A patient in the intensive care unit is receiving mechanical ventilation,has a pulmonary artery catheter in place,and is being monitored continuously with a capnometer.The patient's arterial partial pressure of carbon dioxide (PₐCO₂)is 41 mm Hg and the partial pressure of end-tidal carbon dioxide (PₑₜCO₂)is 36 mm Hg.There is a sudden decrease in the PₑₜCO₂ to 18 mm Hg causing an alarm to sound.The most likely cause of this development is which of the following?
A) Hypovolemia
B) Apneic episode
C) Pulmonary embolism
D) Increased cardiac output

Question

Quizplus · Accepted Answer

Pulmonary embolism will cause a decrease in blood flow to the lungs.This increases alveolar dead space and leads to a decrease in the partial pressure of end-tidal carbon dioxide (PₑₜCO₂).Hypovolemia would also cause a decrease in the PₑₜCO₂,but it would not occur as suddenly as it did in this situation.The fact that the patient has an indwelling pulmonary artery catheter increases the risk of developing a pulmonary embolism,which often will have a quick onset.An apneic episode would have increased the PₑₜCO₂.An increased cardiac output would increase the PₑₜCO₂ because increases in cardiac output result in better perfusion of the alveoli and a rise in PₑₜCO₂.

A Patient in the Intensive Care Unit Is Receiving Mechanical