W8 - Altitude Flashcards
Define hypoxemia
Below-normal level of O2 in blood, specifically in the arteries.
Altitude results in arterial hypoxemia due to what?
Reduced barometric pressure
+
Unchanged fraction of inspired O2
What can altitude chambers + tents do?
Control the fraction of inspired O2 via Nitrogen dilution where nitrogen is added to ambient air.
Why is exercise capacity reduced with increasing altitude?
Due to the reduced arterial O2 pressure evident in a Hb desaturation
What can AMS worsen to at high altitude?
HAPE or HACE
At what altitude can minor impairment on aerobic performance become detectable?
Low altitude
500-2000m
At what altitude can aerobic performance become considerably impaired?
High
3000-5500m
What is exercise-induced hypoxia a key determinant of?
Fall in VO2 max
Why is there a fall in VO2 max at high altitude?
Not enough time for complete O2 saturation of the blood
What can ascending to high altitude to even at rest?
Cause hyperventilation
What can respiratory alkalosis occurring at high altitude cause?
Diuresis
What happens as the rate of breathing increases with high altitude?
Bf to the legs + O2 consumption of the legs decreases
Example of a bronchia agonist?
Cold, dry air
Why do HR + CO increase with altitude?
Due to less pressure driving O2 into the RBC
The increased HR + CO are compensating for the fall in sub maximal O2 saturation.
Why does peripheral vascular resistance decrease with increasing altitude/
Due to the low O2 saturation levels of the blood
= Hypoxia-induced vasodilation
– Does not happen in the lungs
What happens in the lungs instead of hypoxia-induced vasodilation?
Hypoxic Pulmonary Vasoconstriction
What does alveolar hypoxia result in?
Constriction of the small muscles around the pulmonary bv
What are pulmonary artery smooth muscle cells unable to distinguish?
Unable to distinguish between an impaired alveolar air flow + a reduction in the partial pressure of O2.
== Widespread vasoconstriction at altitude for pulmonary vasculature.
What happens to exercise capacity as pulmonary artery pressure increases?
Exercise capacity is compromised.
What is a significant mechanism underlying the fall in exercise capacity at altitude?
Right ventricular after load/HPV
What happens to HR + CO during sub maximal exercise in hypoxia?
Increases
What happens to Vascular resistance + O2 saturation during sub maximal exercise in hypoxia?
Decrease
What is the reduction in performance in hypoxic conditions mainly attributed by?
Altered muscle metabolism due to impaired O2 delivery.
Severe and moderate hypoxia
In which is there much less leg fatigue
Much less leg fatigue in severe hypoxia
Cerebral oxygenation + bf in hypoxia
Dramatic fall
Why is there greater amounts of central fatigue in hypoxia (~3800m)?
Due to suboptimal neural output from the brain due to associated reductions in cerebral O2 availability.
What other mechanisms affect lung physiology during hypoxic exposure?
⬆️ of pulmonary artery pressure
⬆️ endothelial permeability
What does the lower density of air reduce?
⬇️ respiratory resistances
⬆️ inspiratory + expiratory flows.
