Altitude Flashcards
Difference between hypoxia and hypoxaemia
Hypoxia is lack of oxygen in an environment, PO2
Hypoxaemia lack of oxygen in the blood, PaO2
How do we put our body into hypoxic stress
Altitude
Disease - COPD
Exercise
What is the oxygen cascade?
Describes the decreasing oxygen tension from inspired air to respiring cells
The gradient between room air and air in blood
What happens when you hyperventilate?
Remove mixed air out and fresher air in
Increases concentration gradient for CO2 and O2
What drives breathing?
CO2
What should the O2, CO2 levels be like in post alveolar capillaries in normal individuals?
Same amount of each
What should the O2, CO2 levels be like in post alveolar capillaries in defect individuals?
Displaced downwards
Less O2
How does the volume of O2 change at high altitude?
There is the same proportion of oxygen
As there is less volume of air at higher altitude so less volume of oxygen
1/3 of O2 available at high altitude
Capacity of exercise is greatly reduced
What happens if you climb to high altitude steadily vs being in high altitude suddenly?
If steadily: body will adapt to changes and acclimatise
Can use supplemental oxygen
If suddenly: unconsciousness from hypoxia and death from oxygen starvation
Five major challenges of altitude
Hypoxia Thermal stress Solar radiation - less screening Hydration - water lost humidifying inspired air as air is very dry, hypoxia induced diuresis (decrease body water to increase O2 in blood) Dangerous landscape
Acclimatisation
⬇️ atmospheric O2 ⬇️ Alveolar oxygen ⬇️ arterial O2 Activation of peripheral chemoreceptors ⬆️ sympathetic outflow ⬆️ ventilation / ⬇️ arterial CO2 = increase in blood pH = ⬇️ ventilation, ⬇️ O2 ⬆️ alveolar O2 ⬆️ O2 that moves into blood ⬆️ heart rate and CO
Increase un pH detected by carotid bodies
Increase bicarbonate excretion, increase H+ in blood
Increased arterial O2= increased erythropoietin = increase O2 - increase oxidative enzymes, mitochondria
What is acclimation
Like acclimatisation but stimulated by an artificial environment
What could be used as prophylactic treatment for altitude
Carbonic anhydrase inhibitors eg. Acetazolamide
Accelerates renal compensation
Adaptations to altitude
Barrel chest - big lungs, mostly genetic
Increased hematocrit - can carry more O2 in blood
Larger heart - pump more blood
Increased mitochondrial density - more o2 used efficiently
What is chronic mountain sickness
Cause is unclear
Increases hematocrit= blood viscosity increases, cannot travel through body well
Can experience cyanosis (blue discoloration)
Can lead to heart failure and death
To treat bring to lower altitude
What is acute mountain sickness
Caused by failure to acclimatise with recent ascent
Associated with mild cerebral oedema
Symptoms include nausea, dizziness, vomiting
To treat monitor symptoms and do not go higher, hyperbaric O2 therapy
What is high altitude cerebral oedema
Caused by rapid ascent
More blood into capillaries due to hypoxaemia = increased fluid leakage
Cranium is in sealed box - no room to expand
Increase in intracranial pressure
Symptoms: hallucinations, confusion
Can lead to coma or death
Treat with immediate descent, O2 therapy, corticosteroid, mannitol (osmotic diuretic)
What is high altitude pulmonary oedema
Vasoconstriction of pulmonary vessels
Increased fluid leakage and accumulation
Leads to impaired gas exchange due to increased diffusion thickness
Symptoms: dry cough, bloody sputum
Treat by descending, calcium channel blockers (relax pulmonary vessels), viagra (vasodilate pulmonary circulation)
Benefits of training at high altitude
Natural erythropoesis
Increase mitochondrial density and oxidative enzymes
Improvement in oxygen extraction and utilisation
Can acclimatise by sleeping in hypoxic environments
