Lab 10: Altitude

Question 1

what does acute ascent to altitude result in?

Answer 1

environmental hypoxia

Question 2

what is the reduction in the amount of oxygen at altitude due to?

Answer 2

reduced barometric pressure, which reduces the partial pressure of inspired oxygen (PiO2)

Question 3

hypoxia associated with terrestrial altitude exposure

Answer 3

hypobaric hypoxia

Question 4

what is constant regardless of the altitude?

Answer 4

the percentage of oxygen in the ambient air is constant (20.93%)

Question 5

PiO2 for Boulder, Pikes Peak, and Everest compared to sea level

Answer 5

PiO2 in Boulder = 122 mmHg
PiO2 on Pikes Peak = 86 mmHg
PiO2 on Everest = 43 mmHg
PiO2 sea level = 149 mmHg

Question 6

physiological adaptations we undergo with gradual ascent and chronic altitude exposure

Answer 6

acclimatization

Question 7

3 parameters needed to calculate PiO2

Answer 7

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

Question 8

equation to calculate PiO2

Answer 8

PiO2 = (Pb - PH2O) x %oxygen (as decimal)

Question 9

how does an acute reduction in PiO2 affect oxygen levels in the blood?

Answer 9

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)

Question 10

major determinant of arterial hemoglobin O2 saturation (SaO2)

Answer 10

partial pressure of oxygen in arterial blood (PaO2)

Question 11

3 parameters that determine arterial oxygen content (CaO2)

Answer 11

1) hemoglobin concentration
2) SaO2 (arterial hemoglobin O2 saturation)
3) amount of oxygen dissolved in the plasma

Question 12

how does the partial pressure of oxygen in arterial blood (PaO2) influence the amount of oxygen dissolved in the plasma?

Answer 12

PaO2 influences SaO2, determining the amount of oxygen dissolved in the plasma

Question 13

how does the amount of oxygen dissolved in the plasma compare to the amount bound to hemoglobin?

Answer 13

the amount of oxygen dissolved in the plasma is extremely small compared to that bound to hemoglobin ( 3 mL compared to 197 mL)

Question 14

what physiological responses to altitude exposure are we examining in this lab?

Answer 14

heart rate, ventilation, blood pressure, and substrate utilization at rest and during submaximal exercise with simulated altitude exposure

Question 15

how does acute altitude exposure affect oxygen uptake?

Answer 15

VO2 max is reduced with acute altitude exposure, the severity of reduction is greater at higher elevations

Question 16

how do changes in VO2 max in endurance athletes and untrained subjects compare when at altitude?

Answer 16

reductions in VO2 max are greater in endurance athletes compared to untrained subjects

Question 17

how does the decrease in VO2 max affect relative intensity of exercises?

Answer 17

increase the relative intensity of any given absolute (submaximal) power output at altitude

Question 18

how does altitude affect heart rate?

Answer 18

increases resting heart rate and increases heart rate at any given absolute submaximal power output

Question 19

how is max heart rate affected by altitude?

Answer 19

unaffected

Question 20

primary factors influencing ventilation rate at sea level

Answer 20

PaCO2 and arterial pH

Question 21

primary factor influencing ventilation in response to hypoxia

Answer 21

peripheral chemoreceptors that reside in the aortic and carotid bodies that respond to low PaO2

Question 22

how does the fall in PaO2 at altitude affect ventilation at rest and during exercise?

Answer 22

increases ventilation at rest and all absolute workloads compared to sea level

Question 23

how does the increase in ventilation during exercise compare to the increase in ventilation at rest?

Answer 23

increase in ventilation during exercise is significantly greater than the increase in ventilation at rest

Question 24

how does altitude affect substrate utilization

Answer 24

increases carb utilization during absolute submaximal exercise intensities

Question 25

how does altitude affect mean blood pressure?

Answer 25

slight decrease in mean arterial pressure

Question 26

how is altitude simulated in the lab? inducing what kind of hypoxia?

Answer 26

by providing subjects with a hypoxia (<20.93%) gas mixture, inducing normobaric hypoxia

Question 27

describe the procedure generally

Answer 27

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

Question 28

what will the oxygen content of the air the students will breathe during the hypoxic conditions?

Answer 28

15% O2, 85% N2, simulating the hypoxic conditions experienced on Pikes Peak