Summer is over, and diver training activity can be expected to tail off a little over the next few months. Diving instructors can relax a little, draw breath, and reflect on what has been a successful season by all accounts. It is also time for instructors and divemasters/dive controllers to reflect on the issue of their diving-related health.
Without a doubt, diving instruction is one of the most rewarding activities that a diving career can progress to. I have taught diving in New Zealand for 22 years (though not very actively over the last five) and can look back on some remarkable events, some very scary, some very trying, and some very rewarding. There is something about the challenging nature of a diving course that brings people together (witness the astonishing number of relationships that arise on diving courses) and the instructor is the hub of this highly interesting social wheel. The thought of finding time to teach again (and a desire to stay up to date in the recreational industry) keeps me renewing my instructor certification every year.
Sadly, there is often a cost associated with becoming an instructor. There is a tendency for instructors to forget why they became divers in the first place, and do nothing but teach. I have seen too many people lose interest in the sport entirely by teaching too much and âburning outâ. Instructors who can teach and still maintain their passion for diving are literal treasures. However, while this is an issue of philosophical interest to instructors, it is not particularly relevant here. Of more immediate importance are the potential medical dangers of teaching diving.
In theory, instructors are an elite group who have mastered diving (and teaching) techniques to a level sufficient to allow them to teach others to dive safely. It is somewhat paradoxical, then, that in 1995 and 1996 diving instructors were per capita probably the largest group of divers treated for decompression illness (DCI) at the RNZN Hyperbaric Medicine Unit. This begs the obvious question: why?? The disturbing answer is partially provided by the fact that most of the instructors treated became ill as a result of training dives. Yes! Thatâs right, boring old training dives. In several cases the problems arose because other diving was undertaken either before or soon after the training dives.
Similarly, some cases arose when training dives were extended in time and/or depth, eg at the end of Dive 5. However, some instructors suffered decompression sickness simply running by-the-book training dives. The key to how this can happen lies in the nature of the dives themselves. Anyone who has learned to dive on the average dive course will probably be wondering how on earth DCI can arise as a result of training dives. After all, they are usually shallow and comparatively short. Unfortunately though, the dive profiles are not always as favourable as one might think, and the issues of time, depth, and other risk factors which operate during training dives are examined below.
With respect to depth, Open Water Diver course standards allow an instructor to take a group of open water students as deep as 18 metres. No criticism of this standard is implied, but it must be applied sensibly by instructors. Some instructors who have become sick have run their classes too close to this maximum, considering the total time they themselves must spend underwater and the number of ascents they must make (see below). With respect to time, while the average training dive is only 20 to 30 minutes in duration, it must be remembered that an instructor may have to split their class, for example if there are more than the maximum number of students, or if conditions are not ideal. It is not unknown for instructors to repeat the same dive two or even three times. Thus, while an individual student may spend 20 to 30 minutes on a training dive, the instructor may spend up to 90 minutes underwater on the same dive, depending on how many groups have to be run through.
Perhaps more important than consideration of either time or depth is the nature of training dives. Of particular concern is the number of ascents that instructors are required to make with students, practising emergency skills such as the controlled emergency swimming ascent and alternate air source ascent. The significance of these extra ascents is that they modify the risk of DCI for a given time depth profile. Most instructors would point out that, irrespective of any extended time underwater in comparison to their students, they are still within the no-decompression limits specified by their dive table or computer. This may be so. But instructors (or any other divers) who perform multiple ascents during a dive must understand that the no-decompression limits provided by their table or computer are less reliable than normal. This is because the elimination of nitrogen from tissues is considerably altered by the nitrogen bubble formation that inevitably follows ascents. It follows that a dive âwithin the tablesâ but with multiple ascents can certainly result in decompression illness. In addition, multiple ascents (and therefore descents) increase the risk of other diving disorders such as middle and inner ear barotrauma, and pulmonary barotrauma.
How should diving instructors rationalise the above information with their teaching practice? There are several recommendations. 1. Minimise the number of ascents that have to be made on any one dive. Be creative with the distribution of ascent exercises throughout the dives. Standards are becoming more flexible in this regard all the time, and instructors should take full advantage of this flexibility.
2. Never, ever, perform out-of-air ascent exercises from anything approaching the maximum training dive depth of 18 metres. My recommendation is to run these exercises from the minimum depth required by standards.
3. Be very wary of performing other non-training dives after training dives, especially where multiple ascents were involved in those dives. You simply cannot rely on your dive tables or computers in calculating the safety of the subsequent dives.
4. Instructors should remember that they are human, and subject to the same physical and physiological laws as everyone else. The instructor is less likely than an inexperienced diver to get into trouble underwater through panic or procedural failure. But he or she is just as likely to suffer DCI given equivalent dive profiles. It is important not to develop an attitude of indestructibility: this leads to taking risks, such as making that last extra dive to free an anchor instead of buoying it off and collecting it later. It is fine to see yourself as a superior diver, but not a superior organism. Hopefully, attention to this kind of advice will result in fewer instructors visiting the Navy Hospital âon businessâ next summer.