eMedicine Specialties > Radiology > Chest

Pneumothorax

Author: Fahad M Alhameed, MD, AmBIM, FCCP, FRCPC, Deputy Chairman of Intensive Care Department, Consultant Critical Care and Pulmonary Medicine, Department of Intensive Care and Pulmonary Medicine, King Khalid National Guard Hospital, Jeddah, Saudi Arabia
Coauthor(s): Sat Sharma, MD, FRCPC, Professor and Head, Division of Pulmonary Medicine, Department of Internal Medicine, University of Manitoba; Site Director, Respiratory Medicine, St. Boniface General Hospital; Bruce Maycher, MD, Director of Pulmonary Radiology, St Boniface General Hospital; Associate Professor, Department of Radiology, University of Manitoba
Contributor Information and Disclosures

Updated: Dec 11, 2008

Introduction

Background

Pneumothorax is the presence of air within the pleural space; it is considered one of the most common forms of thoracic disease. It is classified as spontaneous (not caused by trauma), traumatic, or iatrogenic.^1,2,3

Spontaneous pneumothorax may be either primary (occurring in persons without clinically or radiologically apparent lung disease) or secondary (in which lung disease is present and apparent). Most individuals with primary spontaneous pneumothorax (PSP) have unrecognized lung disease; many observations suggest that spontaneous pneumothorax often results from rupture of a subpleural bleb.

Traumatic pneumothorax is caused by penetrating or blunt trauma to the chest, with air entering the pleural space directly through the chest wall, through visceral pleural penetration, or through alveolar rupture resulting from sudden compression of the chest.

Iatrogenic pneumothorax results from a complication of a diagnostic or therapeutic intervention.

Frequency

United States

In a study from Olmsted County, Minnesota, reported by Melton et al, 318 patients developed pneumothorax from 1950–1974.⁴ The age-adjusted incidence of PSP was 7.4/100,000/y in men and 1.2/100,000/y in women (the male-to-female ratio was 6.2:1). The incidence of secondary spontaneous pneumothorax (SSP) was 6.3/100,000/y in men and 2/100,000/y in women (the male-to-female ratio was 3.2:1).

International

The worldwide frequency of pneumothorax is not known. In Stockholm, in one of the largest epidemiologic studies performed (reported by Bense et al⁵ ), the annual incidence of PSP in 15,204 individuals was somewhat higher than in the Minnesota study: 18 per 100,000 men and 6 per 100,000 women.

Mortality/Morbidity

Secondary spontaneous pneumothorax is associated with a higher mortality and morbidity than PSP. Patients with HIV with pneumothorax and Pneumocystis carinii pneumonia may have in-hospital mortality rates exceeding 25%, with a median survival rate of 3 months.

Pneumothorax is associated with the following complications:

• In most reported series, the rate of recurrence of spontaneous pneumothorax on the same side is as much as 30%; on the contralateral side, the rate of recurrence is approximately 10%.
• Reexpansion pulmonary edema may occur.
• Tension pneumothorax may occur after spontaneous pneumothorax but is more common after traumatic pneumothorax or with mechanical ventilation.
• Bronchopleural fistula occurs in 3 – 5% of patients.
• Pneumomediastinum and pneumopericardium may develop (see Images below and Images 7-8 in Multimedia).

Race

From limited data, primary spontaneous pneumothorax appears to be more common among Scandinavians, although the reasons for this are unknown.

Sex

The male-to-female ratio of primary spontaneous pneumothorax averages 4 – 5:1. This ratio may vary depending on where the study is done. The male-to-female ratio of secondary spontaneous pneumothorax averages 2 – 3:1.

Age

Primary spontaneous pneumothorax typically occurs in tall, thin males 10 – 30 years of age. PSP rarely occurs in persons older than 40 years.

Secondary spontaneous pneumothorax typically occurs later in life (60 – 65 years), when the incidence of chronic lung disease in the general population increases.

Presentation

Presentation and natural history

In primary spontaneous pneumothorax, subpleural bullae are found in 76-100% of patients during video-assisted thoracoscopic surgery and in virtually all patients during thoracotomy. CT of the chest reveals ipsilateral bullae in 89% of patients with PSP, compared to 20% of control subjects matched for age and smoking status, as reported by Mitlehner et al and Lesur et al.^6,7

In many patients, the pathogenesis of subpleural bullae and PSP is probably related to airway inflammation resulting at least in part from cigarette smoking; however, the exact mechanism of bulla formation remains unclear.

Cigarette smoking increases the risk of PSP in men in a dose-dependent manner. In men who smoke, compared with men who do not smoke, the relative risk of a pneumothorax is 7 times higher in light smokers (1-12 cigarettes per day), 21 times higher in moderate smokers (13-22 cigarettes per day), and up to 102 times higher in heavy smokers (>22 cigarette per day). In women, the relative risk is 4, 14, and 68 times higher in light, moderate, and heavy smokers, respectively.

Familial cases have been reported. Two modes of inheritance have been suggested, including (1) an autosomal dominant gene with incomplete penetrance (50% in males; approximately 20% in females) and (2) more than 1 gene, with some cases inherited as an X-linked recessive disorder and others as an autosomal dominant trait with incomplete penetrance, according to Abolnik et al.⁸

• Spontaneous pneumothorax
  • Primary
  • Secondary
• Traumatic pneumothorax
  • Resulting from direct (blunt) chest trauma
  • Resulting from penetrating chest trauma
• Iatrogenic pneumothorax
  • Resulting from biopsy procedure
  • Resulting from therapeutic procedures
• Catamenial pneumothorax
• Pneumothorax in AIDS

Primary spontaneous pneumothorax

Most episodes (90%) of PSP occur while the patient is at rest. Chest pain and dyspnea, either alone or in combination, are the classic symptoms of spontaneous pneumothorax; pain was the sole complaint of 69% of 72 patients in 1 series reported by Lindskog and Halasz.⁹ Chest pain may be minimal or severe; it is usually sharp and pleuritic. Symptoms usually resolve within 24 hours, even if the pneumothorax remains untreated and does not resolve.

The primary physical sign of pneumothorax is a decrease or absence of breath sounds despite normal or increased resonance on percussion. However, this may be difficult to detect, particularly in patients with a small pneumothorax or in those who have underlying emphysema. In patients with a small pneumothorax (involving <15% of hemithorax), the physical examination may be normal. Tachycardia is the most common physical finding.

A large pneumothorax may be associated with decreased movement of the chest wall, a hyperresonant percussion note, diminished tactile focal fremitus and resonance, and decreased or absent breath sounds on the affected side. Hemodynamic instability, which is indicated by tachycardia, hypotension, and cyanosis, suggests tension pneumothorax. Arterial blood gas may reveal acute respiratory alkalosis and an increased alveolar-arterial oxygen gradient.

Unusual clinical manifestations of pneumothorax include ptosis (which occurs as a result of extension of subcutaneous emphysema), pneumocephalus (secondary to tension pneumothorax associated with a comminuted fracture of the thoracic spine), and recurrent pneumopericardium (in association with pleuropericardial defect).

Secondary spontaneous pneumothorax

Because of impaired pulmonary reserve, SSP results in more severe dyspnea than that occurring in PSP. Typically, chest pain is less common but more severe than in PSP. Life-threatening hypoxemia or hypotension occurs in 15% of patients. Symptoms of SSP do not resolve spontaneously. Suspicion for pneumothorax should remain heightened in patients with chronic obstructive pulmonary disease (COPD) who develop dyspnea and unilateral chest pain.

Physical findings often are subtle and may be masked by underlying lung disease, particularly in patients with COPD.¹⁰ Hypercapnia often occurs, with the partial pressure of arterial carbon dioxide often exceeding 50 mm Hg. Significant hypoxemia is common.

SSP is caused by the following:

• Diseases of the airways: COPD, cystic fibrosis, and status asthmaticus
• Interstitial lung diseases: Langerhans cell histiocytosis, sarcoidosis, lymphangioleiomyomatosis, tuberous sclerosis, rheumatoid disease, idiopathic pulmonary fibrosis, and radiation fibrosis
• Infectious diseases: Necrotizing gram-negative pneumonia, anaerobic pneumonia, staphylococcal pneumonia, AIDS with P jiroveci pneumonia, and Mycobacterium tuberculosis
• Malignancies: Sarcoma, lung cancer
• Pneumoconiosis: Silicoproteinosis, berylliosis, and bauxite pneumoconiosis
• Connective tissue diseases
• Wegener granulomatosis
• Drugs and toxins
• Chemotherapy for malignancy
• Paraquat poisoning
• Hyperbaric oxygen therapy
• Radiation therapy
• Aerosolized pentamidine therapy in patients with AIDS

The above conditions (particularly AIDS, COPD, Langerhans cell granulomatosis, and lymphangioleiomyomatosis) may lead to unilateral or bilateral pneumothorax.

Traumatic pneumothorax

Trauma probably is the most common cause of pneumothorax. Traumatic pneumothorax may be caused by direct communication of the pleural space with the atmosphere through chest wall puncture or by disruption of the proximal tracheobronchial tree or the visceral pleura, as occurs in blunt chest trauma.

Iatrogenic pneumothorax

With the increasing use of invasive diagnostic procedures, iatrogenic pneumothorax likely will become more common, although most cases are of little clinical significance. In a review of 106 cases by Despars et al, 35 cases (33%) were related to transthoracic needle aspiration biopsy, 30 cases (28%) to thoracentesis, 23 cases (22%) to subclavian vein catheterization, 7 cases (7%) to positive-pressure ventilation, and 11 cases (10%) to miscellaneous causes (see Images below and Images 5-6 in Multimedia).¹¹ In 2 of the 106 patients, the pneumothorax was fatal.

Catamenial pneumothorax

Catamenial pneumothorax refers to the development of pneumothorax at the time of menstruation. Catamenial pneumothorax represents 3–6% of cases of spontaneous pneumothorax in women. Typically, it occurs in women 30–40 years of age who have a history of pelvic endometriosis (20–40%). It usually affects the right lung (90–95%) and occurs within 72 hours after the onset of menses. The recurrence rate in women receiving hormone treatment is 50% at 1 year.

Pneumothorax in AIDS

Spontaneous pneumothorax develops in 2–6% of HIV-infected patients; it is associated with P jiroveci pneumonia in 80% of those patients. Pneumothorax is associated with a high mortality in patients with HIV infection with P jiroveci pneumonia. In-hospital mortality exceeds 25%; median survival is approximately 3 months. Pathogenesis of the pneumothorax in this setting is the rupture of large subpleural cysts, which are associated with subpleural necrosis. Recurrent ipsilateral or contralateral pneumothorax also is common.^12,13

Valsalva maneuver and pneumothorax

The Valsalva maneuver is a common cause of pneumomediastinum and pneumothorax. This may occur during emesis, during coughing, and, perhaps most commonly, during pregnancy and labor. Smoking of marijuana and cocaine, possibly associated with the use of a prolonged Valsalva maneuver to augment the "high," also has been associated with these complications in drug users. However, a more frequent mechanism for the production of pneumothorax in addicts is needle puncture while mainlining into neck veins.

Treatment

Current available therapeutic interventions include simple observation, simple aspiration with a catheter, insertion of a chest tube, pleurodesis, video-assisted thoracoscopic surgery, and thoracotomy.^{3,14,15,16,17,18,19,20}

Selection of the interventional approach depends on the size of the pneumothorax, the severity of symptoms, whether a persistent air leak is present, and whether the pneumothorax is primary or secondary.

If a primary spontaneous pneumothorax is small (involving <15% of hemithorax) and the patient has minimal symptoms, high-flow supplemental oxygen will accelerate reabsorption of air by the pleura.

Primary spontaneous pneumothoraces that are large (involving >15–20% of hemithorax) or progressive may be drained by simple aspiration with a plastic intravenous catheter, thoracentesis catheter, or small-bore (7–14F) catheter or by the insertion of a chest tube.

Percutaneous drainage of pneumothorax (simple aspiration) is successful in 65–70% of patients with moderate-sized primary spontaneous pneumothorax and in only approximately 35% of patients with secondary spontaneous pneumothorax. In a randomized study comparing needle aspiration with tube thoracostomy, there was a higher immediate recurrence rate with needle aspiration, although approximately 66% of patients experienced resolution of their pneumothorax.¹⁸ The recurrence rates at 3 months were similar to those for patients treated initially with tube thoracostomy.

The procedure consists of insertion of a 10–18F plastic catheter under local analgesia using sterile technique. The recommended point of insertion is the second anterior intercostal space in the midclavicular line. The catheter is connected to a 3-way stopcock and a large-volume syringe. Aspiration is performed until no further gas can be withdrawn. The catheter is then connected to a Heimlich valve. Follow-up chest radiographs are performed; if residual pneumothorax is present after 12 hours, the catheter may be attached to wall suction or underwater seal. If these maneuvers do not succeed, a tube thoracostomy should be performed.

Preferred Examination

Chest radiography is the first investigation performed to assess pneumothorax because it is simple, inexpensive, rapid, and noninvasive; however, it is much less sensitive than chest CT in detecting a small pneumothorax, blebs, and bullae.^{6,7,10,21,22,23,24}

In erect patients, pleural gas collects over the apex, and the space between the lung and chest wall is most notable at that point. In the supine position, the juxtacardiac area, the lateral chest wall, and the subpulmonic region are the best areas to search for evidence of pneumothorax.

When a pneumothorax is suspected but is not definitively observed on an inspiratory film, an expiratory film may be helpful. At end expiration, the constant volume of the pneumothorax gas is accentuated by the reduction of the hemithorax, and the pneumothorax is recognized more easily. Similar accentuation may be obtained with lateral decubitus studies of the appropriate side (for a possible left pneumothorax, a right lateral decubitus film of the chest should be obtained, with the beam centered over the left lung).

Limitations of Techniques

CT of the chest reveals ipsilateral bullae in 89% of patients with primary spontaneous pneumothorax, as compared with 20% of control subjects matched for age and smoking status. In PSP, subpleural bullae are found in 76 – 100% of patients during video-assisted thoracoscopic surgery and in virtually all patients during thoracotomy.

Differential Diagnoses

[Lung, Trauma]
Abdominal Aortic Aneurysm, Rupture
Emphysema
Myocardial Infarct, Acute

Other Problems to Be Considered

Factors that may mimic pneumothorax (eg, skin fold, clothing, tubing, chest wall artifact, localized bulla, emphysema)

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