Divers may experience sensations while at depth which they would describe as
dizziness, or in some situations may lose consciousness. The causes of these
conditions are not always obvious and surfacing the diver may not be possible
because of decompression obligations. Therefore, it is important to know what
could cause these disorders in order to decide the possibility of injury to the diver.
The sensation of the diver spinning or the environment spinning is called
vertigo. Vertigo is common and usually transient in divers. There are two types of
vertigo: transient and persistent.
Transient vertigo typically lasts less than 1 minute. There are
two common forms of transient vertigo: caloric and alternobaric. Caloric vertigo
may be due to unequal cold water stimulation of the ear. This is seen when passing through thermoclines, slow clearing of the external ear canals, or eardrum rupture.
Alternobaric vertigo may be caused by pressure differences between the middle
ears on ascent or descent, and typically resolves when the ears are cleared. Travel
should be halted until the vertigo resolves. Once the vertigo resolves, then the dive
may be continued.
Persistent vertigo lasts greater than 1 minute. Symptoms may
be caused by inner ear barotrauma, decompression sickness or arterial gas embolism.
If persistent vertigo is suspected, abort the dive and consult Diving Medical
Personnel. All cases of persistent vertigo shall be evaluated by a Diving Medical
Officer.
An unconscious diver on the bottom is a
serious emergency. Only general guidance can be given here. Management decisions
shall 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:
1. Make sure that the breathing medium is adequate and that the diver is
breathing.
2. Check the status of any other divers.
3. If there is any reason to suspect gas contamination, shift to the standby supply.
4. Have the dive partner or standby diver ventilate the afflicted diver to remove
accumulated carbon dioxide in the helmet and ensure the correct oxygen
concentration.
5. When ventilation is complete, have the dive partner or standby diver ascertain
whether the diver is breathing. In the MK 21, the presence of breath sounds
may be audible over the intercom.
6. If the diver appears not to be breathing, the dive partner/standby diver shall
attempt to reposition the diver’s head to open the airway. Airway obstruction
will be the most common reason why an unconscious diver fails to breathe.
7. Check afflicted diver for signs of consciousness.
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If the diver regains consciousness, allow a short period for stabilization
and then abort the dive.
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If the diver remains unresponsive but is breathing, have the dive partner or
standby diver move the afflicted diver to the stage. This action need not be
rushed.
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If the diver appears not to be breathing, make further attempts to open the
airway while moving the diver rapidly to the stage.
8. During recovery of the affected diver:
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If conscious, allow a period for stabilization, then begin decompression.
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If unconscious, bring the diver to the first decompression stop or the
surface at a rate of 30 fsw/min. Decompress the diver using surface
decompression procedures if required.
9. If the diver remains unconscious at the first decompression stop and breathing
cannot be detected in spite of repeated attempts to position the head and open
the airway, an extreme emergency exists. One must weigh the risk of catastrophic,
even fatal, decompression sickness if the diver is brought to the
surface, versus the risk of asphyxiation if the diver remains in the water. If the
affected diver is not breathing, leave the unaffected diver at his first decompression
stop to complete decompression and surface the affected diver at 30
fsw/minute, deploying the standby diver as required. Start CPR or Advanced
Cardiac Life Support (ACLS) on the surface if needed. Recompress immediately
and treat accordingly.
