Peer reviewed version Cyswllt i'r cyhoeddiad / Link to publication Dyfyniad o'r fersiwn a gyhoeddwyd / Citation for published version (APA): Abstract: Aims: Acute mountain sickness (AMS) develops when the body fails to acclimatize to atmospheric changes at altitude. Pre-ascent prediction of susceptibility to AMS would be a useful tool to prevent subsequent harm. Changes to peripheral oxygen saturation (SpO2) on hypoxic exposure have previously been shown to be of poor predictive value. Heart

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... e variability (HRV) has shown promise in the early prediction of AMS, but its use pre-expedition has not previously been investigated. We aimed to determine whether pre-and intra-expedition HRV assessment could predict susceptibility to AMS at high altitude with better diagnostic accuracy than SpO2. Methods: 44 healthy volunteers undertook an expedition in the Nepali Himalaya to >5000m. SpO2 and HRV parameters were recorded at rest in normoxia and in a normobaric hypoxic chamber prior to the expedition. The same data were later collected at various altitudes on the expedition along with daily Lake Louis Score to assess AMS symptomology. Results: Low frequency/high frequency ratio (LF/HF) in normoxia and LF following 15 minutes of exposure to normobaric hypoxia had moderate (area under the curve ≥ 0.8) diagnostic accuracy. LF/HF ratio in normoxia had the highest sensitivity (85%) and specificity (88%) for predicting AMS on subsequent ascent to altitude. In contrast pre-expedition SpO2 measurements had poor (area under the curve < 0.7) diagnostic accuracy and inferior sensitivity and specificity. Conclusions: Pre-ascent measurement of HRV in normoxia has potentially better diagnostic accuracy for AMS prediction than all measures of HRV in hypoxia, and better than peripheral SpO2 saturation monitoring.