primary pneumothorax

[mazen]

A primary spontaneous pneumothorax (PSP) is a pneumothorax that occurs without a precipitating event in a person who does not have known lung disease. In actuality, most individuals with PSP have unrecognized lung disease, with the pneumothorax resulting from rupture of a subpleural bleb [1-5].

In this topic review, the incidence, pathogenesis, presentation, and management of PSP are discussed. Secondary spontaneous pneumothorax, which occurs as a complication of underlying lung disease, is reviewed in detail elsewhere.
population per year in the United States to 37 per 100,000 population per year in the United Kingdom. The incidence is substantially less in women than in men, ranging from 1.2 per 100,000 population per year in the United States to 15.4 per 100,000 population per year in the United Kingdom [6]. The reason for these differences is unknown.

Estimates of the incidence of recurrent PSP range from 25 percent to more than 50 percent, with most recurrences occurring within the first year [6]. As an example, a study of 153 patients with PSP found a recurrence rate of 54 percent [7]. Male gender, tall stature, low body weight, and failure to stop smoking have been associated with an increased risk of recurrence [7,8].

RISK FACTORS — Factors that have been proposed or shown to predispose patients to primary spontaneous pneumothorax (PSP) include smoking, family history, Marfan syndrome, homocystinuria, and thoracic endometriosis.

Smoking — Cigarette smoking is a significant risk factor for primary spontaneous pneumothorax (PSP), probably due to consequences of airway inflammation. As an example, in an analysis of four studies that included 505 patients with PSP, 461 of the patients (91 percent) were smokers [6]. Furthermore, the risk of PSP was directly related to the amount of cigarette smoking. Compared to nonsmokers, the relative risk of PSP in men was seven times higher in light smokers (1 to 12 cigarettes per day), 21 times higher in moderate smokers (13 to 22 cigarettes per day), and 102 times higher in heavy smokers (>22 cigarettes per day). For women, the relative risk was 4, 14, and 68 times higher in light, moderate, and heavy smokers, respectively [9].

Respiratory bronchiolitis, a form of airway inflammation associated with cigarette smoking, may contribute to the development and recurrence of PSP. In a study of 115 patients with PSP who underwent video-assisted thoracoscopic surgery (VATS), pneumothorax recurrence rates were higher in patients with extensive rather than nonextensive respiratory bronchiolitis for both nonoperative and postoperative pneumothorax (p <0.004 and 0.001, respectively) [10].

Family history — Reports have been published describing the clustering of PSP in certain families [11-17]. Autosomal dominant, autosomal recessive, polygenic, and X-linked recessive inheritance mechanisms have all been proposed [12-14]. The autosomal dominant Birt-Hogg-Dube syndrome, which predisposes patients to benign skin tumors and renal cancer, is associated with an increased incidence of PSP [15,16,18-20]. In one study of 198 patients with this syndrome, 48 patients (24 percent) had a history of pneumothorax [18]. The presence of lung cysts was associated with pneumothorax, as well as lung cyst volume, diameter, and number.

The gene responsible for this familial cancer syndrome (called FLCN) has been mapped to chromosome 17p11.2 [15,16]. FLCN and its associated protein, folliculin, appear to have important tumor suppression function. However, other mutations of FLCN have been associated with spontaneous pneumothorax and bullous lung disease in the absence of the oncologic manifestations of Birt-Hogg-Dube syndrome [11,17]. In one Finnish family with an extensive history of PSP, a novel mutation was associated with autosomal dominant inheritance of bullous lung lesions in all carriers (100 percent penetrance) [11].

Genetic testing is available for the Birt-Hogg-Dube syndrome [21]. Periodic screening for renal tumors is recommended in affected patients. (See "Hereditary kidney cancer syndromes", section on 'Birt-Hogg-Dube syndrome'.)

Other — PSP also occurs with increased frequency in patients with Marfan syndrome and homocystinuria. In addition, catamenial pneumothorax may result from thoracic endometriosis, and should be considered in women presenting with PSP temporally related to menstruation [22,23]. (See "Thoracic endometriosis", section on 'Catamenial pneumothorax and hemothorax'.)

Several case reports have described the occurrence of spontaneous pneumothorax among patients with anorexia nervosa [24-26]. It is thought that the pulmonary parenchymal consequences of malnutrition contribute to development of pneumothorax in these patients. (See "Anorexia nervosa in adults and adolescents: Medical complications and their management", section on 'Pulmonary'.)

CLINICAL PRESENTATION — Primary spontaneous pneumothorax (PSP) usually occurs when the patient is at rest [27]. Patients are typically in their early 20s, with PSP being rare after age 40. Patients usually complain of the sudden onset of dyspnea and pleuritic chest pain. The severity of the symptoms is primarily related to the volume of air in the pleural space, with dyspnea being more prominent if the pneumothorax is large.

Characteristic physical findings when a large pneumothorax is present include decreased chest excursion on the affected side, diminished breath sounds, and hyperresonant percussion. Subcutaneous emphysema may be present. Evidence of labored breathing and hemodynamic compromise (eg, tachycardia, hypotension) suggests a possible tension pneumothorax, which necessitates emergency decompression.

Hypoxemia is common because collapsed and poorly ventilated portions of lung continue to receive significant perfusion. In contrast, hypercapnia is unusual because underlying lung function is relatively normal and adequate alveolar ventilation can be maintained by the contralateral lung [1]. Acute respiratory alkalosis may exist if pain, anxiety, and/or hypoxemia are substantial.

Imaging — The presence of a pneumothorax is established by demonstrating a white visceral pleural line on the chest radiograph. The visceral pleural line defines the interface of the lung and pleural air; it is either straight or convex towards the chest wall (picture 1). In most cases, no pulmonary vessels are visible beyond the visceral pleural edge. Inspiratory and expiratory films have equal sensitivity in detecting pneumothoraces; thus, a standard inspiratory chest radiograph is sufficient in most cases [28]. (See "Imaging of pneumothorax".)

The underlying lung parenchyma should be examined for the presence of underlying lung disease that would suggest a secondary spontaneous pneumothorax. (See "Secondary spontaneous pneumothorax in adults".)

Tension pneumothorax may develop in approximately 1 to 2 percent of PSP [29]. However, the sensitivity and specificity of the plain chest radiograph for detection of tension are unclear. Contralateral shift of the trachea and mediastinum is a typical finding in spontaneous pneumothorax and not necessarily suggestive of tension. Conversely, patients may have clinical evidence of tension (eg, tachycardia, hypotension, dyspnea) in the absence of "typical" radiographic findings. (See "Imaging of pneumothorax", section on 'Types of pneumothorax'.)

CT scanning is generally not necessary unless abnormalities are noted on the plain chest radiograph that require further evaluation, or aberrant chest tube placement is suspected [30].

DIAGNOSIS — The diagnosis of primary spontaneous pneumothorax (PSP) is established by detection of a visceral pleural line on the chest radiograph of a patient without underlying lung disease. (See 'Imaging' above.)

The differential diagnosis includes the causes of spontaneous pneumothorax in patients who have underlying lung disease that has not yet been diagnosed (eg, catamenial pneumothorax, chronic obstructive lung disease, interstitial lung disease, lung cancer, lymphangioleiomyomatosis). When managing patients with a persistent air leak or recurrent spontaneous pneumothorax, a CT scan should be considered as well as a lung biopsy at the time of thoracoscopy. The diseases associated with secondary spontaneous pneumothorax are discussed in more detail separately. (See "Secondary spontaneous pneumothorax in adults", section on 'Etiologies'.)

TREATMENT OPTIONS — Initial management is directed at removing air from the pleural space, with subsequent management directed at preventing recurrence. In the discussion that follows, we expand upon published clinical consensus statements [30,31]. These consensus statements were derived using the Delphi method, a process of collecting data from the opinions of published experts using several rounds of questionnaires [32].

Initial management — Initial treatment options for primary spontaneous pneumothorax (PSP) include observation, supplemental oxygen, needle aspiration of intrapleural air, chest tube insertion (ie, tube thoracostomy), and thoracoscopy. The choice of procedure depends on patient characteristics and clinical circumstances:

Patients who are clinically stable and having their first PSP can be administered supplemental oxygen and observed if their pneumothorax is small (≤2 to 3 cm between the lung and chest wall on a chest radiograph) [33].
Patients who are clinically stable and having their first PSP should undergo needle aspiration if their pneumothorax is large (>3 cm rim of air on chest radiograph), or if they are symptomatic with chest pain or dyspnea [30,34,35]. Patients who fail aspiration should have a chest tube inserted (ie, tube thoracostomy) and thoracoscopy should be considered during the same hospitalization. Chemical pleurodesis through the chest tube should be performed, if the air leak persists and thoracoscopy is not readily available.
Patients who are clinically stable with either a recurrent PSP or a concomitant hemothorax (ie, a hemopneumothorax), should undergo thoracoscopy after chest tube insertion. If thoracoscopy is not readily available, chemical pleurodesis through the chest tube may be performed after drainage of the pleural space.
Clinically unstable patients should undergo chest tube insertion. Decompression of the pleural space can be performed by advancing a standard 14 gauge intravenous catheter into the pleural space at the junction of the midclavicular line and the second or third intercostal space, if the chest tube insertion is delayed.

Supplemental oxygen — Observation should last six hours, after which reliable patients with ready access to emergency medical services can be discharged home if a repeat chest radiograph excludes progression of the pneumothorax. While the patient is hospitalized, supplemental oxygen should be administered to facilitate resorption of the pleural air.

The importance of supplemental oxygen should not be underestimated. Air in the pleural space is reabsorbed when the communication between the alveoli and the pleural space (ie, the air leak) closes. The rate of resorption can be markedly increased if supplemental oxygen is administered [36]. As an example, a normal rate of resorption is approximately 1.25 percent of the volume of the hemithorax per 24 hours [6]. However, the rate of resorption increases six-fold if humidified 100 percent oxygen is administered in an animal model [37].

Aspiration — Aspiration is most easily accomplished with a commercially available thoracentesis kit. An 18-gauge needle with an 8 to 9 French (Fr) catheter is inserted into the pleural space, the catheter is threaded deeper into the pleural space, and then the needle is withdrawn. Air is manually withdrawn through the indwelling catheter until no more can be aspirated. It is assumed that there is a persistent air leak if there is still no resistance after four liters of air has been aspirated and the lung has not expanded. Thoracoscopy should be performed if this occurs. Alternatively, a chest tube should be inserted if thoracoscopy is not readily available.

Two equally acceptable approaches exist once no further air can be aspirated [38]:

A closed stopcock can be attached and the indwelling catheter secured to the chest wall. A chest radiograph should be obtained four hours later and, if adequate lung expansion has occurred, the catheter can be removed. Following an additional two hours of observation, another chest radiograph should be performed. The patient can be discharged if the lung remains expanded on this chest radiograph [39].
The catheter can be left in place and attached to a Heimlich (ie, one-way) valve. The patient can then be discharged with follow up within two days [31,40]. (See "Placement and management of thoracostomy tubes", section on 'Tube selection'.)

One of the advantages of aspiration over tube thoracostomy is that the patient need not be hospitalized, whether the catheter is removed after the aspiration or left attached to the Heimlich valve.

Based on evidence from several studies, we prefer to manage most hemodynamically-stable patients initially with aspiration, rather than tube thoracostomy [30,41-45]. As examples:

In a meta-analysis of three randomized, controlled trials (194 patients) that compared aspiration versus tube thoracostomy, aspiration resulted in shorter hospitalizations and similar clinical outcomes at one week and one year [41].
In a randomized trial, 137 patients who had a first episode of PSP were assigned to receive manual aspiration or tube thoracostomy [42]. The groups had similar rates of immediate (62 versus 68 percent) and one-week success (89 versus 88 percent); however, aspiration was associated with a shorter hospital stay (1.8 versus 4 days).

Tube thoracostomy — Most patients with PSP can be managed successfully with a small chest tube (≤22 Fr) or chest catheter (≤14 Fr) [45,46]. The chest tube can be connected to a water seal device, with or without suction and left in position until the pneumothorax resolves. We suggest that suction be applied to the chest tube if the pneumothorax fails to resolve. (See "Placement and management of thoracostomy tubes".)

Once the air leak has resolved, the lung has expanded, and the pleural air has been removed, the chest tube can be removed in a sequential fashion. Specifically, we advocate that the chest tube be clamped twelve hours after the last evidence of an air leak and that a chest radiograph be performed 24 hours after the last evidence of an air leak. The chest tube can be removed if the pneumothorax has not reaccumulated.

Thoracoscopy — Video-assisted thoracoscopy (VATS) is effective in the treatment of spontaneous pneumothorax [5,47-49]. With this procedure, pleurodesis is created by pleural abrasion or a partial parietal pleurectomy; when necessary, an endoscopic stapler can be used to resect bullae, as reported in several uncontrolled observational studies [50-53].

Persistent air leak — We advocate a more aggressive approach if an air leak persists after three days. For patients whose lung is at least 90 percent expanded but who have a persistent air leak, the usual choices include attaching a Heimlich valve to the chest tube, infusing autologous blood into the pleural space, and performing video-assisted thoracoscopy to oversew the area of leak and perform mechanical pleurodesis. (See 'VATS pleurodesis' below.)

The simplest approach is to attach a unidirectional flutter valve (ie, a Heimlich valve) to the chest tube, which usually allows rapid discharge of the patient with subsequent outpatient management.

An alternative technique for patients with a persistent air leak is to perform an autologous blood patch [54,55]. This involves withdrawal of blood from a peripheral arm vein and aseptic infusion of the blood into the pleural space through the chest tube. The ideal amount of blood to infuse into the pleural space is not known. In one series that included both spontaneous and postoperative pneumothoraces, the mean volume of blood infused was 90 mL and the range was 24 to 200 mL [54]. After infusion of the blood, the tubing from the chest tube is draped over a hook approximately 60 cm above the patient's chest and then down to a water seal device on the floor [55]. The chest tube is removed 24 hours after cessation of the air leak. The main side effect is empyema, which occurred in 9 percent of patients in one series [56].

Failure of lung reexpansion — For patients who have a persistent air leak and whose lung is less than 90 percent expanded, the preferred procedure is VATS. (See 'VATS pleurodesis' below.)

Recurrence prevention — We suggest that all patients with recurrent PSP should undergo an intervention to prevent future recurrences once the acute air leak has resolved, the lung has expanded, and the pleural air has been removed. In addition, we suggest that patients experiencing their first PSP should have a preventive intervention if they require VATS or tube thoracostomy as part of their initial management, or have a vocation in which recurrence of the pneumothorax is dangerous to the patient or others (eg, airplane pilot or deep sea diver). Options for preventing recurrence include pleurodesis via VATS, chemical pleurodesis via tube thoracostomy, and thoracotomy.

VATS pleurodesis — Video-assisted thoracoscopic surgery (VATS) is not only effective in the treatment of spontaneous pneumothorax as described above, but also in the prevention of recurrent pneumothorax [5,47-53,57-60]. The rate of recurrent pneumothorax is less than 5 percent after VATS with bleb/bullae resection and pleurodesis. Several techniques have been recommended to induce pleural symphysis including parietal pleurectomy, intrapleural instillation of talc or a tetracycline derivative, laser abrasion of the parietal pleura, and pleural abrasion with dry gauze. We prefer mechanical pleurodesis using pleural abrasion with dry gauze, since it is both simple and effective.

Chemical pleurodesis — In patients who are unable or unwilling to undergo VATS, intrapleural injection of a chemical irritant (most commonly a tetracycline derivative or talc) is another alternative [30]. We prefer to use the tetracycline derivative, doxycycline, for the reasons that follow, although many experts prefer talc.

Chemical pleurodesis with tetracycline decreases the recurrence rate for pneumothorax to 16 to 25 percent. In an unblinded trial of 229 patients with PSP, who were randomly assigned to either undergo or not undergo chemical pleurodesis using tetracycline; tetracycline decreased the rate of recurrent spontaneous pneumothorax (25 versus 41 percent, respectively) [61]. In a series of 390 patients, the pneumothorax recurrence rate was 16 percent with intrapleural tetracycline [62]. Respiratory failure due to an apparent allergic reaction to doxycycline intrapleural instillation has been reported [63]. (See "Chemical pleurodesis".)

Talc slurry administered via chest tube can also be used to treat PSP [58,64,65]. Pneumothorax recurrence rates vary between 5 and 8 percent. However, controversy exists whether talc should be used as the sclerosant agent in young, otherwise healthy individuals because of safety reasons and fear for long-term complications. Intrapleural injection of talc for malignant pleural effusions has been associated with the development of the acute respiratory distress syndrome (ARDS) in 1 to 2 percent of patients [66]. Additionally, in one patient, extensive pleural thickening with calcifications developed [67]. On the other hand, several studies support the safety of talc pleurodesis for prevention of recurrent pneumothorax [58,68,69]. (See "Talc pleurodesis".)

For patients with recurrent PSP, who have a chest tube in place and are not candidates for VATS pleurodesis, we prefer doxycycline for pleurodesis because we believe that its effectiveness is comparable to talc and it has not been associated with the development of ARDS. We suggest using doxycycline (500 mg dissolved in a total volume of 50 mL of normal saline) administered via the chest tube. Intrapleural doxycycline can be very painful; as a result, patients should be premedicated with analgesics (eg, opiates) and, possibly, anxiolytics (eg, midazolam). Some experts also use intrapleural lidocaine 25 mL (250 mg) of a 1 percent solution; however, intrapleural lidocaine alone is ineffective for pain control.

Thoracotomy — The indications for open thoracotomy are the same as those for VATS. Thoracoscopy has essentially replaced open thoracotomy in the management of spontaneous pneumothorax in many medical centers for two main reasons: hospitalization is shorter and postoperative pain is less [70,71]. Thoracotomy is presently recommended only if thoracoscopy is unavailable or has failed. During thoracotomy, apical pleural blebs are oversewn and the pleura is scarified.

Smoking cessation — The strong association between smoking and an initial PSP suggests that smoking cessation may help prevent recurrent pneumothoraces; this benefit has been confirmed by at least one retrospective study [7]. (See "Patterns of tobacco use and benefits of smoking cessation".)

SUMMARY AND RECOMMENDATIONS

A primary spontaneous pneumothorax (PSP) is a pneumothorax that occurs without a precipitating event in a person who does not have known lung disease. In actuality, most individuals with PSP have unrecognized lung disease, with the pneumothorax resulting from rupture of a subpleural bleb. (See 'Introduction' above.).
The incidence is increased in men, smokers, and patients with a family history of PSP. Recurrence is estimated to occur in 25 to 54 percent of patients. (See 'Incidence' above and 'Risk factors' above.).
PSP usually occurs when the patient is at rest and manifests as acute dyspnea and pleuritic chest pain. The peak age is in the early 20s. (See 'Clinical presentation' above.).

Early management

We suggest supplemental oxygen and observation if the patient is clinically stable and the pneumothorax is small (ie, the distance between the lung and the chest wall is ≤3 cm on a chest radiograph), rather than aspiration, chest tube insertion, or video-assisted thoracoscopy (VATS) (Grade 2C). Observation should last six hours, after which the patient can be discharged home, if a repeat chest radiograph excludes progression of the pneumothorax and the patient has access to emergency medical services. (See 'Initial management' above and 'Supplemental oxygen' above.)
We recommend pleural aspiration as initial therapy if the patient is clinically stable and the pneumothorax is large, rather than supplemental oxygen with observation, chest tube insertion, or VATS (Grade 1A). This recommendation is based on the observation that the success of pleural aspiration is sufficiently high to warrant its trial before progressing to options that, although more likely to succeed, are also more likely to have adverse effects. A chest tube should be inserted if aspiration fails and VATS should be considered during the same hospitalization based upon the high success rate of VATS, both short- and long-term. Chemical pleurodesis should be performed through the chest tube if VATS is not readily available. (See 'Initial management' above and 'Aspiration' above.)
We suggest that patients who are clinically stable with a recurrent PSP undergo VATS after chest tube insertion (Grade 2B). This is based upon both the short-term success rate of VATS and our belief that all patients with recurrent PSP should undergo a preventive intervention, which can be accomplished at the same time by VATS. Chemical pleurodesis should be performed through the chest tube if VATS is not readily available. (See 'Initial management' above.)
Clinically unstable patients should undergo chest tube insertion. Decompression performed by advancing a standard 14 gauge intravenous catheter into the pleural space at the junction of the midclavicular line and the second or third intercostal space can be performed as a bridge, if the chest tube insertion is delayed. The chest tube can be connected to a water seal device, with or without suction. We suggest that suction be applied to the chest tube if the pneumothorax fails to resolve (Grade 2C). (See 'Initial management' above and 'Tube thoracostomy' above.)
Patients who require mechanical ventilation or who may have a large air leak should be managed with a 24 to 28 French (Fr) chest tube, rather than a smaller chest tube. All other patients who require chest tube insertion can be managed with a 16 to 22 Fr chest tube or a ≤14 Fr chest catheter, instead of a larger chest tube. (See 'Tube thoracostomy' above.)
For patients being managed with a chest tube whose lung is at least 90 percent expanded but who have an air leak that persists longer than three days, we suggest that the chest tube be attached to a Heimlich valve and the patient discharged home, rather than ongoing management with a chest tube (Grade 2C). An alternative approach is to perform an autologous blood patch. (See 'Persistent air leak' above.)
For patients being managed with a chest tube who have a persistent air leak and whose lung is less than 90 percent expanded, we suggest VATS, rather than ongoing management with a chest tube (Grade 2B). (See 'Failure of lung reexpansion' above.)

Preventing recurrence

We suggest a preventive intervention for patients experiencing their first PSP if they are undergoing VATS or tube thoracostomy as part of their initial management, or have a vocation in which recurrence of the pneumothorax is dangerous to the patient or others (eg, airplane pilot or deep sea diver) (Grade 2B). Otherwise, we prefer to forego preventive interventions until a patient experiences recurrent PSP. (See 'Recurrence prevention' above.)
Once it has been determined that a preventive procedure is required, we recommend VATS with pleurodesis, rather than tube thoracostomy with chemical pleurodesis (Grade 1B). This procedure reduces the recurrence rate to less than 5 percent. (See 'VATS pleurodesis' above.)
For patients who are not operative candidates or who refuse VATS, we recommend tube thoracostomy with chemical pleurodesis, rather than tube thoracostomy drainage alone, once it has been determined that a preventive intervention is indicated (Grade 1A). This procedure reduces the recurrence rate to less than 25 percent. (See 'Chemical pleurodesis' above