Altitude Flashcards
What does acute ascent to altitude result in?
Environmental hypoxia
What is the reduction in the amount of oxygen due to
Reduced barometric pressure at increasing altitudes
How does barometric pressure change partial pressure of inspired oxygen
The lower barometric pressure reduces the partial pressure of inspired oxygen
Hypobaric Hypoxia
The hypoxia associated with terrestrial altitude exposure
What is the percentage of oxygen in ambient air
Constant at 20.93% regardless of the altitude
T/F the percentage of oxygen in boulders is less than at sea level
False
What is the PiO2 in boulder (1630m)
122 mmHg
What is the PiO2 at sea level
149 mmHg
What three parameters need to be considered to to calculate PiO2
- Barometric pressure
- Water vapor pressure
- Percentage of oxygen in the environment
What is barometric pressure dependent on
Altitude
What is water vapor pressure (PH2O) in inspired air
47 mmHg independent on altitude
Sea level PiO2 calculation
(760 mmHg - 47 mmHg) * 0.2093= 149 mmHg
How does acute reduction in PiO2 affect oxygen levels in the blood?
Reduced PiO2 leads to a decrease in alveolar partial pressure of oxygen which leads to a reduction in the partial pressure of oxygen in arterial blood
What is the pressure of oxygen in arterial blood (PaO2) determinant of?
Major determinant of arterial hemoglobin O2 saturation (SaO2)
What happens at the top of the hemoglobin oxygen dissociation curve?
Small changes in PaO2 have minimal effect on SaO2
What happens at the steep portion of the hemoglobin oxygen dissociation curve?
Small changes in PaO2 have large effects of SaO2
What is arterial oxygen content (CaO2) determined by
Hemoglobin concentration, SaO2, and the amount of oxygen dissolved in the plasma
What is PaO2’s influence on SaO2
PaO2 determines the amount of oxygen dissolved in the plasma which reflects the saturation
What is the difference between the amount of O2 dissolved in the plasma compared to bound to hemoglobin
The amount of O2 dissolved in plasma is extreamly small compared to the amount bound to hemoglobin
What physiological effects occur in response to the decrease in PaO2, SaO2 and CaO2 with altitude
Impacts the cardiovascular, respiratory, and immune systems as well as impacts substrate utilization
What happens to VO2 max at acute altitude exposure
VO2 max is reduced with the severity of the reduction greater at higher elevations.
What effect does the reduction of VO2 max have on intensity
Increases the relative intensity of any given absolute power output at altitude
Difference in VO2 max differences depending on training status at altitude
Trained athletes have a greater reduction in VO2 max
What response does heart rate have at acute altitude exposure
Increase in resting heart rate and an elevation in heart rate at any given absolute submaximal power output
What happens to maximal heart rate at acute altitude exposure?
No change
How is the ventilatory response regulated at acute altitude
Peripheral chemoreceptors that reside in the aortic and carotid bodies respond to low PaO2 during hypoxia
What happens to ventilation patterns at altitude?
Decrease PaO2 results in an increase in ventilation at rest and all absolute workloads
What changes happen to substrate utilization at altitude
Increases in carbohydrate utilization during absolute submaximal exercise intensities
MAP response to acute altitude exposure
MAP may decrease due to reductions in TRP and blood pressure
Hypoxia in the lab setting
<20.93 % gas mixture
Normobaric hypoxia
Pressure is normal but the PiO2 is reduced due to artificial reduction in the percentage of inspired oxygen
What components of arterial oxygen content would be most affected by blood doping
Hemoglobin concentration increases
What components of arterial oxygen content would be relatively unaffected by blood doping
Hemoglobin saturation and the rate of hemoglobin unloading to the tissues
2 mechanisms which increased sympathetic activity may increase oxygen delivery with acute altitude exposure
Increased HR and ventilation; increase BP with exercise
