Smartphone-Enabled Heart Rate Variability and Acute Mountain Sickness

INTRODUCTION: The autonomic system and sympathetic activation appears integral in the pathogenesis of acute mountain sickness (AMS) at high altitude (HA), yet a link between heart rate variability (HRV) and AMS has not been convincingly shown. In this study we investigated the utility of the smartphone-derived HRV score to predict and diagnose AMS at HA. METHODS: Twenty-one healthy adults were investigated at baseline at 1400 m and over 10 days during a trek to 5140 m. HRV was recorded using the ithlete HRV device. RESULTS: Acute mountain sickness occurred in 11 subjects (52.4%) at >2650 m. HRV inversely correlated with AMS Scores (r = -0.26; 95% CI, -0.38 to -0.13: P 5 had a sensitivity of 83% and specificity of 60% to identify severe AMS (likelihood ratio 1.9). Baseline HRV at 1400 m was not predictive of either AMS at higher altitudes. CONCLUSIONS: The ithlete HRV score can be used to help in the identification of severe AMS; however, a baseline score is not predictive of future AMS development at HA

Comparison of spontaneous versus paced breathing on heart rate variability at high altitude

© 2018, Journal of Clinical and Diagnostic Research. All rights reserved. Introduction: There is conflicting data at sea-level to suggest that Paced Breathing (PB) versus Spontaneous Breathing (SB) during short-term Heart Rate Variability (HRV) measurement improves data reliability. Aim: This study sought to examine the effects of SB versus PB on HRV, at High Altitude (HA). Materials and Methods: This was a prospective observational study on thirty healthy adult men who were investigated over nine days at altitudes of 800-4107 m. Cardiac inter-beat interval data were measured over 55 seconds, twice daily, using an ithlete finger sensor linked to a mobile phone to generate a HRV score. Agreements in the paired (SB vs PB) HRV scores were examined using paired t-tests, correlation coefficients and F-Testing. A factorial repeated measures ANOVA was used to examine the main effect of altitude and breathing method on the paired differences in HRV scores. Results: HA led to a significant reduction in SpO2 and increase in Acute Mountain Sickness (AMS) Scores. HRV scores (511 paired scores) were consistently higher with PB versus SB (mean difference +6.0; 96.1% within 95% agreement limit), though the variance was lower (F=1.2; p=0.04) and the scores strongly correlated (r=0.78; p<0.0001). HRV scores were lower with AMS (versus without AMS), but this difference was only significant with SB (68.1±12.1 vs. 74.3±11.4 vs; p=0.03) but not PB (76.3±11.8 vs. 80.3±10.4 vs; p=0.13). There was a significant main-effect for altitude (F=5.3; p<0.0001) and breathing (F=262.1; p<0.0001) on HRV scores but no altitude-x-breathing interaction (F=1.2; p=0.30). Conclusion: Ithlete HRV scores obtained with PB and SB strongly correlate at moderate HA but are consistently higher and the variance lower with PB. Whilst the actual per se does not affect this difference, the presence of AMS may be an important confounder

Power Supplies and Equipment for Military Field Research : lessons from the British Service Dhaulagiri Research Expedition 2016

Introduction: The British Service Dhaulagiri Research Expedition (BSDMRE) took place from 27th March to 31st May 2016. The expedition involved 129 personnel, with voluntary participation in 9 different study protocols. Studies were conducted in three research camps established at 3600m, 4600m and 5140m and involved taking and storing blood samples, cardiac echocardiography and investigations involving a balance plate. Research in this remote environment requires careful planning in order to provide a robust and resilient power plan. In this paper we aim to report the rationale for the choices we made in terms of power supply, the equipment used and potential military applicability. Methods: This is a descriptive account from the expedition members involved in planning and conducting the medical research. Results: Power calculations were used to determine estimates of requirement prior to the expedition. The primary sources used to generate power were internal combustion engine (via petrol fueled electric generators), and solar panels. Having been generated, power was stored using lithium-ion batteries. Special consideration was given to the storage of samples taken in the field, for which electric freezers and dry-shippers were used. All equipment used functioned well during the expedition, with the challenges of altitude, temperature, and transport all overcome due to extensive prior planning. Conclusions: Power was successfully generated, stored, and delivered during the BSDMRE, allowing extensive medical research to be undertaken. The challenges faced and overcome are directly applicable to delivering military medical care in austere environments, and lessons learned can help with the planning and delivery of future operations, training exercises, or expeditions

The British Services Dhaulagiri Medical Research Expedition 2016 : a unique military and civilian research collaboration

The British Service Dhaulagiri Research Expedition took place in March-May 2016. A total of 129 personnel took part in the expedition and were invited to consent to a variety of study protocols investigating adaptation to high altitudes and diagnosis of altitude illness. The study took place in a remote and inhospitable environment at altitudes up to 7500m. This paper gives an overview of the challenges involved, the research protocols investigated and the execution of the expedition in Nepal