Lab 10: Altitude Flashcards
what does acute ascent to altitude result in?
environmental hypoxia
what is the reduction in the amount of oxygen at altitude due to?
reduced barometric pressure, which reduces the partial pressure of inspired oxygen (PiO2)
hypoxia associated with terrestrial altitude exposure
hypobaric hypoxia
what is constant regardless of the altitude?
the percentage of oxygen in the ambient air is constant (20.93%)
PiO2 for Boulder, Pikes Peak, and Everest compared to sea level
PiO2 in Boulder = 122 mmHg
PiO2 on Pikes Peak = 86 mmHg
PiO2 on Everest = 43 mmHg
PiO2 sea level = 149 mmHg
physiological adaptations we undergo with gradual ascent and chronic altitude exposure
acclimatization
3 parameters needed to calculate PiO2
1) barometric pressure (Pb) = dependent on altitude
2) water vapor pressure (PH2O) in inspired air = 47 mmHg, independent of altitude
3) percentage of oxygen in the environment = 20.93% independent of altitude
equation to calculate PiO2
PiO2 = (Pb - PH2O) x %oxygen (as decimal)
how does an acute reduction in PiO2 affect oxygen levels in the blood?
reduced PiO2 leads to a crease in alveolar partial pressure (PAO2) which leads to a reduction in the partial pressure of oxygen in arterial blood (PaO2)
major determinant of arterial hemoglobin O2 saturation (SaO2)
partial pressure of oxygen in arterial blood (PaO2)
3 parameters that determine arterial oxygen content (CaO2)
1) hemoglobin concentration
2) SaO2 (arterial hemoglobin O2 saturation)
3) amount of oxygen dissolved in the plasma
how does the partial pressure of oxygen in arterial blood (PaO2) influence the amount of oxygen dissolved in the plasma?
PaO2 influences SaO2, determining the amount of oxygen dissolved in the plasma
how does the amount of oxygen dissolved in the plasma compare to the amount bound to hemoglobin?
the amount of oxygen dissolved in the plasma is extremely small compared to that bound to hemoglobin ( 3 mL compared to 197 mL)
what physiological responses to altitude exposure are we examining in this lab?
heart rate, ventilation, blood pressure, and substrate utilization at rest and during submaximal exercise with simulated altitude exposure
how does acute altitude exposure affect oxygen uptake?
VO2 max is reduced with acute altitude exposure, the severity of reduction is greater at higher elevations
how do changes in VO2 max in endurance athletes and untrained subjects compare when at altitude?
reductions in VO2 max are greater in endurance athletes compared to untrained subjects
how does the decrease in VO2 max affect relative intensity of exercises?
increase the relative intensity of any given absolute (submaximal) power output at altitude
how does altitude affect heart rate?
increases resting heart rate and increases heart rate at any given absolute submaximal power output
how is max heart rate affected by altitude?
unaffected
primary factors influencing ventilation rate at sea level
PaCO2 and arterial pH
primary factor influencing ventilation in response to hypoxia
peripheral chemoreceptors that reside in the aortic and carotid bodies that respond to low PaO2
how does the fall in PaO2 at altitude affect ventilation at rest and during exercise?
increases ventilation at rest and all absolute workloads compared to sea level
how does the increase in ventilation during exercise compare to the increase in ventilation at rest?
increase in ventilation during exercise is significantly greater than the increase in ventilation at rest
how does altitude affect substrate utilization
increases carb utilization during absolute submaximal exercise intensities
how does altitude affect mean blood pressure?
slight decrease in mean arterial pressure
how is altitude simulated in the lab? inducing what kind of hypoxia?
by providing subjects with a hypoxia (<20.93%) gas mixture, inducing normobaric hypoxia
describe the procedure generally
split into two groups: following resting conditions, one group will start with the normoxic exercise protocol and proceed to the hypoxic protocol, the other group does the opposite
resting protocol: sit and rest for 10 mins, measure BP, HR, Ve, O2 saturation measured between mins 9-10
normoxic and hypoxic exercise protocols: subject will pedal at a constant workload for 5 minutes (50 W) measurements taken between 4 and 5 mins (BP, HR, Ve, O2 saturation, RPE) subject immediately proceeds to second submax workload and same measurements taken
what will the oxygen content of the air the students will breathe during the hypoxic conditions?
15% O2, 85% N2, simulating the hypoxic conditions experienced on Pikes Peak
