SCD 2014: High Altitude

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Claude A. Piantadosi, MD

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SCD 2014: High Altitude

  1. 1. HIGH ALTITUDE Claude A. Piantadosi, MD Professor of Medicine Division of Pulmonary and Critical Care Director, Center for Hyperbaric and Environmental Medicine
  2. 2. High Altitude • Objectives • The high altitude “problem” • Altitude illnesses/prevention • Exercise limitations at altitude • Training at altitude • Traditional: Live high-train high (LHTH) • Live high-train low (LHTL) • Live low-train high (LLTH) • SCD and other health risks at moderate altitudes No COI related to the topic of this talk Research funding: NHLBI, VA, ONR, DARPA
  3. 3. High Altitude • 100+ million visitors to high altitude each year • Many sports involve training and/or competition at altitude • Challenges for athlete and clinician • Severe environment • Hydration • Nutrition • Altitude illness • Impact on training intensity and performance Sochi 2014— Elevation 2,300 m (7,500 feet)
  4. 4. High Altitude Definitions Elevation (meters*) Altitude Pressure (mmHg) PIO2 (mmHg) Effects 0-500 Sea level 760-743 159-155 Normal 500-2,000 Low 743-604 155-126 Minor impairment in performance 2,000-3,000 Moderate 604-537 126-112 Altitude illness appears; acclimatization is increasingly important 3,000-5,500 High 537-394 112-82 Considerable decline in performance; altitude illness and acclimatization are clinically important >5,500 Extreme <394 <82 Prolonged exposure leads to progressive deterioration (Zone of Death 8,000 m) *1 meter= 3.28 feet
  5. 5. Arterial Blood Gas Measurements and Calculated Values for Pulmonary Gas Exchange at an Altitude of 8400 m during Descent from Mount Everest GrocottMPetal.NEnglJMed2009;360:140-149.
  6. 6. High Altitude • Hypoxia is the stimulus for acclimatization • Hyperventilation/respiratory alkalosis • HIF-1 and target genes (EPO, VEGF, Glut4) • Individual differences in physiology and genetics • Benefits of acclimatization • Restores mental performance (1-2 d) • Reduces susceptibility to altitude illness (3-5 d) • Improves sleep quality (5-7 d) • Enhances O2 delivery, O2 utilization, work performance (10-14 d)
  7. 7. Acclimatization to High Altitude 0 25 50 75 100 0 50 100 PO2 (mmHg) O2 saturation (%) Altitude Cold CO Fever Exercise 2,3 DPG 5 10 15 20 7 14 21 28 Blood O2 content (mL/100mL) Normal Acclimatized
  8. 8. High Altitude • Failure of physiological adaptation • Associated with rapid ascent rates • Above 3000 m, ascend by 300-600 m/d with a rest day for each gain of 1000 m • High altitude illnesses • Acute mountain sickness (AMS) • 40-50% over 10,000 feet • High altitude pulmonary edema (HAPE) • 2% over 10,000 feet • High altitude cerebral edema (HACE) • 0.1% over 10,000 feet • High altitude retinal hemorrhages • Rare
  9. 9. Acute Mountain Sickness (AMS) • Lake Louise Criteria • Headache after recent gain in altitude plus one of: • Anorexia, nausea, vomiting • Fatigue or weakness • Dizziness or lightheadedness • Sleep disturbance
  10. 10. High Altitude Illness • Prevention • Slow ascent • Hydration • Acetazolamide (125 mg BID)* • Dexamethasone (2 mg QID)* • Nifedipine (HAPE) • Salmeterol (HAPE) • Tadalafil/sildenafil (HAPE) • Treatment • Ibuprofen • O2 • Descend • Dexamethasone *Banned by WADA
  11. 11. Other High Altitude-related Health Issues • Sudden cardiac death (SCD) • Sleep disordered breathing (part of AMS) • Tracheobronchitis • Aggravation of pre-existing COPD, CAD, CVD • Unmasking cardiovascular disease that is asymptomatic at sea level • Chronic mountain sickness (CMS; Brisket disease in cattle; Monge’s disease in people) • Altitude >2,500 m • Hct >65% • Elevated PVR C. Monge 1884-1970
  12. 12. VO2max and Exercise Performance • For untrained subjects and endurance athletes who reside near sea level, lower VO2max can be observed at 400-800 m (~1,300-2,600 ft.) • Above 1,500 m (~5,000 ft.), VO2max is reduced by ~1% for each 100 m altitude Performance decrement at altitude in elite cross country skiers
  13. 13. High Altitude • Adaptation to Altitude • Hypoxia limits exercise capacity American Medical Expedition to Everest (AMREE 1981) 150100500 0 20 40 60 80 100 VO2max(%) Inspired PO2 (mmHg) Summit Mt. Everest 8,848 m Sea Level Limit 9,250 m (PB 240 mmHg) Zone of Death (8,000 m) Acclimatization is complete
  14. 14. High Altitude • Live low train high (LLTH) strategy • Subjects train in hypoxia, but otherwise remain in normoxia • Rationale • Exercise in hypoxia might increase training stimulus • Sleep quality is maintained • No consistent sea level performance benefit of “LLTH” model • May be a consideration when altitude acclimatization is not feasible
  15. 15. Untrained Subjects Training in Hypoxia Vogt M, et al: Molecular adaptations in human skeletal muscle to endurance training under simulated hypoxic conditions. J Appl Physiol 91:173-182, 2001 Vastuslateralis mRNAlevels High intensity Normal Hypoxia Low intensity Normal Hypoxia
  16. 16. High Altitude • Live High–Train Low (LHTL)” • Improves sea level performance and VO2max in elite and sub-elite endurance athletes • Improvements linked to hematological acclimatization (increase in O2 carrying capacity of blood) • Mediated largely by EPO and increased RBC mass • “Threshold” below which there is little or no hematological response (2,100-2,500 m) • Responders and non-responders
  17. 17. High Altitude • LHTL in college track/cross country athletes • Live at one of four altitudes for 4 weeks (as below) • High intensity training at 1,250 m • VO2 max and EPO levels tested pre-, post-, and 2 weeks post-study (~5%) Chapman, RF et al. Defining the dose of altitude training: How high to live for optimal sea level performance enhancement. J Appl. Physiol. In press, 2014.
  18. 18. High Altitude Chapman, RF et al. Defining the dose of altitude training: How high to live for optimal sea level performance enhancement. J Appl. Physiol. In press, 2014.
  19. 19. High Altitude Chapman, RF et al. Defining the dose of altitude training: How high to live for optimal sea level performance enhancement. J Appl. Physiol. In press, 2014.
  20. 20. Metabolic Syndrome and High Altitude • Metabolic syndrome and exercise at altitude • Body weight/composition improve with hypoxic training (≥1,700 m) three times a week • Extreme altitude (>5,000 m) causes loss of fat-free muscle mass • Fasting blood glucose generally improves (≥21days) at moderate altitude (1,500–3,000 m) • Reductions in glucose tolerance observed when subjects exposed to altitude >4,000 m • Resting BP improves with hypoxic training (1,285–2,650 m) by ~26 /13 mmHg in stable medicated hypertensive subjects • Hypoxic exercise training has mixed/no effect on cholesterol/lipids Wee J, Climstein M. Hypoxic training: Clinical benefits on cardiometabolic risk factors. J Sci Med Sport (2013), http://dx.doi.org/10.1016/j.jsams.2013.10.247
  21. 21. SCD at High Altitude • SCD is responsible for 30% of all deaths during mountain sports at altitude • SCD is most frequent cause of non-traumatic deaths at altitude • Palpitations at high altitude are almost universal • Hypoxia, sympathetic activation, and alkalosis predispose to cardiac ischemia and arrhythmia at altitude • Age, CAD, DM, hyperlipidemia, and prior MI are known risk factors for SCD at altitude
  22. 22. SCD at High Altitude • Data from Austrian Alps • Men >34 years • 1 SCD per 802,000 hours of exposure for hikers • 1 SCD per 1,500,000 hours of exposure for downhill skiers • Risk of SCD is 4.2x higher for hikers and 2.2x for skiers compared with SCD in men ages 35-70 at sea level
  23. 23. SCD on First Day at Altitude Lo MY, Daniels JD, Levine BD, Burtscher M. Sleeping altitude and sudden cardiac death. Am Heart J. 2013 Jul;166(1):71-5. SCD Frequency (% dying on first day) Sleeping Altitude (m) <700 700-999 1,000-1,299 1,300+ 80 60 40 20 0 N= 93 87 65 56
  24. 24. High Altitude Recommendations for Pre-existing Conditions • In patients with diseases that affect ventilation, gas exchange, or cardiac function: • For stable disease or mild stable symptoms during exercise (NYHA Functional Class I and II) and stable LV function, stays at altitudes up to 3,000 to 3,500 m are generally safe • Negative exercise test or an ischemic threshold above 6 METs at sea level WITHOUT significant arrhythmia • Contraindications to altitude exposure • Unstable angina • Uncomplicated MI or recent revascularization within last 4 weeks • Complicated MI within last 3 months • Prior VT or AF unless exercise testing has shown cardiac rhythm stability

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