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Cards In This Set
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What is the highest resident altitude in the US?
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Leadville, CO. abtou 7200ft above sea level
-barometric pressure ~ 500mmHg |
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Altitude acclimatization
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*** occurs in a NATURAL environment
*adjustments are progressive and take time *takes about two weeks to adapt to altitudes up to 2300m *for each additional 610m, takes another week up to 5800m -afterwords, it may be impossible to adapt *adjustments can be immediate (acute exposure) or long term (acclimatization) |
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Cause and effect adjustments of acclimatization
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1. decreased bicarbonate in CSF and increased bicarbonate excretion in kidneys
- increased CO2 - H+ control of ventilation, shifts HbO2 curve to the right 2. Increased 2,3 BPG -shifts curve to the right 3.decreased plasma volume; increased RBC, Hb, and hematocrit -improve oxygen carrying capacity 4. Reduction of submax and resting heart rate -restoration of regular circulatory homeostasis 5.increased blood pressure -increased tissue perfusion 6.Increased pulmonary pressure -increases pulmonary perfusion 6.improve pulmonary vasularity - increases pulmonary perfusion 7. increased size and number of mitochondria and increase in oxidative enzymes -improved muscle oxidative biochemistry 8.increased skeletal muscle vasularity -improved oxygen transport 9.increased tissue myoglobin -improved cellular oxygen transport 10. decreased catecholamine secretion (compared to acute exposure) -decreased lactate production |
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Oxyhemoglobin dissociation curve
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 *left shift = trying to bind O2 to Hb -primary effect of altitude exposure *right shift = adjustment to acclimatization |
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Hyperventilation and acclimatization
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* a constant response to high altitude
-increases alveolar oxygen concentration and dilutes alveolar CO2 by blowing it off *PCO2 = 40mmHg at sea level but can fall to ~10mmHg at high altitude -lost of CO2 causes blood pH to rise, become more alkaline -acclimatization of this is accomplished by kidneys excreting HCO3 |
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Acid-base equilibrium and acclimitization
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*the new established acid-base equilibria results in a lower alkaline reserve
-results in a lower tolerance in OBLA -anaerobic endurance is unchanged |
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Hematologic changes to altitude exposure
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*decreased plasma volume: Hemoconcentration results in increased arterial O2 levels compared to levels observed in acute exposure
*increased RBCs: within 15 hrs of exposure, kidneys release more erythropoieten to stimulate polycythemia due to decreased arterial pO2 -within weeks RBC production from long bone marrow increases dramatically and remains elevated for remainder of residence at that altitude |
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Comparison of oxygen carrying capacity of altitude and sea level natives
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*natives of andes have a 28% higher O2 carrying capacity
*mountaineers blood oxygen content is 25-31mL O2 per 100mL blood compared to 19.7 in sea level natives -although Hb saturation is lower at higher altitude,amount of oxygen in arterial blood exceeds normal values |
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Cellular adaptions to acclimatization
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1. capillaries become more concentrated in muscle tissue
- results in less distance of oxygen diffusion between blood and muscle 2.muscle myoglobin increases up to 16% after acclimatization, due to increase in mitochondria and quantity of aerobic enzymes 3.increase in 2,3-DPG -favors oxygen to tissues for a given drop in cellular O2 |
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The 4 H's
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*hypoxia, hypoventilation, hypohydration, hypoglycemia
-the effect of altitude illnesses, is determined by the elevation, speed of ascent, and length of time at altitude |
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Effects of acute exposure to altitude
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1. increased resting and submax heartrate
-to increase O2 transport to tissues -increases alveolar PO2 -decreases CO2-H+ in CSF and blood -predominate hypoxic ventilatory drive -left shift oxyhemoglobin curve -acute mountain sickness 2. increased blood pressure -increased vascular resistance 3. increased catecholamine secretion -increased vasular resistance and increased OBLA 4. decreased VO2 max -decreased exercise capacity *few acute changes in blood, muscle and liver |
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Circulatory response to acute altitude exposure
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*increased submax heartrate and Q
-50% above sea level values -compensates for lower PO2 in arterial blood *Stroke volume unchanged *during exercise, increased heart rate does not compensate for lower PO2 -VO2 max and exercise capacity are reduced |
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Hyperventilation at altitude
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*reduced PO2 stimulates chemoreceptors
- this stimulates increase alveolar ventilation causing alveolar oxygen concentration to increase * the more hyperventilation the more the alveolar O2 represents the ambient O2 -helps to facilitate O2 loading into the lung |
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Performance and altitude
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*gravity decreases by .3cm per sec^2 every 1000m altitude and wind resistance decreases with lower air density
-jumping, throwing, cycling and sprinting sports are more advantageous *endurance events that require rate of O2 consumption suffer -should compete after 3-4 weeks at an altitude or immediately after you arrive |
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Live high train high
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*athletes that live and train at high altitudes (2200m) for about 4 weeks can experience performance benefits for 2-3 weeks after they return back to sea level
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