Evidence that cardiopulmonary baroreceptor unloading coincident with hyperthermia attenuates the elevation in skin blood flow

Whole-body heating decreases central venous pressure (CVP) and presumably cardiopulmonary baroreceptor loading in humans. We sought to identify whether this occurrence attenuates the elevation in skin blood flow (SkBF) during a hyperthermic challenge. Four subjects were exposed to indirect whole-body heating while SkBF (laser-Doppler flowmetry), CVP, mean arterial pressure (MAP), and esophageal temperature (T_es) were monitored. Cutaneous vascular conductance (CVC) was indexed from the ratio of SkBF to MAP. At peak heat stress, 15 ml·kg^-1 warmed saline was infused intravenously to return CVP to pre-heat stress levels. Rates of elevation in CVC and T_es were calculated 5 min prior to, and 5 min during, saline infusion using linear regression on data sampled at 1 Hz. Rate of CVC elevation (CVC units·min^-1) Rate of T_es elevation °C·min^-1) CVP (mmHg) MAP (mmHg) Pre-HS - - 7.8±0.9 89±6 Peak-HS 0.9±0.1 0.023±0.009 4.9±0.6a 73±7a Saline 3.2±0.6* 0.019±0.008 8.0±0.7* 69±8a HS: heat stress, 1: Significantly different from pre-HS period (P<0.05). *: Significantly different from peak-HS period (P<0.05). Data are expressed as mean±SEM. Significant increases in the rate of elevation in CVC following the return of CVP to pre-heat stress levels, coupled with a lack of change in the rate of T_es elevation, suggest unloading of the cardiopulmonary baroreceptor coincident with hyperthermia attenuates the elevation in SkBF.