Spontaneous pneumothorax occurs in persons who do not have clinically apparent lung disease. Two other types of pneumotharaxes are traumatic and iatrogenic. Secondary pneumothorax occurs as a complication of preexisting pulmonary disease (see the accompanying table). Sahn and Hefner recently reviewed the clinical condition of spontaneous pneumothorax.
The incidence of spontaneous pneumothorax is 7.4 to 18 cases per 100,000 population in men per year. In women, the reported incidence is 1.2 to six cases per 100,000 population per year. The typical patient is a tall, thin male between 10 and 30 years of age. The risk of pneumothorax is much greater in cigarette smokers—up to 20 times greater, depending on the number of cigarettes smoked daily.
Patients with spontaneous pneumothorax do not have clinically apparent lung disease. However, studies have found that 76 to 100 percent have subpleural bullae diagnosed by video-assisted thoracoscopic surgery. Studies using computed tomographic (CT) scanning have found that almost 90 percent of affected patients have ipsilateral bullae. The exact mechanism by which bullae formation occurs has not been determined.
Most patients who sustain a spontaneous pneumothorax do so at rest. They typically experience ipsilateral chest pain described as initially sharp and later becoming a steady ache. Dyspnea is often a common symptom. Even in the absence of treatment, symptoms often resolve within 24 hours.
The physical examination may be normal in patients with a small pneumothorax (less than 15 percent of the hemithorax). Tachycardia is the most common finding and, depending on the amount of lung involved, other physical findings include decreased chest wall movement, a hyperresonant percussion note, diminished fremitus and diminished or decreased breath sounds.
The initial treatment of spontaneous pneumothorax involves removing air from the subpleural space. For a small pneumothorax, supplemental oxygen rapidly accelerates the reabsorption of air by the pleura. Healthy young patients can be managed in this manner, usually being discharged from the emergency department after six hours of observation, if close follow-up can be assured. If the pneumothorax is more than 15 percent, aspiration of air with a plastic intravenous catheter, thoracentesis catheter, no. 7 to no. 14 French small-bore catheter or chest tube can be done. These techniques are usually successful in about 70 percent of patients. Discharge is appropriate if a follow-up chest radiograph beyond six hours shows resolution of the pneumothorax. In some cases, a chest tube can be left in for one or two days and can be attached to a one-way Heimlich valve or to a water-seal device allowing ambulation. The success rate in this scenario is usually 90 percent but decreases to about 50 percent or less in patients who sustain a recurrence.
Surgical intervention is rarely necessary in patients with primary pneumothorax and does not become a consideration unless the air leak persists for four to seven days. The appearance of bullae on CT scanning has not been correlated with the success of spontaneous resolution of air. The authors of this review feel the presence or absence of bullae should not be a sole criterion for surgical intervention.
The decision to use sclerosing agents such as talc to prevent recurrence must be individualized. Some centers recommend this procedure after a first episode. The authors recommend preventive interventions after a second ipsilateral pneumothorax. Age has been shown to be an independent risk factor for recurrence, with a declining incidence in persons older than 40 years. The instillation of talc (usually a 2-g dose) can be performed with video-assisted thoracoscopy or a limited thoracotomy. The former procedure is less invasive but carries a slightly higher failure rate, which may be institution-dependent.