High Altitude Physiology & Medicine - KIN 424 - PDF

High Altitude Physiology & Medicine- KIN 424 Michael Koehle MD PhD Sports Medicine & School of Kinesiology Outline Physiology of Altitude Medical Syndromes at altitude Sleep at altitude Other Issues at Altitude Himalayan Rescue Association www.himalayanrescue.org Non-profit Nepali run organisation M...

High Altitude Physiology & Medicine- KIN 424 Michael Koehle MD PhD Sports Medicine & School of Kinesiology Outline Physiology of Altitude Medical Syndromes at altitude Sleep at altitude Other Issues at Altitude Himalayan Rescue Association www.himalayanrescue.org Non-profit Nepali run organisation Mandate to reduce illness & mortality in the Himalayas – Education Foreigners and Nepalese – Medical care of travellers – Medical care of locals (subsidised by foreigners) 3 Permanent clinics in Nepal 1 Emergency Clinic – Lake Gosainkunda (LangTang Region) CLINIC Manang Village 3680 Metres, Annapurna, Nepal Manang Aid Post, Nepal Operate an aid post Daily lecture to trekkers and guides House calls to villagers and nearby monasteries Organise evacuations when necessary 3 physicians, 1 RN, 1 cook, 1 chef de mission LAKE GOSAINKUNDA 4380 METRES, LANGTANG NEPAL GOSAINKUNDA HEALTH CAMP ~12,000 NEPALESE ASCEND TO 4380 METRES 68% GET ACUTE MOUNTAIN SICKNESS (AMS) TEMPORARY CAMP EVERY YEAR 350-700 PATIENTS IN 48-72 HOURS Case August 2010, 2100 hrs MOUNTAIN MEDICINE SOCIETY OF NEPAL NEWSLETTER JANUARY 2011 WHAT IS THE: DIAGNOSIS? TREATMENT? Relationship among altitude, barometric pressure, and inspired PO2 ~25% O2 ~50% O2 West, J. B. Ann Intern Med 2004;141:789-800 Example Elevations Altitude (m) 6000 4500 3000 Threshold for Altitude Illness 1500 0 Vancouver Whistler Boulder Boeing 787 Flagstaff Mexico Cty Iten, Kenya Jet (not 787) Leadville EBC Methods to Estimate VO2max upon Acute Hypoxia Exposure. MACINNIS, MARTIN; NUGENT, SEAN; MACLEOD, KRISTIN; LOHSE, KEITH Medicine & Science in Sports & Exercise. 47(9):1869-1876, September 2015. DOI: 10.1249/MSS.0000000000000628 FIGURE 2. A. Observed V[spacing dot above]O2max at highaltitude test (circles) for each independent participant group as a function of average baseline V[spacing dot above]O2max and test altitude. The size of each circle is inversely proportional to the variance of each study. B. Predicted V[spacing dot above]O2max at high-altitude test as a function of test altitude and baseline V[spacing dot above]O2max (shown as separate lines). These predictions are based on the curvilinear model. © 2015 American College of Sports Medicine. Published by Lippincott Williams & Wilkins, Inc. 9 Predicted Aerobic Capacity – Sea Level VO2max = 70ml/kg/min Altitude (m) 49. 47.25 45.5 43.75 42. 40.25 38.5 Boeing 787 Flagstaff, AZ Whistler Summit Mexico City Iten, Kenya Passenger Jet (not 787) Leadville, CO Acclimatisation – Occurs over days to months – Increased ventilation, cardiac output and hemoconcentration to enhance oxygen delivery – Sleep improves after first few days – Graded ascent where possible – In weeks to months, red blood cell mass increases End of Intro/Physiology Video Altitude Illness Syndromes Acute Mountain Sickness (AMS) High Altitude Cerebral Oedema (HACE) High Altitude Pulmonary Oedema (HAPE) AMS Risk factors Rate of ascent Previous history of AMS Exertion Obesity Possible Risk factors – Previous neck dissection – Dehydration – Infection AMS Symptoms Symptoms: – – – – – Headache Sleep disturbance, insomnia Anorexia, nausea, vomiting Light-headedness, dizziness Fatigue Differential Diagnosis: – Dehydration, hangover, migraine, overexertion, viral illness, subarachnoid haemorrhage, carbon monoxide exposure High-Altitude Cerebral Oedema Believed to be the severe end of the AMS spectrum Can be lethal within 12 hours Symptoms: – AMS symptoms, plus: – Ataxia – Confusion, lethargy, altered LOC High-Altitude Pulmonary Oedema (HAPE) Most lethal altitude illness Separate condition from AMS/HACE – Often co-exist Onset after 2-5 days Aggravated by cold, exertion Risk Factors: – – – – Rate of ascent Exertion Previous History Primary pulmonary hypertension, unilateral pulmonary artery HAPE Symptoms Dyspnoea at rest Cough Bloody cough – Pink frothy sputum Poor exercise tolerance Orthopnoea May be febrile Man with HAPE seated on a stretcher Altitude Illness Prevention Medications – Most medications are NOT permitted by WADA – AMS AND HACE Acetazolamide - PROHIBITED Dexamethasone - PROHIBITED – HAPE - RARE Tadalafil (Cialis™) – PREVIOUSLY MONITORED Nifedipine - PERMITTED Prevention of Altitude Illness Acclimatisation – Graded ascent to allow acclimatisation – Often overlooked – The general recommendations are: – at altitudes above 3000 m, – individuals can ascend by 300 to 600 m/day – In sleeping altitude – rest day for every 1000 m gained Prevention of Altitude Illness Hydration and Nutrition – Easy to get dehydrated at altitude-dry air, increased ventilation – Some evidence that altitude illness is more common with dehydration – High CHO diet may reduce incidence of altitude illness, seems to improve performance at altitude Previous History Important for rare conditions – HAPE and probably HACE Not as helpful for AMS Effects of intense exercise on: Lung Volume Lung Density Lung Mass Numbers of lymphatics in susceptible and resistant lungs Measuring Balance The Balance Error Scoring System (BESS) 35 BESS Chamber Study simulated altitude (4500 metres) measure balance with force plate and BESS assess severity of AMS with Lake Louise Score (LLS) cognitive function (CogState) cerebral oxygenation (NIRS) 36 BESS and mBESS 37 Balance Error Scoring System In the Field 38 BESS for AMS 39 What are some flaws for this study? Is it the low pressure or the hypoxia? 41 SFU Environmental Chamber 42 43 Conditions Simulated Altitude: Low Pressure, Low Oxygen Hypoxia Only: Normal Pressure, Low Oxygen Hypobaria Only: Low Pressure, Normal Oxygen Sham: Normal Pressure, Normal Oxygen 44 Main Outcomes AMS Symptoms Breathing Control (Hypoxia/CO ) cardiovascular parameters 2 45 46 Altitude Illness Treatment Descent and Oxygen - PERMITTED Medications – Most medications are not permitted by WADA – AMS AND HACE Acetazolamide - PROHIBITED Dexamethasone - PROHIBITED – HAPE Tadalafil (Cialis™) – MONITORED Nifedipine - PERMITTED Altitude Illness Not as common at these altitudes Can mimic dehydration, migraine, hangover, exhaustion For all cases, consult your physician Be extra careful around medications Increased physiological stress – think overtraining Gamow Bag -inflate to 2 psi -simulated descent -equivalent to ~1600 metre descent -temporizing measure Altitude Illness in Athletes (training camps) Typically occurs above 2500m (8000’) in climbers and trekkers Destination altitude training usually occurs at 1800-2500m Intense exercise at these lower altitudes changes the picture – AMS reported at 1950 and 2100 m in athletes at training camps – Incidence up to 44% – Recommended to lower intensity on first few days Iron A large proportion of endurance athletes have low iron stores – Increased red cell destruction – sweat loss of iron – impaired iron absorption post-exercise Iron is necessary for red cell synthesis Other Health Effects Ultraviolet radiation – Increased at altitude UV radiation increases between 11% and 19% per 1000 m of elevation – Increased potential for burns, UV keratitis (snow blindness) – Reflection off snow (water for rowers/paddlers) Immunosuppression – Susceptibility to infection Immunization – Stay up to date Sickle Cell Trait – Heterozygous HbS – At risk for splenic infarctions Albedo fraction of light that a surface reflects. If it is all reflected, the albedo is equal to 1. If 30% is reflected, the albedo is 0.3. – nasa.gov Sleep Hypoxia impairs sleep directly – More frequent arousals – less restful – impacting recovery Jet Lag often an issue with altitude training or competition Poor sleep environment (teammates/tents) Sleep Hygiene Quiet, dark, comfortable temperature environment Caffeine, alcohol nicotine interfere with sleep Exercise in the late afternoon/early evening Light bedtime snack Electronics and devices interfere with sleep – Bedroom only for sleep and intimate activity Aggressive management of jet lag Sleep Medications Consider carefully – adverse effects Consult with physician May help with jet lag as well – Safe at altitude: temazepam (10mg) zolpidem, zaleplon (10mg) Acetazolamide effective for sleep at altitude but PROHIBITED Pre-acclimatisation Strategies Intermittent Hypoxia Training Immediate Arrival – Less sleep debt, illness and dehydration Prolonged (>7-10 days) Acclimatisation – Overcome early issues Summary Anticipate a significant decrease in aerobic capacity at altitude Be aware of Altitude Illness Syndromes Optimize iron status Optimize sleep and travel arrangements Optimize hydration and nutrition Choose the best possible pre-acclimatisation strategy for your athletes WHATS THE: DIAGNOSIS? TREATMENT? CASE 1 Junior National Indoor Climbing Team Upcoming competition in Bolivia La Paz– 3640 metres What issues might the team face when competing at this altitude? How should the team prepare? CASE 2 50 year-old male mining executive Mine site visit (4500m) in Argentina Sulfa allergy On Viagra prn for ED Treated hypertension How should he be managed? Case 3 46 year-old mountaineer Climbing Everest (8850m) in 3 months time Previous history of LASIK surgery Worried about the vision