1. Migraine, 2. Tension-type headache, 4.2 Primary exercise headache, 4.5 Cold-stimulus headache, 4.6.1 External compression headache and 11.2.1 Cervicogenic headache can occur during a dive. In these instances, diving should be considered a precipitating factor rather than the cause, and the headache should be coded as these disorders accordingly.
Headache caused by diving below 10 metres, occurring during the dive and often intensified upon resurfacing, in the absence of decompression illness. It is usually accompanied by symptoms of carbon dioxide intoxication. It remits quickly with oxygen or, if this is not given, spontaneously within three days after the dive has ended.
A. Any headache fulfilling criterion C
B. Both of the following:
1. the patient is diving at a depth greater than 10 m
2. there is no evidence of decompression illness
C. Evidence of causation demonstrated by at least one of the following:
1. headache has developed during the dive
2. either or both of the following:
a) headache has worsened as the dive is continued
b) either of the following:
i. headache has spontaneously resolved within 3 days of completion of the dive
ii. headache has remitted within 1 hr after treatment with 100% oxygen
3. at least one of the following symptoms of CO2 intoxication:
a) mental confusion
c) motor incoordination
e) facial flushing
D. Not better accounted for by another ICHD-3 diagnosis.
There is some evidence that hypercapnia in the absence of hypoxia is associated with headache. The best clinical example of headache attributed to hypercapnia is 10.1.3 Diving headache. Hypercapnia (arterial pCO2 >50 mm Hg) is known to cause relaxation of cerebrovascular smooth muscle, leading to intracranial vasodilatation and increased intracranial pressure. Carbon dioxide may accumulate in a diver who intentionally holds his or her breath intermittently (skip breathing) in a mistaken attempt to conserve air, or takes shallow breaths to minimize buoyancy variations in the narrow passages of a wreck or cave. Divers may also hypoventilate unintentionally when a tight wetsuit or buoyancy compensator jacket restricts chest wall expansion, or when ventilation is inadequate in response to physical exertion. Strenuous exercise increases the rate of CO2 production more than 10-fold, resulting in a transient elevation of pCO2 to more than 60 mm Hg. 10.1.3 Diving headache usually intensifies during the decompression phase of the dive or upon resurfacing.