eMedicine Specialties > Emergency Medicine > Pulmonary

Pneumothorax, Iatrogenic, Spontaneous and Pneumomediastinum

Author: Andrew K Chang, MD, Associate Professor, Department of Emergency Medicine, Albert Einstein College of Medicine, Montefiore Medical Center
Coauthor(s): Pinaki Mukherji, MD, Assistant Professor, Attending Physician, Department of Emergency Medicine, Montefiore Medical Center
Contributor Information and Disclosures

Updated: Jul 7, 2009

Introduction

Background

Pneumothorax is air in the potential space between the visceral and parietal pleura of the lung. Air can enter the intrapleural space through a communication from the chest wall or through the lung parenchyma across the visceral pleura.  

Pneumothoraces secondary to trauma are relatively straightforward and usually require tube thoracostomy. Spontaneous pneumothorax, however, is a commonly encountered problem with approaches to treatment that can vary from observation to aggressive intervention. This article focuses on differentiating primary spontaneous (no obvious underlying lung disease), secondary spontaneous (underlying lung disease), and iatrogenic pneumothoraces (which are traumatic but typically are smaller and more easily managed). In addition, pneumomediastinum (free air in the mediastinal structures) is discussed.

Classification

Primary spontaneous pneumothorax

• Air in the intrapleural space without preceding trauma and without underlying clinical or radiologic evidence of lung disease
• Typically in patients who are between 18 and 40 years of age

Secondary spontaneous pneumothorax

• Occurs in patients with underlying pulmonary structural pathology
• Air enters the pleural space via distended, damaged, or compromised alveoli
• May present with more serious clinical symptoms and sequelae due to comorbidity

Iatrogenic pneumothorax

• Medical procedure resulting in traumatic pneumothorax (usually from a small-bore hollow needle)

Pneumomediastinum

• Gas in the mediastinal structures occurs spontaneously or following procedures or trauma
• Pneumothorax may occur secondary to pneumomediastinum

Pathophysiology

Spontaneous pneumothoraces in most patients occur from the rupture of blebs and bullae. While primary pneumothorax is defined as a lack of underlying pulmonary disease, these patients have blebs and bullae detected on CT scans or upon thoracotomy. These may be due to congenital abnormalities or increased shear forces at the apex of the lung. Until a bleb ruptures and causes a pneumothorax, no clinical signs or symptoms are present. 

The pleural space has a negative pressure, with the chest wall tending to spring outward and the lung's elastic recoil tending to collapse. If the pleural space is invaded by gas from a ruptured bleb, the lung collapses until equilibrium is achieved or the rupture is sealed. As the pneumothorax enlarges, the lung becomes smaller.

The main physiologic consequence of this process is a decrease in the vital capacity and a decrease in the partial pressure of oxygen. Young and otherwise healthy patients can tolerate these changes fairly well, with minimal changes in vital signs and symptoms, but those with underlying lung disease may have respiratory distress.

With pneumomediastinum, excessive intra-alveolar pressures lead to rupture of perivascular alveoli. Air escapes into the surrounding connective tissue, with subsequent dissection into the mediastinum. Esophageal trauma or elevated pressures may also allow air to dissect into the mediastinum. Air may then dissect superiorly into the visceral, retropharyngeal, and subcutaneous spaces of the neck. From the neck, the subcutaneous compartment is continuous throughout the body; thus, air can diffuse widely. Mediastinal air can also pass inferiorly into the retroperitoneum and other extraperitoneal compartments. If the mediastinal pressure rises abruptly or if decompression is not sufficient, the mediastinal parietal pleura may rupture and cause a pneumothorax (in 10-18% of patients).

Frequency

United States

Incidence of primary spontaneous pneumothorax (age-adjusted) is 7.4-18 cases per 100,000 persons per year for men and 1.2-6 cases per 100,000 persons per year for women. Incidence of secondary spontaneous pneumothorax (age-adjusted) is 6.3 cases per 100,000 persons per year for men and 2 cases per 100,000 persons per year for women. Chronic obstructive pulmonary disease (COPD) is a common cause of secondary spontaneous pneumothorax that carries an incidence of 26 cases per 100,000 persons. It is likely that the incidence for spontaneous pneumothorax is underestimated. Up to 10% of patients may be asymptomatic, and others with mild symptoms may not present to a medical provider. 

The incidence of iatrogenic pneumothorax is not known, but it probably occurs more often than primary and secondary spontaneous pneumothoraces combined. Pneumomediastinum occurs in approximately 1 case per 10,000 hospital admissions.

Mortality/Morbidity

• Although some view primary spontaneous pneumothorax as more of a nuisance than a major health threat, deaths have been reported. Secondary spontaneous pneumothoraces can be life threatening, depending on the severity of the underlying disease and the size of the pneumothorax. Compared with similar patients without pneumothorax, age-matched patients with COPD have a 3.5-fold increase in relative mortality when a spontaneous pneumothorax occurs. Mortality percentages in patients with COPD and spontaneous pneumothorax vary from 1-17%.
• Iatrogenic pneumothorax may cause substantial morbidity and, rarely, death.
• Pneumomediastinum is generally a benign, self-limited condition. Malignant pneumomediastinum (unvented mediastinal or pulmonary adventitial air causing pressure so high that circulatory or ventilatory failure occurs) was described in 1944; all patients in this report had serious comorbid conditions. No reports of fatal outcomes in patients with spontaneous pneumomediastinum in the absence of underlying disease exist in the recent literature. The mortality rate is as high as 70% in patients with pneumomediastinum secondary to Boerhaave syndrome, even with surgical intervention.

Sex

• Incidence is higher in men than in women, at a ratio of 6.2:1 for primary pneumothorax and 3.2:1 for secondary pneumothorax.
• A slight predominance exists for males with pneumomediastinum.

Age

• Primary spontaneous pneumothorax occurs most often in persons early in the third decade of life and rarely occurs in persons older than 40 years.
• Secondary spontaneous pneumothoraces occur more frequently after age 60 years.
• Spontaneous pneumomediastinum generally occurs in young, healthy patients without serious underlying pulmonary disease, mostly in the second to fourth decades of life.

Clinical

History

Acute onset of chest pain, often pleuritic and associated with shortness of breath, is typical. Both of these symptoms occur in 64-85% of patients. Chest pain in primary spontaneous pneumothorax often improves over the first 24 hours, even without resolution of the underlying air accumulation. Well-tolerated primary pneumothorax can take 12 weeks to resolve. In secondary pneumothorax, chest pain is more likely to persist with more significant clinical symptoms. 

Despite descriptions of Valsalva maneuvers and increased intrathoracic pressures as inciting factors, spontaneous pneumothorax usually develops at rest. This must be differentiated from pneumomediastinum (see below). Many affected individuals do not seek medical attention for days after symptoms develop. This trend is important, because the incidence of reexpansion pulmonary edema increases in patients whose chest tubes have been placed 3 or more days after the pneumothorax occurred.

Smoking increases the risk of a first spontaneous pneumothorax by more than 20-fold in men and by nearly 10-fold in women compared with risks in nonsmokers.¹  Increased risk of pneumothorax and recurrence appears to rise proportionally with number of cigarettes smoked.

The most common underlying abnormality in secondary spontaneous pneumothorax is COPD. Cystic fibrosis carries one of the highest associations, with more than 20% reporting spontaneous pneumothorax.

A history of previous pneumothorax is important, as recurrence is common, with rates reported between 15 and 40%. Up to 15% of recurrences can be on the contralateral side. Secondary pneumothoraces are often more likely to recur, with cystic fibrosis carrying the highest recurrence rates at 68-90%. No study has shown that the number or size of blebs and bullae found in the lung can be used to predict recurrence.

Pneumomediastinum usually occurs when intrathoracic pressures become elevated. This elevation may occur with an exacerbation of asthma, coughing, vomiting, childbirth, seizures, and a Valsalva maneuver. In many patients who present with pneumomediastinum, it occurs as a result of endoscopy and small esophageal perforation.

Symptoms of primary and secondary spontaneous pneumothorax, iatrogenic pneumothorax, and pneumomediastinum may include the following:

• Spontaneous pneumothorax
  • Chest pain (acute onset, ipsilateral)
  • Dyspnea (in secondary cases may be disproportionate to the size of the pneumothorax)
  • Cough
  • Generalized malaise (In one old series, 3% of patients had generalized malaise, while 6.5% were asymptomatic.) 
• Iatrogenic pneumothorax: Symptoms are similar to those of a spontaneous pneumothorax and, depend on the age of the patient, presence of underlying lung disease, and extent of the pneumothorax.
• Pneumomediastinum: Patients may or may not have symptoms, as this is typically a well-tolerated disease, although mortality in cases of esophageal rupture is very high.
  • In a recent retrospective review of cases presenting to an academic medical center from 1993-2000, 24 patients were identified. Of these, 67% had chest pain; 42% had persistent cough; 25% had sore throat; and 8% had dysphagia, shortness of breath, or nausea/vomiting.
  • Substernal chest pain, usually radiating to the neck, back, or shoulders and exacerbated by deep inspiration, coughing, or supine positioning
  • Dyspnea
  • Neck pain
  • Jaw pain
  • Dysphagia, dysphonia, and/or abdominal pain (unusual symptoms)

Physical

The general appearance of the patient may vary from asymptomatic to respiratory distress. Findings on lung auscultation also vary depending on the extent of the pneumothorax, but they may include diminished or absent breath sounds, or hyperresonance on percussion of the affected side. General clinical signs include the following:

• Spontaneous pneumothorax
  • Tachycardia (most common)
  • Tachypnea
  • Hypoxia
• Iatrogenic pneumothorax: Signs are similar to those of spontaneous pneumothorax and depend on the underlying lung disease and extent of the pneumothorax.
• Pneumomediastinum
  • Subcutaneous emphysema (most consistent sign)
  • Hammas sign (precordial crunching noise synchronous with the heartbeat, often accentuated during expiration; occurrence varies—one series reported 10%.)
  • None (Physical findings are absent in some patients.)

Causes

Causes of pneumothorax and pneumomediastinum may include the following:

• Primary spontaneous pneumothorax
  • Spontaneous pneumothorax is heavily associated with smoking, with 80-90% of primary spontaneous pneumothorax cases occurring in smokers.
  • Physical height: It has been noted that typical patients tend to have a tall and thin body habitus. Whether height affects development of subpleural blebs or whether more negative apical pleural pressures cause preexisting blebs to rupture is unclear.
  • Valsalva results in increased intrathoracic pressure. However, contrary to popular belief, most spontaneous pneumothoraces occur while the patient is at rest.
  • Changes in atmospheric pressure, proximity to loud music, and low frequency noises have also been reported to be associated with pneumothorax
  • Familial associations have been noted in more than 10% of patients. Some are due to rare connective tissue diseases, but recently, mutations in the gene encoding folliculin (FLCN) have been described. These patients may represent an incomplete penetrance of a genetic disorder. Birt-Hogg-Dube syndrome is characterized by benign skin growths, pulmonary cysts, and renal cancers and is caused by mutations in the FLCN gene.
• Secondary spontaneous pneumothorax
  • COPD or emphysema
  • Asthma
  • Cystic fibrosis
  • Interstitial lung disease
  • Tuberculosis
  • Bronchogenic or metastatic carcinoma
  • Pneumonia (fungal, caseating, HIV)
  • Collagen vascular disease including Marfan syndrome
  • Catamenial pneumothorax (see Special Concerns)
• Iatrogenic pneumothorax
  • Transthoracic needle aspiration procedures (most common cause, accounting for 32-37% of cases)
  • Subclavian and supraclavicular needle sticks
  • Thoracentesis
  • Mechanical ventilation (directly related to peak airway pressures)
  • Pleural biopsy
  • Transbronchial lung biopsy
  • Cardiopulmonary resuscitation (Consider the possibility of a pneumothorax if ventilation becomes progressively more difficult.)
  • Tracheostomy
• Pneumomediastinum
  • Acute production of high intrathoracic pressures (often as a result of inhalational drug use)
  • Smoking marijuana
  • Inhalation of cocaine
  • Asthma
  • Athletic competition
  • Respiratory tract infection
  • Parturition
  • Emesis
  • Severe cough
  • Mechanical ventilation
  • Trauma or surgical disruption of the oropharyngeal, esophageal, or respiratory mucosa

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