Table 1. Cardiorespiratory and cerebrovascular hemodynamic responses during normothermia (baseline) and heat stress (Heat1–4).
| Baseline | Heat1 | Heat2 | Heat3 | Heat4 | ||
|---|---|---|---|---|---|---|
| Tes (°C) | 37.05±0.24 | 37.35±0.27* | 37.73±0.30*# | 38.24±0.30*#$ | 38.41±0.23*#$& | P<0.001 |
| ΔTes (°C) | +0.30±0.10 | +0.69±0.16 | +1.20±0.15 | +1.42±0.08 | ||
| Tty (°C) | 37.01±0.26 | 37.34±0.32* | 37.66±0.32*# | 38.11±0.39*#$ | 38.32±0.36*#$& | P<0.001 |
| Tsk (°C) | 33.52±1.27 | 37.29±1.73* | 38.20±0.88*# | 38.58±0.85*#$ | 38.60±0.70*#& | P<0.001 |
| HR (bpm) | 64±10 | 78±9* | 86±10*# | 93±11*#$ | 96±11*#$ | P<0.001 |
| MAP (mm Hg) | 90±8 | 89±7 | 86±5 | 87±8 | 84±6*# | P=0.024 |
| Q (L/min) | 5.6±1.6 | 7.0±1.9* | 7.9±2.0*# | 8.2±1.9*# | 8.9±2.4*# | P<0.001 |
| SV (ml) | 89±20 | 90±20 | 92±19 | 88±18 | 94±23 | P=0.577 |
| TVC (L/mm Hg) | 0.062±0.016 | 0.079±0.018* | 0.092±0.023*# | 0.094±0.022*# | 0.105±0.030*#$ | P<0.001 |
| PETCO2 (mm Hg) | 40.4±2.8 | 38.3±3.2 | 37.5±4.6 | 34.7±6.2*#$ | 33.7±6.3*#$ | P<0.001 |
| VE (L/min) | 9.1±3.3 | 12.0±4.2 | 12.2±3.6 | 12.7±5.8 | 16.2±6.8* | P=0.021 |
| SkBFforehead (AU) | 74±33 | 150±47* | 202±48*# | 214±57*# | 211±51*# | P<0.001 |
| SkBFforearm (AU) | 17±12 | 112±79* | 161±48*# | 167±42*# | 165±51*# | P<0.001 |
| CVCforehead (AU/mm Hg) | 0.83±0.38 | 1.68±0.50* | 2.35±0.56*# | 2.35±0.54*# | 2.49±0.54*# | P<0.001 |
| CVCforearm (AU/mm Hg) | 0.19±0.12 | 1.24±0.85* | 1.88±0.60*# | 1.98±0056*# | 1.97±0.62*# | P<0.001 |
| MCAVmean (cm/s) | 53±17 | 45±12* | 45±12* | 39±14* | 41±16* | P<0.001 |
| ICA BF (ml/min) | 290±53 | 275±62 | 275±68 | 254±48* | 238±72*#$ | P=0.001 |
| ECA BF (ml/min) | 188±72 | 271±128* | 351±163# | 398±199*# | 442±189*#$ | P<0.001 |
| VA BF (ml/min) | 89±38 | 82±41* | 81±34* | 78±33* | 74±35* | P=0.002 |
| MCAVmean CON (cm/s/mm Hg) | 0.60±0.19 | 0.51±0.22 | 0.47±0.20* | 0.45±0.15* | 0.48±0.20* | P=0.009 |
| ICA CON (ml/min/mm Hg) | 3.29±0.86 | 3.13±0.79 | 3.20±0.83 | 2.95±0.69 | 2.87±1.00 | P=0.037 |
| ECA CON (ml/min/mm Hg) | 2.11±0.81 | 3.03±1.44* | 4.08±1.87*# | 4.60±2.35*# | 5.21±2.16*#$ | P<0.001 |
| VA CON (ml/min/mm Hg) | 1.00±0.44 | 0.93±0.47 | 0.95±0.42 | 0.90±0.41 | 0.88±0.40 | P=0.091 |
BF, blood flow; bpm, beats per minute; CON, conductance; CVC, cutaneous vascular conductance; ECA, external carotid artery; HR, heart rate; ICA, internal carotid artery; MAP, mean arterial pressure; MCAVmean, middle cerebral artery mean blood velocity; min, minute; PETCO2, partial pressure of end-tidal carbon dioxide; Q, cardiac output; s, second; SkBF, skin blood flow; SV, stroke volume; Tes, esophageal temperature; Tsk, mean skin temperature; Tty, external canal temperature; TVC, total vascular conductance; VA, vertebral artery; VE, minute ventilation.
Values are mean±s.d. *P<0.05 different from the baseline; #P<0.05 different from Heat1; $P<0.05 different form Heat2; &P<0.05 different from Heat3.