Acclimatisation Flashcards
What are the 2 types of high altitude exposure?
Acute hypoxia eg skiers
Chronic hypoxia eg residents at altitude (>2500m)
What do common lung disease lead to?
Reduced PaO2
What is a therapy for hypoxaemia?
O2 supplementation
Define acclimatisation.
Compensatory changes observed when native sea-level dweller moves to high altitude (short term)
How can hypoxia be corrected at any altitude?
Adding supplemental oxygen to inspired gas
When alveolar PO2 falls with altitude, what also falls with it?
VO2 - aerobic exercise performance
What equation gives rate of oxygen perfusion through alveoli?
V’gas = D.A.(p1-P2)/T
What happens to rate of oxygen diffusion into blood at high altitude?
Slows down - takes longer for oxygen in alveolus to come into equilibrium with capillary blood
What is hypoxemia?
Low O2 levels in arterial blood
What does altitude induced hypoxemia allow the study of?
integrated hypoxic responses in absence of other complicating factors due to disease
What does reduced PaO2 trigger?
Increased PAC discharge (carotid) -> hyperventilation
Is hyperventilation efficient?
Yes especially during excercise
What does hypocapnia inhibit and why?
Ventilation through elevated pH centrally & peripherally
What organ compensates for respiratory alkalosis?
Kidneys -> excrete HCO3-
What is the result of prolonged hypoxia?
Reductions in PACO2 and increases in PAO2
What is the Po2 limit when hyperventilation at altitude starts?
35mmHg
What are 3 changes to the gas exchange membrane at high altitude?
Increase area of perfused pulmonary capillaries
Reduce thickness of ‘membrane’
capillary angiogenesis in lung (long)
How is membrane thickness reduced?
Hematocrit is increased so proportion of plasma is diminished
What are 2 advantages of capillary angiogenesis?
SA increased
RBCs spend more time in capillaries and gas exchange region - more time to come into equilibrium
