Sex differences during a cold-stress test in normobaric and hypobaric hypoxia: A randomized controlled crossover study

Abstract

Cold and hypoxia are two stressors that are frequently combined and investigated in the scientific literature. Despite the growing literature regarding normobaric hypoxia (NH) and hypobaric hypoxia (HH), responses between females and males are less often evaluated. Therefore, this study aims to investigate the physiological sex differences following a cold-stress test under normoxia, normobaric- and hypobaric hypoxia. A total of n = 10 females (24.8 ± 5.1 years) and n = 10 males (30.3 ± 6.3 years) from a university population volunteered for this study. The cold-stress test (CST) of the right hand (15°C for 2 min) was performed using a randomised crossover design in normobaric normoxia, NH and HH. The change (∆) from baseline to post-CST up to 15 min was analysed for cutaneous vascular conductance (CVC) and the hands’ skin temperature, whilst the mean values across time (post-CST up to 15 min) were assessed for peripheral oxygen saturation (SpO2), thermal sensation- and comfort. Pressure pain threshold (PPT) was assessed after the post-CST 15 min period. The hands’ skin temperature drop was higher (p = 0.01) in the female group (∆3.3 ± 1.5°C) compared to the male group (∆1.9 ± 0.9°C) only in NH. Females (−0.9 ± 0.5) rated this temperature drop in NH to feel significantly colder (p = 0.02) compared to the males (−0.2 ± 0.7). No differences were observed between sexes in NN, NH, and HH for ∆CVC, SpO2, thermal comfort and PPT. In conclusion, females and males show similar reactions after a CST under normoxia and hypoxia. Sex differences were observed in the local skin temperature response and thermal sensation only in NH.

Sex comparisons in physiological and cognitive performance during hypoxic challenge

“…Though accounting for a small percentage of SpO 2 , these results are consistent with Archiza et al (2020) findings regarding sex differences in diaphragmatic muscle fatigue under acute hypoxia. However, our finding of lower SpO 2 for females is inconsistent with prior work using less severe altitudes that found no sex differences ( Hohenauer et al, 2022 ; Karayigit et al, 2022 ). The altitudes examined here most closely align with the 8% O 2 used by Archiza et al (2020) .…”

“…The altitudes examined here most closely align with the 8% O 2 used by Archiza et al (2020) . Moreover, given the small sample sizes used in previous work ( Hohenauer et al, 2022 ; Karayigit et al, 2022 ), their null result for sex differences in SpO 2 was possibly due to inadequate power. The larger sample size used in our study afforded us a better opportunity to assess these differences, and our results did indicate that the effect was quite small with sex, age, and BMI only accounting for 6% variance in SpO 2 ( Table 3 ).…”

“…Also looking at respiratory effects of hypoxia, Camacho-Cardenosa et al (2022) found that males had an increase in minute ventilation and a steeper initial decrease in peripheral oxygen saturation (SpO 2 ) compared to females during a 7 h moderate hypoxia exposure (15% O 2 ). Two additional studies examined sex differences in the effects hypoxia have on cold stress ( Hohenauer et al, 2022 ) and muscle endurance ( Karayigit et al, 2022 ), but both studies found no difference in SpO2 between sexes during those moderate hypoxia exposures. These inconsistent findings suggest that there may be sex differences in physiological response to hypoxic challenge.…”

Acute physiological responses and muscle recovery in females: a randomised controlled trial of muscle damaging exercise in hypoxia

“…Furthermore, Vento et al (2022) identified markedly diminished capillary oxygenation levels and an increased occurrence of headache in females compared to males during acute hypoxia [28]. Despite the existence of studies that didn't observe sex differences [29,30], the inconsistence outcomes underpin the significance of investigating female responses to hypoxic stimuli. Therefore, our study aimed to compare the acute physiological effects after a single session of muscle damaging exercise, carried out under hypoxia (HYP) and normoxia (CON), and to evaluate the effects on subjective and objective recovery during a 72-hrs follow-up period.…”