Pulmonary embolism is the obstruction of pulmonary arterial blood flow by thrombus, air, fat, or amniotic fluid. Large emboli may lead to a sudden decrease in end-tidal carbon dioxide tension due to an acute increase in dead space. Other signs include an increase in end-tidal nitrogen tension, as well as an increased CVP, hypoxemia, hypotension, tachyarrhythmias or bradyarrhythmias, and ventricular ectopy.