Lab 10 Quiz Flashcards
Acute ascent to altitude results in
environmental hypoxia
The reduction in the amount of oxygen with ascent to altitude is due to the reduced
barometric pressure at increasing altitudes which reduces the partial pressure of inspired oxygen (PiO2)
(ie. lower barometric pressure and pp of inspired oxygen)
What is the hypoxia associated with terrestrial altitude exposure called
hypobaric hypoxia
Percentage of oxygen in ambient air
20.93%
Constant regardless of altitude
What are the physiological responses to altitude dependent on
the severity of hypoxia
What is the partial pressure of inspired oxygen (PiO2) in Boulder vs sea level, Pikes Peak, and Mt. Everest
122 mmHg in Boulder (~1630m)
149 mmHg at sea level
86 mmHg at Pikes Peak
43 mmHg at Mt. Everest
Magnitude of responses if a sea level resident traveled to Boulderβs altitude vs. Pikes peak or Mt. Everest
Acute exposure to Boulderβs altitude would cause some physiological responses but magnitude of responses is remarkably different than if acutely exposed to Pikes peak or Everest (acute exposure to PiO2 of 43 mmHg would lead to loss of consciousness within minutes to hours)
What enables humans to successfully tolerate altitudes that would cause major problems acutely
With gradual ascent and chronic altitude exposure we can undergo physiological adaptations (acclimatization)
In the altitude lab, we will focus exclusively on
acute hypoxia
Three parameters required to caluculate PiO2
& whether each parameter is dependent on altitude
- barometric pressure (Pb): dependent on altitude
- water vapor pressure (PH2O) in inspired air: 47 mmHg, independent of altitude
- percentage of oxygen in the environment: 20.93%, independent of altitude
PiO2 equation
π·π°πΆπ = (π·π β π·π―ππΆ) Γ % ππππππ (ππ π ππππππ)
Find the PiO2 at sea level if the barometric pressure is 760 mmHg
PIO2 at sea level = (760 mmHg - 47 mmHg) * 0.2093 = 149 mmHg.
Effect of an acute reduction in PiO2 on oxygen levels in the blood
Reduced PiO2 leads to a decrease in the alveolar partial pressure of oxygen (PAO2) which leads to a reduction in the partial pressure of oxygen in arterial blood (PaO2)
The partial pressure of oxygen in artierial blood (PaO2) is the major determinant of
arterial hemoglobin O2 saturation (SaO2): how saturated (with oxygen) your RBCs are
recall that the hemoglobin oxygen dissociation curve is sigmoidal; what does this mean for small changes in PaO2 at the top of the curve vs the steeper part of the curve
Near the top of the curve, small changes in PaO2 have a minimal effect on arterial hemoglobin O2 saturation (SaO2)
On the steeper part, small changes in PaO2 have a large effect on SaO2
arterial oxygen content (CaO2) is determined by what three parameters
& what influences two of the them
- hemoglobin concentration
- arterial hemoglobin O2 saturation (SaO2)
- amount of oxygen dissolved in plasma
PaO2 influences SaO2 and determines the amount of oxygen dissolved
Amount of oxygen dissolved in plasma compared to amount bound to hemoglobin
the amount of O2 dissolved in plasma is extremely small compared to the amount bound to hemoglobin. For ex: for a male at sea level, ~3 mL of O2 per liter of arterial blood are dissolved in plasma, whereas ~197 mL O2 per liter of arterial blood are bound to hemoglobin.
The decrease in these three things with altitude exposure result in physiological responses
PaO2, SaO2, and CaO2
The decrease in PaO2, SaO2, and CaO2 with altitude exposure results in physiological responses in what areas
physiological responses in the cardiovascular, respiratory, and immune system and influences substrate utilization
During the altitude lab, we will examine changes in what 5 parameters
- SaO2
- HR
- Ventilation
- Blood pressure
- Substrate utilization
What are the two overall conditions at which we will be examining changes to parameters
at rest and during submaximal exercise with simulated altitude exposure
Effect of altitude exposure on VO2max
VO2max is reduced with acute altitude exposure; greater reduction at greater altitudes
Reductions in VO2max in edurance training athletes vs untrained subjects
percent reductions in VO2max are greater in endurance trained athletes compared to untrained subjects
In trained athletes, reductions in VO2max have been reported at as low as 580m (1900 feet) above sea level
VO2max and relative intensity at altitude
The decrease in VO2max increases the relative intensity of any given absolute (submaximal) power output at altitude
Effect of altitude exposure on heart rate
Acute altitude exposure results in an increase in resting HR and an elevation in HR at any given absolute submax power output
BUT Maximal HR is unaltered
Primary factors in the blood influencing ventilation rate at sea level vs those at altitude/during hypoxia
at sea level, factors influencing ventilation rate = PaCO2 and arterial pH
at altitude/hypoxia, chemoreceptors in the aortic and carotid bodies respond to low PaO2 & play the predominant role in ventilatory response
Effect of drop in PaO2 on ventilatory rate
The fall in PaO2 at altitude results in an increase in ventilation at rest and all absolute workloads compared to sea level.
The increase in ventilation during exercise at altitude is significantly larger than the increase in ventilation at rest.
Effect of altitude on substrate utilization
ascent to high altitude increases carbohydrate utilization during absolute submax exercise intensities
Effect of altitude on blood pressure
- Mean arterial pressure may decrease slightly
- Small reductions in total peripheral resistance and blood pressure due to local factors that blunt the peripheral vasoconstriction caused by sympathetic NS activity
Individual variability at altitude
the magnitiude of physiological responses and the level of hypoxia incurred at a given altitude varies between individuals
How can we simulate altitude without going to altitude
Normobaric hypoxia: normal pressure but reduced fraction of oxygen in the ispired gas (PiO2)
the percentage of oxygen can be artifically modified by providing subjects with a hypoxic (<20.93%) gas mixture
Hypoxic protocol
student will be breathing a 15% O2/ 85% N2 gas mixture that simulates the hypoxic condition experienced at Pikes Peak (4300 m, 14,110 ft above sea level)
What are the effects of acute altitude exposure on the 5 parameters weβre examining (SaO2, HR, Ventilation, BP, and Substrate utilization)
what about oxygen uptake?
- Decreased SaO2
- Increases resting and submax HR (HRmax = same)
- Increased ventilation
- Slight decrease in MAP
- Increased CHO utilization
Decreased VO2max
Name of the hypoxia associated with terrestial altitude exposure vs. the one we use in lab
- Hypobaric hypoxia: reduced pressure (can also be recreated in lab using hypobaric chamber)
- Normobaric hypoxia: reduced fraction of oxgyen in the inspired gas
What are the two submax workloads during the exercise conditions
50W and 100W
6 different conditions and what weβll be measuring at each
- Rest hypoxia (10 min): BP, HR, VE, O2 sat
- Rest normoxia (10 min): BP, HR, VE, O2 sat
- Exercise hypoxia (5 min @ 50 watts): BP, HR, VE, O2 sat, RPE
- Exercise hypoxia (5 min @ 100 watts): BP, HR, VE, O2 Sat, RPE)
- Exercise normoxia (5 min @ 50 watts): BP, HR, VE, O2 sat, RPE
- Exercise normoxia (5 min @ 100 watts): BP, HR, VE, O2 sat, RPE
When are measurements collected during rest and exercise
During minute 9-10 if rest and minute 4-5 of exercise
