Lecture 22 - High Altitude Physiology PDF

Exercise at High Altitude 1  Gas Exchange at Sea Level low pressurehypoberia Above 5000 ft V02Max goesdown 81000 ft is maxpplcan live in Air has weight Thinnerlessweightathigheralt Its weight is related to barometric pressure...

Exercise at High Altitude 1  Gas Exchange at Sea Level low pressurehypoberia Above 5000 ft V02Max goesdown 81000 ft is maxpplcan live in Air has weight Thinnerlessweightathigheralt Its weight is related to barometric pressure 2 The Ideal Gas Law pressure Vol temp PV = nRT 3  The Ideal Gas Law PV = nRT P = Pressure (in kPa) V = Volume (in L) T = Temperature (in K) n = moles R = 8.31 kPa L K mol R is constant. If we are given three of P, V, n, or T, we can solve for the unknown value. Recall, From Boyle’s Law: volume is inversely proportional at constanttemp V α 1/P to its pressure From Charles’ law: volumeof gas w altitude at constantpressure V α T 11 it underwater 4  Dalton's Law The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases in the mixture. e78t pp.to barrette 5 Partial Pressures of Air  Standard atmospheric pressure (at sea level) = 760 mmHg  Nitrogen (N2) is 79.04% of air; 79.04 76 the partial pressure of nitrogen (PN2) = 600.7 mmHg  Oxygen (O2) is 20.93% of air; PO2 = 159.1 mmHg  Carbon dioxide (CO2) is 0.03%; PCO2 = 0.2 mmHg 6 Partial Pressures of Air 7 Partial Pressures of Air 71314 x 8 PO2 AND PCO2 IN BLOOD Partial Pressures of Respiratory Gases at Sea Level Partial pressure (mmHg) % in Dry Alveolar Venous Diffusion Gas dry air air air blood gradient Total 100.00 760.0 760 760 0 H2O 0.00 0.0 47 47 0 O2 20.93 159.1 104 40 64 CO2 0.03 0.2 40 45 5 N2 79.04 600.7 569 573 0 11 OXYGEN-HEMOGLOBIN DISSOCIATION CURVE 12 Higher pressureabovethelicaidthemore Jes willgointotheliquid Henry’s Law The effect of partial pressure on solubility of gases At pressure of few atmosphere or less, solubility of gas solute follows Henry Law which states that the amount of solute gas dissolved in solution is directly proportional to the amount of pressure above the solution. c=kP c = solubility of the gas (M) k = Henry’s Law Constant P = partial pressure of gas oceanw menpressure Erelatedsite 13 Henry’s Law & Soft Drinks conpressurized andputintosoda Soft drinks contain “carbonated water” – water with dissolved carbon dioxide gas. The drinks are bottled with a CO2 pressure greater than 1 atm. When the bottle is opened, the pressure on CO2 decreases and the solubility of CO2 also decreases, according to Henry’s Law. Therefore, bubbles of CO2 escape from solution. 14  ALTITUDE Atmospheric pressure – Decreases at higher altitude Partial pressure – Same percentages of O2, CO2, and N2 in the air Easter – Lower partial pressure of O2, CO2, and N2 – Terms Eipitsameto Hypoxia: low PO2 (altitude) atlower barometric Normoxia: normal PO2 (sea level) pressure Hyperoxia: high PO2 15  Conditions at Altitude the challenge is Reduced PO2 The low POL ofoxygen partialpressure Reduced air temperature cold Low humidity dryair nosebleeds Increased solar radiation sunburn 16 Changes in Barometric Pressure (PB ) and Partial Pressure of Oxygen (PO2) at Different Altitudes barometri pressure Altitude (m) PB (mmHg) PO2 (mmHg) 0 (sea level) 760 159.2 1,000 674 141.2 2,000 596 124.9 3,000 526 110.2 4,000 462 96.9 9,000 231 48.4 17  inspired 802 goesdown diseaseneed to ptmanary manypts w travelw oxygen 18  Esaturated medianwill homeOr give 88 Sea Level Pikes Peak Mount Everest  Oxygen Transport Ventilation – Diffusion Hemoglobin – O2 affinity Cardiac output Peripheral circulation Metabolism (aerobic energy production) 22  Oxygen Transport Pulmonarydiffusion is themajorfactorlimitingperformanceathighalt 23  ALTITUDE higher High altitude = 10,000 feet or 3048 meters Moderate altitude = 4,921 feet or 1,500 meters above 5,000 24 Acute and Chronic Adaptations becomes alkaloticfromblowingoff 102 Whenyou getupto alt Youhyperventilate Blood body bicarbtofixpH excretes more02 1 1heatedin tableat s 25  Pulmonary Hyperventilation (immediate) – Reduced arterial PO2 – Chemoreceptors chemoreceptos – “Hypoxic drive” naturally or peripheral don'trespondto0218ha to Variations in strength of hypoxic drive – Stronger drive; better tolerance to altitude 26 RESPIRATORY REGULATION Pulmonary Response vet art level sea 28  Pulmonary Hyperventilation leads to reduced CO2 in the alveoli More CO2 diffuses out of the blood This increases the pH of the blood CO2 + H20 H2CO3 HCO3 + H (acid) “Respiratory alkalosis”. Kidneys excrete more HCO3 (after 2-5 days) This decreases the buffering of HCO3 and increases the acid level (lowers the pH) 29  Pulmonary Lower PO2 inside the alveoli Less O2 saturation in the blood Also, lower PO2 in the blood Less pressure gradient at the muscles 30 Oxygen Uptake th energyto dotheseen task Butless V02Max Vormax 3 forevery40031ft above5,000 at 6,000you're  S VO2max No effect until altitudes greater than 1,600 m (5,249 ft). Above 5,000 ft, VO2max decreases 3% per 1,000 ft increase in elevation. 32  VO2max VO2max decreased from about 62 ml/kg/min at sea level to 15 ml/kg/min at the top of Mount Everest If VO2max is 50 ml/kg/min at SL, then it will be 5 ml/kg/min at ME V02 max C altitude 33  Cardiovascular Responses Increase in norepinephrine Higher blood pressure Higher heart rate bcuz of increase of NE Takes time to equilibriatebut alwayshigherthan at sea lol 34  Cardiovascular Responses Air at alt is reallydrythenhe exhalewelosefluidthrubreathing Winevolumeloss fromhumidification Blood Volume – Plasma volume decreases (up to 25%) from respiration and increased urine production – Increases RBC concentration and hematrocrit – Eventually, plasma volume returns ms E.IEa thati wine Midwis respondto bias Soi winprod 35  Cardiovascular Responses Cardiac Output – Submaximal exercise Similar or higher Q: Lower or similar stroke volume but a higher heart rate The higher Q offsets the lower O2 content – Maximal exercise Lower Q: Lower stroke volume and lower heart rate ppltend tohave a lover MaxHRand JV 4 altitude 36  Cardiorespiratory and Metabolic Changes submit Note: Greater differences are at maximal exercise 37  Altitude-Related Conditions Acute Mountain Sickness (AMS) High-Altitude Pulmonary Edema (HAPE) High-Altitude Cerebral Edema (HACE) High-Altitude Retinal Hemorrhage cancause (HARH) braininjury 38 Acute Mountain Sickness shatain  Headache, nausea, vomiting, dyspnea, insomnia  Appears 6 to 96 h after arrival at altitude  Critical height ~ 11,000 ft canhappensoonerorlater in someppl 6,000 a14,000  May result from carbon dioxide accumulation  Avoid by ascending no more than 300 m (984 ft) per day above 3,000 m (9,843 ft) Once you get to 10100ft trynottogo higher thanlidt ft a day 39 High-Altitude Pulmonary Edema (HAPE)  Shortness of breath, excessive fatigue, blue lips and fingernails, mental confusion, dry cough, “rales” rattlingsoundwhen  Occurs after rapid ascent above 10,000 ft  Accumulation of fluid in the lungs which interferes with air movement see  Cause unknown  Administer supplemental oxygen and move to lower altitude 40 High-Altitude Cerebral Edema (HACE) fluid inbrain  Mental confusion, progressing to coma and death  Most cases occur above 4,300 m (14,108 ft)  Accumulation of fluid in cranial cavity  Cause unknown  Administer supplemental oxygen and move to lower altitude 41  High-Altitude Retinal Hemorrhage All climbers experience if above 6700 m. Blood pressure surges during exercise cause ruptures in retinal capillaries. Small vessels in eyes rupture verydelicate 42  Acclimatization to Altitude You tryto becomemore aerobic 2 weeks at 7500 ft (2300 m) and an additional week for every additional 2000 ft (610 m) Hyperventilation Excretion of base (HCO3) via the kidneys Elevated submaximal HR Depressed submaximal SV Depressed submaximal Q and maximal Q 43  Acclimatization to Altitude Decreased plasma volume Increased hematocrit and RBCs Possible increase in capillarization Increase in 2, 3-DPG Increase mitochondrial density Increase in aerobic enzymes Loss of body weight and lean body mass 44  Aerlimatized Hematologic Changes they home back came I 45  Hematologic Changes Plasma volume decrease – Shift away from blood to increase RBC concentration – Diuresis Polycythemia – Increase in erythropoietin (EPO) 40-50% increase in RBCs Increase of 5-6 ml of O2 per 100 ml of blood – Dependant upon iron levels inside the body 46  Cellular Changes Increase capillarization Increase myoglobin Increase mitochondria Increase 2, 3-diphosphoglycerate (2, 3- DPG) 47  Performance Vormax plummets VO2max decreases 3% per 1000 ft Threshold for decrements occurs at 5,000 ft events and higher 48  Performance at Altitude  At altitude, endurance activity is affected the most due to reliance on oxygen transport and the aerobic energy system.  Endurance athletes can prepare for competitions at altitude by performing high-intensity endurance training at any elevation to increase their VO2max.  Anaerobic sprint activities are the least affected by altitude.  The thinner air at altitude provides less aerodynamic resistance and less gravitational pull, thus potentially improving jumping and throwing events. 49  Fluid Loss Dehydration is fairly common Let inlungs dumvironment Water loss through the kidneys is increased Increased respiratory evaporation Increased ventilation is the leading cause of dehydration Estimated water loss during 7 hours of climbing is 1, 072 ml 50  Fluid Loss Average daily water loss at altitude includes: – Urination: 1.3 L – Feces:.1-.2 L – Sweat:.1L – Water that passes through lungs & skin:.7-1.1L 51  Fluid Recommendations Additional 2 liters if at moderate altitude 5,0010,0W ft Additional 4 liters if at high altitude s10100 ft Urine should be light in color 52  Optimal Nutrition Adequate caloric intake & proper selection of nutrients is essential High carbohydrate diet (75% of calories) Joe recommended to reduce risk of mountain sickness needenergy 53 fyi if General Nutrition Hints you'restuck in snowandneedwater Gradually increase calories as activity increases Plan one pot meals that cook in 15 minutes Drink 3-5 L of water per day Drink frequently Know that it takes 15 minutes to melt snow to water and 10-15 minutes to boil water Increase carbohydrate intake drastically Avoid alcohol 54  Safety Recommendations Ascend slowly Conduct climb in stages. Limit ascent to 300 m per day Climb with an experienced guide or team Avoid dehydration & overexertion Eat a high-carbohydrate diet to reduce AMS symptoms Use medication as a preventive measure Ei 55 Altitude Training for Sea-Level Performance  Increased red blood cell mass on return to sea level  Not proven that altitude training improves sea-level performance  Difficult to study since intensity and volume are reduced at altitude  Live at high altitude and train at lower altitudes bettersinceyoucantrain higherintensity 56 Training for Optimal Altitude Performance if you'reliving  Compete within 24 hours of arrival to altitude high training  Train at 1,500 to 3,000 m above sea level for at least 2 weeks before competing.  Increase VO2max at sea level to be able to compete at a lower relative intensity 57  Effect of Altitude on Performance Short-term anaerobic performance – Lower PO2 at altitude should have no effect of performance – Lower air resistance may improve performance Long-term aerobic performance – Lower PO2 results in poorer aerobic performance 58  Effect of Altitude on VO2max Decreased VO2max at higher altitude Up to moderate altitudes (~4,000m) – Decreased VO2max due to decreased arterial PO2 At higher elevations – Rate of VO2max reduction also due to fall in maximum cardiac output 59 Changes in VO2max With Increasing Altitude 60  Effect of Altitude on Submaximal Exercise Elicits higher heart rate – Due to lower oxygen content of arterial blood Requires higher ventilation – Due to reduction in number of O2 molecules per liter of air 61  Effect of Altitude on Submaximal Heart Rate Response 62  Effect of Altitude on Submaximal Ventilation Response 63  Adaptation to High Altitude Production of more red blood cells – Counter desaturation caused by lower PO2 In those who grew up at altitude – Have complete adaptations in arterial oxygen content and VO2max In those recently arriving at altitude – Adaptations are less complete 64  Training for Competition at Altitude Effect of training at altitude on VO2max varies between athletes – Due to degree of saturation of hemoglobin Some athletes can improve VO2max by training at altitude, others cannot – May be due to training state before arriving at altitude Some athletes have higher VO2max upon return to low altitude, while others do not – Could be due to “detraining” effect Cannot train as intensely at altitude 65  The Quest for Everest Mount Everest was climbed without oxygen in 1978 – Previously thought that VO2max at summit would be just above rest – Actually, VO2max estimated at 15 ml kg-1 min-1 Due to miscalculation of barometric pressure at summit 66  Challenges of High Altitude Climbing Successful climbers have great capacity for hyperventilation – Drives down PCO2 and H+ in blood – Allows more O2 to bind with hemoglobin at same PO2 Climbers must contend with loss of appetite – Results in loss of weight – Reduction muscle fiber diameter 67 Altitude acclimatisation Living at altitudes above about 2000m leads to enough tissue anoxia to stimulate EPO release and red cell production. For example, a group who spent 30 days at the top of Pikes Peak (4300m) in Colorado had average increases in Hb from 13.7 on arrival to 16.2 at departure, with parallel increases in hematocrit (from 43-48%). These are similar to the increases seen with blood doping or EPO use. 68 Altitude acclimatisation However, on return to sea level, little if any increase in endurance performance is found. The reasons are complex. First, it is not possible to train at maximum intensity at altitude just because the atmospheric oxygen level is lower. Secondly, the adjustments of the circulation to altitude involve more than just an increased Hb. Hyperventilation, a normal response to the lowered oxygen level, leads to increased carbon dioxide excretion and eventually to a reduction in the buffering power of the blood. This may reduce performance levels as lactic acid produced during high intensity exercise will not be so well neutralised. There may also be reductions in blood volume and shifts in the Hb dissociation curve, changes that may impair performance. Note, however, that for competitions held at altitude, suitable acclimatisation is essential. 69 Live high, train low To get round some of these problems you live and sleep up the mountain, but travel down to sea level to train. This option is now available to those of us who do not live conveniently close to a suitable mountain – the nitrogen tent or house. Athletes live in nitrogen tents with the oxygen level reduced to 15-16% (equivalent to being at 2500m altitude). These strategies allow you to train in the normal way, but should provoke a useful boost in blood Hb due to the time spent at simulated altitude. There will still be problems with other, disadvantageous, circulatory adaptations. Data on the efficacy of this approach are not very extensive. Preliminary results from the nitrogen house set up by the Australian Institute of Sport have stimulated interest. They found no increase in Hb, but claimed there were small increases (