A tension pneumothorax occurs when the initial defect in the chest wall or lung acts as a one-way valve, allowing air to enter the thorax with inspiration but not escape with exhalation. With each breath, pressure within the hemithorax increases, further deflating the lung. As pressure continues to increase, the mediastinum is pushed toward the unaffected side. This shift causes the vena cava to kink, resulting in decreased venous return. This creates a chain reaction of decreased preload, decreased stroke volume, decreased cardiac output and, ultimately, decreased blood pressure. Further shifting of the mediastinum will start to interfere with expansion of the lung on the opposite side to the injury, decreasing tidal volume in the healthy lung. Obstructive shock and hypoxia are the results of tension pneumothorax.
Clinical exam findings
A closed pneumothorax may present with obvious soft tissue trauma to the chest wall if blunt force trauma was the cause. An open pneumothorax will present with a penetration in the chest wall; an impaled object may still be in place. Auscultation of lung fields may reveal normal lung sounds in the event of a small pneumothorax, or diminished or absent lung sounds with a larger one. In severe cases tachycardia and tachypnea may present. Pulse oximetry may be normal or decreased, depending on the size of the pneumothorax; often, slight tachycardia and a slightly low SpO2 (92%–94%) are all that accompany a small pneumothorax.
Though the clinical exam findings associated with simple pneumothorax may be fairly unimpressive, the signs associated with a developing tension pneumothorax can be dramatic. Initial anxiety, difficulty breathing, tachycardia and tachypnea will worsen as the affected lung collapses. SpO2 will start to fall, and skin will become increasingly pale, cool and diaphoretic as obstructive shock physiology begins.
If the tension pneumothorax progresses and a mediastinal shift occurs, tachycardia and hypotension will become profound, soon followed by decreased mental status. Lung sounds will diminish on the unaffected side, and JVD will occur as a result of decreased venous return to the heart in the absence of concomitant hypovolemia. Tracheal deviation, if observable at all, is a very late sign and occurs low in the neck. Worsening cyanosis, unconsciousness and eventually death will occur.
Treatment of simple and closed pneumothorax consists of ensuring adequate ventilation and oxygenation. In cases of isolated simple pneumothorax, patients will often be able to maintain their own airway and ventilate adequately. In such cases, administer oxygen by a device that will ensure an SpO2 of at least 94%, place the patient on the cardiac monitor and establish IV access. Monitor EtCO2 if possible and immobilize the spine if warranted. Patients will rarely require ventilatory assistance or endotracheal intubation.
In the absence of a commercial occlusive dressing, cover the penetration accompanying an open pneumothorax with an occlusive dressing taped on three sides. This effectively creates a one-way valve that will prevent air from entering the chest through the penetration during inspiration, yet allow air to escape during exhalation, preventing development of a tension pneumothorax. There are times when the occlusive dressing will not function properly, and air will accumulate in the thorax. If an occlusive dressing is applied and signs and symptoms of tension pneumothorax develop, lift the corner of the dressing to allow the chest to decompress.
The definitive treatment for a tension pneumothorax is needle decompression, a skill typically available only to ALS providers. BLS providers should provide PPV to these patients while quickly transporting to an emergency department or rendezvousing with a paramedic. Perform needle decompression (also termed needle thoracostomy) immediately after tension pneumothorax is diagnosed, prior to any other treatment. In this procedure, a large-bore needle is inserted into the second or third intercostal space at the midclavicular line just over the top of the rib. It is important to use a needle of adequate length, as needles less than 4.5 cm have been shown to have failure rates up to 65%.5 Inserting the needle into the pleural space results in a rush of air through the needle, immediate decompression of the thorax, and fairly rapid correction of the cardiorespiratory insult characteristic of tension pneumothorax. The needle is left in place, typically with a flutter valve to allow air to escape the thorax but not enter. Commercial needle thoracostomy kits are available from several manufacturers, or a kit can be made with equipment normally found on an ambulance, such as a latex glove finger.