Systemic cardiovascular and carotid baroreflex support of arterial pressure during recovery from passive heat stress in young and older adults

Figures

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  FIGURE 1. Mean skin, rectal, and body temperature at normothermic baseline (Pre), every 10 min during 60 min of passive heating, and every 30 min during 2 h of normothermic post‐heating recovery in young (open circles, n = 16) and older individuals (filled circles, n = 9). Values are means ±95% confidence intervals. Inferences were drawn from two‐way mixed‐effects models (age X time) using Dunnett's multiple comparisons test for changes over time versus baseline within each age group and Šidák's multiple comparisons test to compare between groups at the same time point.

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  FIGURE 2. Mean (a), systolic and diastolic (b) arterial pressure, cardiac output (c), systemic vascular conductance (d), heart rate (e), and stroke volume (f) at normothermic baseline (Pre) and every 30 min throughout 60 min of passive heating and 2 h of normothermic post‐heating recovery in young (open circles, n = 16) and older individuals (filled circles, n = 9). Values are means ±95% confidence intervals. Inferences were drawn from two‐way mixed‐effects models (age X time) using Dunnett's multiple comparisons test for changes over time versus baseline within each age group and Šidák's multiple comparisons test to compare between groups at the same time point.

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  FIGURE 3. Calf blood flow (a) and vascular conductance (b) at normothermic baseline (Pre) and every 30 min throughout 60 min of passive heating and 2 h of normothermic post‐heating recovery in young (open circles, n = 16) and older individuals (filled circles, n = 9). Values are means ±95% confidence intervals. Inferences were drawn from two‐way mixed‐effects models (age X time) using Dunnett's multiple comparisons test for changes over time versus baseline within each age group and Šidák's multiple comparisons test to compare between groups at the same time point.

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  FIGURE 4. Calf cutaneous vascular conductance via integrated (a) and single point probes (b), and percent of maximal cutaneous vascular conductance via single point probes (c) at normothermic baseline (Pre), every 10 min throughout 60 min of passive heating, and every 30 min throughout normothermic post‐heating recovery in young (open circles, n = 16) and older individuals (filled circles, n = 9). Values are means ±95% confidence intervals. Due to technical challenges, cutaneous vascular conductance was not obtained in one young participant 10 and 20 minutes into heating (Panels a–c), one young participant 50 min into heating (Panels b and c), one young participant 60 min into post‐heating recovery (Panel a), and one older participant 30 min into post‐heating recovery (Panels a–c). Maximal cutaneous vascular conductance was not obtained in one older participant (Panel c: n = 8 older). Inferences were drawn from two‐way mixed‐effects models (age X time) using Dunnett's multiple comparisons test for changes over time versus baseline within each age group and Šidák's multiple comparisons test to compare between groups at the same time point.

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  FIGURE 5. Cardiac (a), brachial vascular (b), and blood pressure (c) responses to 50 mmHg neck pressure at normothermic baseline (Pre), at the end of 60 min of passive heating, and every 30 min throughout 2 h of normothermic post‐heating recovery in young (open bars, n = 16) and older individuals (filled bars, n = 9). Each box represents the median and the 25th and 75th percentile. Whiskers represent the 5th and 95th percentiles. The symbol within each box represents the mean. Due to technical challenges, cardiac, brachial vascular, and blood pressure responses were not obtained in one older participant at 60 and 90 min into post‐heating recovery, and brachial vascular responses were not obtained in one older participant at baseline and one older participant at the end of heating. Inferences were drawn from two‐way mixed‐effects models (age X time) using Dunnett's multiple comparisons test for changes over time versus baseline within each age group and Šidák's multiple comparisons test to compare between groups at the same time point.