eMedicine Specialties > Emergency Medicine > Trauma & Orthopedics

Pneumothorax, Tension and Traumatic

Author: Jeffrey Glenn Bowman, MD, MS, Consulting Staff, Highfield MRI, Columbus, Ohio
Contributor Information and Disclosures

Updated: Feb 5, 2009

Introduction

Background

A pneumothorax refers to a collection of gas in the pleural space resulting in collapse of the lung on the affected side. A tension pneumothorax is a life-threatening condition caused by air within the pleural space that is under pressure; displacing mediastinal structures and compromising cardiopulmonary function. A traumatic pneumothorax results from blunt or penetrating injury that disrupts the parietal or visceral pleura. Mechanisms include injuries secondary to medical or surgical procedures.

Pathophysiology

A tension pneumothorax results from any lung parenchymal or bronchial injury that acts as a one-way valve and allows free air to move into an intact pleural space but prevents the free exit of that air. In addition to this mechanism, the positive pressure used with mechanical ventilation therapy can cause air trapping.

As pressure within the intrapleural space increases, the heart and mediastinal structures are pushed to the contralateral side. The mediastinum impinges on and compresses the contralateral lung.

Hypoxia results as the collapsed lung on the affected side and the compressed lung on the contralateral side compromise effective gas exchange. This hypoxia and decreased venous return caused by compression of the relatively thin walls of the atria impair cardiac function. The decrease in cardiac output results in hypotension and, ultimately, in hemodynamic collapse and death to the patient, if untreated.

Frequency

United States

A study conducted from 1959-1978 involving a US community with an average of 60,000 residents reported an incidence of primary spontaneous pneumothorax of 7.4 cases per 100,000 persons per year for men and 1.2 cases per 100,000 persons per year for women. When these figures are extrapolated, about 8,600 individuals develop primary spontaneous pneumothorax in the United States per year.

Tension pneumothorax is a complication in approximately 1-2% of the cases of idiopathic spontaneous pneumothorax. Until the late 1800s, tuberculosis was a primary cause of pneumothorax development. A 1962 study showed a frequency of pneumothorax of 1.4% in patients with tuberculosis.

Undoubtedly, the incidence of pneumothorax and/or tension pneumothorax in US hospitals has increased as intensive care treatment modalities have become increasingly dependent on positive-pressure ventilation, central venous catheter placement, and other causes that potentially induce iatrogenic pneumothorax.

International

Acupuncture is a traditional Chinese medicine technique used worldwide by alternative medical practitioners. Although generally considered to be a safe form of therapy, acupuncture's most frequently reported serious complication is pneumothorax. In a recent Japanese report of 55,291 acupuncture treatments, an approximate 1 incidence of 1 pneumothorax in 5000 cases was documented.

Mortality/Morbidity

The clinician should assume that a tension pneumothorax results in hemodynamic instability and death, unless immediately treated.

Sex

The male-to-female ratio is about 6:1 for primary spontaneous pneumothorax development.

• In men, the risk of spontaneous pneumothorax is 102 times higher in heavy smokers than in nonsmokers. Spontaneous pneumothorax most frequently occurs in tall, thin men aged 20-40 years.
• Catamenial pneumothorax is a rare phenomenon that generally occurs in women aged 30-50 years. It frequently begins 1-3 days after menses onset. Its etiology may be primarily related to associated diaphragmatic defects.

Men undergoing treatment for tension pneumothorax are more likely to have a larger body habitus with wider chest wall. Tension pneumothorax patients with wider chest walls undergoing needle thoracostomy may need a catheter longer than 5 cm to reliably penetrate into the pleural space.

Harcke et al using CT scan analysis of deployed male military personnel determined that, at the second right intercostal space in the midclavicular line, the mean horizontal thickness was 5.36 cm, and that an 8-cm angiocatheter would reach the pleural space in 99% of the male soldiers in this series.¹

Age

Pneumothorax occurs in 1-2% of all neonates. The incidence of pneumothorax in infants with neonatal respiratory distress syndrome is higher. In one study, 19% of such patients developed a pneumothorax.

Clinical

History

The signs and symptoms produced by tension pneumothorax are usually more impressive than those seen with a simple pneumothorax. Unlike the obvious patient presentations oftentimes used in medical training courses to describe a tension pneumothorax, actual case reports include descriptions of the diagnosis of the condition being missed or delayed because of subtle presentations that do not always present with the classically described clinical findings of this condition.

Symptoms and signs of tension pneumothorax may include the following:

• Chest pain (90%)
• Dyspnea (80%)
• Anxiety
• Acute epigastric pain (a rare finding)
• Fatigue

Physical

Findings at physical examination may include the following:

• Respiratory distress (considered a universal finding) or respiratory arrest
• Unilaterally decreased or absent lung sounds (a common finding; but decreased air entry may be absent even in an advanced state of the disease)
• Adventitious lung sounds (crackles, wheeze; an ipsilateral finding)
• Lung sounds transmitted from the nonaffected hemithorax are minimal with auscultation at the midaxillary line
• Tachypnea; bradypnea (as a preterminal event)
• Hyperresonance of the chest wall on percussion (a rare finding; may be absent even in an advanced state of the disease)
• Hyperexpansion of the chest wall
• Increasing resistance to providing adequate ventilation assistance
• Cyanosis (a rare finding)
• Tachycardia (a common finding)
• Hypotension (should be considered as an inconsistently present finding; while hypotension is typically considered as a key sign of a tension pneumothorax, studies suggest that hypotension can be delayed until its appearance immediately precedes cardiovascular collapse)
• Pulsus paradoxus
• Jugular venous distension
• Cardiac apical displacement (a rare finding)
• Tracheal deviation (an inconsistent finding; while historic emphasis has been placed on tracheal deviation in the setting of tension pneumothorax, tracheal deviation is a relatively late finding caused by midline shift)
• Mental status changes, including decreased alertness and/or consciousness (a rare finding)
• Abdominal distension (from increased pressure in the thoracic cavity producing caudal deviation of the diaphragm and from secondary pneumoperitoneum produced as air dissects across the diaphragm through the pores of Kohn)
• When examining a patient for suspected tension pneumothorax, helpful indications of subtle thoracic size and thoracic mobility differences may be elicited by performing careful visual inspection along the line of the thorax. In a supine patient, by lowering oneself to be in level with the patient.
• Tension pneumothorax may be a difficult diagnosis to make and may present with considerable variability in signs presented. Respiratory distress and chest pain are generally accepted as being universally present in tension pneumothorax. Tachycardia and ipsilateral air entry are also common findings.
• The development of tension pneumothorax in patients who are ventilated will generally be of faster onset with immediate, progressive arterial and mixed venous oxyhemoglobin saturation decline and immediate decline in cardiac output.
• Cardiac arrest associated with asystole or pulseless electrical activity (PEA) may ultimately result.

Causes

A wide variety of disease states and circumstances increase the patient's risk of a pneumothorax. If a pneumothorax is complicated by a one-way valve effect, tension pneumothorax may result.

• Infants requiring ventilatory assistance and those with meconium aspiration have a particularly high risk for tension pneumothorax. Aspirated meconium may serve as a one-way valve and produce a tension pneumothorax.
• Trauma may cause a pneumothorax.
  • Tension pneumothorax may be the result of blunt trauma with or without associated rib fractures.
  • Incidents that may cause tension pneumothoraces include unrestrained head-on motor vehicle accidents, falls, and altercations involving laterally directed blows.
  • Any penetrating wound that produces an abnormal passageway for gas exchange into the pleural spaces and that results in air trapping may produce a tension pneumothorax.
  • Significant chest injuries carry an estimated 10-50% risk of associated pneumothorax. In about half of these cases, the pneumothorax may be occult; therefore, chest CT should always be performed.
  • In a recent study, 12% of patients with asymptomatic chest stab wounds had a delayed pneumothorax or hemothorax.
  • McPherson et al, analyzing data from the Vietnam Wound Data and Munitions Effectiveness Team study, determined that tension pneumothorax was the cause of death in 3-4% of fatally wounded combat casualties.²
• Many procedures performed in an intensive care or emergency setting can result in an iatrogenic pneumothorax and tension pneumothorax. Examples of these procedures include incorrect chest tube insertion, mechanical ventilation therapy, central venous cannulation; cardiopulmonary resuscitation; hyperbaric oxygen therapy; needle, transbronchial, or transthoracic lung biopsy; liver biopsy or surgery; and neck surgery.
• Secondary or spontaneous tension pneumothorax is possible in many medical conditions.
  • Pneumothorax is associated with asthma, chronic obstructive pulmonary disease, pneumonia (especially with Staphylococcus, Klebsiella, Pseudomonas, and Pneumocystis species), pertussis, tuberculosis, lung abscess, and cystic fibrosis.
  • In pulmonary disorders such as asthma and emphysema, hyperexpansion disrupts the alveoli.
  • Increased pulmonary pressure due to coughing with a bronchial plug of mucus or phlegm bronchial plug may play a role.
  • Marfan syndrome is associated with an increased risk of pneumothorax.
  • Individuals may inherit a predisposition for primary spontaneous pneumothorax.
  • Although rare, spontaneous pneumothorax occurring bilaterally and progressing to tension pneumothorax has been documented.

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