Tension penumothorax Tension pneumothorax is a medical emergency that occurs when air accumulates in the pleural space under pressure, compressing the lungs and decreasing venous return to the heart.  It typically develops when a lung or chest wall injury is such that it allows air into the pleural space but not out of it, creating a one-way valve. The trapped air does not continue accumulating, and some of the air is also able to escape during expiration. Clinical features:  Patients with pneumothoraces typically complain of dyspnea and chest pain.  In tension pneumothorax, patients are distressed with rapid labored respirations, cyanosis, profuse diaphoresis, and tachycardia.  Investigations:  A tension pneumothorax can be diagnosed using a chest X-ray, although a computerized tomography scan or ultrasound imaging may be needed to provide more detailed images.   Treatment:  tension pneumothorax involves immediate intervention to decompress the involved hemithorax, either through ne