An assessment of hypercapnia-induced elevations in regional cerebral perfusion during combined orthostatic and heat stresses

Shibasaki, Manabu; Sato, Kohei; Hirasawa, Ai; Sadamoto, Tomoko; Crandall, Craig G.; Ogoh, Shigehiko

doi:10.1186/s12576-020-00751-4

Table 1 Thermal, hemodynamic, respiratory variables, and blood flows

From: An assessment of hypercapnia-induced elevations in regional cerebral perfusion during combined orthostatic and heat stresses

	Condition	Stage			ANOVA			T test
	Condition	Norm baseline	Heat baseline	Heat–CO₂	Condition	Stage	Interaction	T test
T_sk, °C	Air	33.8 ± 0.7	39.0 ± 0.7	38.9 ± 1.0	0.959	< 0.001	0.471	0.724
T_sk, °C	CO₂	33.9 ± 0.5	38.9 ± 1.0	38.9 ± 1.0	0.959	< 0.001	0.471	0.724
T_ca, °C	Air	37.2 ± 0.3	38.6 ± 0.2	38.7 ± 0.1	0.775	< 0.001	0.365	0.060
T_ca, °C	CO₂	37.3 ± 0.1	38.6 ± 0.1	38.7 ± 0.1	0.775	< 0.001	0.365	0.060
HR, bpm	Air	61.7 ± 7.1	104.3 ± 11.9	102.6 ± 8.7	0.083	< 0.001	0.128	0.067
HR, bpm	CO₂	60.4 ± 7.5	98.3 ± 7.4	102.6 ± 8.7	0.083	< 0.001	0.128	0.067
MAP, mmHg	Air	76.4 ± 8.5	77.9 ± 8.9	86.3 ± 8.7	0.207	0.717	0.171	0.045
MAP, mmHg	CO₂	85.1 ± 14.4	82.0 ± 9.1	86.3 ± 8.7	0.207	0.717	0.171	0.045
VE, L/min	Air	7.1 ± 1.5	9.3 ± 2.8	17.0 ± 4.4	0.876	0.011	0.971	0.002
VE, L/min	CO₂	7.3 ± 1.9	9.6 ± 2.0	17.0 ± 4.4	0.876	0.011	0.971	0.002
RR, n	Air	14.7 ± 2.4	15.9 ± 5.0	18.1 ± 5.9	0.227	0.309	0.894	0.414
RR, n	CO₂	14.1 ± 2.6	16.4 ± 3.4	18.1 ± 5.9	0.227	0.309	0.894	0.414
P_ETCO₂, mmHg	Air	42.9 ± 2.6	40.0 ± 5.4	49.3 ± 3.6	0.876	0.054	0.902	0.002
P_ETCO₂, mmHg	CO₂	43.0 ± 2.4	40.3 ± 4.0	49.3 ± 3.6	0.876	0.054	0.902	0.002
VA, mL/min	Air	143.5 ± 43.8	141.8 ± 51.5	171.1 ± 51.7	0.045	0.439	0.619	0.010
VA, mL/min	CO₂	132.0 ± 41.2	123.0 ± 34.4	171.1 ± 51.7	0.045	0.439	0.619	0.010
ICA, mL/min	Air	398.2 ± 72.9	352.2 ± 87.8	459.8 ± 100.5	0.586	0.039	0.645	0.019
ICA, mL/min	CO₂	369.8 ± 70.8	337.9 ± 73.0	459.8 ± 100.5	0.586	0.039	0.645	0.019
%VA, %baseline	Air	100	99.2 ± 18.7	133.0 ± 33.1	0.632	0.582	0.632	0.010
%VA, %baseline	CO₂	100	94.7 ± 17.7	133.0 ± 33.1	0.632	0.582	0.632	0.010
%ICA, %baseline	Air	100	88.7 ± 16.2	127.0 ± 35.7	0.685	0.040	0.685	0.040
%ICA, %baseline	CO₂	100	91.5 ± 9.5	127.0 ± 35.7	0.685	0.040	0.685	0.040

Blood flow values are depicted in absolute units and relative changes from the normothermic baseline prior to LBNP challenge. Values are mean ± SD were averaged from steady-state supine data at normothermic (Norm baseline) and during heat stress (Heat baseline). Prior to the LBNP challenge, the hypercapnic gas was applied in the CO₂ trial (Heat CO₂) only. T_sk, mean skin temperature; T_ca, external canal temperature; VE, minute ventilation; RR, respiratory rate; P_ETCO₂, partial pressure of end-tidal carbon dioxide; MAP, mean arterial blood pressure; HR, heart rate; ICA, internal carotid artery; VA, vertebral artery blood flow. ICA and VA blood flows were depicted in absolute units and relative changes (i.e., normalized relative to the respective normothermic baselines). Subjects performed two progressive lower body pressure during heat stress with (CO₂ trial) or without (Air trial) an application of hypercapnic gas mixture on different day. Thermal, hemodynamic, respiratory, and cerebrovascular variables were evaluated by a two-way repeated measures analysis of variance (ANOVA). The paired T test (Heat baseline vs. Heat CO₂) performed to evaluate the effect of inhaling hypercapnic gas on these variables

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ISSN: 1880-6562

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