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Ann Emerg Med. 2009;54:704-73 1.

Pneumothorax

Michelle Sergei, MD

Brian Krieger, MD

Key Points

• Tension pneumothorax is a clinical diagnosis that should

be considered in any patient with shock and respiratory

distress. Treatment should not be delayed for radiologic

confirmation.

• Appropriate treatment of a tension pneumothorax is a

needle thoracostomy, followed by tube thoracostomy.

INTRODUCTION

Pneumothorax is an accumulation of air within the pleural

space. Spontaneous pneumothorax is acquired in the

absence of trauma. A primary spontaneous pneumothorax

is found in patients without underlying pulmonary pathology. A secondary spontaneous pneumothorax is found in

patients with underlying lung disease and damage to the

alveolar-pleural barrier (most commonly seen with chronic

obstructive pulmonary disease [COPD] or asthma).

Spontaneous primary pneumothoraces have the

greatest incidence of occurrence in young adults. They

are more common in males than females (6:1), greater

height-weight ratios, and smokers. Smoking is the most

important modifiable risk factor, with a lifetime risk of

12% compared with 0. 1 o/o in nonsmokers. Spontaneous

secondary pneumothoraces are most common in patients

older than 40 years with COPD. Recurrence rates range

from 30-45%.

The parietal pleura lines the thoracic cavity and closely

adheres to the visceral pleura, which surrounds the lungs.

The potential area between these 2 layers is known as the

pleural space. If air accumulates within this potential

space, the pressure causes the thoracic cavity to expand

and the lung to collapse, creating a pneumothorax.

• Unless a pneumothorax is spontaneous, small ( <20%),

minimally symptomatic, and prima ry, definitive

treatment is tube thoracostomy.

Secondary spontaneous pneumothoraces are the result of

a damaged alveolar-pleural barrier or underlying lung

problems that cause an increase in intrabronchial pressures. Tension pneumothoraces occur when air enters the

pleural space on inspiration but cannot escape on expira ­

tion (known as ball-valve effect). There is progressive

accumulation of air in the pleural space, resulting in collapse of the affected lung and shift of the mediastinal

structures to the opposite side. This ultimately causes

compression of the contralateral lung, impairment of

venous return, decreased cardiac output, and signs of cardiovascular collapse requiring immediate intervention

with a needle thoracostomy.

CLINICAL PRESENTATION

� History

Symptoms can vary, but are predicated on the pneumothorax size, rate of formation, and cardiorespiratory reserve. A

typical history includes a sudden onset of ipsilateral pleuritic chest pain and/or dyspnea with a nonproductive

cough. Patients, however, range from clinically silent to

agitated, restless, altered mental status, and/or cardiac

arrest if severe respiratory compromise is present.

1 05

CHAPTER 24

..... Physical Examination

The physical examination can range from unremarkable to

a patient in shock. Vital signs typically include a mild

tachycardia and tachypnea, although only 5% of patients

have a respiratory rate greater than 24. Findings on the

lung examination may be subtle if there is a small pneumothorax. Decreased breath sounds occur in 85%, whereas

hyperresonance to percussion occurs in less than 33%.

Patients with tension pneumothorax present in extremis

with hypotension, cyanosis, severe respiratory distress, and

tracheal deviation to the contralateral side.

DIAGNOSTIC STUDIES

..... Laboratory

Laboratory studies do not assist in making the diagnosis of

pneumothorax, but may be helpful in evaluating other

causes of the patient's symptoms.

.... Imaging

A standard inspiratory posteroanterior chest x-ray (CXR)

is obtained initially. The edge of the collapsed lung runs

parallel to the chest wall, and lung markings cannot be

identified beyond that border (Figure 24-1). The size of the

pneumothorax can be roughly estimated as a percentage

with each centimeter equal to approximately 10% decreased

lung volume. Pneumothoraces > 2 em are considered large.

If a pneumothorax is not seen on the film, but still highly

suspected, an expiratory, lateral, and/or decubitus film may

help. The intrapulmonary pressure is decreased during

expiration, causing decreased lung volumes and a relative

increase in the size of the pneumothorax. Computed

Figure 24-1. Complete pneumothorax of the left lung.

tomography (CT) has higher sensitivity for the detection

of pneumothoraces, especially in the supine patient. CT

also has high specificity in differentiating bullae from

pneumothoraces. Patients with pneumothoraces identified

solely on a CT, however, uncommonly require treatment.

Ultrasonography is another modality to detect a pneumothorax that capitalizes on changes in artifact when comparing normal lung with collapsed lung. The utility of

ultrasound, however, is vastly tied to the ability of the

operator.

PROCEDURES

Needle decompression is performed if a tension pneumothorax is suspected. Using a long 14- or 16-gauge angiocatheter, puncture the second intercostal space at the

mid-clavicular line on the affected side. A gush of air will

be heard, as the hemodynamics improve. Ultimately, a tube

thoracostomy must be placed. Tube thoracostomy is discussed in detail in Chapter 7.

Complications include re-expansion pulmonary edema,

extrapleural placement, intraparenchymal placement,

empyema, and penetration of solid organs.

MEDICAL DECISION MAKING

Suspicion for a pneumothorax begins with the history and

physical examination. If a pneumothorax is suspected, the

vital signs are critical in the medical decision making.