Coronary blood flow during +Gz stress in +Gz conditioned adult miniature swine.

Four female adult miniature swine were acceleration conditioned for a period of 1 month using repeated acute exposure to simulated aerial combat maneuver profiles which exposed the animals to an average of +4.5G, for 106s. This period of conditioning produced adaptation as evidenced by decreased maximal heart rates during +Gz and by the absence of any +Gz induced gross cardiac pathology. Coronary blood flow was measured in these conditioned animals with the radiolabeled microsphere technique. Blood flows were measured under resting conditions, during 60s exposures to +3Gz and +5Gz and 10 min after +5Gz exposure. Coronary flow was increased 2-3 fold during +3Gz and +5Gz. The regional distribution of coronary blood flow during +Gz was similar to that under resting control conditions. There were no significant differences between coronary blood flows during +Gz in these conditioned animals and the values previously reported from the initial exposure of miniature swine to similar levels of +Gz. These results indicate that 1 month of acceleration conditioning of the types used in these studies has no significant effect on the response of coronary blood flow to +3Gz and +5Gz stress.