By Dr Simon Mitchell
I remember a diver I treated for decompression illness several years ago, who told me how his symptoms came on dramatically while he was alone in a small boat at anchor. He hailed another boat with three divers, who immediately responded to his calls for help, and on seeing their approach my patient collapsed onto the floor of his boat with relief. This relief was somewhat short-lived, however. The three rescuers pulled up alongside and stood motionless, staring at him like possums transfixed by a headlight. After what seemed an age, one of them finally broke the silence with a pithy observation: âShit, heâs fâed.â
It is a matter of record that these heroes eventually overcame their inertia and took the fellow ashore where he received oxygen from paramedics and was evacuated to our unit, making a full recovery after several treatments. The less than professional ârescueâ described here is not unusual. However, to be fair, I could also relate stories of diving accidents where the on-site management has been exemplary. Almost invariably, what separates those incidents managed well and those managed poorly is the training of the divers that are thrust into the role of first responders. Fear of doing anything arises when you donât know what to do, and I have no doubt that this explains the initial inertia in the three rescuers in the story above.
In this article I will review the current advice for the management of decompression illness (DCI). However, I would stress that merely reading this is no substitute for proper training. If you want to be ready for the diving accident you may have to manage one day, then combine a PADI Rescue Diver or SSI Stress/Rescue course with a DAN Oxygen Provider Course. This is the training you need. DCI can present in a wide variety of ways. At the severe end of the spectrum, a diver may develop rapidly progressive symptoms such as pain, numbness and weakness while still at the dive site. More mild DCI may not be apparent until well after the dive, perhaps not until the next day, when the diver might complain of mild pain, tingling, and/or feeling âoff colour.â Assessment and treatment can be approached in a more relaxed manner in the latter case, while in the former, early and appropriate intervention may be critical in determining the diverâs outcome. I will focus on the management of the diver who develops symptoms early after the dive. First aid for the diver who develops symptoms of DCI on the same day as diving can be broken down into the following steps.
It is not appropriate to discuss the technique of CPR in an article such as this. It must be learned with proper practice-based tuition, and all divers should be trained. DCI rarely results in respiratory or cardiac arrest and CPR is therefore rarely required in this context. The most likely scenario for CPR in diving is a drowning event.
A diver developing symptoms of DCI soon after a dive should be laid flat (horizontal). If consciousness is compromised, then the diver should be either in the recovery position, or flat on the back with the rescuer actively managing the airway. Only those with proper training should attempt the latter. Despite dogmatic preaching to the contrary, if the diver is fully conscious it does not matter whether they are on their back, side, or front, provided they are horizontal and comfortable. The horizontal position should be maintained no matter what improvement the patient makes. This is particularly so if the diver develops rapid onset of neurological symptoms such as unconsciousness, weakness, numbness, or difficulty speaking. Bubbles in the arterial blood are sometimes responsible for such symptoms and postural changes may cause any further bubbles trapped in places like the heart chambers to enter the blood vessels supplying the brain. Old-timers may remember that the advice until 1990 was to place the diver 30Âº head down. This was an attempt to keep bubbles in blood away from the brain. The 30Âº guideline was introduced in response to divers being brought in hanging by their feet from gamefish weigh-in gantries on the backs of trucks. Just so there is no confusion, we have moved away from the head-down advice for several reasons which are beyond the scope of this article. The current advice is to place the diver horizontal.
Administration of 100% oxygen is the single most important component of the early management of DCI. Oxygen administration should be maintained from diagnosis throughout any evacuation unless advised otherwise. Oxygen breathing markedly accelerates the elimination of nitrogen from blood and tissues, thereby promoting resolution of any nitrogen bubbles. It also enhances oxygenation of tissues that have had their oxygen supply compromised by any of the pathological processes of DCI. The response to oxygen administration in the field has often been quite dramatic. Near complete recovery has been recorded with 100% oxygen administration, although such a response does not eliminate the need for review at a specialist hyperbaric unit. Failure to administer 100% oxygen is the most common error made by divers at the scene. There are two main reasons for such failures: not knowing how to do it, and not having the appropriate equipment (or enough oxygen). I am not going to explore this issue further since the space available would result in trivialising a critically important subject. However, be aware that the simple plastic masks connected to oxygen tubing that are an inevitable accessory for all patients in TV medical melodramas do not deliver 100% oxygen or anything close to it. Education is the key. All divers are eligible to do a DAN Oxygen Provider Course. Armed with the knowledge of how to administer 100% oxygen, owning your own equipment to do it becomes a less scary proposition. Give it some thought.
4. Fluid administration
For a variety of reasons, divers tend to be dehydrated. Dehydration is thought to be a risk factor for the exacerbation of DCI, although there is little solid evidence. Nevertheless, correction of dehydration is a priority in treatment at hyperbaric units. The aggressiveness with which rescuers in the field should attempt to correct dehydration has always been a controversial subject. If someone qualified to initiate and maintain an intravenous fluid infusion is present, then this should always be done. The situation is less clear for oral fluids. There is a risk that if oral fluids are taken and the patientâs condition deteriorates, then they might become unconscious and aspirate the fluids into their lungs. If the patientâs level of consciousness is decreased, or if they have rapidly progressive disease, then I would withhold oral fluids. I would also advise against oral fluids if the diver is likely to be in the care of someone qualified to start an intravenous infusion within 45-60 minutes. Where the patient is fully conscious and stable, and rescue is likely to be delayed longer than 45-60 minutes, bland oral fluids should be given in frequent small amounts. The horizontal position should not be compromised in order to administer fluid. In this regard, those trendy water bottles with straws (which are otherwise only useful for passing disease from person to person!) can come into their own. The amount given should always be recorded.
If a diver is desperately unwell (unconscious or having difficulty breathing), donât worry about any assessment, just contact the emergency services immediately. Under these circumstances it is probably best to directly contact ambulance control on 111 if calling from a cellphone (as most seem to do these days). If the diver is conscious, and breathing is not compromised, pause briefly to gather the following information before contacting the Diving Emergency Service: the name, age and gender of the patient; the times and depths of the dives performed in the last 24 hours; the number and nature of ascents (for example, were any ascents rapid for any reason); the nature of the symptoms and when they came on after the dive. In general, we would discourage non-medical people from performing ârapid field neurological examinationsâ before contacting us. After initial contact has been made, any information gleaned from such examinations would be very useful, provided the horizontal position is not compromised and evacuations are not delayed.
6. Contact the Diver Emergency Service
The DES is based at the RNZN Hospital, Auckland, and is manned 24 hours with a diving medicine specialist available directly or on a cellphone. The number is 0-9-445 8454, and thanks to sponsorship from New Zealand Underwater, this is a toll free number. It should be copied down and kept in a prominent place on your boat.
Once you have contacted the DES, the evacuation will be coordinated by them in cooperation with the appropriate ambulance service. You will be given instructions. In general, divers from the North Island are evacuated to the RNZN Hospital at Auckland, and divers from the South Island are evacuated to the Hyperbaric Unit at Christchurch Hospital. These are the only hyperbaric facilities in New Zealand with the expertise and equipment to safely and effectively treat sport divers with DCI. Methods of evacuation vary according to the location of the diver and the circumstances. Sometimes divers are first taken to a local centre for evaluation, particularly if there is any doubt about the diagnosis. For short distances, helicopters maintaining a low altitude are used. Helicopters are also used if divers need to be winched off boats at sea. For longer distances, a one-atmosphere pressurised fixed-wing air ambulance is the favoured means of transport.
Later onset of symptoms
Those cases of DCI at the mild end of the spectrum who report their symptoms on the day following diving (or later) do not need to be positioned and put on oxygen/fluids as above as a matter of absolute urgency. The best advice in this situation is to gather the sort of information listed under âAssessmentâ above and to discuss the case with the DES. In describing these cases as âless urgent,â I would nevertheless advise divers to contact the DES immediately once the situation is brought to your attention, at any time of day. The decision about the need for haste in the evacuation should be made by a diving medicine specialist. Thankfully, DCI is a rare complication of a safe and enjoyable sport. However, the longer you remain involved and the more dives you do, the greater the chances of being involved in managing a case in the field. It has happened to me (in sport diving) three times over a 26 year diving career. Being prepared is the key. Think about that rescue course and Oxygen Provision training.