Hemodynamic changes during whole body surface cooling and lower body negative pressure.

Abstract

Six young healthy male subjects were studied to evaluate the use of whole body surface cooling (WBSC) as an antiorthostatic intervention. Previous studies in our laboratory have demonstrated the perfusion of an Apollo cooling garment with 16 degrees C water produced a significant increase in stroke volume and decrease in heart rate at rest and during lower body negative pressure (LBNP). However, optimal perfusion temperatures have not been determined. The present study examined the effects of WBSC using perfusion of water at a temperature of 10 degrees C. This perfusion temperature produced a greater decrease in mean skin temperature (Tsk) than water at 16 degrees C, -4 degrees C drop compared to -2 degrees C respectively. The hemodynamic effects were also more prominent with 10 degrees C water as shown by the increase in stroke volume of 11% at rest and of 35% during LBNP at -50 torr compared to control measurements at ambient temperature. Heart rates were lowered significantly (8 beats/min) and systolic arterial blood pressure was higher (8 torr). Cooling with 10 degrees C water produced a slight increase in muscle tone, reflected by a small but significant increase (+84 ml/min) in oxygen uptake. These data suggest that WBSC is an effective nonpharmacologic means of controlling preload and deserves further investigation as an antiorthostatic intervention.