Headache caused by hypoxia and/or hypercapnia and occurring in conditions of exposure to either or both.

Diagnostic criteria:
  1. Any headache fulfilling criterion C
  2. Exposure to conditions of hypoxia and/or hypercapnia
  3. Evidence of causation demonstrated by either or both of the following:
    1. headache has developed in temporal relation to the exposure
    2. either or both of the following:
      • a) headache has significantly worsened in parallel with increasing exposure to hypoxia and/or hypercapnia
      • b) headache has significantly improved in parallel with improvement in hypoxia and/or hypercapnia
  4. Not better accounted for by another ICHD-3 diagnosis.