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Hypoxia acts as a physiological stressor that directly influences heart rate, as evidenced by the observed increases in heart rate under hypoxic conditions [1], [2]. Studies confirm that hypoxia triggers vagal withdrawal and sympathetic modulation, which are key mechanisms for the observed changes in heart rate [3], [2], and these variables are frequently measured together in cardiorespiratory research [4], [5].
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Sex differences in cardiorespiratory control under hypoxia - Frontiers frontiersin.org 9 facts
claimAugmented heart rate under hypoxia is often a result of vagal withdrawal triggered by the aortic bodies.
claimBoos et al. observed that females experience a greater increase in heart rate than males under hypoxia, while also tending to maintain higher oxygen saturation levels.
claimThe time effect of hypoxia was similar for both male and female groups, increasing heart rate, cardiac output, and total vascular conductance while decreasing mean blood pressure.
measurementUnder normoxia, males have a heart rate (HR) of 74 ± 10 bpm and females have 83 ± 6 bpm; under iso-saturation hypoxia, males have 77 ± 8 bpm and females have 90 ± 7 bpm.
procedureIn the study on sex differences in cardiorespiratory control under hypoxia, heart rate, stroke volume, and cardiac output were recorded using a noninvasive trans-thoracic bioimpedance device (PhysioFlow), R-R intervals were recorded via electrocardiogram (ECG Module), and continuous blood pressure was recorded via infrared photoplethysmography (Finometer PRO).
procedureThe experimental protocol for the study on sex differences in cardiorespiratory control under hypoxia involved recording hemodynamic variables (heart rate, stroke volume, cardiac output, blood pressure) and respiratory variables (breathing frequency, tidal volume, minute ventilation, SpO2) after a 20-minute rest period in a sitting position.
referenceHalliwill and Minson studied the effect of hypoxia on arterial baroreflex control of heart rate and muscle sympathetic nerve activity in humans in a 2002 study published in the Journal of Applied Physiology.
measurementUnder hypoxia, both males and females exhibit increased heart rate, vagal withdrawal, and augmented sympathetic modulation, shifting the sympatho-vagal balance towards sympathetic dominance.
claimSome studies indicate that under hypoxic conditions, females exhibit higher heart rates and sympathetic activity compared to males, despite similar levels of oxygen desaturation.
Sex differences in respiratory and circulatory cost during hypoxic ... nature.com 2 facts
measurementIn a study of physiological responses to hypoxia, multiple regression analysis showed that the change in heart rate (ΔHR) was a significant factor in predicting the change in oxygen saturation (ΔSpO2) for both men (t(8) = -6.54, P = 0.001) and women (t(8) = -4.04, P = 0.010).
procedureThe researchers calculated changes in SpO2 with hypoxia and used multiple regression analysis to test for the independent, additive effects of energy expenditure (EE), ({\dot{{\rm{V}}}}{{\rm{E}}}), and heart rate (HR) on SpO2 after logarithmic transformation.