Larger emboli can cause a reflex increase in ventilation (tachypnea), hypoxemia due to ventilation / perfusion (V / Q) mismatch and low mixed venous oxygen content as a result of low cardiac output, atelectasis due to alveolar hypocapnia and abnormalities in surfactant, and an increase in pulmonary vascular resistance caused by mechanical obstruction and vasoconstriction resulting in tachycardia and hypotension.