Registered Respiratory Therapist (RRT-TMC) Practice Exam

Wedge pressure from a pulmonary artery catheter best estimates left atrial pressure. When the inflated catheter tip wedges in a small branch of the pulmonary artery, blood flow is occluded beyond the balloon and the pressure measured distal to the balloon equilibrates with the pressure in the pulmonary capillary bed, which directly reflects the pressure in the left atrium. This makes the pulmonary capillary wedge pressure a convenient indirect measure of left-sided filling pressures. In contrast, pressures in the pulmonary artery itself reflect the arterial side, central venous pressure reflects right atrial pressure, and cardiac output is a flow, not a pressure. Keep in mind that wedge readings can be influenced by factors like chest pressure changes or certain cardiac conditions, which can affect interpretation.