The intricacies of pneumothorax

Management depends on accurate classification

H. Erhan Dincer, MD; Randolph J. Lipchik, MD

WEB EXCLUSIVE / DECEMBER 2005 / POSTGRADUATE MEDICINE

The authors disclose no financial interests in this article.

Preview: Categorizing a spontaneous pneumothorax as either primary or secondary and detecting its size and the concomitant amount of lung collapse together determine appropriate management. A small primary spontaneous pneumothorax usually requires no treatment, whereas a secondary spontaneous pneumothorax--especially if recurrent--calls for hospitalization, aggressive intervention, and careful follow-up. In this article, Drs Dincer and Lipchik enumerate the types and causes of pneumothorax and outline treatment approaches to each.
Dincer HE, Lipchik RJ. The intricacies of pneumothorax: management depends on accurate classification. Postgrad Med 2005;118(6) (online article)

Pneumothorax is defined as the presence of air between the visceral and parietal pleura that leads to lung collapse. It is usually classified on the basis of its cause. Trauma (iatrogenic or accidental) is a common cause of pneumothorax. When pneumothorax occurs without preceding trauma, it is classified as spontaneous pneumothorax, either primary (without clinically or radiographically apparent lung or chest wall disease) or secondary (when such disease is present).

Treatment of pneumothorax has not been standardized, and a number of therapeutic options have been used in different clinical scenarios. However, because secondary spontaneous pneumothorax has a high recurrence rate and increases mortality risk, accepted practice dictates that it should be treated aggressively. A more conservative approach is reasonable in patients with an initial episode of primary spontaneous pneumothorax.

Underestimated incidence

The incidence of pneumothorax is probably underestimated, since patients with a small spontaneous pneumothorax may not seek medical attention. In a study from Olmsted County, Minnesota, 318 patients received a diagnosis of pneumothorax between 1950 and 1974. The age-adjusted annual incidence of primary pneumothorax was 7.4 per 100,000 men and 1.2 per 100,000 women. The annual incidence of secondary pneumothorax was 6.3 per 100,000 men and 2.0 per 100,000 women (1).

In a large study in Israel (2), spontaneous pneumothoraces occurred in 723 (60.3%) of 1,199 cases; of these, 218 were primary and 505 were secondary. Traumatic pneumothorax occurred in 403 (33.6%) patients, 73 (18.1%) of whom had iatrogenic pneumothorax. In a Department of Veterans Affairs cooperative study (3), the most common causes of iatrogenic pneumothorax were thoracic needle aspiration, subclavian central line placement, and thoracentesis.

Causes of pneumothorax

The underlying cause of pneumothorax depends on whether the condition is spontaneous or traumatic.

Primary spontaneous pneumothorax
Although primary spontaneous pneumothorax, by definition, occurs in patients without a precipitating event or underlying lung disease, most of these patients have a variety of emphysematous lesions detected by computed tomography of the chest or during thoracoscopic surgery (4).

The pathogenesis of these blebs has been attributed to inflammation of bronchioles and cigarette smoking. In fact, the risk of having the lesions increases with increasing numbers of cigarettes smoked (5). Primary spontaneous pneumothorax is most common in tall, thin men in the third decade of life. Whether or not sex and body habitus have an impact on the development of subpleural blebs is unclear.

Secondary spontaneous pneumothorax
Although almost every lung disease can result in secondary spontaneous pneumothorax, chronic obstructive pulmonary disease is the most common cause (table 1). It is believed that many cases are associated with formation of subpleural cystic areas related to emphysema or interstitial fibrosis. The incidence of secondary spontaneous pneumothorax increases with age.

Table 1. Causes of secondary spontaneous pneumothorax according to frequency

Airway disease Chronic obstructive pulmonary disease Cystic fibrosis Status asthmaticus Infectious lung disease Pneumocystis carinii pneumonia Necrotizing pneumonias Interstitial lung disease Sarcoidosis Idiopathic pulmonary fibrosis Pulmonary Langerhans cell histiocytosis Lymphangioleiomyomatosis Tuberous sclerosis Connective tissue disease Ankylosing spondylitis Polymyositis, dermatomyositis Scleroderma Marfan syndrome Ehlers-Danlos syndrome Cancer Sarcoma Lung cancer Miscellaneous Catamenial pneumothorax Pneumothorax ex vacuo Aerosolized pentamidine isethionate (NebuPent, Pentacarinat, Pentam) therapy Adapted, with permission, from Sahn SA and Heffner JE. Spontaneous pneumothorax. N Engl J Med 2000;342(12):868-74.

Iatrogenic pneumothorax
Transthoracic needle aspiration or biopsy is the leading cause of iatrogenic pneumothorax (table 2). The overall incidence is about 20%, and risk increases with deeper insertions, multiple passes, and smaller lesions, in addition to the presence of underlying obstructive lung disease (6,7). Other common causes include thoracentesis and central line placement.

Table 2. Causes of iatrogenic pneumothorax according to frequency

Transthoracic needle aspiration or biopsy Thoracentesis Closed pleural biopsy Transbronchial biopsy Subclavian or jugular vein catheterization Mechanical ventilation Cardiopulmonary resuscitation Nasogastric tube placement Tracheostomy Liver biopsy

Clinical presentation

In general, the severity of symptoms is related to the degree of lung collapse and underlying lung pathology. The most common presenting symptoms of pneumothorax are acute onset of ipsilateral pleuritic chest pain and dyspnea. The pain is usually intense and may radiate to the shoulder. In patients with primary spontaneous pneumothorax, the chest pain usually resolves within 24 hours despite persistent pneumothorax, whereas the pain and dyspnea of secondary spontaneous pneumothorax do not abate. Patients with decreased functional lung reserve or larger pneumothoraces may experience life-threatening hypotension (tension pneumothorax) and hypoxemia. Cough, palpitations, and ptosis (Horner syndrome) are other, less frequent manifestations of pneumothorax.

Findings on physical examination include decreased chest excursion on the affected side, hyperresonance to percussion, and diminished breath sounds. The presence of hypotension, cyanosis, and marked tachycardia should alert the physician to the possibility of tension pneumothorax that requires emergency drainage.

Diagnosis

The diagnosis of pneumothorax is established by demonstrating a visceral pleural line outlining the edge of the lung on x-ray film (figure 1). This appears as a white line outlined by air, with an absence of lung markings on the outer aspect. An erect chest radiograph (figure 2a) is usually sufficient. A skin fold can mimic such a line, but lung markings are visible on both sides. The abnormal line can sometimes be followed beyond the thorax, precluding a process in the lung.

Pneumothorax may be harder to detect on a supine x-ray film, but the presence of a depressed costophrenic sulcus (deep sulcus sign) suggests the diagnosis. In some cases, a computed tomographic scan of the chest may be useful as a confirmatory test. For example, a large subpleural bulla may mimic a pneumothorax. In most cases, the medial border of the bulla is concave (figure 2b).

In patients receiving mechanical ventilation, pneumothorax must be considered when there is worsening hypoxemia, increased ventilator plateau pressures, new right axis deviation, diminished precordial R-wave progression, low-voltage electrocardiogram, or pulseless electrical activity.

Recurrence rates

Patients with primary spontaneous pneumothorax have a high risk of recurrence, particularly within the first year. In one study (8), 39% of patients experienced a second episode during 54 months of follow-up, most in the first year. Of these recurrences, 15% developed on the contralateral side. No relationship has been shown between the presence and size of blebs and the risk of recurrence. It is a reasonable assumption that patients who are tall, thin, and actively smoking and who have had previous episodes of pneumothorax are prone to have recurrences.

In secondary spontaneous pneumothorax, recurrence is expected at a somewhat higher incidence rate than in primary spontaneous pneumothorax. This risk is significantly lower in patients who have had pleurodesis (9).

Treatment

The therapeutic approach to pneumothorax depends on its type, size, and clinical presentation; the number of prior episodes; comorbid diseases; and underlying lung pathology. An important factor informing appropriate treatment is the amount of lung collapse. A practical method to classify pneumothorax size uses the distance between the lung apex and the ipsilateral dome of the thoracic cavity as determined by an upright chest radiograph. A pneumothorax is small when that distance is less than 3 cm (1.2 in). When the distance is equal to or greater than 3 cm, the pneumothorax is considered large.

Although there are no evidence-based medical standards of practice for treatment of pneumothorax, the American College of Chest Physicians and the British Thoracic Society have both published guidelines based on expert consensus (10,11). The ultimate goal is to decrease the likelihood of recurrence after an initial episode of pneumothorax.

Primary spontaneous pneumothorax
A treatment algorithm for primary spontaneous pneumothorax is shown in figure 3. Small pneumothoraces usually do not require intervention unless there is an ongoing air leak; short-term observation is usually sufficient. No further management or follow-up is required if the chest x-ray film reveals a stable or smaller pneumothorax in 24 hours. High-flow oxygen should be given when possible, decreasing the amount of nitrogen in the blood and creating a nitrogen gradient between the air in the pleural cavity and the pleural capillaries that results in gas resorption. It should be noted that the effect is modest (about 1% to 2% of the volume in the chest in 24 hours).

Patients with large pneumothoraces, regardless of clinical stability, usually require placement of small-bore catheters or standard chest tubes. Drainage with or without suction should continue until the lung expands and the air leak resolves. Most of these patients should be hospitalized. In those who expand the lung without an air leak, the chest tube can be removed quickly. Most experts do not recommend pleurodesis for the initial episode in stable patients. If an air leak persists for more than 4 days, a thoracic surgery consultation for surgical pleurodesis is warranted. Some form of pleurodesis should be considered if there is recurrence.

Secondary spontaneous pneumothorax
In contrast to a small primary spontaneous pneumothorax, a small secondary spontaneous pneumothorax is cause for hospitalization. The threshold for chest tube placement is lower in secondary spontaneous pneumothorax and depends on the severity of underlying lung disease and on clinical stability (figure 4). Large pneumothoraces should be drained with a chest tube. Many patients with secondary spontaneous pneumothorax should undergo surgical pleurodesis to prevent another episode, which could be fatal (12). Indications for surgical intervention include bilateral spontaneous pneumothorax, second ipsilateral pneumothorax, first contralateral pneumothorax, persistent (>4 days) air leak in spite of continuous tube drainage, and high-risk professions (eg, pilots and deep-sea divers).

Chemical pleurodesis may be an alternative for patients in whom surgery is contraindicated. Commonly used chemical agents are talc slurry, doxycycline, and bleomycin sulfate (Blenoxane). Talc slurry is found to be the most effective, but there have been reports of acute respiratory distress syndrome after its instillation into the pleural space. A detailed debate about the use of talc for pleurodesis (13) has been published. Consultation with a pulmonologist or thoracic surgeon--or both--is recommended.

Iatrogenic pneumothorax
Treatment of iatrogenic pneumothorax is usually simple, and therapy to prevent future occurrence is not needed. Simple aspiration of air with a small-bore catheter and oxygen supplementation are sufficient. However, in the setting of mechanical ventilation, the risk of tension pneumothorax is high and chest tube drainage is necessary (14).

Special considerations

Special treatment may be needed for patients who deep-sea dive, pilot aircraft, or have HIV infection. Types of pneumothorax that call for particular consideration include catamenial pneumothorax, pneumothorax ex vacuo, and familial spontaneous pneumothorax.

Diving and air travel
During ascent from a deep-sea dive, expanding gas-filled spaces may rupture and result in pneumothorax, especially in patients with lung bullae, lung cysts, or active asthma. In patients with previous spontaneous pneumothorax, diving is contraindicated unless definitive bilateral surgical pleurectomy has been performed (10,15,16).

Pneumothorax is extremely rare on commercial flights, perhaps because of adequate pressurization. However, cases of spontaneous pneumothorax during flight, due to bronchogenic cysts, have been described (17). As with diving, excessive expansion of trapped air due to a reduction in barometric pressure may lead to barotrauma. Patients with a pneumothorax should avoid air travel until complete resolution has been confirmed.

HIV infection
HIV infection is a recognized cause of secondary spontaneous pneumothorax. Pneumothorax may be an initial presenting symptom of a patient with AIDS. The risk of pneumothorax is increased in patients who have active or prior Pneumocystis carinii infection (figure 5), Kaposi sarcoma, or toxoplasmosis or are using prophylactic inhaled pentamidine isethionate (NebuPent, Pentacarinat, Pentam). The high incidence of spontaneous pneumothorax in these patients appears to be due to the presence of multiple subpleural lung cysts associated with subpleural necrosis (18,19).

Ipsilateral or contralateral recurrences are common, and treatment and prevention of recurrence are difficult. Long-term chest tube drainage or surgical repair is needed in most patients, because chemical pleurodesis is often less effective in these patients than in patients who do not have HIV infection.

Catamenial pneumothorax
This is a rare syndrome of recurrent pneumothorax in menstruating women. Eighty cases were found in a review of the literature from 1958 to 1995. Its pathogenesis is not fully established. Subpleural endometrial implants reaching the thorax via diaphragmatic defects are the most likely explanation (20).

Patients usually present with chest pain and shortness of breath in the first 24 to 48 hours of menstruation. Most of the time, the symptoms are on the right side, as is the pneumothorax, and concurrent symptoms of endometriosis may be present. No symptoms occur between menses. Radiographic features are indistinguishable from those of primary spontaneous pneumothorax. Treatment is aimed at the ectopic endometrium and can be achieved by ovulation suppression with oral contraceptives. Surgical intervention is rarely needed.

Pneumothorax ex vacuo
This is an uncommon condition that may occur secondary to acute bronchial obstruction. It is a result of a sudden increase in negative intrapleural pressure because of lobar collapse, which leads to air accumulation originating from blood and adjacent tissues (21). Relief of the bronchial obstruction is the treatment of choice, not insertion of a chest tube.

Familial spontaneous pneumothorax
Familial spontaneous pneumothorax is a rare condition and inherited in two modes: autosomal dominant and X-linked recessive with incomplete penetrance. Although an increased risk of recurrent pneumothorax has been found in one family with HLA haplotype A₂,B₄₀ and the alpha₁-antitrypsin phenotype M1M2 (22), this has been variable in other family studies (23,24).

Conclusion

Pneumothorax can occur in a variety of clinical settings. Categorizing a pneumothorax as primary or secondary, as well as determining its size, is a rational approach to treatment. Small primary spontaneous pneumothoraces often require no intervention, while a secondary spontaneous pneumothorax almost always requires drainage because of the high risk of complications for the patient.

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Dr Dincer, formerly a senior fellow, division of pulmonary and critical care medicine, Medical College of Wisconsin, Milwaukee, is now in the division of pulmonary, critical care, and sleep medicine, VA Southern Nevada Health Care System, Las Vegas. Dr Lipchik is professor of medicine, division of pulmonary and critical care medicine, Medical College of Wisconsin. Correspondence: Randolph J. Lipchik, MD, Division of Pulmonary and Critical Care Medicine, Medical College of Wisconsin, 9200 W Wisconsin Ave, Milwaukee, WI 53226.