Exercise Physiology I - AS24 Hypobaric Conditions PDF

Department of Health Sciences and Technology Institute of Human Movement Sciences and Sport Hier steht der Titel der Präsentation Exercise Physiology I - AS24 Dieser kann, wenn immer nötig, über zwei oder sogar drei Zeilen laufen Hypobaric conditions - altitude...

Department of Health Sciences and Technology Institute of Human Movement Sciences and Sport Hier steht der Titel der Präsentation Exercise Physiology I - AS24 Dieser kann, wenn immer nötig, über zwei oder sogar drei Zeilen laufen Hypobaric conditions - altitude Prof. Dr. Beat Muster Prof. Dr. Beat Muster Funktion des Präsentierenden Funktion des Präsentierenden TT. Monat JJJJ, Ort TT. Monat Kyle JJJJ, Geoffrey Ort Boyle, PhD P.J.M. Learning Objectives Students are able to… Discuss physiological changes associated with an increasing hypobaric environment (altitude) Describe the differences between acute and chronic physiological adaptations to altitude Discuss how such physiological changes can impact exercise performance in sea-dwellers and high- altitude natives at altitude Discuss the evidence behind “high altitude training” methods to improve sea-level performance Reflect on risks associated with being / exercising at (high) altitude both acutely and chronically Exercise Physiology I - Exercise in hypobaric conditions - altitude 2 Levels of altitude Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 3  Famous expeditions British expeditions 1952 Swiss 29 May 1953 8 May 1978 1921 - 1924 Mount Everest (1st with oxygen) (1st without oxygen) Expedition Foto: ORF/ORF-T/Robert Barth https://en.wikipedia.org ”because it’s there” Peter Habeler George Mallory Tenzing Norgay https://en.wikipedia.org Edouard Wyss-Dunant www.tz.de/sport Raymond Lambert and others, all from Geneva + Tenzing Norgay reached 'only' 8'595 m Reinhold Messner Andrew Irvine Spotted 240 m from summit Edmund Hillary Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 4 Into thin air? Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 5 Barometric pressure (Pb) drops with altitude Exponential (not linear) decrease in Pb 8848 m above sea level 243 mmHg (32%) 5500 m above sea level 380 mmHg (50%) Sea level 760 mmHg What happens to oxygen availability? Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 6 Barometric pressure (Pb) and ambient partial pressure of oxygen (PO2) Partial pressure decreases! Percentage of oxygen does not! Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 7 Consequences of reduced PO2 – the Fick equation Alveolar/capillary partial pressure difference (𝑝! − 𝑝" ) 𝐷̇ = 𝐴 % 𝑘 % 𝑑 Gas exchange surface area Krogh diffusion coefficient Layer thickness Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 8 Change in diffusion gradient (𝑝! − 𝑝" ) Remember: 𝐷̇ = 𝐴 % 𝑘 % 𝑑 Costill et al. Physiology of Sports and Exercise McArdle, Katch, Katch. Exercise Physiology Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 9 Levels of altitude – the full picture Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 10 Hypobaric vs. normobaric hypoxia Hypobaric Hypoxia: Reduced ambient pressure 21% Oxygen Normobaric Hypoxia: "normal" ambient pressure (e.g. Zurich) reduced % oxygen Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 11 Hypobaric vs. normobaric hypoxia Hypobaric Hypoxia: Reduced ambient pressure 21% Oxygen How do we overcome the environment? What environments have we tackled? Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 12 Adaptation and acclimatization to altitude – a brief outline Acute adaptations (hours to several days) Chronic adaptations = Acclimatization (weeks – months) Reaction to altitude exposure is individual and depends on genetics, fitness, speed of ascent, frequency of exposure on equivalent altitudes and more. Up to about 2500 m above sea level, physiological changes can (partially) be normalized via acclimatization, above it is rare to impossible. In greater heights, different types of 'mountain sickness' can develop (acute mountain sickness, AMS; high-altitude pulmonary edema, HAPE and high-altitude cerebral edema, HACE). Whether a person will be affected also depends on many different factors, including the ones listed above. Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 13 The Fick equation Alveolar/capillary partial pressure difference (𝑝! − 𝑝" ) 𝐷̇ = 𝐴 % 𝑘 % 𝑑 Gas exchange surface area Krogh diffusion coefficient Layer thickness Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 14 Adaptations to altitude Do not need to know Lake Qinghai 3260 m Public domain Public domain (𝑝! − 𝑝" ) 𝐷̇ = 𝐴 % 𝑘 % 𝑑 Copyright 2024 The Company of Biologists Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 15 Combating limitations to altitude (𝑝! − 𝑝" ) 𝐷̇ = 𝐴 % 𝑘 % 𝑑 Positive end-expiratory pressure HP2 Laboratorie Resting 0 cm 5 cm 10 cm breathing pressure pressure pressure (control) Nespoulet et al. (2013), Plos one Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 16  Adaptations to altitude – ventilatory changes Instantanous increase in ventilation (seconds - minutes; acute adaptation) Driven by an increase in peripheral chemoreceptor activation (carotid bodies) ons projecti Pons d nerve t caroti Afferen Medulla Increased ventilatory response NOTE: carotid recepters sense partiral pressure of oxyen, not oxygen content which can return to “sea-level” values ACSM, Advanced Exercise Physiology with acclimitization! Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 17 Consequences of increased ventilation (𝑝! − 𝑝" ) 𝐷̇ = 𝐴 % 𝑘 % 𝑑 Hyperventilation = er R e m em b éPO2 êPCO2 é pH (Respiratory alkalosis) à Shift in O2-binding curve West’s Pulmonary Physiology, Wolters Kluwer Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 18 'Interview' on top of Makkalu (8470 m ü. M.) – observe resting breathing Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 19  Ventilation adaptations over time (chronic) “Typical” resting ventilation response in a sea-level resident at 4300 m 20 100 15 Ventilation continues to increase for up to Minute ventilation (L min) PaO2 (mmHg) & SPO2 (%) 80 two weeks 60 10 Ventilation returns to normal upon return 40 to sea level 5 Minute ventilation PaO2 20 SPO2 0 0 Sea level Altitude day 1 Altitude day 7 Altitude day 14 Figure created with data from ACSM, Advanced Exercise Physiology, Wolters Kluwer Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 20 Hyperventilation at rest and during exercise The magnitude of ventilation increase is dependent on altitude Maximal ventilation is generally preserved Increased submaximal ventilation increases the oxygen cost of breathing (more energy requirement) ACSM, Advanced Exercise Physiology, Wolters Kluwer Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 21 Substrate utilization with exercise in hypobaric hypoxia Preference of carbohydrates in hypoxia More O2 efficient than fat: CHO = 6.0 - 6.3 mole ATP per mole O2 oxidized FAT = 5.6 mole ATP per mole O2 oxidized ACSM, Advanced Exercise Physiology, Wolters Kluwer Absolute = Same absolute power (e.g. W) Relative = Same relative power, e.g. % V̇O2max Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 22 Shift in O2-binding curve echanism Com pensating m Hyperventilation à épH (respiratory alkalosis) Increases 2,3 DPG-concentration à Shift of the O2-binding curve to left à Shift of the O2-binding curve to right So what is optimal for humans at altitude? Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 23  Shift in O2-binding curve At higher altitudes (> 2500 m) Up to moderate altitudes (∼ 2'500 m) à left-shift is dominant (increase O2 affinity) à slight right-shift (decrease O2 affinity) (despite the increase 2,3 DPG à compensation of respiratory alkalosis via concentration, since alkalosis cannot be kidneys (over several days) compensated anymore) …(2,3 DPG é – effect dominant over pH é) Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 24 Shift in O2-binding curve – extreme examples Andean goose Do not need to know Public domain Bar-headed goose Weber et al. (1993), J. Appl. Physiol. Can fly ~𝟖𝟖𝟎𝟎 𝐦 Public domain Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 25  Adaptations to altitude – stroke volume Reduction in blood plasma volume within hours of hypoxia (acute) - Increased hematocrit and hemoglobin concentrations à larger O2-transport capacity / liter blood - Hypoxia-driven diuresis (likely only acutely) - Redistribtuion of water (intravascular to extravascular) Stroke volume rises back towards baseline after weeks to months. Why? Impact on stroke volume during exercise Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude Wagner (1999), Respir. Physiol. 26 Polycythemia above 2500 m Hypoxia Hemoglobin concentration (g/dl) Eg. altitude Andean Peaks within 2 - 4 days Kidney Red blood cells Height (m) Bone marrow O2 sensing cells in kidney initiate synthesis of EPO Thieme, Physiologie EPO stimulates the production of erythrocytes EPO peaks within 2 – 4 days Too much = increase in blood viscosity! ACSM, Advanced Exercise Physiology, Wolters Kluwer Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 27 Thieme / ACSM / West report Adaptations to altitude – sympathetic tone Acute exposure to hypoxia increases sympathetic activation - Increased sympathetic activation also seen during exercise - Assessed via epinephrine and norepinephrine Blood pressure increased during exercise Studied in simulated altitude (hypobaric chamber)…increases within 30 minutes…fast acute response! Normoxia epl Hypoxia (FiO2 = 12%) ACSM, Advanced Exercise Physiology, Wolters Kluwer Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude Vogiatzis et al., J Physiol, 2011 28 Adaptations to altitude – heart rate Resting heart rate rises for hours to days (peaks ~5 days) - Decreases with acclimitization but stays elevated - Elevated due to increased sympathetic tone and decreased SV Studied in simulated altitude (hypobaric chamber)…fast acute response! epl SL Acute Day(s) Weeks(s) Months(s) Bàrtsch & Saltin (2008), Scand J Med Sci Sports ACSM, Advanced Exercise Physiology, Wolters Kluwer Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 29 Adaptations to altitude – heart rate Resting heart rate rises for hours to days (peaks ~5 days) - Decreases with acclimitization but stays elevated - Elevated due to increased sympathetic tone and decreased SV Maximal heart rate is reduced (within 4-8 hours), and stays reduced with acclimitization (reduces further at higher altitudes) - Due to increased parasympathetic tone at maximal exercise (reversed with a parasympathetic blocker) - Reasons unclear but could be to decrease transport SL Acute Day(s) Weeks(s) Months(s) time in capailaries to prmote more oxygen loading Bàrtsch & Saltin (2008), Scand J Med Sci Sports Both resting and maximal heart rate are impacted by elevation! Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 30  Adaptations to altitude – heart rate What about submaximal heart rate? 1 hour of exposure Wagner (2000), Respir. Physiol. Submaimal exercise heart rate is elevated compared to sea What does this all mean for cardiac output? level …and in turn V̇O2,max? ̇ ",$%& = 𝐶𝑂 & 𝑆𝑉 & (𝐶% 𝑂" − 𝐶' 𝑂" ) 𝑉𝑂 Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 31 Adaptations to altitude – cardiac output 1 hour of exposure Wagner (2000), Respir. Physiol. More blood distributed to essential organs during exercise than at sea level Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 32 Changes in maximal oxygen consumption (V̇O2,max) with increasing altitude V̇O2,max reduces with rising altitude Oxygen extraction at the working muscle similar to sea level and altitude ∴ reduction in V̇O2,max primarily due to decreased cardiac output What happens to V̇O2,max with acclimatization? ACSM, Advanced Exercise Physiology, Wolters Kluwer Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 33  Changes in maximal oxygen uptake following acclimatization V̇O2max – change (% sea level, SL) ca. 3000 – 3500 (Slight) increase in V̇O2max with acclimatization below 4000 m Why acclimatization doesn’t increase V̇O2max at higher ca. 1500 – 2000 asl altitudes has been debated. Possibilities include: 1. Adaptations may not be enough to overcome the increased hypoxic burden 2. Adaptations may become maladaptive if ca. 3000 – 3500 asl prolonged to exposure for a long time 3. Increased central fatigue with higher altitudes (earlier cessation) SL Acute Day(s) Weeks(s) Months(s) Bàrtsch & Saltin (2008), Scand J Med Sci Sports Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 34 Changes in submaximal aerobic exercise performance Race times at submaximal exercise decline with increasing altitude and event duration Performance declines due to a reduction in V̇O2max à makes submaximal speed or wattage a higher relative workload What happens with acclimatization? ACSM, Advanced Exercise Physiology, Wolters Kluwer Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 35 Submaximal aerobic exercise Acclimatization improves submaximal aerobic exercise performance to a greater extent than maximal exercise performance. Example study: Time to exhaustion in constant-load test at 80% V̇O2max at 2340 m è Should an athlete spend ≥ 14 days at the respective altitude before the competition or... ? ACSM, Advanced Exercise Physiology, Wolters Kluwer Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 36 2 Strategies for competitions 1. Competition asap after arrival too early for negative effects no benefits of acclimatization 2. Train ≥ 2 weeks prior to competition at specific altitude most negative effects passed, acclimatization has started BUT: Aerobic training at altitude may not be as effective as at lower levels Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 37 Non-aerobic exercise No decline in performance: Improvements in performance - Short duration - Short duration - Rely mainly on aerobic capacity - Air density is a factor NOTE: REPETITIVE SPRINTS Eg. Weight lifting Eg. Hammer throwing, sprinting IMPACTED BY SLOWER RECOVERY Public domain Public domain Public domain Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 38 Altitude / hypoxic training 1. Live high, train high? 2. Live high, train low? 3. Sleep high, train low Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 39 1. Live high, train high Rationale: accumulate red blood cells and increase training stimulus Study examples: 1. Four-week training at 2500 m increased V̇O2,max but not time-trial running performance Accumulating red blood cell mass = increase V̇O2max …but training intensity at high altitudes likely not maintained = no increase in performance 2. Three-week training at 2100-2600 m improved running time-trial performance 3. Four-week training at 1500, 1740 and 2000 m showed no change in V̇O2max and time-trial running performance Altitude may not have been high enough to accumulate enough red blood cell mass Conclusions: Evidence is mixed! No concrete conclusions drawn, but current recommendations suggest elevation should be between 2000 and 3000 m, and no less than 3 to 4 weeks duration Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 40 2. Live high, train low Rationale: accumulate red blood cells and maintain training stimulus Study examples: 1. Four-weeks at 2500 m increased V̇O2,max and time-trial running performance in college runners 2. Four-weeks at 2500 m increased running performance on elite national runners 1/3 of athletes achieved their personal best Conclusions: Evidence suggests better improvement than live high, train high BUT magnitude of improvements appears to be variable between individuals Magnitude of differences seen not high enough to recommend to amateurs Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 41 3. Sleep high, train low Rationale: same as live high, train low…accumulate red blood cells and maintain training stimulus à however, more feasible for those who cannot travel to altitude à home environment hypoxic due to increasing nitrogen concentration Study examples: 1. Three studies at 3000 m simulated hypoxia for 8 - 10 hours for 3 weeks showed no change in red blood cell mass 2. 2860 m simulated hypoxia for 8 – 9 hours for 46 nights increased V̇O2max but not hemoglobin mass 3. Cross country skiers spending 11 hours in 2500– 2500 m simulated hypoxia for 18 nights showed no change in hemoglobin mass and performance 4. Swimmers spending 16 hours in 2500 – 3000 m simulated hypoxia for 13 days increased hemoglobin concentration and V̇O2max 5. Long and short distance runners spending 11 hours in 3000 m simulated hypoxia for 29 nights showed no change in V̇O2max and hemoglobin mass Conclusions: hemoglobin is only increased when… 1. Altitude exceeds 2100 m 2. Duration of exposure is approximately three weeks 3. Daily exposure >14 hours …but is variable! Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 42 Sleep High – Train Low (a Randomized Controlled Trial) 1'135 m asl 4 weeks LH: "3'000" m above sea level Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 43 Siebenmann et al., JAP, 2012 Sleep High – Train Low (a Randomized Controlled Trial) Maximal Oxygen Consumption Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 44 Siebenmann et al., JAP, 2012 Sleep High – Train Low (a Randomized Controlled Trial) Time Trial Performance (26.15 km, bicycle) Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 45 Siebenmann et al., JAP, 2012 Sleep High – Train Low (a Randomized Controlled Trial) Hemoglobin Mass No positive group effect with the current protocol … level of adaptation to altitude is individual ! Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 46 Siebenmann et al., JAP, 2012 High-altitude natives and exercise Review cites ”high-altitude natives” as anyone born and riased > 2500m High-altitude natives show greater exercise capacity in hypoxia compared to sea-level natives Brutsaert (2008), Appl. Physiol. Nutr. Metab. Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 47 High-altitude natives Less impacted by the decrease in partial pressure due to their increased pulmonary diffusion capacity - Increased lung volumes + hypoxia during maturation in animal models induces: 1. Increased alveolar surface area (𝑝! − 𝑝" ) 𝐷̇ = 𝐴 % 𝑘 % 2. Reduced diffusion barrier membrane thickness 𝑑 Display elevated hematocrit and hemoglobin levels compared to lowlanders - Triggered by increased nocturnal EPO concentrations (same during the day) … can there be too much? Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 48  Excessive erthyrocytosis at high altitude Characterized by [Hb] >21 g/dl in males, and >19 g/dl in females + the presence of clinical symptoms including breathlessness, sleep disturbances, cyanosis, paresthesia, headache, tinnitus and more… No excessive Excessive erythrocytosis erythrocytosis Excessive erthrocytosis is more apparent in North/South American highlanders compared to Asian highlanders - Genetic factors! Down regulated transcription of HIF-2 à big driver of hypoxic adaptations! Blood viscosity increases! No excessive Excessive erythrocytosis erythrocytosis Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude Anza-Ramirez et al. (2023), J. Appl. Physiol. 49 Excessive erthyrocytosis at high altitude Increased blood viscosity and volume in La Rinconada highlanders (5300 m) increases: 1. Right atrial dialation and left ventricle concentric remodelling 2. Increased pulmonary arterial pressure Champigneulle et al. (2023), J. Physiol. Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 50  Excessive erthyrocytosis and exercise at high altitude Possible reasons for decline in exercise performance: Increased viscosity disrupts diffusion capacity both at the lungs and the working muscles Example study in Andean highlanders living at 4340 m Non statistically significant decrease in exercise performance Note: small sample in each group (n = 6; only men) Further work being done at 5300 m (highest living inhabitant on earth) No excessive Excessive More info: https://expedition5300.com/ erythrocytosis erythrocytosis Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude Anza-Ramirez et al. (2023), J. Appl. Physiol. 51 Altitude-associated health problems 1. Sleep - Disturbance 2. AMS: Acute Mountain Sickness 3. HACE: High Altitude Cerebral Edema 4. HAPE: High Altitude Pulmonary Edema Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 52 1. Sleep disturbance Lahiri et al. (1983), Resp. Physiol. Wiel (2004), High Alt. Med. Biol. Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 53 1. Sleep disturbance – Periodic breathing (Cheyne-Stokes) Trigger 1. Hypoxia à induces hyperventilation Trigger 2. Hypocapnia (reduced PaCO2) à Respiratory alkalosis à hypoventilation Trigger 3. Increasing alkalosis à Apnea Sutton et al. (1980), Sleep Wiel (2004), High Alt Med Biol Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 54 1. Sleep disturbance Nightly arrousals increase with altitude Nightly arrousals does not decrease over time Berhold et al. Alpin- und Höhenmedizin. Springer Verlag. Burgess et al. (2013), J. Appl. Physiol. Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 55 1. Sleep disturbance Treatments: Periodic breathing remidied with supplemental O2 Lahiri et al. (1983), Resp. Physiol. Acetazolamide suppresses apnea in 50 – 80% of people at altitude Berhold et al. Alpin- und Höhenmedizin. Springer Verlag. Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 56 Incidence of AMS, HACE, HAPE ≥ 2'000 m 20 - 60% of adults, depending on altitude, (epi)genetics, speed of ascent, level of physical exertion, previous exposures, etc * Effect of slow ascent and acclimatization * T : Threshold altitude range for symptoms to be induced by hypoxia at rest Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude Bärtsch & Saltin, SJMSS, 2008 57 2. Acute Mountain Sickness (AMS) – Symptoms and Mechanism Symptoms Severe headache No appetite, nausea, vomiting Fatigue up to lethargy Dizziness Peripheral edema (eye lids, hands, feet) Mechanism Natala Menezes, creative common 4.0 license Unclear – possibly similar to HACE but less severe? Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 58 2. AMS: assessment in studies (not a clinical score) - Lake Louise Score Assessed after recent ascent and at least 6h at altitude AMS is present with ≥ 3 points from 4 Symptoms including at least 1 pt from headache No scientific evidence for severity ranking “but if someone wants to rank, the suggested ranking is”: Recommended 3 - 5 pts = mild to be assessed 6 - 9 pts = moderate but not included 10 - 12 pts = severe in LLS score Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 59 2. Acute Mountain Sickness (AMS) – Risk Factors and Prevention Risk Factors Prior history of high-altitude illness (or parents with AMS history) Rapid ascent, i.e. from low elevation to sleeping altitudes > 2400 m faster than 500 - 1000 m per day to sleeping altitudes > 2700 m Absolute altitude reached Not exposed to altitude in the previous few weeks Exercise or alcohol before adjusting to the change in altitude Medical problem that affects breathing Prevention Ascend slowly: ≤ 300m per day if > 2500 m asl (international guidelines differ!) 1st Acetazolamide, 2nd Dexamethasone (details see treatment) Not recommended: Theophyllin; No data on Gingko, Koka, Vitamins C or E Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 60 Selection of guidelines for ascent (for information only) Source Recommended daily increase in Rest days sleeping height Basnyat & Murchoch (2003) > 3000 m, limit up to 300 m / day Every 2 - 3 days or every 1000 m Hackett & Roach (2001) > 2500 m, limit up to 600 m / day Every 600 – 1200 m MedEx > 3000 m, limit up to 300 m / day Every 2 – 3 days Union Internationale des > 2500 – 3000 m, limit up to 300 – Every 3 days associations d’alpinism (UIAA) 500 m per day depending on terrain Wilderness Medical Society (Luks > 3000 m, limit up to 500 m / day Every 3 – 4 days et al., 2010) Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 61 AMS and HACE - Pathophysiology The pathophysiology of AMS and HACE are still under discussion, and widely remains unclear It has been apparent for a long time however, AMS and HACE arise from altered brain function “…Taking it, therefore, as se2led that mountain sickness is due to oxygen want, the ques 3000 m) - Mobile pressure chamber (usually only used for HAPE and HACE) Volitional hyperventilation or increase respiratory drive via Acetazolamide (Diamox®) [also Prevention] à Carboanydrase inhibition à slows CO2 + H2O à H+ + HCO3- à slight acidic pH shift à increases respiratory drive No respiratory depressive drug i.e. no alcohol, central acting pain medication, sleep drug Glucocorticoids (Dexamethasone) à reduces permeability of blood brain barrier NSAR: non-steroidal anti-rheumatics (e.g. Ibuprofen 3x 600mg) Protection from cold Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 64 3. High Altitude Cerebral Edema (HACE) Cave: 40% deaths à be fast – this is an emergency! Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 65 http://www.altitudemedicine.org High Altitude Cerebral Edema (HACE) - Symptoms Ataxia (leading symptom) Reduced consciousness Extreme headache (resistant to pain medication) Nausea, vomiting Dizziness Hallucinations Photophobic, Vision distortion, Papillary edema (in eyes) Irrational behaviour, reduced cognitive performance Neurological problems (nystagmus, altered reflexes, hemiparesis, paresis of eye muscles, neck stiffness) Subfebrile core temperature Coma Low urine volume (< 0.5 l within 24h) Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 66 http://www.altitudemedicine.org High Altitude Cerebral Edema (HACE) – Treatment / Therapy Treatment as with AMS + upper body elevated by 30o à fast descent to a medical clinic Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 67 http://www.altitudemedicine.org 4. High-Altitude Pulmonary Edema (HAPE) http://www.altitudemedicine.org Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 68 High-altitude Pulmonary Edema (HAPE) – Predisposing factors Prominent pulmonary hypoxic vasoconstriction Large increase in pulmonary arterial pressure in response to exercise in normoxia Elevated sympathetic response to hypoxia Reduced endothelial NO-production in hypoxia (i.e. reduced vasodilation) Elevated endothelial endothelin-production in hypoxia (i.e. increased vasoconstriction) Reduced lung volume Reduced increase in lung diffusion capacity with hypoxia and under exertion Reduced hypoxic ventilatory response (ventilatory control) Reduced natriuretic responses in acute hypoxia (kidneys) à No single factor is the only cause Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 69 High-altitude Pulmonary Edema (HAPE) – Risk Factors and Symptoms Risk factors – same as for AMS Symptoms (usually start 2-4 days after arrival) Breathlessness / Air hunger with activity and even at rest Cough (often with pink, frothy sputum) Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 70 High-altitude Pulmonary Edema (HAPE) – Pathophysiology (suggested) Generalized hypoxic vasoconstriction in the lung à Increased pulmonary vascular resistance Uneven distribution of constriction à Capillaries without constriction see very high pressures à Ultrastructural changes à leakage à High-Altitude Pulmonary Edema (HAPE) Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 71 High-Altitude Pulmonary Edema (HAPE) – Therapy and Prevention Most important treatments (in this order) : Descent (accompanied) Oxygen (from bottle) Mobile pressure chamber (usually only for HAPE and HACE) Nifedipin (20 mg retard; evtl. Sildenafil 50 mg), a Ca2+- Antagonisten à Vasodilatation -> Reduction of peripheral resistance Preventive measures: Slow ascent Low physical exertion the first 3-5 days at new altitude Medication in sensitive persons: 3 x 20 mg Nifedipin retard Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 72  After this Lecture, ask yourself "Can I …. " Outline the consequences of increasing altitude on PO2, SaO2 and V̇O2max? Discuss short and long-term physiological adaptations to altitude? Discuss changes in performance and responsible mechanisms related to different sports and levels of altitude? Discuss advantages / disadvantages of live high–train low (and vice versa) in the context of training and competitions? Describe and discuss symptoms, suggested pathophysiological mechanism(s) and treatment of sleep disturbances at altitude, AMS, HAPE and HACE? Summarize predisposing and risk factors as well as preventive measures for AMS, HAPE and HAPE? Exercise Physiology I - Exercise in hyperbaric and hypobaric conditions - diving and altitude 73