Altitude Sickness

• Denver , Aspen, and capitals (Quito, Bogota, Bhutan) are at this altitude
• Commercial flights are also pressurized to these altitudes

• Altitude of highest inhabited cities and highest capital in the world, La Paz (3700m)

• Not able to acclimate to this altitude

1. Higher altitude = Lower Patm ~ pO2
2. Low pO2 → ↑ respiratory rate (mediated by medulla)
3. Respiratory alkalosis → compensatory metabolic acidosis
4. In the lung, hypoxia leads to vasoconstriction which leads to vicious cycle as described by (3)
5. Heme:
   1. Acute ↑ in hematocrit due to volume contraction
   2. Over weeks there is an ↑ in Hgb production

**While all these occur at extremely high altitudes, acclimatization cannot occur with this degree hypobaric hypoxia

1. Acute Mountain Sickness
   1. Cough, periodic breathing of altitude, pHTN, retinal hemorrhage
2. Acute Altitude Headache
   1. Improves with descent and gets worse with exertion
   2. Can be treated with NSAIDS or tylenol
3. High Altitude Pulmonary Edema (HAPE)
   1. Presentation: Cough, low grade fevers, dyspnea (out of proportion to activity),
   2. Pathophysiology: Hypoxic vasoconstriction → increased pulmonary arterial pressure → pulmonary edema
   3. Imaging: CXR may show infiltrates
   4. Treatments
      1. supplemental oxygen
      2. Hyperbaric bag (Gamow bag)
      3. Immediate descent
      4. Warming
      5. Salmetrol (lacking evidence)
      6. Nifedipine
      7. Sildenafil
4. High Altitude Cerebral edema (HACE)
   1. Presentation: Headache, ataxia (often first finding), decreasing levels of consciousness
   2. Pathophysiology: ↑ in blood flow to compensate for hypoxia → vasogenic edema 2/2 blood flow exceeds ability of auto-regulation
   3. Imaging:

1. Treatment: Supplemental O2, Hyperbaric treatment, Dexamethasone, Diuretics (Acetazolamide)
2. Prevention:
   1. Advise against travel to high altitudes if there is a history of pHTN, poorly controlled asthma, poorly controlled COPD, HAPE, or HACE
   2. Acetazolamide started days proper to trop
   3. Graded ascent (600m/day) and sleep at lower altitude than your highest climb