SYSTEMIC HEMODYNAMICS DURING HYPERBARIC-OXYGEN EXPOSURE IN RATS

The effect of 1-5 bar O2 on left ventricular pressure (LVP), maximal v elocity of LVP rise (+dP/dt) and fall (-dP/dt), systolic arterial pres sure (APsys), pulse pressure (DELTAAP), heart rate (HR), and respirato ry frequency (RF) was studied in anesthetized and conscious rats. At 1 bar O2, all blood pressure parameters increased significantly (9-56%) in both groups of rats, while RF fell (11-12%). HR fell only in consc ious rats, while arrhythmias occurred in both groups. Compression to 5 bar O2 induced a significant further increase in all blood pressure p arameters. HR fell further in the conscious rats. Arrhythmias were obs erved in increasing number during compression and at 5 bar O2. Elevati on in estimated oxygen-consumption of the heart was found both during compression and at 5 bar O2. We conclude that O2 exposure markedly sti mulates the myocardium by elevating the LVP, +dP/dt, and -dP/dt, thus elevating APsys and DELTAAP. Arrhythmias developed in both groups, whi le bradycardia occurred only in conscious rats.