Ch 24 - Exercise at Medium & High Altitude Flashcards
What is the main physiological challenge does high altitude pose?
The direct problem of altitude on human physiology is the decrease of ambient PO2
Not the reduction of barometric pressure per se or and change in relative concentrations (%) of gases in inspired ambient air
What is ambient air PO2?
20.93 or 21%
Air density decreases when…
one ascends above sea level
What is the barometric pressure to sea level?
Pb = 760 mm Hg
T of F: PO2 of air decreases directly with the fall in barometric pressure
True: PO2 = 0.2093 x Pb
Stress of Altitude at sea level vs mt. Everest
Ambient PO2 at seal level = 159 mm Hg
Mt. Everest PO2 = 50 mm Hg
This is 30% of the O2 available at sea level
Acclimatization
the adaptations produced by a change in the natural enviroment
Acclimation
The adaptation produced in a controlled lab environment as in chambers the can simulate high altitude
Reduction in PO2 and accompanying arterial hypoxia
Speeds up the immediate physiologic adjustments to altitude and longer-term acclimatization
What can cause a shift in OxyHb dissociation curve?
Varibles that effect curve = Temp, pH, CO2, 2,3 BPG
Shift to the RIGHT = decrease pH, increase in CO2 and temperature
Shift to the LEFT = increase in pH, decrease in CO2 and temperature
What can cause a shift in OxyHb dissociation curve?
Varibles that effect curve = Temp, pH, CO2, 2,3 DPG
Shift to the RIGHT = decrease pH, increase in CO2 and temperature
Shift to the LEFT = increase in pH, decrease in CO2 and temperature
What is 2,3 DPG?
Biphophoglycerate, which is a byproduct of glycolyisi in RBC. Production increase during hypoxia. Binds to deoxygenated forms of Hb and assists in unloading O2 from Hb
Moderate altitude does not decrease short-term anaerobic performance or sprints, Why? What is the primary energy system?
anaerobic performance does not utilize O2 to functionast less than 2 minutes of activity. Utilizes phosophe creatine (0-10 sec), glycolysis (45 sec - 2/2.5 min) Myocondrial respiration is aerobic respiration anaerobic respiration and glycolysis.
Can sprinting times or anaerobic power event improve at altitude?
Think about air density, is it high or low? What does this do to air resistance or drag?
Less resistance or drag occurs at high altitude
In the transition from moderate to hight altitude arterial PO2 values are on what part of the OxyHb dissociation curve?
The steep part of the curve
How does high elevation effect oxygen loading?
O2 loading of Hb decreases and physical activity becomes difficult to sustain
How is mild aerobic activities effected by moderate to high altitude changes?
This change in altitude negatively effects Hb oxygenation and O2 transport capacity
Sudden exposure to 4300 m would cause a…
32% reduction in aerobic capacity compared to sea level values
At what elevation is supplemental O2 typically required?
At altitudes above 5200m / 1700 ft
What happened at 5500m/1800ft?
Arterial PO2 averages 38 mm Hg
Hb maintains only 73% O2 saturation
What is the PO2 and arterial blood O2 saturation at Mt Everest summit
arterial PO2 = 25 mm Hg
blood O2 saturation = 58%
What would happen to an unacclimatized person is they were placed on mt. Everest summit?
Unconscious within 30 sec
what is the simulated summit acclimatized man?
average male VO2max decreases by 70% form 4.13 L/min to 1.17 L/min.
This is equivalent to sedentary male 80 you or a female cardiac patient
Pugh et al (1964) VO2max in relation to terrestrial elevation
VO2max decreased from seal level upward and declined steeply above 6000 m to reach an average of 1.42 L/min @ 7440 m
Respiratory exchange ratio during graded exercise at sea level and 5800m
Shows a tendency for a higher respiratory exchange ratio (RER) at all exercise levels at 5800 m than at sea level
RER increased vertically at 5800m
This is indicative of hyperventilation and increased La- at high altitude
Altitude acclimatization
adaptive responses in physiology to high altitude. Metabolism that improve tolerance to altitude hypoxia. Corrective responses to altitude occurs almost immediately while other adaptions take weeks or even months.
How long can someone retain the benefits of altitude acclimatization?
Many of the beneficial submaximal exercise responses associated with 16 days of acclimatization at 4300m
Immediate and longer-term adjustments to altitude hypoxia - PULMONARY ACID-BASE
Immediate
Hyperventilation
Bodily fluids become more alkaline due to reduction in CO2 (H2CO3) with hyperventilation
Longer-Term
Hyperventilation
Excretion of base (HCO3-) via the kidneys and concomitant reduction in alkaline reserves
Immediate and longer-term adjustments to altitude hypoxia - PULMONARY ACID-BASE
Immediate
Hyperventilation
Bodily fluids become more alkaline due to reduction in CO2 (H2CO3) with hyperventilation
Longer-Term
Hyperventilation
Excretion of base (HCO3-) via the kidneys and concomitant reduction in alkaline reserves
Immediate and longer-term adjustments to altitude hypoxia - CARDIOVASCULAR
Immediate
Increase in sub maximal heart rate
Increase in sum maximal cardiac output
Strike volume remains the same or decreases slightly
Maximum cardiac output remains the same or decreases slightly
Longer-term Submaximal heart rate remains elevated Submaximal cardiac output falls to or below sea-level values Stroke volume decreases Maximum cardiac output decreases
Immediate and longer-term adjustments to altitude hypoxia -HEMATOLOGIC
No immediate effects
Longer-Term Decreased plasma volume Increased hematocrit increased hemoglobin concentration Increased total number or RBC
Immediate and longer-term adjustments to altitude hypoxia -LOCAL SYSTEMS
Possible increased capillarization of skeletal muscle Increased RBG, 2,3-DPG Increased mitochondrial density Increased aerobic enzymes in muscles loss of body weight and lean body mass
At an elevation of 2300 m (2546 ft) & higher how doe the moody immediately reacts to altitude
At 2300 m the body needs to adapt to thinner air and decreased PO2
- increase in the respiratory drive to produce hyperventilation
- Increase in blood flow during rest & submaximal exercise
Hyperventilation in response to altitude changes
Hyperventilation is the first line of defense against high altitude
Peripheral Chemoreceptors sense low PO2 levels. Receptors signal an increase of alveolar ventilation by hyperventilation. Hyperventilation increased O2 loading in the lungs
Cardiovascular response to High Altitude
Increase resting BP
submit HR and Q increase as much as 50%
SV remains unchanged
Increased submit exercise blood flow at altitude compensates for arterial desaturation
Comparison of oxygen cost and relative strenuousness of submacimal exercise at seal level and high altitude
While O2 cost of submax exercise at 100 W of power output at sea level & high altitude remains unchanged at about 2.0 L/min, the relative strenuousness of the effort increases at altitude
Submax exercise representing 50% of sea level VO2max = 70% of VO2 max at 4300 m
Comparison of oxygen cost and relative strenuousness of submacimal exercise at seal level and high altitude
While O2 cost of submax exercise at 100 W of power output at sea level & high altitude remains unchanged at about 2.0 L/min, the relative strenuousness of the effort increases at altitude
Submax exercise representing 50% of sea level VO2max = 70% of VO2 max at 4300 m
Catecholamine Response to Altitude
NE activity progressively increases over time during rest and exercise with altitude
*Increased HR/BP at altitude coincide with a steady rise in plasma level of NE
NE levels peak after what day of high altitude exposure?
NE levels peak after day 4 and then remain stable
NE levels peak after what day of high altitude exposure?
NE levels peak after day 4 and then remain stable
How does the body compensate for the blood’s decreased O2 content?
By increasing Blood flow (Q)
How doe the body increase blood flow (Q)?
In high altitude the body increases blood flow (Q) by increasing HR, SV remains the same
What is the difference between Sea level & altitude submax exercise O2 consumption?
Due to the increase of blood flow (Q) O2 consumption remains basically the same between seal level and altitude
What happens to arterial O2 saturation during high altitude submaz exercise?
Arterial O2 saturation decreases from 96% at sea level to 70% at altitude during all exercise intensities
What happens during max effort at a short-term altitude exposure (<7days)
Ventilatory and circulatory adjustments fail to compensate for the depressed arterial O2 content
What happens after each 1000 m increase in altitude?
For each 1000 m increase in altitude there is a proportionate increase in exercise ventilation volume
What happens when exercise O2 consumption exceeds 2.0 L/min?
When O2 levels exceed 2.0 L/min, pulmonary ventilation increased disproportionately at progressively higher elevation
What are the complication of body water evaporation due to the ambient air of the mountainous regions?
With the mountainous regions remain cool and dry the considerable body water evaporates as inspired air becomes warmed and moistened in the respiratory passages, This loss of body water can lead to moderate dehydration - symptoms of dryness of the lips, mouth, and throat.
