Which of the following conditions contribute to the development of hypoxemia in a patient with pulmonary emboli?
1. Cardiogenic shock
2. Destruction of lung parenchyma
3. Intrapulmonary shunt
4. Mismatch
a. 1, 2, and 3 only
b. 1 and 4 only
c. 2 only
d. 1, 3, and 4 only
ANS: D
Hypoxemia develops because of mismatch, intrapulmonary shunt, and cardiogenic shock. Shock is caused by obstruction of the pulmonary vasculature by massive emboli or by numerous small emboli in the presence of cardiopulmonary disease. Cardiac output decreases and oxygen deliv-ery falls. With the decrease in oxygen delivery, the peripheral tissues increase oxygen extraction causing venous oxygen desaturation. In patients with significantly increased right heart pressures, intracardiac right-to-left shunt may develop when blood flows through a patent foramen ovale.
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