Acclimatizing to High Altitude

What is acute mountain sickness(AMS)?

Altitude illness impacts 25% to 85% of travelers to high-altitude regions. The most prevalent form, acute mountain sickness, usually presents within six to twelve hours of reaching higher elevations, causing symptoms like headache, nausea, insomnia, malaise and general discomfort.

Who does acute mountain sickness effect?

  • Mountain sickness can affect a diverse range of individuals traveling to high altitudes. The prevalence varies based on several key factors:

  • Altitude Reached:
    At moderate altitudes - 8,200–11,500 feet, 25–40% of individuals develop acute mountain sickness (AMS). For reference, Vail CO altitudes range from 8,200 to 11,570 at the top of Vail Mountain.
    At higher altitudes - above 11,500 feet, 40–90% of unacclimatized individuals experience AMS.
  • Individual Susceptibility:
    Certain groups are at higher risk, including:
    • Younger individuals (under 60 years old).
    • Women.
    • People with poor physical fitness.
    • Individuals with underlying lung conditions.
    • Those with a history of altitude sickness.
    • Obese individuals.
  • Home Altitude:
    Residents living below 3,000 feet have a 3.5 times higher risk of developing AMS compared to those who live above 3,000 feet.

Acclimatizing at High Altitude

  • Acclimatization refers to the process by which the human body adjusts to the reduced air pressure and resultant decreased oxygen levels at higher altitudes.
  • As altitude increases, pressure decreases (Pb=exp(6.6328 - 0.1112 h - 0.00149 h*2), where Pb is barometric pressure and h is the altitude in kM. Correspondingly, inspired PO2 concentrations decrease PI02=0.2094(Pb-47) where PI02 is the partial pressure of inspired 02 (14).
  • Although directly related, as shown above, it is the decreased PI02, not reduced barometric pressure, that reduces exercise performance and increases the risk of altitude sickness (14).
  • Acclimatization can take days or even weeks, depending on the altitude, and can be influenced by factors like individual health, hydration, proper nutrition/supplementation and genetics.

Severe Acute Mountain Sickness (AMS)

  • Severe cases of AMS can lead to high-altitude cerebral edema (HACE) and high-altitude pulmonary edema (HAPE), which are life-threatening conditions.
  • If you experience symptoms of HACE or HAPE it is imperitive that you urgently seek medical care.