Altitude sickness
High Yield Notes
7 pages
![ALTITUDE SICKNESS osms.it/altitude-sickness PATHOLOGY & CAUSES ▪ Reaction to exposure to low oxygen concentrations when traveling to high altitude ▫ AKA high altitude illness (HAI), acute mountain sickness (AMS) ▪ Partial pressure of oxygen of inspired air calculated by PiO2 (mmHg) = FiO2 (%) x [Pb (mmHg) - 47mmHg] ▫ FiO2: fraction of inspired oxygen, not affected by altitude, remains unchanged in 21% ▫ Pb: barometric pressure ▫ 47mmHg: vapor pressure of water at 37°C/98.6°F ▪ In high altitudes, ↓ Pb → ↓ PiO2 ▪ Partial pressure of alveolar oxygen (PAO2) ▫ Pressure in alveolar space after equilibration with blood ▪ PAO2 lower than PiO2 ▫ Air enters lungs, humidified by upper airway, partial pressure of water vapor reduces partial pressure of oxygen ▫ Continual uptake of oxygen from alveoli by pulmonary capillaries ▫ Continual diffusion of CO2 from capillaries into alveoli ▪ ↓ PiO2 → ↓ PAO2, ↓ PaO2 → hypoxemia ▪ HAI starts at 1.5km/5,000ft, symptoms noticeable above 2.4km/8,000ft Adaptive mechanisms ▪ Hypoxemia → hyperventilation → ↑ expiration of CO2 by lungs → ↓ PCO2 → ↑ pH (respiratory alkalosis) ▪ ↓ PCO2 , ↑ pH inhibit central, peripheral chemoreceptors, decrease ventilation rate ▪ Within several days ↑ HCO3-, ↓ H+ kidney excretion → ↓ pH → stimulation of respiratory center to further increase ventilation ▪ ↑ erythropoietin production → ↑ red blood 870 OSMOSIS.ORG cell production ▪ ↑ 2,3 BPG synthesis → ↓ hemoglobin affinity for O2 → ↑ release of oxygen to tissues Measures to avoid HAI ▪ Acclimatization: ascending slowly to high altitudes, to adjust to decreasing oxygen levels ▪ Preventative medications: acetazolamide (diuretic); increases bicarbonate kidney excretion RISK FACTORS ▪ ▪ ▪ ▪ History of HAI episodes Prior exercise/alcohol consumption Rapid ascent to high altitude Comorbidities that affect breathing (e.g. asthma) COMPLICATIONS ▪ Can lead to potentially fatal conditions ▫ High altitude cerebral edema (HACE), high altitude pulmonary edema (HAPE) SIGNS & SYMPTOMS ▪ Usually appear within 6–12 hours of ascent ▪ Headache, dizziness, fatigue, nausea, vomiting, loss of appetite, sleep disturbance ▪ Often improves with time if person does not ascend to higher altitude ▪ HACE ▫ Excessive fatigue, confusion, neurologic deficits (e.g. ataxia, altered mental state) ▪ HAPE ▫ Dry cough, dyspnea](https://d16qt3wv6xm098.cloudfront.net/CKAbwy8uT6C2YlccDa298JG0TSezd2-2/thumb-4.jpg)
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Summary
Altitude sickness, also called acute mountain sickness (AMS), is a sickness that people can get when they climb quickly to high altitudes. It can also happen if they live at high altitudes but have not been there long. There are three types of altitude sickness: acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). When people get AMS, their body does not get enough oxygen because the air pressure is lower than at sea level. This can cause headaches, nausea, vomiting, and death in severe cases.