TY - JOUR
T1 - Effect of thermal stress on Frank-Starling relations in humans
AU - Wilson, T. E.
AU - Brothers, R. M.
AU - Tollund, C.
AU - Dawson, E. A.
AU - Nissen, P.
AU - Yoshiga, C. C.
AU - Jons, C.
AU - Secher, N. H.
AU - Crandall, Craig G.
PY - 2009
Y1 - 2009
N2 - The Frank-Starling 'law of the heart' is implicated in certain types of orthostatic intolerance in humans. Environmental conditions have the capacity to modulate orthostatic tolerance, where heat stress decreases and cooling increases orthostatic tolerance. The objective of this project was to test the hypothesis that heat stress augments and cooling attenuates orthostatic-induced decreases in stroke volume (SV) via altering the operating position on a Frank-Starling curve. Pulmonary artery catheters were placed in 11 subjects for measures of pulmonary capillary wedge pressure (PCWP) and SV (thermodilution derived cardiac output/heart rate). Subjects experienced lower-body negative-pressure (LBNP) of 0, 15 and 30 mmHg during normothermia, skin-surface cooling (decrease in mean skin temperature of 4.3 ± 0.4°C (mean ± s.e.m.) via perfusing 16°C water through a tubed-lined suit), and whole-body heating (increase in blood temperature of 1.0 ± 0.1°C via perfusing 46°C water through the suit). SV was 123 ± 8, 121 ± 10, 131 ± 7 ml prior to LBNP, during normothermia, skin-surface cooling, and whole-body heating, respectfully (P = 0.20). LBNP of 30 mmHg induced greater decreases in SV during heating (-48.7 ± 6.7 ml) compared to normothermia (-33.2 ± 7.4 ml) and to cooling (-10.3 ± 2.9 ml; all P < 0.05). Relating PCWP to SV indicated that cooling values were located on the flatter portion of a Frank-Starling curve because of attenuated decreases in SV per decrease in PCWP. In contrast, heating values were located on the steeper portion of a Frank-Starling curve because of augmented decreases in SV per decrease in PCWP. These data suggest that a Frank-Starling mechanism may contribute to improvements in orthostatic tolerance during cold stress and orthostatic intolerance during heat stress.
AB - The Frank-Starling 'law of the heart' is implicated in certain types of orthostatic intolerance in humans. Environmental conditions have the capacity to modulate orthostatic tolerance, where heat stress decreases and cooling increases orthostatic tolerance. The objective of this project was to test the hypothesis that heat stress augments and cooling attenuates orthostatic-induced decreases in stroke volume (SV) via altering the operating position on a Frank-Starling curve. Pulmonary artery catheters were placed in 11 subjects for measures of pulmonary capillary wedge pressure (PCWP) and SV (thermodilution derived cardiac output/heart rate). Subjects experienced lower-body negative-pressure (LBNP) of 0, 15 and 30 mmHg during normothermia, skin-surface cooling (decrease in mean skin temperature of 4.3 ± 0.4°C (mean ± s.e.m.) via perfusing 16°C water through a tubed-lined suit), and whole-body heating (increase in blood temperature of 1.0 ± 0.1°C via perfusing 46°C water through the suit). SV was 123 ± 8, 121 ± 10, 131 ± 7 ml prior to LBNP, during normothermia, skin-surface cooling, and whole-body heating, respectfully (P = 0.20). LBNP of 30 mmHg induced greater decreases in SV during heating (-48.7 ± 6.7 ml) compared to normothermia (-33.2 ± 7.4 ml) and to cooling (-10.3 ± 2.9 ml; all P < 0.05). Relating PCWP to SV indicated that cooling values were located on the flatter portion of a Frank-Starling curve because of attenuated decreases in SV per decrease in PCWP. In contrast, heating values were located on the steeper portion of a Frank-Starling curve because of augmented decreases in SV per decrease in PCWP. These data suggest that a Frank-Starling mechanism may contribute to improvements in orthostatic tolerance during cold stress and orthostatic intolerance during heat stress.
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U2 - 10.1113/jphysiol.2009.170381
DO - 10.1113/jphysiol.2009.170381
M3 - Article
C2 - 19417092
AN - SCOPUS:67650364359
SN - 0022-3751
VL - 587
SP - 3383
EP - 3392
JO - Journal of Physiology
JF - Journal of Physiology
IS - 13
ER -