No sex differences in the cardiac responses during high altitude sojourn to 4300 m

Ascent to high altitude reduces oxygen availability and provokes compensatory cardiovascular responses. Females may exhibit attenuated hypoxic ventilatory responses compared to males, which could subsequently exaggerate the cardiovascular response to high altitude among females. The purpose of this study was to examine sex differences in cardiac responses during high altitude sojourn in young, healthy males and females. We hypothesized that females would exhibit a greater reduction in arterial oxygen saturation, and greater cardiac dysfunction compared to males. 17 healthy adults (8 males, 24±4 yrs, BMI 25.7±3.1 kg/m 2 ; 9 females, 23±4 yrs, BMI 24.5±3.0 kg/m 2 ) underwent cardiac assessment via echocardiography at 1400 m and after an 8-day ascent to 4300 m. Left ventricular (LV) systolic function was assessed via ejection fraction and fractional shortening. Diastolic function was assessed as the ratio between early and late mitral filling velocities (E:A ratio). The subendocardial viability ratio (SEVR) was derived from carotid tonometry, and carotid pressure waves were integrated with echocardiography derived measures of left ventricular ejection to estimate a left ventricular pressure-volume loop and calculate stroke work. Ascent from 1400 m to 4300 m resulted in reduced end-tidal CO 2 (-Δ8±3 males, -Δ8±2 mmHg females, p<0.001), oxygen saturation (-Δ11±3 males, -Δ11±5 % females, p<0.001), and LV fractional shortening (-Δ7.9±7.5% males -Δ1.0±6.4 % females, p=0.028) in both groups. Despite greater stroke work among males (p=0.002), high altitude-induced changes were not statistically different compared to females (+Δ35±184 males, +Δ3±113 mL/mmHg females). Changes in LV ejection fraction (-Δ1.9±14.4 males, -Δ1.5±18.7 % females) mitral E:A (-Δ0.33±0.53 males, -Δ0.09±0.64 au females), and SEVR (-Δ0.06±0.33 males, +Δ0.15±0.20 au females) from 1400 to 4300 m were not statistically different between sexes. Ascent from 1400 to 4300 m decreased end-tidal CO 2 , arterial oxygen saturation, and select metrics of LV systolic function (e.g., fractional shortening), but LV diastolic function, stroke work, and SEVR was preserved in both males and females. We observed no apparent sex differences in the effects of 8-day sojourn to 4300 m on arterial oxygen saturation, or cardiac systolic and diastolic function. Additional research is necessary to confirm these results in the context of longer-term altitude exposure and acclimatization, and in older populations (middle-aged and older adults). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.