube drainage (59% vs. 23%, respectively; P=0.011) (24). More prospective studies and RCTs are necessary for patients with SSP to investigate simple aspiration compared to chest tube drainage.

Observation vs. intervention

Concurrently, there is accumulating evidence that supports conservative observation as an effective management strategy for many stable patients with PSP, including large PSPs. One retrospective study found that the rate of PSP air resorption as determined by CT volumetry was ~2.2% of the hemithorax volume every 24 hours without intervention, although the study did not differentiate whether the patient received oxygen supplementation or not (50). A 2021 meta-analysis (51) including 2 RCTs and 6 cohort studies compared conservative observation and interventional management strategies—including simple aspiration, chest tube drainage, video-assisted thoracoscopic surgery (VATS), and open thoracotomy (52-59). The meta-analysis found that the success rate (defined as re-expansion of lung within 8 weeks) for conservative observation was similar to interventional treatments (88% vs. 84%, RR 1.05, 95% confidence interval: 0.94–1.17). Only the VATS and open thoracotomy studies (54,58) had recurrence rates favoring interventional management, which is not surprising as these are pneumothorax definitive therapies. All non-surgical intervention groups had worse or equivalent recurrence rates compared to conservative observation, although meta-analysis did not reveal a statistically significant difference. In addition, the observation group trended toward lower complication rates than the intervention groups (6% vs. 27%) but did not reach statistical significance. Of note, the VATS and open thoracotomy studies were not included in the complication rate analysis. A recent meta-analysis in the 2023 BTS Guideline Supplemental Appendix found that the risk of recurrence was lower in patients managed with conservative observation compared to chest tube drainage with a risk ratio of 0.62 (0.45–0.87) (21,52,56,60,61).

A meta-analysis of 22 studies between 2000 and 2020 including adults and pediatrics compared conservative observation vs. simple aspiration vs. chest tube drainage for PSP initial management (62). The study demonstrated that both chest tube drainage (relative risk 0.81) and simple aspiration (relatively risk 0.73) were more likely to resolve the PSP compared to observation alone. However, those who failed conservative observation did well with subsequent interventions and had no increased morbidity identified. Further, observation and simple aspiration involved shorter hospital stays with similar 2-year recurrence rates compared to chest tube drainage. Observation also had the most favorable complication rate, healthcare costs, and healthcare utility. Eamer et al. (62) endorsed that observation should be first-line management in appropriately selected patients with PSP and that simple aspiration should be considered second-line therapy.

The Eamer et al. meta-analysis’s (62) largest RCT was that of Brown et al. (52), which included 316 stable patients <50 years of age with a moderate-to-large unilateral PSP. This RCT found that initial conservative observation with or without supplemental oxygen was non-inferior to chest tube drainage in achieving lung reexpansion by 8 weeks (94.4% vs. 98.5%, respectively; P=0.002 for noninferiority). 85% of patients in the conservative observation group did not require an invasive intervention; in addition, the observation group compared to the intervention group had a significantly shorter length of hospitalization (1.6±3.5 vs. 6.1±7.6 days), lower likelihood of pneumothorax recurrence within 12 months (9% vs. 17%), and a lower risk of serious adverse events (4% vs. 12%) or any adverse event (8% vs. 27%). However, if patients lost to follow-up were all deemed as “treatment failures”, then the conservative observation group would have been inferior in achieving lung re-expansion at 8 weeks. The authors concluded that “the trial provides modest evidence that conservative management of (moderate-to-large) primary SP was noninferior to interventional management…”

Based on this newest data, the 2023 BTS guidelines recommend that most asymptomatic/minimally symptomatic patients with a PSP, regardless of size, be managed with conservative observation. When referencing these studies, it is important to note that the initial observation arms have rigorous inclusion and exclusion criteria for patients including symptoms and healthcare accessibility.

In contrast, there are no prospective or RCT studies dedicated to SSP management comparing conservative observation to interventional approaches. A retrospective case series and cohort study suggest that some patients with an SSP larger than 1 cm can be managed with conservative observation, but such data is highly prone to selection bias (63,64). In light of the new 2023 BTS guidelines, prospective studies and RCTs are essential to determine the efficacy of observation vs. intervention in SSP management.

Ambulatory care vs. inpatient

Consistent with the trend toward more conservative management, several studies have investigated ambulatory care of SPs and support that stable patients with asymptomatic/minimally symptomatic PSPs can be effectively managed in the outpatient setting. Ambulatory care options include conservative observation, simple aspiration, and/or chest catheter with an attached 1-way valve. Simple aspiration studies already reviewed in Sections VIIa were also done in the ambulatory care setting and supported the use of ambulatory simple aspiration and outpatient follow-up in select patients (38,39,43). Studies investigating ambulatory 1-way valves demonstrate a successful outpatient management rate of 72–85.4% (54,65-68). Ambulatory 1-way valve management also demonstrated significantly fewer total procedures, decreased length of hospital stay, and reduction in hospital stay-related costs compared with simple aspiration, chest tube drainage, or both. However, an RCT noted that the ambulatory 1-way valve (8 F chest catheter) group compared to the inpatient care group (undergoing simple aspiration, chest tube drainage, or both) had a higher incidence of adverse events (55% vs. 39%, respectively) and more serious adverse events, including device malfunction/dislodgment, enlarging pneumothorax, and asymptomatic pulmonary edema (68).

In line with these findings, most societal guidelines endorse ambulatory care in select stable patients with PSP, including both small and large PSP (16-18,20,21,27). In order for ambulatory care to be viable, clinically stable patients need an organized outpatient care system to facilitate follow-up consultation and radiology images. The recommended timing of this follow-up varies from 24 hours to 2–4 weeks, depending on which societal guidelines and the clinical scenario (17,18,20,21). Upon discharge, patients should avoid staying alone for the first 24–48 hours. In addition, discharged patients should have acute medical care readily available, receive appropriate phone numbers, and receive clear verbal and written instructions to seek emergency medical care if new or progressive symptoms develop and to restrict air travel and high-risk activities (e.g., scuba diving) (19-21,27,35,36).

There are far fewer studies that have investigated ambulatory care of SSPs. A systematic review of retrospective case series and cohorts found that Heimlich 1-way valves had a success rate of 88.7% for SSPs (110 of 124 cases; 95% confidence interval: 81.9–93.4%), as defined as no additional chest tubes or surgery needed to manage the SSP (69). Of note, the Heimlich chest catheter/tube sizes varied from 5.5–20 F. A prospective comparative case series assessed ambulatory management of PSP vs. SSP (70). Of those deemed eligible for the ambulatory pathway, patients with SSP (n=49) underwent 12 F chest catheter placement with initial water seal followed by conversion to 1-way valve drainage. In the PSP group (n=62), patients with large PSPs or significant breathlessness underwent single manual aspiration; if pneumothorax persisted after aspiration, then chest tube drainage was performed (29 of 62 cases). Complete re-expansion by day 5 was achieved in 79% of PSP and 65% of SSP cases (P=0.108). Ipsilateral recurrence within 12 months was also similar with 12% for PSP and 14% for SSP. Surgical referral occurred in 11 PSP cases (18%) and 9 SSP cases (18%). The remaining 8 SSP patients without complete re-expansion declined surgical referral and “most” underwent slurry talc medical pleurodesis with subsequent resolution of pneumothorax.

For SSPs, a small RCT (71) comparing ambulatory 1-way valve (n=21) to chest tube drainage (n=20) found that the ambulatory 1-way valve group was discharged earlier (1 vs. 3.5 days, respectively) but had a higher early treatment failure and readmission rate resulting in the same number of related in-hospital days as chest tube drainage (6 vs. 6 days; P=0.77). Of note, the use of an 8 F catheter 1-way valve system accounted for all of the ambulatory treatment failures [46% (6/13) failure rate]; whereas a different ambulatory 12 F catheter 1-way valve system had no treatment failures (0 of 8). The 8 F 1-way valve subgroup required an average of 9 hospital days, whereas the 12 F 1-way valve subgroup required only 1.5 hospital days. These differences failed to reach statistical significance but may suggest that small 8 F catheters are unable to manage the higher air leak flow rates in SSP compared to PSP (68,71) and/or are more prone to kinking/dislodgment. Additional prospective studies and RCTs are necessary in SSP patients to investigate ambulatory vs. inpatient management.

Supplemental oxygen

Supplemental oxygen is generally accepted to enhance the rate of resorption of air from the pleural space. This is based on the physiologic principle that oxygen therapy reduces the alveolar nitrogen partial pressure and creates a greater intrapleural to alveolar diffusion gradient, allowing intrapleural nitrogen to more expeditiously diffuse into the alveoli and resolve the pneumothorax. However, clinical evidence to support supplemental oxygen therapy in pneumothorax is limited. The classically referenced study by Northfield was a mixed retrospective and prospective cohort study that only included 10 patients who received oxygen therapy (72). A retrospective study of 160 patients with PSP also suggested that supplemental oxygen increases the pneumothorax resolution rate from 2.06%/day with room air to 4.27%/day with supplemental oxygen. However, pneumothorax size was a stronger predictor of pneumothorax resolution rate than oxygen supplementation (the larger the pneumothorax, then the faster the resolution rate), and the oxygen supplementation group had significantly larger starting pneumothoraces compared to the room air group (73). Therefore, well-controlled prospective studies are necessary to confirm the benefit of supplemental oxygen in improving pneumothorax resolution rate. In addition, the ideal amount of oxygen supplementation and method of delivery is uncertain. Oxygen delivery methods that introduce positive airway pressures (e.g., high flow nasal cannula, continuous positive airway pressure, non-invasive positive pressure ventilation) should generally be avoided or limited whenever possible due to concerns that increased airway pressures may cause fistulas to worsen or persist. Particular care should also be taken in patients with chronic obstructive pulmonary disease (COPD) to avoid hyperoxia due to the risk of developing hypercapnia. Therefore, blood gas monitoring is recommended in COPD patients with an SSP (19,74).

Based on the lack of evidence, the German S3 guidelines state that “a general recommendation for oxygen application cannot be made for conservative pneumothorax therapy” but that supplement oxygen should be applied in hypoxic patients or symptomatic patients with SSP in addition to other necessary interventions (19). The SPLF/SMFU/SRLF/SFAR/SFCTCV group specifically states that it does not recommend the systematic use of oxygen therapy in patients treated for PSP (20). The prior 2010 BTS guidelines recommended oxygen supplementation at 10 liters/min in symptomatic patients with SP (27), but the 2023 BTS guidelines do not comment on oxygen supplementation (21). The ACCP, BeRS, and SECT guidelines also do not specifically comment on supplemental oxygen therapy (16-18).

IP

Although not an SP, an IP associated with medical procedures is perhaps the most common type of pneumothorax. IPs most commonly occur with thoracic surgeries, thoracentesis, lung biopsies (transthoracic or transbronchial), bronchoscopic lung volume reduction (BLVR) endobronchial valve (EBV) placement, central line placement, and mechanical ventilation, among many others (19,27,75). In most non-surgical cases, the iatrogenic injury leads to an APF. If a post-procedure pneumothorax occurs, most patients develop symptoms or radiologic signs within 4 hours, and the risk of delayed onset IP is very small. An exception to this is with EBV placement, where delayed onset IP is common (19). As such, EBV placement requires admission with close clinical and radiologic monitoring. Typically, IPs are well tolerated in non-critically ill patients. However, due to the associated conditions necessitating the medical procedures, some patients may be more at risk for symptoms and clinical instability than patients with PSP.

Unfortunately, there is a paucity of quality prospective or randomized study data to guide IP management. Based on retrospective and experiential data, most IPs tend to resolve relatively easily. Thus, they are generally treated similarly to PSPs with an emphasis on patient stability rather than pneumothorax size (19,21,27). In patients without dyspnea and a small IP, conservative observation is typically practiced. Chest tube drainage may be indicated if the IP is large, is causing significant symptoms or clinical instability, and/or occurred in a patient on positive pressure ventilation (19,27). Simple aspiration or Heimlich 1-way valve could also be considered, depending on the clinical scenario (19). However, patients with a post-procedure pneumothorax should be carefully assessed to determine whether a pressure-dependent pneumothorax is present, which would not require an intervention (76). Unlike SP, travel or activity limitations are generally not necessary after an IP has resolved (19). These practices and recommendations may evolve and change as evidence for conservative management has increased for other types of pneumothoraces. Overall, good quality evidence is lacking, and prospective studies on IP management are needed.

Pneumothorax definitive management and recurrence prevention

Pneumothorax definitive therapy is an intervention performed with the purpose of preventing pneumothorax recurrence. Reported PSP recurrence rates are highly variable, but most studies report a 1-year recurrence rate between 5–33% with a rate of 20–30% most commonly cited (4,16,19,38,39,42,45,65,66,77,78). Hence, about 67–95% of patients with their first PSP will not relapse, and relapse is generally well-tolerated when it does occur (34). The likelihood of recurrent PSP also decreases as time progresses from the initial event (4,27). Reported SSP recurrence rates are also highly variable with 1–3 year recurrence risk of 25–56% (4,65,66,79,80). A more recent epidemiologic study in patients admitted for SSP places the <1-year recurrence risk at 25–27%. In comparison, the same study had a <1-year recurrence risk of 13–15% for patients with PSP (4).

Definitive management recommendations for SP vary and are evolving, with modern practice moving in a more conservative direction. Due to the lower risk of recurrence or clinical instability with PSP, definitive intervention is generally thought to be too invasive after the first episode of PSP and is not recommended in most instances (16,17,19-21). However, recall that PSPs and SSPs likely exist on a continuum, for those with PSP often have subpleural defects and/or pleural porosity. Due to this, some have argued that a more nuanced approach depending on the presence of blebs or bullae should help guide management with the first PSP occurrence (10). One retrospective study suggests that CT imaging to help stratify the risk of PSP recurrence may be beneficial (81). The study found that patients with at least one air-containing lesion had a 68% risk of ipsilateral recurrence compared to a 6% risk in patients without an air-containing lesion. Further, the study presents a “dystrophic severity score” that can be calculated based on the presence, number, and distribution of blebs or bullae. In a dose-dependent response, the 3-year risk of ipsilateral PSP recurrence increased from 7% with no lesions, to 46% with a single unilateral bleb, and up to 78% with multiple bilateral bullae (plus an additional 20% risk of contralateral occurrence). However, this data has yet to be validated in prospective studies. One RCT in patients with their first PSP found that VATS with resection of bullae/blebs and mechanical pleurodesis resulted in significantly lower PSP recurrence if bullae of ≥1 cm were present (and particularly if ≥2 cm) compared to chest tube drainage alone (82). However, the clinical utility of CT imaging, classifying blebs or bullae, and definitive therapy in first-time PSPs remains controversial (10) and is not generally recommended by respiratory societies. Nonetheless, options should be discussed with each patient on a case-by-case basis, and patient preference should be taken into account. Definitive treatment after a recurrent PSP is also somewhat debated, but there is general agreement among commenting societies that it should be offered (16,17,20,21). See Table 3 for other definitive therapy indications in PSP management.

Due to an SSP’s higher likelihood of recurrence and clinical instability, definitive management has classically been recommended after any SSP, including the first SSP episode (16,17,27,80). However, the 2023 BTS guidelines astutely point out the dearth of quality evidence to direct optimal management after the first episode of SP. Thus, the 2023 BTS guidelines have a more limited approach: consider definitive intervention if a first-time SP caused a tension pneumothorax or if recurrence prevention is deemed important, such as in persons with severe underlying lung disease or high-risk occupations/hobbies (e.g., divers, airline pilots, military personnel). Definitive therapy is uniformly recommended after recurrent SSP in patients that can tolerate an intervention (16,17,19,21). See Table 3 for definitive therapy indications in SSP management.

If a patient presents with a clear indication for definitive management, then the aforementioned acute management methods are still generally recommended before definitive treatment is arranged. However, select stable populations (e.g., recurrent asymptomatic/minimally symptomatic PSP) could potentially be referred for definitive treatment without prior interventions.

Definitive treatment options include medical chest tube pleurodesis, VATS, or open thoracotomy (16,17,19-21). Surgical technique is a controversial topic with many nuanced considerations and is outside the scope of this article, but techniques typically include one or more of the following: resection of pleural lung lesions, repair of pleural defects, pleurectomy mechanical abrasion, and/or surgical chemical pleurodesis. When possible, a definitive intervention during the same hospitalization is preferred as the recurrence risk is greatest within the first weeks to month after discharge (83).

Multiple studies demonstrate that medical chemical pleurodesis, VATS, and open thoracotomy techniques all decrease risk of SP recurrence compared to chest tube drainage alone (21,82,84-87). Medical chemical pleurodesis and surgical approaches have not been directly compared in an RCT. However, prospective and retrospective studies have shown lower recurrence rates for surgical approaches than medical chemical pleurodesis (84,85,87). Recurrence rates for chemical pleurodesis are 9–25% (21,85,87), and a systematic review found recurrence rates of 5.4% for VATS and 1.1% for open thoracotomy (84). Consequently, surgical management is preferred over medical chemical pleurodesis when feasible (16,17,20,21,84,85). If a patient is medically unfit or unwilling to undergo surgery, then medical chemical pleurodesis is appropriate (17,20,21). Caution should also be taken when assessing patients with fibrotic lung disease for definitive therapy. In fibrotic lung diseases, medical pleurodesis may be preferred over operative management (19) because retrospective studies found that surgical operations of SSP with lung fibrosis vs. SSP with COPD were associated with higher ipsilateral recurrence rates (15% vs. 8%) and higher in-hospital mortality (15–21% vs. 1–2%) (88,89).

Since its introduction, VATS has become increasingly used over open thoracotomy in SP definitive therapy due to its better side effect profile, lower post-operative pain scores, and shorter hospital length of stay (21,84,90-92). Thus, most societal guidelines favor VATS over open thoracotomy (16,19-21,93). Most recently, the 2023 BTS guidelines recommend VATS in the general management of SP definitive therapy but mention that open thoracotomy should be considered in those that need the absolute lowest risk of recurrence—such as those with high-risk occupations (21).

Air leak

Measuring air leak

Depending on the clinical severity, etiology, and size of a pneumothorax, management oftentimes includes chest tube drainage. After a chest tube is placed and connected to a water seal drainage device, the presence of air bubbling into the device is known as an “air leak”. The etiologies of an air leak are multifold, but after the initial intrapleural air is evacuated then it may be indicative of a persistent APF or BPF (94).

Cerfolio created the “RDC system” to classify air leaks based on qualitative and quantitative aspects. Qualitatively, Cerfolio identified 4 types or grades of leaks based on the timing of the air leak during the respiratory cycle—continuous (C; grade 4), inspiratory (I; grade 3), expiratory (E; grade 2), and forced expiratory (FE; grade 1). Quantitatively, the air leak is scored based on how many columns the air leak bubbles reach on the Pleur-evac air leak meter (see Figure 4A). Thus, an E4 classification would represent an air leak that occurs only during expiration with bubbles reaching the 4^th column of the Pleur-evac air leak meter (see Figure 4B). The RDC classification system was initially developed in the post-operative lung resection setting. Air leaks from lung resection surgeries have a different underlying mechanism and typically higher flow rates than SPs. Nonetheless, the RDC system may be applied to other pneumothorax etiologies to help communicate the severity of the air leak (95,96).

Figure 4 RDC System—characterizing air leak severity. In the RDC system, an air leak is classified by the combination of a quantitative measurement via an air leak meter (A) and a qualitative type/description of air leak (B). (A) 7-column air leak meter (Pleur-evac). (B) Grading of air leaks from largest to smallest (95). C, continuous; I, inspiratory; E, expiratory; FE, forced expiratory.

The RDC classification system remains a relatively crude and imprecise form of measurement; this is particularly true for air leaks with low flow rates. Thus, real-time digital meters have been developed to directly quantify the rate of airflow through the drainage system in milliliters per minute (mL/min) and measure intrapleural pressure (97). Studies have demonstrated that digital drainage systems reduce the duration of chest tube placement and hospital length of stay and improve patient satisfaction compared to conventional chest tube drainage systems (97-100). However, these digital drainage system studies have been primarily performed in the post-operative context of lung resection surgery. In the context of SP, emerging data also demonstrates that the digital drainage system may reduce the duration of chest tube drainage, the duration of hospital stay, and hospitalization costs compared to conventional chest tube drainage and may help predict medical treatment failure (101,102). Based on the surgical studies (97-100) and Jablonski’s study in SP (101), the National Institute for Health and Care Excellence (NICE) recommends the use of digital drainage systems in the management of pneumothorax (103). However, Jablonski’s study is small, and major societal recommendations do not yet comment on the use of digital drainage systems in SP management. Further investigation is needed to determine how digital drainage systems may alter prognosis or management compared to conventional chest tube drainage systems in the context of SPs.

Water seal vs. suction

Overall, RCTs comparing initial water seal vs. suction have not identified a consistent difference for chest tube management (21,104). Further, the available evidence-based data on this topic arise largely from post-lung resection studies, so it is unclear how that translates to SP management. Most major societal guidelines recommend initially using a water seal drainage device without suction or 1-way valve before considering the application of suction if the lung fails to reexpand (16,17,19-21). Some argue that suction draws air through the pleural defect, promoting continued patency of the defect, and may actually worsen or extend the duration of the APF or BPF. Suction also may allow pressure-dependent air leaks to go unrecognized as suction increases the pressure gradient between the subpleural lung parenchyma and pleural space, possibly leading to prolonged hospital stays or unnecessary interventions (76,104). Additionally, water seal may allow for easier transition to 1-way valve and ambulatory management in certain inoperable cases. However, others argue that suction helps to achieve pleural apposition, which allows for the pleural defect to heal and possibly undergo autopleurodesis (104). Overall, the decision to use water seal vs. suction should be patient-specific rather than dependent on a particular size or type of pneumothorax.

PAL review

If a chest tube water seal drainage system air leak from an APF or BPF persists for more than 5–7 days, then this is defined as a PAL (84,90,94,105). There is dispute on what exact duration of air leak defines a PAL, ranging anywhere from 2–14 days, but an arbitrarily chosen timepoint of 5–7 days has been generally accepted in more recent studies and review articles (94,105-107). PALs most commonly occur with thoracic surgery, trauma, malignant conditions, severe underlying lung disease, necrotizing lung infections, or barotrauma from mechanical ventilation. Due to underlying lung pathology, an SSP is more likely to produce a PAL than a PSP; an SSP-related PAL is also less likely to resolve with chest tube drainage alone compared to a PSP-related PAL (7).

The incidence of PALs has been best studied in the realm of thoracic surgery (105,108-112), as PALs are one of the most common complications in this somewhat homogenous context. For instance, PALs (study definitions varying from 3–7 days) occur in 24–46% of lung volume reduction surgeries, 6–26% of lobectomies, 8% of segmentectomies, 7% of bulla resections, and 3% of wedge resections. Risk factors for PALs after lung resection surgery include COPD, reduced FEV1, reduced FEV1/FVC, smoking history, corticosteroid use (inhaled or systemic), presence of pleural adhesions, open thoracotomy approach (compared to VATS), malignant pulmonary pathology, and upper lobe resection. The incidence of PAL after lung resection has decreased over time likely due to improvements in preoperative PAL risk stratification, surgical technique, intraoperative measures to address pleural leaks, and adoption of low-tidal volume ventilation practices (108,113). Additional assessment of the surgical approaches to prevent and manage post-resection pneumothorax and PAL is outside of the scope of this article. In contrast, the incidence of PALs in non-surgical procedures is not well studied. Based on the relatively low frequency of pneumothorax in general and the very low rate of BPFs in non-surgical procedures, the incidence of PALs is likely extremely low.

In the post-operative setting, PALs are associated with increased morbidity, longer hospital length of stay, and infections (108,111). Increased mortality has also been described in some study groups (94,106,107). Additional complications of PALs include pneumonia, empyema, ventilation/perfusion mismatching, and limiting the ability to utilize high positive end-expiratory pressure (PEEP) mechanical ventilation settings (111).

PAL management

Very little prospective or randomized control evidence on the management of SP-related PALs exists, and clinical practice varies considerably (94,106). The lack of evidence and variation in clinical practice is likely because PALs tend to occur in complex patients with differing underlying lung pathology. Thus, PAL management decisions are largely dependent on several factors, including the presence of an APF vs. BPF, underlying cause of the air leak, air leak flow rate, duration of the air leak, amount of lung reexpansion, presence of pneumomediastinum or subcutaneous emphysema, clinician’s expertise, patient’s surgical candidacy, and patient’s preference. Given the complexity, a multidisciplinary team with pulmonary specialists and thoracic surgeons should be formed early on with decisions made in a patient-specific manner. The exact timing to consult thoracic surgery is debatable. Some societal guidelines suggest anywhere from 2 to 5 days (16,19,27), but each case should be assessed individually (21).

In the first 5–7 days of an active air leak, it is primarily managed with non-procedural methods. If the patient is intubated, then useful steps to reduce mean airway pressure may include reducing PEEP, tidal volume, peak inspiratory pressure, inspiratory time, and respiratory rate, limiting negative intrapleural pressures, and weaning off the ventilator as soon as able (107,114). One retrospective study also suggests that small-bore pigtail catheters are more likely to fail when the pneumothorax is due to barotrauma injury compared to other iatrogenic causes (115). Thus, larger or additional chest tube placement may be warranted in that context. There are also case reports of single-lung ventilation and extracorporeal membrane oxygenation in mechanically ventilated patients to help facilitate fistula closure (114,116).

For those that fail ongoing chest tube drainage and other non-procedural attempts, potential management strategies include surgery, pleural-based procedures, bronchoscopic techniques, or ambulatory Heimlich 1-way valve. Historically, surgical and chemical pleurodesis approaches have been the most utilized modalities (94,106), but there is increasing literature on bronchoscopic and other pleural-based modalities (94,106,107,117). Relevant surgical methods and techniques are nuanced and outside the scope of this article. Nonetheless, there is currently insufficient evidence to suggest any particular modality over another (21).

Likewise, the optimal time for PAL procedural intervention is unclear. Some have suggested operative management for active air leak should be considered as early as 3 days (86), >7 days (118), or >14 days (119). Others have endorsed that delayed surgical referral for SP-associated PAL reduces the ability to perform VATS, based on a single center cases series that noted patients who were able to undergo VATS were generally referred earlier (median 10 days) compared to those that required open thoracotomy instead (median 22 days) (120). The authors note that the inability to perform VATS was primarily due to the development of pleural sepsis, pleural adhesions, and development of more friable lung tissue. Thus, early surgical referral and intervention for an SP-related PAL had previously been emphasized. However, all these published endorsements are more than 25 years old and are centered upon likely biased retrospective analyses. Ultimately, no compelling evidence currently exists to suggest an ideal timepoint for a PAL procedural intervention (19,21,27). It is generally recommended that each case be assessed on an individual basis.

For etiologies of PAL other than SP, ongoing non-procedural conservative therapy is frequently practiced, as most APF air leaks spontaneously resolve if given enough time (119). Patients with incomplete lung reexpansion or severe PAL are more likely to fail conservative therapy (102). Thus, digital drainage system can be considered to assess PAL severity most accurately; this could potentially help prognosticate and guide management during this stage, but more evidence is needed (94,106,107,117). Additionally, management of infections, nutrition, and comorbidities should be optimized wherever possible (106,117). If the PAL improves, then further extension of non-procedural conservative management is often employed. The optimal duration and maximal duration to extend conservative management are not known and likely vary from patient to patient. If PAL does not further improve or resolve, then steps to localize the leak should be followed, as discussed in section “Leak localization and determination of collaterals”. Depending on the identified source of air leak, surgical intervention is still recommended whenever possible for unresolving APFs (16,94,106). PALs due to BPFs should be managed surgically if there are no contraindications. However, many patients with PALs are unfit for surgery. Thus, in patients who refuse surgery or are inoperable, then medical pleurodesis and/or endobronchial management may be reasonable. See Figure 5 for general APF management.

Figure 5 Initial management of alveolar-pleural fistula persistent air leak in spontaneous pneumothorax (121). VATS, video-assisted thoracoscopic surgery.

Leak localization and determination of collaterals

If conservative measures have failed, then the next steps in PAL management are to attempt APF or BPF localization (see Table 4) and to determine the presence of collateral ventilation (94,106,107,117). CT imaging should be performed (117) to assess the lung airways, parenchyma, and pleura, which may reveal a source of the PAL, such as a necrotic lung infection, lung mass, bulla, surgical site, etc. However, the identification of an SP-related APF or BPF on CT imaging is rare. The CT image may also help to determine fissure integrity and assess interlobar collateral ventilation. CT image analysis software can be used to assist with fissure integrity evaluation, for patients identified to have ≥90% fissure integrity on CT collateral ventilation analysis were associated to have more successful treatment (124). If the defect is not localized on CT, then a careful flexible bronchoscopy airway examination should be performed to attempt direct visualization of a BPF in the proximal airways (106,117). An APF or distal BFP may require more extensive evaluation to localize the bronchial segment or subsegment leading to the defect.

Methods to identify more distal lesions include sequential endobronchial balloon occlusion, endobronchial collateral ventilation assessment system (e.g., Chartis^®), or intrapleural methylene blue instillation (94,106,117,122,123). Sequential endobronchial balloon occlusion is performed during flexible bronchoscopy with a balloon catheter to systematically occlude the proximal airways and segments, starting at the mainstem bronchus of the affected side. When the balloon blocks ventilation to the culprit airway, then the chest tube drainage system’s air bubbling should stop. Thus, the sequential balloon occlusion method requires the presence of persistent air bubbling in the chest tube drainage system to work. If air bubbling does not stop despite complete balloon occlusion of the affected side’s mainstem bronchus, then there is either a leak within the chest tube drainage system’s circuitry or the PAL is not from an APF or BPF. Proprietary systems measuring pressure and air flow in occluded lungs have been used during BLVR procedures to assess for interlobar collateral ventilation, and such systems may also help identify interlobar collateral ventilation in the context of the PAL (123). If the target lobe’s interlobar fissure is >90% complete and the leak decreases by >50% with balloon occlusion, then bronchoscopic management is typically feasible (123).

Alternatively, or in addition, methylene blue can be diluted and instilled through the chest tube drainage system and allowed to dwell in the intrapleural space (94,106,107,117). During this intrapleural instillation and dwell time, careful flexible bronchoscopy airway examination is performed to observe where the methylene blue arises in the distal subsegmental/segmental airways. Once the defect is localized, then treatment options can be tailored accordingly.

Inoperable PAL management

If a patient is not a surgical candidate and conservative management fails, then bronchoscopic intervention and/or medical pleurodesis options can be evaluated for viability (19,21,94,106,107,117). The 2023 BTS guidelines note that endobronchial therapies or autologous blood pleurodesis should be considered in patients not fit for surgery (21). Similarly, the German S3 guidelines also describe endobronchial procedures as a potential non-operative SSP-related PAL treatment option in inoperable patients (19). In contrast, the ACCP consensus statement (16) specifically notes that patients with PALs “should not undergo… bronchoscopy with attempts to seal endobronchial sites of air leaks (very good consensus).” However, there have been significant advancements in endobronchial treatment options since those guidelines were published in 2001.

Despite a lack of RCTs or comparative studies, endobronchial valves (EBV) have a growing number of supportive case series in the management of PAL (106,107,117,125-129). One case series utilizing the Spiration Intrabronchial Valve System (Spiration Inc.) found that 80% of thoracostomy tubes were successfully removed after EBV insertion (127). A meta-analysis of retrospective and prospective cohorts noted that the majority of PALs (62%) completely resolved within 24 hours of EBV placement (130). After the PAL resolves, then the EBV(s) are generally removed weeks later (Figure 6). Currently, EBVs are approved in Europe for the management of PAL in SP. None of the devices are approved for use by the United State’s Federal Food and Drug Association, but select devices have received humanitarian device exception for refractory PAL management. Numerous other bronchoscopic interventions have also been attempted, although not as prominently in the literature (see Table 5). Across the board, prospective RCTs are needed for PAL endobronchial management options.

Figure 6 Endobronchial one-way valve—Spiration^® Valve System prior to planned removal after placement within bronchus for persistent air leak with resolution.

When bronchoscopic intervention is not feasible or fails, then alternative treatment options include medical chemical pleurodesis, medical autologous blood pleurodesis, or ambulatory 1-way valve (19,21,94,106,117). Medical pleurodesis procedures can be performed with the already indwelling thoracostomy catheter or tube. In chemical pleurodesis, the agent of choice is controversial but, generally, graded talc or doxycycline is utilized. In the medical autologous blood pleurodesis (“blood patch”) procedure, the patient’s own venous blood is instilled into the pleural cavity to coagulate and seal the air leak. The volume of instilled intrapleural blood varies by study protocol, but 1–2 mL/kg body weight (~50–200 mL) is generally used (94,106,107,117,131,132). Autologous blood pleurodesis has been used effectively in retrospective studies with a success rate of up to 92% (131,132). As such, the 2018 German S3 guidelines “recommend chemical pleurodesis or autologous blood via an indwelling chest drain in patients with SSP in expanded lung and persistent air leakage or recurrent pneumothorax, if an operation is contraindicated” (19). The 2023 BTS guidelines also endorse autologous blood pleurodesis as a considered treatment for PAL (21). Long-term ambulatory 1-way valve pleural drainage can be considered when other treatment options failed, are not feasible, or are not desired by the patient (106,131).

Conclusions

A pneumothorax is a relatively common clinical occurrence among patients arriving to the emergency department and among inpatients. Historically, SP management practices have varied widely between providers, institutions, and societal recommendations. However, modern management strategies have embraced more conservative approaches, as supported by a growing body of literature. This trend is most clearly demonstrated in the new 2023 BTS Guideline for Pleural Disease. Essentially all patients with an SP who are unstable or symptomatic with high-risk characteristics should be managed with emergent intervention, most commonly being chest tube drainage. Most stable and asymptomatic/minimally symptomatic patients with PSP should be managed with conservative observation, regardless of PSP size, unless there is another indication for intervention. For PSPs in stable but symptomatic patients without high-risk characteristics, patient preference and clinician expertise should predominantly drive management decisions. The management of SSPs in asymptomatic/minimally symptomatic patients is more controversial. There is less concrete prospective evidence on this clinical scenario, and societies deviate widely on recommendations. Options range from conservative inpatient observation, ambulatory device placement, simple aspiration, or chest tube drainage.

Persistent pneumothorax and PALs are particularly challenging clinical scenarios. Overall, there is a paucity of data to support any particular interventional approach. PAL management is highly dependent on patient stability and PAL clinical characteristics, and cases should be assessed on an individual basis. When extended conservative chest tube drainage has failed to resolve an SP-related PAL, then first-line therapy would generally be surgery, followed by bronchoscopic intervention vs. medical autologous blood pleurodesis. Among bronchoscopic intervention options, EBVs have the most supportive retrospective cases series data. Overall, additional prospective RCTs to better determine treatment algorithms for SP (particularly SSP) and PAL management are urgently needed.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editors (Jonathan Kurman and Bryan S. Benn) for the series “Diagnostic & Therapeutic Bronchoscopy” published in AME Medical Journal. The article has undergone external peer review.

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://amj.amegroups.com/article/view/10.21037/amj-23-168/rc

Peer Review File: Available at https://amj.amegroups.com/article/view/10.21037/amj-23-168/prf

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://amj.amegroups.com/article/view/10.21037/amj-23-168/coif). The series “Diagnostic & Therapeutic Bronchoscopy” was commissioned by the editorial office without any funding or sponsorship. G.Z.C. reports that he does not have any specific COI pertaining to this article. He serves as consultant or on scientific advisory board for the following companies: Intuitive Surgical, Olympus, Boston Scientific, Cook, Pinnacle Biologics, Biodesix. G.Z.C. has received research funding from: Intuitive Surgical, Medtronic, Boston Scientific, Lung Therapeutics, Bodyvision. He has stock interest in Restor3D and Leadoptik. G.Z.C. also serves on the Board of Directors in American Association of Bronchology and Interventional Pulmonology. The authors have no other conflicts of interest to declare.

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