Original Contributions Progressive Hypoxemia Limits Left Ventricular Oxygen Consumption (original) (raw)

To study the cardiac effects of progressive hypoxemia, we measured the left ventricular end-systolic pressure-volume relation (ESPVR), myocardial oxygen consumption (MVOj), and myocardial oxygen delivery (MQOi) in eight thoracotomized dogs anesthetized with fentanyl and droperidol. We specifically looked for evidence of oxygen supply limitation of MVOj and depressed contractility (altered ESPVR) during stepwise decreases in inspired oxygen fraction. We hypothesized that the reported relation between MVOj and left ventricular pressure-volume area (PVA) may hold when inadequate MQOj determines MVOj, which then may limit PVA, manifested partly as a change in the ESPVR. Initially, as arterial oxygen saturation was decreased from 95 ±3 % to 64 ±14%, coronary blood Bow increased so that MQo? was maintained with no change hi myocardial extraction ratio (ER,, = MV(VMQOi). During this first phase, lactate utilization, PVA, and ESPVR did not change. When oxygen saturation was further reduced,...