INTERACTIONS BETWEEN SURFACE COOLING AND LBNP-INDUCED CENTRAL HYPOVOLEMIA

  • 1 January 1980
    • journal article
    • research article
    • Vol. 51  (5) , 497-503
Abstract
The interaction between whole body surface cooling (WBSC) and progressive lower body negative pressure (LBNP) to -50 torr [conditions of bed rest and space flight are associated with orthostatic intolerance] was evaluated in 9 healthy male volunteers, mean age 29 .+-. 1.7 yr. WBSC, accomplished by circulating 16.degree. C water through an Apollo cooling garment. A significant drop in mean skin temperature of 1.96.degree. C (P < 0.001) was produced. Cardiac output (.ovrhdot.Q) was measured by the C2H2 rebreathing technique. Changes in leg volume (LgV) were monitored by a Whitney strain gauge. WBSC at rest produced a significant decrease in leg volume of 0.27 l (P < O.01). Heart rate decreased (-7 bpm, P < 0.01) and systolic arterial blood pressure was increased (+6 torr, P < 0.02). The hemodynamic effects of cooling were maintained throughout progressive levels of LBNP with consistently lower leg volumes and heart rates and higher stroke volumes and systolic pressure (P < 0.01 for all measurements). WBSC produces a central displacement of cutaneous venous volume resulting in an increase in stroke volume.