Altitude

2021-11-23 links: !Ecology CO2 reference:

Altitude #

• Humans at altitude: physiology and pathophysiology: a lot of calculations.
  • The summit of Mount Everest is 8848m. Acute exposure to >5500m (18,000ft) may lead to loss of consciousness.
  • Atmospheric O2 stays at 20.9%, but it’s the atmospheric partial pressure ($P_{O_2}$) which reduces, proportionately with barometric pressure ($P_B$).
    • i.e, at 8400m, atmospheric $P_B$ = 36.3 kPa, and $P_{O_2}$ = 7.6 kPa.
• INTERACTION OF CO2 AND HYPOXIC STIMULI ON VENTILATION AT HIGH ALTITUDE (1962)
  • The hyperventilation provoked by chronic hypoxia gives rise to a respiratory alkalosis which is largely compensated by the end of the first week: the volume of ventilation progressively increases. Elevated CO2 tensions are poorly tolerated and an augmented ventilatory response to CO2 stimulus is manifest.
  • Yet when acclimatization is complete, hyperoxia does not restore ventilation to sea-level values.
• Blood gas transport at high altitude
  • “Hypoxia stimulates spleen and bone marrow leading to: (1) progressive increase of circulating Hemoglobin over a period of several months (but the advantage of increased blood O2 capacity are set off by increased blood viscosity)”.
    • Apparently blood is thicker at high altitude. Introducing: Aspirin.