14-16 Change A
U.S. Navy Diving ManualVolume 3
shallower after a 2 hour interval of chamber air. See USN Treatment Tables 4 and
7 (Chapter 21) for guidance on additional oxygen breathing.
In all cases of deep blowup, the services of a Diving Medical Officer shall be
sought at the earliest possible moment.
Light Headed or Dizzy Diver on the Bottom. Dizziness is a common term used to
describe a number of feelings, including light headedness, unsteadiness, vertigo (a
sense of spinning), or the feeling that one might pass out. There are a number of
potential causes of dizziness in surface supplied diving, including hypoxia, a gas
supply contaminated with toxic gases such as methylchloroform, and trauma to the
inner ear caused by difficult clearing of the ear. At the low levels of oxygen
percentage specified for surface supplied diving, oxygen toxicity is an unlikely
cause unless the wrong gas has been supplied to the diver.
Initial Management. The first step to take is to have the diver stop work and venti-
late the rig while topside checks the oxygen content of the supply gas. These
actions should eliminate hypoxia and hypercapnia as a cause. If ventilation does
not improve symptoms, the cause may be a contaminated gas supply. Shift banks
to the standby helium oxygen supply and continue ventilation. If the condition
clears, isolate the contaminated bank for future analysis and abort the dive on the
standby gas supply. If the entire gas supply is suspect, place the diver on the EGS
and abort the dive. Follow the guidance of paragraph 14-4.2 for ascents.
Vertigo. Vertigo due to inner ear problems will not respond to ventilation and in
fact may worsen. One form of vertigo, however, alternobaric vertigo, may be so
short lived that it will disappear during ventilation. Alternobaric vertigo will
usually occur just as the diver arrives on the bottom and often can be related to a
difficult clearing of the ear. It would be unusual for alternobaric vertigo to occur
after the diver has been on the bottom for more than a few minutes. Longer lasting
vertigo due to inner ear barotrauma will not respond to ventilation and will be
accompanied by an intense sensation of spinning and marked nausea. Also, it is
usually accompanied by a history of difficult clearing during the descent. These
characteristic symptoms may allow the diagnosis to be made. A wide variety of
ordinary medical conditions may also lead to dizziness. These conditions may
occur while the diver is on the bottom. If symptoms of dizziness are not cleared by
ventilation and/or shifting to alternate gas supplies, have the dive partner or
standby diver assist the diver(s) and abort the dive.
Unconscious Diver on the Bottom. An unconscious diver on the bottom consti-
tutes a serious emergency. Only general guidance can be given here. Management
decisions must be made on site, taking into account all known factors. The advice
of a Diving Medical Officer shall be obtained at the earliest possible moment.
If the diver becomes unconscious on the bottom:
Make sure that the breathing medium is adequate and that the diver is breath-
ing. Verify manifold pressure and oxygen percentage.