Pulmonary artery catheter readings

A pulmonary artery catheter tells the team how the heart is filling, how hard it is pushing and what it is putting out — the right atrial pressure from its proximal port reporting the preload of the right ventricle, the pulmonary artery pressures and the occlusion or wedge pressure obtained by briefly floating the balloon reporting the preload of the left ventricle, the cardiac output measured by thermodilution and indexed to body size, the systemic vascular resistance derived from them reporting afterload, and the mixed venous oxygen saturation reporting whether oxygen delivery is meeting demand — and those numbers guide fluid, inotrope, vasopressor and diuretic decisions only when they are read together as a pattern against the patient's perfusion rather than singly, and only when they can be trusted: the transducer leveled to the phlebostatic axis and zeroed, the reading taken at end-expiration, the waveform confirming where the tip sits, and the balloon inflated slowly with the least volume that wedges for the few seconds a reading takes and then deflated with the pulmonary artery waveform seen to return, because a tip that has migrated forward or a balloon left inflated infarcts or ruptures the segment of lung it is wedged in.