Author(s): TAYLOR, C., COSTELLO, J., MILLER-DICKS, M., HUDSON, L., WARREN, J., WHITE, D., MAYES, H., TIPTON, M., WILLIAMS, T., Institution: UNIVERSITY OF PORTSMOUTH, Country: UNITED KINGDOM, Abstract-ID: 2029

INTRODUCTION:
Studies investigating physiological and cognitive responses to high altitude exposure often use normobaric hypoxia to overcome the logistical challenges of real hypobaric exposures. Such investigations commonly require participants to wear an oronasal facemask to measure respiratory data and/or deliver a hypoxic gas mixture. We hypothesised that discomfort and/or altered breathing mechanics associated with mask use would influence the symptoms associated with acute mountain sickness (AMS) and cognitive performance.
METHODS:
Eighteen healthy adults (4 females, mean ± SD: age 25 ± 4 y; height 175 ± 7 cm; mass 76 ± 8 kg) completed three 2-hour exposures (continuous mask [CM], no mask [NM], intermittent mask [IM]) to normobaric hypoxia (FiO2 0.13) in a randomised, counterbalanced design. Participants completed the Stroop task, a mood scale, Lake Louise Questionnaire (LLQ), and Environmental Symptoms Questionnaire (ESQ) at baseline and after each hour of exposure. Peripheral oxygen saturation (SpO2; finger and ear) and prefrontal oxygenation were recorded continuously. Participants were blinded to the true purpose of the study. Post-visit interviews were conducted to provide contextual insight about participants’ individual experiences and comfort; responses were coded using content analysis.
RESULTS:
Symptoms of AMS, particularly headache, were reported more frequently in CM (n = 8; 44%) compared to NM and IM (both n = 3; 16%). A repeated-measures ANOVA revealed a significant time × condition interaction for SpO2 (P = < 0.0001) and a main effect of condition (P = 0.011). Post-hoc comparisons showed mean SpO2 was significantly lower in CM (ear: 86.1 ± 3.1, finger: 82.9 ± 3.2 %) compared to NM (ear: 88.8 ± 3.3, finger: 84.8 ± 3.2 %) and IM (ear: 87.6 ± 3.3, finger: 84.2 ± 3.2 %) (both P < 0.001). Feelings of fatigue, depression and restlessness increased in CM compared to NM and IM, alongside reductions in happiness and vigour (P < 0.05). Stroop performance and prefrontal oxygenation did not differ between conditions. Post-visit interview analysis indicated that 17 participants (94%) experienced discomfort due to the mask. Of these, 13 participants (72%) felt the mask may have increased symptoms associated with AMS and 10 (56%) believed the mask had an impact on their cognitive performance.
CONCLUSION:
Wearing an oronasal facemask during simulated high-altitude exacerbates arterial desaturation and was associated with a greater incidence of symptoms of AMS including headache and a reduction in mood. Despite these physiological and perceptual changes, prefrontal oxygenation and performance of the Stroop task remained consistent between conditions, partially supporting our hypothesis. These findings suggest that an oronasal facemask may alter symptomatology during simulated high-altitude exposures. Future research should determine whether cognitive performance is preserved across other cognitive domains and elucidate the mechanisms underlying the observed reductions in SpO2.