A left-to-right shunt, due to a leaking septum wall in the heart, is best determined by an increase in mixed venous oxygen saturation. From what location would the respiratory therapist recommend blood extraction for analysis to determine mixed venous oxygen saturation?

A. aorta
B. pulmonary artery
C. vena cava
D. pulmonary vein

Answer: B. Mixed venous blood, for the assessment of oxygen saturation, is taken from the distal port of the pulmonary artery catheter, or the pulmonary artery.