1. Intermittent Hypoxic Preconditioning may Reduce Prevalence of Acute Mountain Sickness on Ascent to High Altitude: A Case Study Steven Gowling, Rachael Dawe & Lisa Board Dept of Sport & Exercise Sciences, University of Sunderland, Sunderland SR1 3SD. Introduction: Introduction: The acclimatisation process begins as the human body is exposed to hypoxic conditions found at high altitude (HA). The recommended method of acclimatisation is a slow and gradual ascent. This provides sufficient time for physiological changes to occur thus reducing the incidence and severity of acute mountain sickness (AMS) (Imray et al, 2010). The increase in adventure tourism has seen the number of visitors to the high altitude regions of the world increase dramatically. Many are on tight schedules and may leave insufficient time for appropriate acclimatisation. Current evidence suggests the prevalence of AMS ranges between 25% to 90% and is dependant upon location, ascent profile and altitude gain. Despite years of research there remains no clear predictive marker for AMS susceptibility. Changes in the regulation of the autonomic nervous system by assessing alterations of heart rate variability (HRV) parameters are considered useful in monitoring hypoxic coping mechanisms. Intermittent hypoxic (IH) exposure has been shown to enhance ventilatory acclimatisation but only one study to date (Povea, et al, 2005) has evaluated the effect of IH exposure on autonomic nervous acclimatisation responses. IH exposure using normobaric hypoxia (NH) offers potential to provide a timesaving alternative to improve cardiovascular acclimatisation during ascent to HA (Wille et al, 2012: Burtscher et al, 2008). Methods References Figure 1 a, LF/HF low frequency to high frequency ratio; b, SpO 2, oxygen saturation; c, HFnu, high frequency (normalised units); d, LFnu, low frequency (normalised units). Conclusions: Conclusions: HRV appeared to show signs of acclimation following IH. These autonomous nervous system adaptations appear to have benefitted this participant on arrival to HA. These findings are among the first to demonstrate the practical and worthwhile importance of modest HRV adjustments to be gained from IH exposures prior to ascent to HA. Results: Results: Two participants were diagnosed with AMS. The IH participant did not develop AMS and maintained good SpO 2 levels throughout the expedition. SpO 2 at HA decreased in all participants from SL baseline by 7% in IH participant, 12% in other non AMS participants and 16% in those with AMS. IH participant displayed lower levels of HFnu at SL than other non AMS participants however these levels did not decrease on ascent to HA in comparison to the rapid decline experienced by all other participants. No increase in LFnu was recorded in the IA participant at any altitude. Sympathetic dominance signified by the LF/HF ratio was higher in IA participant at SL but 34% lower than non AMS group and 83% lower than those who developed AMS at HA. Aim: Aim: In this study, we speculated that an 8 day pre- acclimatisation intervention using a short term normobaric IH protocol (2 h continuous, IH [F I O 2 =12.2%, ~4300 m] daily) may prevent AMS during ascent to high altitude or ameliorate the symptoms. Ethics - This study was approved by the University of Sunderland Research Ethics Sub-Committee for Sport. Burtscher, M., Brandstätter, E. & Gatterer, H. (2008) Preacclimatization in Simulated Altitudes. Sleeping & Breathing. 12 2, 109-114. Imray, C., Wright, A., Subudhi, A. & Roach, R. (2010) Acute Mountain Sickness: Pathophysiology, Prevention, and Treatment. Progress in Cardiovascular Diseases. 52, 467- 483. Povea, C., Schmitt, L., Brugniaux, J., Nicolet, G., Richalet, J.P. & Fouillot, J.P. (2005) Effects of Intermittent Hypoxia on Heart Rate Variability during Rest and Exercise. High Altitude Medicine & Biology. 6 3, 215-25. Wille, M., Gatterer, H., Mairer, Phillippe, M., Schwarzenbacher, H., Faulhaber, M. & Burtscher, M. (2012) Short Term Intermittent Hypoxia Reduces the Severity of Acute Mountain Sickness. Scandanavian Journal of Medicine and Science in Sports. 22, 79-85.. Participants 5 healthy and injury free male volunteers (age 48 ± 2 years, height 176 ± 0.03 cm, body mass 87 ± 12 kg). All participants were lowland residents and recreational mountaineers although none had been exposed to altitudes of over 1500 m within 3 months prior to the study. None were taking medications such as acetazolamide or any other drug considered prophylactic toward AMS. NH Protocol All participants were familiarised with the study and subsequently completed 4 trials in the laboratory. Resting HRV indices were measured using a Polar RS800CX heart rate monitor in a supine position. Participants breathed spontaneously. Measurements were taken at sea level (SL) and at 3 normobaric simulated altitudes (F I O 2 ; 1200 m (20.1%), 2500 m (15.7%), & 3200 m (14.8 %). HH Protocol The same resting SpO 2 and HRV measures were collected on the mountain at the corresponding altitudes 1200, 2500, 3200 m. AMS was defined by a Lake Louise Score of >3 plus headache. Pre-conditioning Protocol One participant (height 1.79 m, body mass 93 kg) underwent an intermittent NH acclimatisation protocol consisting of 8 x 2 hour sessions (F i O 2 12.2%, ~ 4300 m) over 10 days prior to expedition. IH sessions were performed using a portable hypoxic unit (Higher Peak, Mag-10 hypoxicator). Analytical Techniques HRV data was uploaded from the Polar RS800CX Pro Trainer watches into the Polar Pro Trainer 5 software programme for labelling and error correction. Data was then exported into Kubios HRV software (Finland). Indices of HRV were calculated according to recommendations set out by The Task Force of the European Society of Cardiology and the North American Society of Pacing Electrophysiology (1996). LF/HF Ratio a b c d HF (nu) LF (nu) SpO 2 (%) IH AMS NON AMS 80 70