Hypotension and vagally mediated bradycardia.
Ventricular fibrillation-induced cardiac arrest.
Right axis deviation on electrocardiogram.
Hyperresonance to percussion on the affected side.
Tension pneumothorax is characterized by dyspnea, hypotension, decreased venous return to the heart, midline shift of the trachea and mediastinal structures away from the side of tension, a hyperresonant percussion note, and tachycardia. Untreated tension pneumothorax can quickly deteriorate to cardiac arrest and pulseless electrical activity. Although sometimes clinically indistinguishable from tamponade, a tension pneumothorax is the more common occurrence and a clinical diagnosis is usually possible. Treatment is needle decompression followed by tube thoracostomy.