The most likely diagnosis with this history is spontaneous pneumothorax. The differential diagnosis at this point includes pulmonary embolus, acute bronchospasm, myocardial infarction, and less probably, dissecting aortic aneurysm.

The workup on admission should consist of a complete blood count, electrolytes, blood urea nitrogen and creatinine levels, cardiac enzymes, a chest radiograph, and an electrocardiogram (ECG).

The chest radiograph confirms the diagnosis suggested by the history and physical examination. A 3-cm pneumothorax in a symptomatic patient necessitates drainage. Supplemental oxygen should be administered to maintain an oxygen saturation above 92%, and a peripheral intravenous line should be started. Information about Mr. Robinson’s arterial blood gases is not useful at this point because it does not add any pertinent information and only delays the necessary procedure.

This is a secondary spontaneous pneumothorax because it occurs in a patient who probably has an underlying pulmonary disorder: chronic obstructive pulmonary disease (COPD). Primary spontaneous (or idiopathic) pneumothoraces occur in young, healthy persons with no underlying pulmonary disease. The general classification of pneumothoraces is given in Table 27.1.

Primary spontaneous pneumothoraces occur with an incidence of 6 to 7 per 100,000 men and 1 to 2 per 100,000 women in North America (1). The rupture of a small subpleural bleb within the visceral pleura allows air to escape into the pleural cavity, where it accumulates and collapses the lung. These pneumothoraces are most prevalent in young adults; 85% of patients are younger than 40 years of age. Typically, the patient is a tall, slim 20- to 25-year-old man with a smoking history. Without definite therapy, the recurrence rate is high, estimated at 25% after a first episode, 40% to 50% after a second episode, and more than 60% after a third episode (2,3).

The formation of subpleural blebs results from the rupture of apical alveoli. The gradient between the intrabronchial and intrapleural pressures is greater at the lung apices, creating more tension on the walls of the apical alveoli, which leads to their overexpansion and eventual rupture. Once the alveolus ruptures, gas escapes and dissects peripherally along the lobular septa and collects as blebs beneath the visceral pleura. These blebs are generally found at the lung apex, in the superior segment of the lower lobes, and along the fissures. By definition, they are smaller than 2 cm in diameter.

A pneumothorax causes a reduction in pulmonary volumes, lung compliance, and diffusing capacity. Blood shunting through a lung that is poorly ventilated creates a ventilation/perfusion (/) mismatch, and hypoxemia results.

Secondary spontaneous pneumothoraces accompany underlying pulmonary disease. They account for only 20% of spontaneous pneumothoraces overall (80% are primary or idiopathic) and most often are associated with COPD. The mean age of patients is older than 50 years, and as pulmonary functions are compromised, they are more commonly symptomatic (4).

Other pulmonary disorders include cystic fibrosis, bullous disease, interstitial diseases (e.g., idiopathic pulmonary fibrosis, sarcoidosis, eosinophilic granuloma), and infectious processes (e.g., pneumonia, tuberculosis, abscesses). Neoplasms, whether primary or metastatic, also may cause a pneumothorax, but this is rare.

The size of a chest tube depends on what type of substance is being drained from the pleural cavity. Generally, a size 20-French chest tube is sufficient for pneumothorax. When draining blood, pus, or thick fluid, a large-bore tube (size 28 to 36 French) is recommended. The chest tube for a pneumothorax is inserted in the fifth intercostal space on the midaxillary or anterior axillary line, and it is directed toward the apex of the pleural cavity. A chest tube for an apical pneumothorax also may be inserted through the anterior chest wall in the second intercostal space on the midclavicular line. A pleural effusion is drained with a chest tube in the fifth or sixth intercostal space directed posteriorly and inferiorly (5).

Suction on a chest tube is used to ensure optimal drainage of the pleural cavity. Suction is required for pneumothorax when chest radiograph does not show the lung to be completely expanded after tube thoracostomy or if there is a large air leak. Once the lung is completely expanded, suction should be reduced to a minimum or stopped to help seal the air leak.

All patients with a symptomatic pneumothorax need drainage. Some patients who meet specific criteria may be treated with observation alone. These criteria include no symptoms, a pneumothorax less than 20% or 2 cm, and a young and reliable patient (i.e., primary spontaneous pneumothorax). Patients with secondary pneumothorax have much less pulmonary reserve and thus are at higher risk for complications or even death if the pneumothorax progresses rapidly. Conservative management is possible in 15% to 20% of patients overall (2,6).

The rate of resorption of air from the pleural cavity is estimated to be 1.25% of the volume of the pneumothorax per 24 hours (50 to 70 mL per day) or the equivalent of 1 mm a day. A 2-cm pneumothorax takes up to 3 weeks to resolve completely.

A spontaneous pneumothorax may be drained by simple needle aspiration using a 16- to 18-gauge needle catheter and a three-way stopcock. However, this procedure is associated with a 50% to 70% failure rate and thus is rarely used (4). Drainage of the pleural space may be obtained with any of a variety of small-caliber catheters (10 to 16 French) to which suction usually can be applied. Although less traumatic on insertion and more comfortable for the patients, these small-bore tubes easily become clogged with fibrin and blood clots. Conventional tube drainage with a 20- to 24-French chest tube remains the gold standard because it is safe, effective, and reproducible and is associated with an 80% to 90% success rate in the management of spontaneous pneumothorax (7).

The Heimlich valve is a one-way flutter valve that is connected to the end of a chest tube, eliminating the need for an underwater seal drainage bottle or suction. The valve is designed to let air out of the pleural cavity in the presence of an air leak (8). The valve is ideally suited for outpatient management of uncomplicated spontaneous pneumothorax and for persistent air leaks. It is recommended only for patients whose lungs are fully reexpanded and for reliable patients with adequate pulmonary function. Regular chest radiographs and follow-up are necessary. The chest tube is removed once the air leak has resolved.

Complications include pleural effusion (15%), persistent air leak (10%), tension pneumothorax (5%), hemothorax (3%), pneumomediastinum (2%), and empyema (less than 1%).

When a pneumothorax occurs suddenly, adhesions between the parietal and visceral pleura may tear as the lung collapses. These adhesions may contain blood vessels, so when they are torn, bleeding results. Avulsion of a subclavian vein also has been reported in association with a spontaneous pneumothorax. When the hemorrhage is massive or continuous, an exploratory thoracotomy is indicated.

The patient’s spontaneous pneumothorax is managed the same as the first episode. At this point, surgical therapy must be considered.

Some occupations carry an inherent risk of pneumothorax. Airline pilots and scuba divers are managed more aggressively, and surgery is considered after a first episode. Patients who live far from medical centers also are managed surgically after an initial episode of spontaneous pneumothorax (4).

The foremost objective of surgery for spontaneous pneumothorax is preventing recurrences. Other objectives include ensuring complete expansion of the lung, treating complications, and managing bronchopleural fistulas.