You are in: eMedicine Specialties > Radiology > CHEST PneumothoraxArticle Last Updated: Sep 18, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 8
  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 Fahad M Alhameed is a member of the following medical societies: American College of Chest Physicians, American Thoracic Society, Canadian Medical Association, and Royal College of Physicians and Surgeons of Canada Coauthor(s): Sat Sharma, MD, FRCP(C), FCCP, FACP, DABSM, Program Director, Associate Professor, Department of Internal Medicine, Divisions of Pulmonary and Critical Care Medicine, University of Manitoba; Site Director of 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; Sean Tsuyuki, MD, Assistant Professor, Department of Radiology, University of Manitoba at Winnipeg, St Boniface Hospital Editors: Satinder P Singh, MD, Associate Professor of Radiology, Director of Cardiac CT, Director of Combined Cardiopulmonary and Abdominal Radiology, Department of Radiology, University of Alabama at Birmingham; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; W Richard Webb, MD, Chief of Thoracic Imaging, Professor, Department of Radiology, University of California at San Francisco; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Consulting Staff, Department of Radiology, Virginia Mason Medical Center Author and Editor Disclosure Synonyms and related keywords: spontaneous pneumothorax, primary spontaneous pneumothorax, secondary spontaneous pneumothorax, traumatic pneumothorax, iatrogenic pneumothorax, pneumomediastinum, catamenial pneumothorax, pneumothorax in AIDS INTRODUCTIONSection 2 of 8
  BackgroundPneumothorax is the presence of air within the pleural space and is considered one of the most common forms of thoracic disease. It is classified as spontaneous (not caused by trauma), traumatic, or iatrogenic. Spontaneous pneumothorax can 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, since 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. PathophysiologyIn PSP, 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.1, 2 The pathogenesis of subpleural bullae and PSP is probably related to airway inflammation resulting at least in part from cigarette smoking in many patients; 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.3 FrequencyUnited StatesIn a study based in Olmsted County, Minnesota, and reported by Melton et al,4 318 patients developed pneumothorax from 1950-1974. The age-adjusted incidence of PSP in men was 7.4/100,000/y and in women 1.2/100,000/y (male-to-female ratio was 6.2:1). The incidence of secondary spontaneous pneumothorax (SSP) in men was 6.3/100,000/y and in women 2/100,000/y (male-to-female ratio was 3.2:1). InternationalWorldwide 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/MorbiditySSP 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:
RaceFrom limited data, PSP appears to be more common in the Scandinavian population, although reasons for this are unknown. SexMale-to-female ratio of PSP averages 4-5:1. This ratio may vary depending on where the study is done. The male-to-female ratio of SSP averages 2-3:1. AgePSP typically occurs in tall, thin males aged 10-30 years. PSP rarely occurs in persons older than 40 years. SSP typically occurs later in life (60-65 years) when the peak incidence of chronic lung disease increases in the general population. Clinical DetailsPneumothorax is classified into the following categories:
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.6 Chest pain may be minimal or severe and usually is 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. Patients with a small pneumothorax (involving <15% of hemithorax) may have a normal physical examination. Tachycardia is the most common physical finding. A large pneumothorax can cause 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 (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. 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:
The above conditions (particularly AIDS, COPD, Langerhans cell granulomatosis, and lymphangioleiomyomatosis) can lead to unilateral or bilateral pneumothorax. Traumatic pneumothorax Trauma probably is the most common cause of pneumothorax. Traumatic pneumothorax can 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,7 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 5-6). In 2 of the 106 patients, the pneumothorax was fatal. The incidence of iatrogenic pneumothorax in mechanically ventilated patients has been estimated at 0.5-15%, depending on the duration of ventilation and the nature of the underlying disease. Alveolar rupture more likely occurs when peak inspiratory pressure is high. 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 aged 30-40 years with 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 and is associated with P carinii pneumonia in 80% of those patients. Pneumothorax is associated with a high mortality in patients with HIV infection with P carinii pneumonia. In-hospital mortality exceeds 25%, and 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. Valsalva maneuver and pneumothorax The Valsalva maneuver is a common etiology of pneumomediastinum and pneumothorax. This can 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. Preferred ExaminationChest radiograph 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. 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 suggested pneumothorax 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 can 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 TechniquesCT of the chest reveals ipsilateral bullae in 89% of patients with PSP, as compared to 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. DIFFERENTIALSSection 3 of 8
[Lung, Trauma] Abdominal Aortic Aneurysm, Rupture Emphysema Myocardial Infarct, Acute Other Problems to Be ConsideredFactors that may mimic pneumothorax (eg, skin fold, clothing, tubing, chest wall artifact, localized bulla, emphysema) RADIOGRAPHSection 4 of 8
FindingsThe diagnosis of pneumothorax is established by demonstrating the outer margin of the visceral pleura (and lung), known as the pleural line, separated from the parietal pleura (and chest wall) by a lucent gas space devoid of pulmonary vessels (see Image 2). The pleural line may be difficult to detect with a small pneumothorax unless high-quality posteroanterior and lateral chest films are obtained and viewed under a bright light. A skin fold may mimic the pleural line, but usually, the patient is asymptomatic (see Image 3). In erect patients, pleural gas collects over the apex, and the space between the lung and chest wall is most notable at that point (see Image 1). 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 (see Image 4). The presence of a deep costophrenic angle on a supine film may be the only sign of pneumothorax; this has been termed the deep sulcus sign. When a suggested pneumothorax 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 can 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). The most common radiographic manifestations of tension pneumothorax are mediastinal shift, diaphragmatic depression, and rib cage expansion (see Image 5). Any significant degree of displacement of the mediastinum from the midline position on maximum inspiration, as well as any depression of the diaphragm, should be taken as evidence of tension (see Image 6), although a definite diagnosis of tension pneumothorax is difficult to make on the basis of radiographic findings. The degree of lung collapse is an unreliable sign of tension, since underlying lung disease may prevent collapse even in the presence of tension. Pleural effusions occur coincident with pneumothorax in 20-25% of patients, but they usually are quite small. Hemopneumothorax occurs in 2-3% of patients with spontaneous pneumothorax. Bleeding is believed to represent rupture or tearing of vascular adhesions between the visceral and parietal pleura as the lung collapses. False Positives/NegativesDifferentiating the pleural line of a pneumothorax from that of a skin fold, clothing, tubing, or chest wall artifact is important. Careful inspection of the film may reveal that the artifact extends beyond the thorax or that lung markings are visible beyond the apparent pleural line. In the absence of underlying lung disease, the pleural line of a pneumothorax usually parallels the shape of the chest wall (see Images 2-3). Artifactual densities usually do not parallel the course of the chest wall over their entire length. Avascular bullae or thin-walled cysts can be mistaken for a pneumothorax. The pleural line caused by a pneumothorax usually is bowed at the center toward the lateral chest wall. Unlike in pneumothorax, the inner margins of bullae or cysts usually are concave rather than convex and do not conform exactly to the contours of the costophrenic sulcus. A pneumothorax with a pleural adhesion also may simulate bullae or lung cysts. CT SCANSection 5 of 8
FindingsCT of the chest is used with increasing frequency in patients with pneumothorax. CT may be necessary to diagnose pneumothorax in critically ill patients in whom upright or decubitus films are not possible. CT may prove helpful in predicting the rate of recurrence in patients with spontaneous pneumothorax. One study by Warner et al demonstrated that patients with larger or more numerous blebs demonstrated on thoracic CT are more likely to experience recurrences.8 CT demonstrates focal areas of emphysema in more than 80% of patients with spontaneous pneumothorax, even in lifelong nonsmokers. These areas are situated predominantly in the peripheral regions of the apex of the upper lobes. In patients in whom emphysema is not apparent on CT, it often is evident at surgery or on pathologic examination. In one study by Jordan et al, in 116 consecutive patients who had undergone thoracotomy for recurrent or persistent PSP or SSP, emphysema with bulla formation was identified histologically in 93 patients (80%), emphysema without bulla formation in 13 patients (11%), isolated bullae in 2 patients (1.7%), blebs in 2 patients (1.7%), and other pulmonary or pleural abnormalities in 6 patients (5%).9 In another study, by Mitlehner et al, localized emphysema with or without bulla formation was identified on CT in 31 of 35 patients (89%) and on radiographs in 15 of 35 patients (43%). Abnormal findings were observed in the lung ipsilateral to the pneumothorax on 28 of 35 CTs (80%) and on 11 of 35 chest radiographs (31%) and were observed in the contralateral lung on 23 of 35 CTs (66%) and on 4 of 35 chest radiographs (11%). In most patients, the abnormal findings consisted of a few localized areas of emphysema (n <5) measuring less than 2 cm in diameter.1 The mechanism of cyst or bulla rupture in SSP probably also is multifactorial. Local airway obstruction caused by pneumonia, mucous plugs, or bronchoconstriction may be important. In a retrospective study by Wait and Estrera of 120 patients with spontaneous pneumothorax admitted from 1983-1991 to Parkland Memorial Hospital in Dallas, 31 patients (26%) had localized areas of emphysema, bullae, or blebs; 12 patients (10%) had COPD; 32 patients (27%) had AIDS; and 45 patients (37%) had other underlying lung diseases. Of those with AIDS, 25 patients (78%) had P carinii pneumonia, and the remaining 7 patients (22%) were infected with M tuberculosis or nontuberculous mycobacteria.10 INTERVENTIONSection 6 of 8
Current available therapeutic interventions include simple observation, simple aspiration with a catheter, insertion of a chest tube, pleurodesis, video-assisted thoracoscopic surgery, and thoracotomy. 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 the primary spontaneous pneumothorax is small (involving <15% of hemithorax) and patients have 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 of needle aspiration versus tube thoracostomy, there was a higher immediate recurrence rate with the needle aspiration, although approximately 66% of patients experienced resolution of their pneumothorax. The recurrence rates at 3 months were similar to those for patients treated initially with tube thoracostomy.11 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 can be attached to wall suction or underwater seal. If these maneuvers do not succeed, a tube thoracostomy should be performed. Medical/Legal Pitfalls
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REFERENCESSection 8 of 8
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