W8 - Altitude

Question 1

Define hypoxemia

Answer 1

Below-normal level of O2 in blood, specifically in the arteries.

Question 2

Altitude results in arterial hypoxemia due to what?

Answer 2

Reduced barometric pressure

+

Unchanged fraction of inspired O2

Question 3

What can altitude chambers + tents do?

Answer 3

Control the fraction of inspired O2 via Nitrogen dilution where nitrogen is added to ambient air.

Question 4

Why is exercise capacity reduced with increasing altitude?

Answer 4

Due to the reduced arterial O2 pressure evident in a Hb desaturation

Question 5

What can AMS worsen to at high altitude?

Answer 5

HAPE or HACE

Question 6

At what altitude can minor impairment on aerobic performance become detectable?

Answer 6

Low altitude

500-2000m

Question 7

At what altitude can aerobic performance become considerably impaired?

Answer 7

High

3000-5500m

Question 8

What is exercise-induced hypoxia a key determinant of?

Answer 8

Fall in VO2 max

Question 9

Why is there a fall in VO2 max at high altitude?

Answer 9

Not enough time for complete O2 saturation of the blood

Question 10

What can ascending to high altitude to even at rest?

Answer 10

Cause hyperventilation

Question 11

What can respiratory alkalosis occurring at high altitude cause?

Answer 11

Diuresis

Question 12

What happens as the rate of breathing increases with high altitude?

Answer 12

Bf to the legs + O2 consumption of the legs decreases

Question 13

Example of a bronchia agonist?

Answer 13

Cold, dry air

Question 14

Why do HR + CO increase with altitude?

Answer 14

Due to less pressure driving O2 into the RBC

The increased HR + CO are compensating for the fall in sub maximal O2 saturation.

Question 15

Why does peripheral vascular resistance decrease with increasing altitude/

Answer 15

Due to the low O2 saturation levels of the blood

= Hypoxia-induced vasodilation

– Does not happen in the lungs

Question 16

What happens in the lungs instead of hypoxia-induced vasodilation?

Answer 16

Hypoxic Pulmonary Vasoconstriction

Question 17

What does alveolar hypoxia result in?

Answer 17

Constriction of the small muscles around the pulmonary bv

Question 18

What are pulmonary artery smooth muscle cells unable to distinguish?

Answer 18

Unable to distinguish between an impaired alveolar air flow + a reduction in the partial pressure of O2.

== Widespread vasoconstriction at altitude for pulmonary vasculature.

Question 19

What happens to exercise capacity as pulmonary artery pressure increases?

Answer 19

Exercise capacity is compromised.

Question 20

What is a significant mechanism underlying the fall in exercise capacity at altitude?

Answer 20

Right ventricular after load/HPV

Question 21

What happens to HR + CO during sub maximal exercise in hypoxia?

Answer 21

Increases

Question 22

What happens to Vascular resistance + O2 saturation during sub maximal exercise in hypoxia?

Answer 22

Decrease

Question 23

What is the reduction in performance in hypoxic conditions mainly attributed by?

Answer 23

Altered muscle metabolism due to impaired O2 delivery.

Question 24

Severe and moderate hypoxia

In which is there much less leg fatigue

Answer 24

Much less leg fatigue in severe hypoxia

Question 25

Cerebral oxygenation + bf in hypoxia

Answer 25

Dramatic fall

Question 26

Why is there greater amounts of central fatigue in hypoxia (~3800m)?

Answer 26

Due to suboptimal neural output from the brain due to associated reductions in cerebral O2 availability.

Question 27

What other mechanisms affect lung physiology during hypoxic exposure?

Answer 27

⬆️ of pulmonary artery pressure

⬆️ endothelial permeability

Question 28

What does the lower density of air reduce?

Answer 28

⬇️ respiratory resistances

⬆️ inspiratory + expiratory flows.