Upright water immersion of the nonhuman primate as a model of cardiovascular adaptations to micro gravity

During space flight there is a central shift of blood volume supposedly producing a diuresis, that results in hypovolemia, and resetting of the arterial baroreflex resulting in cardiovascular deconditioning upon return to normal gravity. To study these changes in a primate model four Rhesus monkeys were instrumented with aortic and right atria] catheters, and aortic (2) and carotid flow probes (2). A urinary catheter was inserted and lactated Ringers solution infused continuously. The monkeys were placed in a water tight suit and then into a primate chair for three hours prior to upright water immersion They were then immersed for 72 hours. Heart rate (HR) blood pressure (BP) and flow were recorded continuously. HR-BP curves were determined before, during and after the immersions Reported in the table are the changes between the control (C), 3 hrs of immersion, just prior to de-immersion (72hr) and post immersion (PI). Three hours into the immersion the barocurve had shifted downward and to the left. Just after the completion of the immersions. the curve had shifted upwards and to the right when compared to control. C-3hrs Im hr3-hr72 72-P1 Cnt-P1 Delta BP 9.41±3.8 8.09 ± 8.4 -11.4±3.3 5.05±9.8 Delta HR -23.2±+5.7 -8.8±14 44.2±13.9 8.9±13.5 Delta RAP 6.5±0.41 -0.5±1.4 -4.45±0.8 1.6±1.37 Delta CO 27.4 229.5 -211.7 45.2 Delta CQ 114.7 528.6 -482.8 52.9 The changes observed in the monkey during 72 hr water immersion are similar to those reported during space flight making this a useful model for studying the cardiovascular adjustments to micro gravity' in man Supported by NASA pranl NA W(i 4362.