Which determinations would help screen a mechanically ventilated patient for pulmonary embolism?

To effectively screen a mechanically ventilated patient for pulmonary embolism, the most pertinent determinations would include calculating the arterial-venous oxygen content difference (C(a-v)O2) and measuring the end-tidal carbon dioxide (PetCO2).

C(a-v)O2 provides insight into the amount of oxygen extracted by the tissues, which can be altered in cases of pulmonary embolism due to reduced blood flow and impaired gas exchange in the lungs. In the context of an embolism, the oxygen delivery to the tissues decreases, leading to an increased C(a-v)O2 value, as more oxygen would be utilized by the tissues without adequate replenishment from the lungs.

PetCO2 measurement reflects the concentration of carbon dioxide in the patient's exhaled breath. A significant reduction in PetCO2 can indicate a dead space ventilation increase, commonly found in pulmonary embolism, due to the mismatching of ventilation and perfusion where the lungs are ventilated but not adequately perfused due to obstruction.

While other options include additional parameters like PaCO2 and the P/F ratio, these may not provide as direct or immediate insight into the specific pathophysiological changes present in pulmonary embolism as C(a-v)O2 and PetCO