How well would you do?
By Dr Simon Mitchell
The fins of the diver executing the Polaris Missile Manoeuvre (rapid, buoyant, panic ascent) do not quite clear the water at the highest point of their trajectory, but they come damn close. The diver slumps back into the sea, vomiting lots of white frothy material (water by any other name), and appears to be breathing, but is unresponsive. The buddy recovers the diver back into the boat, and without any need for resuscitation the diver becomes responsive again. After ten minutes or so, apart from having a headache and feeling âwashed outâ, the diver appears to have made a good recovery. What do you do?
Choose from the following:
A: Move the dive boat to a new site and suggest the diver has another dive to get their confidence back?
B: Move the dive boat to a new site and suggest the diver sit this one out so that you can keep a close eye on them?
C: Put the diver on oxygen, lie them flat, and initiate an evacuation?
If you chose A, take your laminated certification card to the nearest toilet, cast it in and choose full flush. If you chose B, please read this article, because there are some holes in your knowledge. If you chose C, congratulations, you are right, but read the article anyway for some useful insights. After my recent article describing early management of decompression illness (DCI), I thought it might be useful to back it up with a couple of real life stories which illustrate some important points. I published these in a Dive New Zealand article several years ago, but itâs time they were re-run. Both cases were managed by experienced divers, but the responses were significantly different.
If you thought that no-one would ever choose option A above, read on. The first case was a novice diver completing his first dive after entry-level training. He dived to 30 metres for 21 minutes, at which time there was some difficulty with his weight belt which had become loose. Some time was spent adjusting this, during which he ran out of air. An attempt was made to buddy breathe, but the diver panicked and made a rapid uncontrolled ascent from 20 metres. He became unconscious on arrival at the surface and was picked up by the charter boatâs inflatable which took him back to the charter boat. He regained consciousness during the transfer, and complained of feeling tired. He rested, was given oxygen, and was allowed to mobilise. Diving was terminated, and the Diving Emergency Service was contacted. Since the history was very suggestive of arterial gas embolism, a helicopter evacuation was organised and the diver was treated with a single recompression. There were no subsequent complications.
The second case was also of a novice diver, also completing her first dive some two months after her entry level course. She dived with her buddy, of similar experience, to a maximum depth of 28 metres for 25 minutes. At this time she noted she had only 50 bar of air remaining, and with her buddy commenced an ascent. At 21m she decided to add some air to her BCD since she felt too heavy, but unfortunately, this exhausted her air supply and she attempted to find her buddyâs alternate air source. She was unable to secure the alternate air source and she and her buddy unsuccessfully tried to buddy breathe. At 15m she panicked, dropped her weight belt, and made a rapid uncontrolled ascent. At the surface, her buddy found her âunresponsiveâ and vomiting copious amounts of water. She was recovered to the boat and seemed to be much more responsive by this time. Although it was never established whether this diver actually did become unconscious, there was a clear history of reduced responsiveness, and the diver herself did not remember being retrieved to the boat.
Within ten to 20 minutes of the accident, she was left with a mild headache and a feeling of fatigue. Experienced divers aboard the boat advised her that she should rest until the second dive, and that if she felt well enough, a second dive might be a good idea to get her confidence back. The diver declined this opportunity. Over the following two days she experienced fatigue, chest pain and a sensation of chest tightness. She presented to her GP, who referred her to our unit for assessment. She was found to have abnormal reflexes, and assessed on the basis of the history, to have suffered DCI secondary to arterial gas embolism. She was treated with several recompressions and made a good recovery.
These cases are remarkably similar in many respects, and both contain numerous lessons for all divers, particularly those with less experience. However, I will leave the accident causation commentary to people like Rex Gilbert or Chris Acott. The illustrative point I wish to draw from these cases concerns their early medical management. Test yourself. On the basis of what you are told in these histories, what diving medical problems are important to consider. These possibilities and the accompanying explanation should be common knowledge for any divemaster/divecon or instructor.
To begin with, in both cases the divers were either near or in excess of the no-decompression limits (depending on which table you use) for the depths they visited. Add to this the fact that a rapid ascent occurred, and it must be obvious that both divers were at high risk of developing decompression illness. Even if no symptoms had occurred (that is, assuming the divers had not become unconscious and had felt perfectly well after their ascents), an omitted decompression situation should have been deemed to exist, and further diving should not have been contemplated.
The occurrence of unconsciousness following soon after any ascent using scuba should alert those present to the probability of an arterial gas embolism (âair embolismâ). Whenever it occurs, it is a diving medical emergency, and evacuation of the victim to a hyperbaric facility while delivering appropriate first aid (ABCs, positioning, 100% oxygen, fluids) takes precedence over most other considerations. Note that recovery of consciousness by the victim is common in arterial gas embolism, but is not to be interpreted as recovery from the problem. Other bubbles may be present which could cause a relapse, particularly if the victim is allowed to adopt an upright posture. This possibility cannot be discounted until after the victim has received adequate recompression therapy.
Finally, any person, diver or otherwise, who has become unconscious (and therefore lost control of their airway) while immersed in water, is at high risk of aspirating water into their lungs. The effect of this may not be apparent until sometime later, and the potentially dangerous phenomenon of âsecondary drowningâ may result. It is my belief that anyone with a clear history of unconsciousness in the water must be evacuated for assessment by a medical practitioner as soon as possible. In the case of divers, this should be coordinated through the Diver Emergency Service because of the possibility of concomitant decompression illness.
Reflecting on the two cases described above, it can be seen that the response to a very similar situation was quite different. In the first case, it would seem that despite the apparent recovery of the victim, the potential seriousness of the events were recognised by those present and an evacuation initiated promptly. With the exception of the victim being allowed to walk around, the early accident management in this case was exemplary. In the second case, it would seem that the strong possibility of an arterial gas embolism having occurred was either missed or discounted. Also, given that further diving was contemplated, it would seem that the omitted decompression and the possibility of salt water or vomit aspiration were overlooked.
To be fair, it is always easier to see these things retrospectively. It is also a very difficult call indeed to turn an entire charter boat full of divers back to shore after only half the dayâs diving, especially when the victim seems to have recovered. However, knowledge of these things is what being an experienced diver is all about, especially if professional level qualifications are held. No matter how difficult, consultation with the Diving Emergency Service and evacuation is what should have happened in this case. A quiet, routine trip is what every diver, divemaster or divecon always wants. It is what we usually get, too. But the unfortunate corollary of 99.999% of trips going smoothly is that when the âreal thingâ occurs, we may be either unable or unwilling to depart from our routine. âMust get the dive finished – the day must go smoothly!â Experienced divers and professionals must provide on-site leadership in this regard. Take charge and use your knowledge. Remember, the Diving Emergency Service at the Naval Hospital is always available for advice. If unsure what to do – ask.