tension pneumothorax [L, tendere, to stretch; Gk, pneuma, air, thorax] , the presence of air in the pleural space when pleural pressure exceeds alveolar pressure, caused by a rupture through the chest wall or lung parenchyma associated with the valvular opening. Air passes through the valve during coughing but cannot escape on exhalation. Unrelieved pneumothorax can lead to respiratory arrest.
