Lecture 16: High Altitude Flashcards
What is High Altitude (HA)?
1500-3000m
Increasing Altitude causes a __________ in pressure which results in __________ PPO2 and __________ in Hb Saturation
Decrease
Decrease
No change
How does HA affect O2 diffusion?
Lower PPO2 in inspired air and so it reduces the driving force
What is the Alveolar gas equation?
PAO2 = PiO2 - (PACO2/RQ)
Acclimatization depends on:
- Severity of HA hypoxic stress
- Rate of hypoxia onset
- Individuals body
What happens to the carotid bodies during prolonged hypoxia?
Increase in O2 sensitivity
Why does HA lead to hypoxia?
- decreased diffusion due to lower driving force
- lower affinity of Hb for O2
- Decreased and inadequate time for equilibration due to increased HR
What is the PP of H20 at sea level?
47mmHg
Outline hypoxia-induced hyperventilation:
Hypoxia –> chemoreceptors –> act on respiratory centers in the medulla –> increase ventilation –> increased O2
However increased V’ blows off more CO2 which then inhibits the respo centers => decrease V’
What does respo alkalosis do to central drive?
inhibits central drive
How does the body compensate for respo alkalosis due to increased ventilation?
Kidneys excrete more bicarb
Outline the short-term acclimatization mechanisms:
- Low PaO2 causes vasodilation in systemic circuit
- Transient increase in CO
- Increase pulmonary blood flow
Outline the long-term acclimatization mechanisms:
- Polycythemia (mediated by HIF and Epo) = Increased O2 carrying capacity but increase blood viscosity (more work needed to pump)
- Increase blood volume
- Increase diffusion capacity (increase lung volume, increase pulmonary blood volume and pressure)
- Increase number of mitochondria and oxidative enzymes
- angiogenesis due to HIF
When does acute mountain sickness occur?
8500ft
What are the symptoms of acute mountain sickness?
Headache Dizzy Sleep disturbance Nausea Loss of judgment
