High Altitude Related-Conditions

Aka: High Altitude Related-Conditions, Atmospheric Pressure at High Altitude, Inspired Oxygen Pressure at High Altitude, Fraction of Inspired Oxygen at High Altitude, FIO2 and PiO2 at Altitude

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II. Background: Atmospheric Pressure (Patm), Inspired Oxygen Pressure (PiO2), and Fraction of Inspired Oxygen (FIO2)

  1. 0 m (sea level) Patm: 760 mmHg, PiO2: 150 mmHg, FIO2: 21%
    1. PiO2 = (760 mmHg - 47 mmHg) * 0.21 = 150 mmHg
    2. Where Atmospheric Pressure at sea level = 760 mmHg
    3. Where Fully saturated Water Vapor Pressure = 47 mmHg
    4. Where FiO2 (fraction of inspired air that is Oxygen) = 0.21
      1. Most of remaining inspired air is Nitrogen (0.78)
  2. 1500 m (4920 ft) Patm: 641 mmHg, PiO2: 124 mmHg, FIO2: 17%
    1. Definition of high altitude starts here
  3. 2000 m (6562 ft) Patm: 604 mmHg, PiO2: 116 mmHg, FIO2: 16%
    1. Sante Fe, New Mexico (2194 m or 7200 ft)
  4. 2500 m (8200 ft) Patm 570 mmHg, PiO2: 110 mmHg, FIO2: 15%
    1. Risk of Altitude Sickness increases above 2500 meters
    2. Bogota, Columbia (2620 m or 8596 ft)
  5. 3000 m (9843 ft) Patm 537 mmHg, PiO2: 102 mmHg, FIO2: 14%
    1. Ski altitude (3048 m or 10,000 ft)
    2. Cusco, Peru (3,399 m or 11,152 ft)
  6. 3500 m (11482 ft) Patm 505 mmHg, PiO2: 96 mmHg, FIO2: 13%
    1. Definition of very high altitude starts here
    2. La Paz, Bolivia (3,640 m or 11,942 ft)
  7. 4000 m (13123 ft) Patm 475 mmHg, PiO2: 90 mmHg, FIO2: 13%
    1. Longs Peak in Colorado, U.S. (4345 m or 14,255 ft)
  8. 4500 m (14764 ft) Patm 447 mmHg, PiO2: 84 mmHg, FIO2: 12%
    1. Mont Blanc in Alps, France\Italy (4810 m or 15,781 ft)
  9. 5000 m (16464 ft) Patm 420 mmHg, PiO2: 78 mmHg, FIO2: 11%
  10. 5500 m (18045 ft) Patm 394 mmHg, PiO2: 73 mmHg, FIO2: 10%
    1. Definition of extreme altitude starts here
    2. Mt. Kilimanjaro in Tanzania (5895 m or 19341 ft)
  11. 6000 m (19685 ft) Patm 369 mmHg, PiO2: 68 mmHg, FIO2: 10%
    1. Mt. McKinley in Alaska, U.S. (6190 m or 20,308 ft)
  12. 6500 m (21325 ft) Patm 346 mmHg, PiO2: 63 mmHg, FIO2: 9%
  13. 7000 m (23000 ft) Patm 324 mmHg, PiO2: 58 mmHg, FIO2: 8%
  14. 7500 m (24606 ft) Patm 303 mmHg, PiO2: 54 mmHg, FIO2: 8%
  15. 8000 m (26247 ft) Patm 284 mmHg, PiO2: 50 mmHg, FIO2: 7%
    1. Annapurna 1 Main in Himalayas (8091 m or 26,545 ft)
  16. 8500 m (27887 ft) Patm 265 mmHg, PiO2: 46 mmHg, FIO2: 6%
    1. Mount Everest (8849 m or 29,035 feet)
  17. 9000 m (29528 ft) Patm 248 mmHg, PiO2: 42 mmHg, FIO2: 6%
  18. References
    1. Roach, Lawley and Hackett in Auerback, Cushing and Harris (2016) Auerbach's Wilderness Medicine, p. 4

III. Associated Conditions: General

  1. Acute Mountain Sickness
  2. Altered Sleep at high altitude
    1. Fragmented Sleep Stages
    2. Frequent awakenings
    3. Sleep Apnea
    4. Periodic breathing occurs normally above 3000 meters
  3. Physical wasting above 18,000 feet
    1. Weight loss
    2. Increased lethargy
    3. Muscle Weakness
    4. Polycythemia
    5. Acclimatization above 18,000 feet offers no benefit
  4. Peripheral Edema
    1. Self limited with spontaneous resolution
    2. Consider Diuretics if needed
  5. Thrombosis (higher Incidence at altitude)
  6. Immune Suppression
    1. Infections common and difficult to treat at altitude
    2. T Lymphocyte depression
    3. Descend for refractory infectious symptoms and signs

IV. Associated Conditions: Neurologic

  1. High Altitude Cerebral Edema

V. Associated Conditions: Respiratory

  1. High Altitude Pulmonary Edema
  2. High altitude Pharyngitis or Bronchitis
    1. Dry cough results from respiratory irritation at altitude (multi-factorial)
    2. Reduced with throat lozenges, oxygen Face Mask breathing
    3. Cough may be severe enough to cause Rib Fractures (Cough fracture)

VI. Associated Conditions: Ocular

  1. Ultraviolet Keratitis
  2. High altitude Retinopathy
    1. Retinal Hemorrhage at high altitude
    2. Resolves spontaneously in 1-2 weeks at sea level
    3. Predictive of more severe High Altitude Sickness including HACE and HAPE
  3. Vision change (refractive shift)
    1. Occurs in those with Radial Keratotomy history

VII. References

  1. Comp and Rogich (2021) Crit Dec Emerg Med 35(4): 3-8

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