High Altitude Dynamics in Cerebral Oxygenation of Mountain Rescue Personnel: A Prospective Alpine Proof-of-Concept Field Study

Background: Mountain Rescue Services (MRS) are a vital link in the chain of survival when it comes to emergencies at high altitudes. Cognitive impairment in hypobaric hypoxic conditions is known, and previous studies have shown suboptimal performance of MRS members after a steep ascent. These impairments may be linked to regional cerebral oxygenation (rSO2). Therefore, this study aimed to investigate whether there are dynamics in rSO2 between “baseline” and “working” altitudes after climbing up to a potential patient. Methods: In this alpine proof-of-concept field study, experienced mountaineers of the Austrian MRS had to perform an active rapid ascent of 1,200 meters on foot to 3,454 meters above sea level. Near-infrared spectroscopy (NIRS) was used to measure rSO2 before and after the climb. Continuous data were compared among subgroups using Mann-Whitney-U tests, and categorical data were compared with χ²-square tests. Statistical significance was defined by two-tailed P values of <.05. Results: Twenty MRS members were assessed. Their rSO2 values at baseline altitude were significantly higher than at working altitude (70 [SD = 1]% versus 60 [SD = 1]%; absolute difference 10 [95% CI, 6-15]; P <.001). When assessing the single dynamics of each mountain rescuer, there was a wide variability in delta rSO2, ranging from a minimum of 0% to a maximum of 32% (mean 10 [SD = 8]%). Conclusion: Overall, low rSO2 values were found in mountain rescuers at high altitudes, and there were considerable interpersonal differences of changes in cerebral oxygenation after an ascent. Using rSO2 to assess performance-readiness in mountain rescuers and individual proneness to potential cognitive dysfunction or acute mountain sickness (AMS) could be further research goals.