Application:
• Consequences of high altitude for gas exchange
Partial pressure is the pressure exerted by a single type of gas when it is found within a mixture of gases
The partial pressure of a given gas will be determined by:
- The concentration of the gas within the mixture (e.g. oxygen forms roughly 21% of the atmosphere)
- The total pressure of the mixture (e.g. atmospheric pressure)
At high altitudes, air pressure is lower and hence there is a lower partial pressure of oxygen (less O2 because less air overall)
- This makes it more difficult for haemoglobin to take up and transport oxygen (lower Hb % saturation)
- Consequently, respiring tissue will receive less oxygen – leading to symptoms such as fatigue, headaches and rapid pulse
Over time, the body may begin to acclimatise to the lower oxygen levels at high altitudes:
- Red blood cell production will increase in order to maximise oxygen uptake and transport
- Red blood cells will have a higher haemoglobin count with a higher affinity for oxygen
- Vital capacity will increase to improve rate of gas exchange
- Muscles will produce more myoglobin and have increased vascularisation to improve overall oxygen supply
- Kidneys will begin to secrete alkaline urine (removal of excess bicarbonates improves buffering of blood pH)
- People living permanently at high altitudes will have a greater lung surface area and larger chest sizes
Professional athletes will often incorporate high altitude training in order to adopt these benefits prior to competition
- Athletes may commonly either train at high altitudes (live low – train high) or recover at high altitudes (live high – train low)
Relationship between Altitude and Air Pressure
