Tension Pneumothorax (Mediastinal Shift)
By Sara DiCenzo, MSN, RN, CCRN, CRNP
J.R., a 67-year-old male, had triple coronary artery bypass surgery and an aortic valve replaced four days ago. His ejection fraction prior to surgery was 20 percent and initially postop he required inotropic support for a decrease in cardiac output and hypotension. He was unable to be successfully weaned from the ventilator. A triple lumen CVP line was necessary for TPN and a right subclavian line was placed.
The initial chest X-ray was checked and no pneumothorax was found at this time. Three hours later, J.R. became restless and peak inspiratory pressures were rising. He was tachycardic and frequent PVCs were noted. An ABG revealed a PO2 of 60 and a CO2 of 56. Breath sounds, which had been equal, were now slightly decreased on the right side. A stat portable chest X-ray revealed a tension pneumothorax on the right side from the CVP line placement. A chest tube was inserted on the right side with re-expansion of the lung and resolution of his symptoms.
A tension pneumothorax is a collection of air in the pleural space that results in the collapse of the lung on the affected side. With a tension pneumothorax, the leak of air into the pleural space is a ball-valve type where air is allowed to enter into the space from the lung with each breath but the air is unable to escape because the chest wall is intact.
The build-up of pressure in the pleural cavity causes the mediastinum, which contains the heart, trachea, esophagus and great vessels, to shift to the unaffected side (see Fig. 1).
This mediastinal shift also causes compression of the lung on the unaffected side. This is a life-threatening situation because the pressure on the great vessels causes a decrease in venous return, reduced cardiac output, decrease in blood pressure and hypoxia, which will lead to shock.
A simple pneumothorax is leakage of air in the pleural space from either surgery or trauma. There is a break in the integrity of the chest wall, which allows air to enter the pleural cavity. The air in the pleural space increases the intrapleural pressure from negative to positive pressure and the lung collapses. This collapse can either be partial or complete but there is no mediastinal shift (see Fig. 2). If the air becomes trapped and unable to escape, it can develop into a tension pneumothorax.
A hemothorax (see Fig. 2) is a collection of blood in the pleural space and a hemopneumothorax is a collection of both blood and air in the pleural space with no mediastinal shift. This blood may be from a laceration of chest wall, heart or great vessels.
Trauma is one major cause of tension pneumothorax. The injury can be a blunt trauma with or without rib fractures. Examples of trauma that can cause a tension pneumothorax are unrestrained motor vehicle accidents, falls and a direct blow to the chest. A penetrating wound can also cause a tension pneumothorax if the air becomes trapped in the pleural space.
Mechanical ventilation or bag (valve) mask ventilation can cause a tension pneumothorax due to barotrauma. Barotrauma means pressure-induced injury to the lungs, which is usually the result of overinflation and air ruptures through the visceral pleura. Excessive inflation volumes and high intrathoracic pressures can predispose patients to tension pneumothorax.
Invasive procedures such as insertion of central lines, transthoracic lung biopsy, liver biopsy, mediastinoscopy, bronchoscopy or cardiopulmonary resuscitation can cause a pneumothorax.
Dyspnea, chest pain and anxiety are the most common complaints of the patient. Examination reveals tachycardia, tachypnea, jugular venous distension and hypotension. In the mechanically ventilated patient, an increase in peak pressure needed to deliver the tidal volumes is noted along with an increase in end-expiratory pressure. A sudden increase in pulmonary artery pressures may be noted. Tracheal deviation toward the unaffected side is a late finding. Auscultation of the chest may reveal distant heart sounds.
Palpation over the affected lung will reveal the absence of tactile fremitus, which is the palpable vibration of the chest wall during speech. Percussion over the affected side will reveal hyperresonant (boomlike) or tympanic (drumlike) instead of resonant (hollow). Auscultation will reveal the absence of breath and voice sounds over the affected lung.1
ECG may reveal a right axis deviation, low voltage in the precordial lead with T wave inversions. Tension pneumothorax should be considered in a patient with pulseless electrical activity (PEA). Arterial blood gas will reveal hypoxia, hypercarbia and respiratory acidosis.2
Chest X-ray will show air in the pleural cavity with deviation of mediastinal structures toward the opposite side. The intercostal spaces on the affected side may be widened. A tension pneumothorax will also be seen on a CT scan of the chest.
A tension pneumothorax can be a life-threatening situation and there may be little time for a chest X-ray. As soon as the diagnosis is apparent in an unstable patient, a diagnostic needle tap is indicated. A large bore (14 gauge or larger) catheter-over-needle device is inserted into the second intercostal space in the midclavicular line on the affected side over the top of the rib and perpendicular to the chest wall. A rush of air should be heard, which would confirm the diagnosis. This will relieve the pressure on the mediastinum and create an open pneumothorax, which is less likely to be lethal. The needle is removed and the catheter is left in while setting up for chest tube placement. A chest tube insertion will follow and will be inserted in either the second intercostal space or the fifth intercostal space. The chest tube will then be connected to an underwater drainage system and a chest X-ray will be necessary to confirm the placement of the chest tube and re-expansion of the lung.
Early recognition through acute assessment skills is an essential nursing consideration because treatment of a tension pneumothorax can be life saving for the patient. Failure to recognize a tension pneumothorax can lead to cardiac arrest and death. A tension pneumothorax should be considered in a patient who suddenly becomes hypoxic and hypotensive after a central line placement or a liver or lung biopsy. A stat portable chest X-ray should be done if time permits and preparation for chest tube insertion or needle insertion should be initiated. Ventilator dependent patients are also at risk for a tension pneumothorax. In addition to hemodynamic compromise, a ventilator dependent patient with a tension pneumothorax will present with increasing peak inspiratory pressures.
The prognosis of a patient with tension pneumothorax is good if detected early and the underlying cause is treated. Emergency personnel are trained to recognize and treat tension pneumothorax in the field so that valuable time is not lost. Nurses in the hospital setting, especially in critical care units, should also be able to recognize and intervene in order to prevent a fatal outcome. *
1. DeGowin, R.L. (1994). Diagnostic examination (pp. 317-318). New York: McGraw-Hill, Inc.
2. Bowman, J. (1999). Pneumothorax, tension and traumatic. Retrieved April 27, 2000 from the World Wide Web: http://www.emedicine.com/emerg/topic470.htm
American Heart Association (1997-1999). Advanced cardiac life support (pp. 14-4--14-5). Dallas: Author.
& Reid, P. (1999). Taking the tension out of traumatic pneumothoraxes. Nursing 99, 29(4), 41-47.
Sara DiCenzo is a cardiology nurse practitioner, Hahnemann University Hospital, Philadelphia.
Treatment of Tension Pneumothorax
* A tension pneumothorax can be life threatening; there may be no time for a chest X-ray
* When the diagnosis is apparent, a diagnostic needle tap is indicated
* A large bore (14 gauge or larger) catheter-over-needle device is inserted into the second intercostal space in the midclavicular line on the affected side over the top of the rib and perpendicular to the chest wall; a rush of air should be heard, which confirms the diagnosis
* A diagnostic needle tap relieves the pressure on the mediastinum and creates an open pneumothorax, which is less likely to be lethal
* The needle is removed and the catheter is left in while setting up for chest tube placement
* A chest tube insertion follows and is inserted in either the second intercostal space or the fifth intercostal space
* The chest tube is then connected to an underwater drainage system and a chest X-ray is needed to confirm the placement of the chest tube and re-expansion of the lung