Altitude and oxygen delivery

Overview

Barometric pressure and pO₂ at altitude, slower diffusion at the alveoli, lower haemoglobin saturation and VO₂ max, heart rate, stroke volume and ventilation on arrival, dehydration, and endurance and explosive events at Mexico City 1968.

What you need to know

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Questions from this subtopic

Each one with the model answer underneath.

1. 1

   How does barometric pressure change as altitude increases?

   Model answer

   Barometric pressure falls as altitude increases. The air is less dense, so each breath contains fewer oxygen molecules.

2. 2

   Does the percentage of oxygen in the air change at altitude?

   Model answer

   The percentage of oxygen stays at about 20.9% at altitude. The partial pressure of oxygen falls because the total air pressure is lower.

3. 3

   Why does a reduced pO₂ at altitude slow oxygen diffusion at the alveoli?

   Model answer

   Alveolar pO₂ is lower, so the gradient between the alveoli and the blood is shallower. Less oxygen diffuses into the blood.

4. 4

   How does altitude affect the saturation of haemoglobin?

   Model answer

   Haemoglobin is less saturated with oxygen at altitude. The arterial blood therefore carries less oxygen to the muscles.

5. 5

   Why is oxygen delivery to the muscles impaired at altitude?

   Model answer

   Arterial pO₂ is reduced, so the gradient between the blood and the muscle is smaller. Less oxygen diffuses into the muscle for aerobic respiration.

6. 6

   How does altitude affect VO₂ max?

   Model answer

   VO₂ max falls at altitude because less oxygen reaches the muscles. Aerobic performance declines and fatigue sets in sooner.

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