Practical considerations in dive’accident’ scenarios
by Lynn Taylor and Simon Mitchell
In this article we have focussed on the first aid management of various dive ‘accident’ scenarios. In doing this, it would be easy to state text book model answers to particular problems but, in the real world, cases are often complex and there is not necessarily a definitive ‘right’ or ‘wrong’ response to a situation. What we will do here is give some example cases and take you through the thought processes that may help you decide the most appropriate course of action. It is important to remember that, whatever action you do decide to take, it is likely to result in a better outcome for the victim than taking no action at all.
Although taking proper training in diving rescue and first aid will equip you with skills and knowledge to make the most appropriate decisions, you cannot be expected to know everything about the victim or the cause of the situation. You would not be criticised for making a decision which was less than 100% ideal.
We have used three case studies of decompression illness (DCI) across a range of severities, to illustrate some important decision dilemmas, weigh up the benefits and risks of possible actions, and give our recommendations. The cases described below are based on a combination of cases from the DAN database and from our own observations. Similarities to specific cases are purely coincidental.
John has done a deep dive to 25 metres and slowly worked his way up to 14 metres. He swims too close to his buddy in front and gets his mask dislodged by the diver’s fin. He spends several minutes clearing water from it, and before continuing the dive he checks his air gauge and is shocked to see there is only 5 bar remaining. He panics, drops his weight belt and makes a rapid ascent to the surface from 14 metres. He doesn’t want to make a scene so snorkels to the boat and, only when he is asked to hand up his weight belt, does he explain what happened. He seems well. His computer registered a dive time of 22 minutes. Someone suggests he should grab another tank and go straight back down to do some ‘deco stops’. Someone else suggests he should breathe oxygen for a while. What would you do and what advice would you give him about doing a second dive?
The clear concern in this situation is John’s risk of developing DCI, either because of lung expansion injury or, formation of bubbles from dissolved nitrogen. The immediate concern, as with any rapid or panic ascent, is the danger of a lung expansion injury. This could result if John didn’t exhale fast enough to allow the expanding air from his lungs to escape. The over-expansion of his lungs could rupture the respiratory tissue leading to several possible injuries including: arterial gas embolism (AGE), mediastinal emphysema, subcutaneous emphysema and pneumothorax. The most serious (and most common) of these is AGE, in which bubbles may enter the arterial circulation and travel to the brain where they interrupt blood flow and deprive the brain of oxygen. Symptoms of AGE and the other lung expansion injuries usually appear quickly, often immediately after surfacing. The symptoms of AGE are similar to a stroke, and include: sudden unconsciousness, visual changes, dizziness, loss of coordination, weakness, sensory changes, disorientation, difficulty with speech, and personality change. The symptoms of the other lung expansion injuries include: bloody froth from the mouth, breathlessness, coughing, chest pain, cyanosis (blue tinge to the lips and tongue), fullness in the neck area with a crackling sensation when touched, difficulty in swallowing, voice changes, and in serious cases, respiratory/cardiac arrest. Any suggestion of lung expansion injury or its consequences should result in immediate initiation of the first aid sequence involving the administration of 100% oxygen, as detailed in Case 2 below.
However, several minutes have elapsed during John’s surface swim back to the boat and he seems well. Lung expansion injury therefore seems unlikely.
Next, we must acknowledge the provocation for nitrogen bubble formation inherent in John’s dive. Although his time/depth profile was within the recreational dive limits, his rapid ascent must be regarded as a form of ‘omitted decompression’.
Remember, even normal ascents are a form of ‘decompression’. During his rapid ascent there was less time for elimination of the nitrogen that John had accumulated during his dive. The nitrogen is therefore more likely to form bubbles as it comes out of the tissues. It is the formation of these bubbles that causes the tissue injury and symptoms associated with DCI. Rapid ascents are associated with about a quarter of all cases of DCI worldwide (DAN database).
With these facts in mind, John should be monitored for symptoms of DCI, the most diagnostic of which are pain, tingling, numbness, reduced muscle power, or dizziness. If any of these symptoms appear, the first aid sequence of giving 100% oxygen should be initiated, as described in case two below. But since he is well, what about those preventative measures suggested by the other divers?
We would be dubious about the benefit of re-entering the water with a second cylinder to perform some ‘deco stops’, especially if more than five to 10 minutes had elapsed since he had surfaced. If an asymptomatic diver felt strongly about doing this, another diver should escort them on the stop and be present at all times. The potential for development of symptoms during such a procedure is why most training agencies advise divers not to re-enter the water after omitted decompression. Moreover, the performance of such stops after an omitted decompression would not alter our advice about further diving (see below).
There would certainly be no harm in breathing oxygen at the surface immediately after a rapid ascent. It would probably reduce the risk of developing symptoms of DCI, although the true benefit has not been measured. To be of real value, oxygen breathing would need to be prolonged, and there is the concern that such manoeuvres merely deplete your oxygen supplies should you subsequently need them for a true emergency. In a gross omission of decompression, surface oxygen breathing would probably be justified even in the absence of symptoms, and in that setting urgent contact with a diving physician would also be indicated. However, John’s case does not constitute a gross omission.
In view of John’s omitted decompression, and the potential for bubbles formed on the first dive to confound dive table calculations on the second, we would have little option but to recommend that he does not dive for the remainder of the day.
Thus, in summary, we would manage John by observing him for symptoms of DCI, and advise him not to dive again for 24 hours. We would do nothing more proactive than that, provided he remains well. Before leaving the boat he would be provided with contact information for the DES service, advised that symptoms of DCI may be delayed, and advised to immediately report the development of any symptoms. It is notable that DAN data report a one-hour median latency to the first symptom of DCI.
Although there was wide individual variation, 95% cases reported their first symptom appearing within 28 hours of surfacing.
A group of young people on a diving holiday enjoyed an evening of socialising and a few drinks until late into the night. The next morning they did their first dive of the day on a reef starting at 18m, with a direct slow ascent to the surface from 12m, after 48 minutes. No one had any problems on the dive and they surfaced right next to the boat. One girl, Sarah, felt a little cold towards the end of the dive and so took a hot shower before putting some warm clothes on between dives. About an hour into the surface interval Sarah noticed a slight tingling and numbness in the elbow and fingertips of her left hand. She put this down to the fact that she must have knocked her ‘funny bone’ on something, didn’t think much of it, and geared up for her second dive. The second dive continued with no problems, a dive to 12m (max) for 55 minutes with the group making a slow direct ascent to the surface. Very shortly after getting aboard, Sarah noticed a dull aching pain in her left elbow and again felt the tingling down the fingers of her left hand. She thought this was a bit unusual and mentioned it to her dive buddy. If you were her buddy, what action would you take?
In this case it is easy to see the warning signs in hindsight, but they may not be so obvious at the time. The dive profiles themselves are both within standard recreational dive planning table limits and ascents were slow and controlled. Despite this, Sarah clearly developed symptoms of DCI after the first dive but these were not recognised until after the second dive. This is not uncommon. In the 1999 edition of the DAN report on DCI and fatalities, 68 divers (16.8%) reported having experienced symptoms of DCI before their last dive, and over 80% reported to have been diving within table/computer limits. This case raises two questions, firstly ‘What treatment should she receive at the dive site?’ and secondly ‘how could she develop DCI whilst diving within limits?’
To answer the first question is relatively easy and the answer indisputable. These apparently ‘mild’ symptoms must not be ignored. Provision of 100% oxygen is the single most important immediate first aid treatment for divers with suspected DCI. Sarah should be layed down, her breathing and pulse monitored and given 100% oxygen via a demand valve system until supplies are exhausted or she is handed over to the emergency medical services. The emergency services should be contacted and an immediate rendezvous arranged. The DAN database indicates that the progression from mild symptoms to severe symptoms might be preventable through early treatment with emergency oxygen.
There are two possible reasons for the occurrence of this ‘undeserved’ case of DCI.
First, Sarah was exposed to several risk factors that predictably increase the likelihood of DCI. Cold-induced constriction of peripheral blood vessels at the end of a dive causes reduced blood flow to the tissues and therefore reduced clearance of nitrogen during ascent. Development of symptoms of DCI immediately following a hot shower has also been documented and is thought to be due to a reduction of nitrogen solubility as the temperature of cold superficial tissues suddenly increases. There may have been other issues. For example, Sarah could have been dehydrated (a theoretical risk factor in DCI) due to a combination of alcohol late into the night and a lack of non-alcoholic drinks during the morning. In the most recent DAN report, approx 40% of divers with DCI reported drinking alcohol the night before. Admittedly we don’t know the percentage of divers who did not get DCI after a few drinks the night before, but any such possible risk factors should be considered and allowances made by diving a more conservative profile.
Second, there is a considerable variability from person to person, and within the same person from day to day. Simply put, what you can get away with one day, you can’t necessarily get away with on another. Our advice to Sarah and her friends for the future would also be to include a safety stop (for at least three minutes) at the end of every dive, regardless of whether or not it is required according to the tables/computer. Such stops markedly reduce the risk of DCI.
Andrew and Elizabeth are a middle-aged couple who have been diving together for many years. During a dive they both find things of interest to occupy themselves with and lose visual contact with each other, as they often do for a few minutes. On this occasion, about 30 minutes into a 15 metre dive, Elizabeth swam over a rock and saw Andrew floating limply in the water with his regulator dangling free. Elizabeth hurried over to him, realised he was unconscious and that she had to get him to the surface. She quickly took firm hold of his BCD straps, partially inflated her BCD and swam him to the surface, while supporting his chin just past the horizontal position. As he surfaced frothy blood was coming from his mouth. Elizabeth waved her arm and shouted to the boat for assistance. She then dropped both weight belts, removed both masks, and quickly established that Andrew was not breathing. Immediately she gave two slow full rescue breaths and started to tow him towards the boat. By now the boat had arrived and others were in the water and could help with removal of his gear, whilst Elizabeth continued to give a rescue breath every five seconds. On the boat she was able to check for a pulse, which was absent, and begin CPR (repeated cycles of 15 compressions followed by two breaths). After a few minutes, Andrew began to splutter water and started sharp, shallow breaths, but remained unconscious. He now had a weak pulse. The quick thinking crew already had the oxygen kit assembled, and had radioed for help. Unfortunately they were not trained in oxygen use and so were unsure of whether to give him demand valve or constant flow, or what flow rate to set as they didn’t think the supply would last until they reached the shore. Would you know what to do?
In this difficult situation Elizabeth had the appropriate training which she applied in a systematic way and, as a result, undoubtedly saved her partners life. It is an example of an accident which was well managed but which leaves a few practical considerations to comment upon. Most importantly, the issues pertaining to oxygen delivery. Oxygen equipment can only be used effectively if people know how to use it! There is no substitute for attending a proper oxygen provider course such as those run by DAN.
In answering the question, several facts require consideration. Firstly, Andrew experienced loss of consciousness underwater and so it should be assumed that there is a high probability (if not a certainty) that he will have water in his lungs, as evident from the spluttering of water observed later. Thus, in addition to any concerns about DCI, he should be treated as a victim of ‘near drowning’. This is a serious condition resulting in the collapse of the small ‘air sacks’ (alveoli) in the lungs, meaning less surface area is available for exchange of oxygen between alveoli and blood. This may result in life-threatening hypoxia (a reduction of oxygen delivery to the body’s tissues), which may become worse over time as the seawater causes the lining of the lungs to become swollen. Administration of oxygen is the only practical first aid strategy. Secondly, at the surface Andrew exhibited a classic symptom of lung expansion injury and may therefore be suffering arterial gas embolism (AGE).
Although the standard advice in management of DCI (including AGE) is to administer 100% oxygen for as long as the supply lasts, we would modify that advice when near drowning is a prominent problem. In such a case we believe it is important to be able to provide at least some supplemental oxygen until a further supply is obtained from the emergency services. Failure to do so may result in the patient becoming dangerously hypoxic after exhaustion of the limited oxygen supply. Thus, in this case, we would budget the oxygen to last until rendezvous with the emergency services. Andrew should be maintained in a horizontal position making sure his airway is actively open, for example in the recovery position. His respirations and pulse must be continuously monitored. Oxygen administration is best achieved in this situation using a constant flow device such as a non-rebreather mask, since the patient is unable to cooperate in the use of a demand valve.
It may also be of value when liaising with medical personnel to establish from Elizabeth, whether Andrew had any relevant medical conditions. A note of his dive profile can also be helpful.
It is hoped that these scenarios have assisted you with some of the more practical considerations in managing a dive accident. We also hope that you will consider upskilling your abilities by taking a dive rescue and a first aid course as well as an oxygen provider course. These provide not only theoretical knowledge, but important practical experience. Dive accidents are rare, but they do happen, and knowing what to do could save a life.
Lynn Taylor (PhD) is a PADI Staff Instructor and a DAN Oxygen Instructor who writes regular articles on topics related to diver safety, and lives in Auckland.
Dr Simon Mitchell is diving physician who was previously Director of the Diving Medicine Unit at the Royal New Zealand Navy Hospital. He is now Medical Director of the Wesley Centre for Hyperbaric Medicine, Brisbane. He holds diving instructor qualifications with PADI, SSI and CMAS.