By Sara Rich
When new divers are first learning the trade, we are generally taught that good physical condition is important, and that diving is good exercise. Having an annual medical evaluation to ensure that divers are medically ‘fit to dive‘ is standard or at least suggested practice in most places. But that’s for recreational diving. For commercial diving, the medical is mandatory, and in the UK, it’s just become a lot more intimidating. Because British regulations often function as templates for other countries, especially in the EU, the recent changes here may be about to become more commonplace abroad too.
The UK’s Health and Safety Executive (HSE) has recently introduced a more stringent medical policy for professional divers, including those using SCUBA. Whether dive instructor, underwater photographer, commercial or scientific diver, anyone who effectively gets paid to dive must pass the new medical examination and assessment. When the policy was first introduced in October 2015, it raised quite a controversy because divers not passing the medical would quickly find themselves out of a job.
Why the change?
Presumably, the policy change was introduced in the UK in effort to mitigate the number of dive accidents and the number of accompanying law suits – in other words, it’s partly a financial move. It stands to reason, somewhat, that if the standards for health in the industry are higher, then there will be fewer dive accidents. Many diving deaths occur due to cardiovascular failure of some sort, which can be predicated on individual health. So despite the HSE’s systematic attempt to remove the need for common sense in the workplace, the medical exam does consider common-sense factors, such as disabilities, immune disorders, medications, smoking, and obesity, that could point toward a watery demise.
In the UK, these latter two, smoking and obesity, are particular issues of concern, even in the diving community. Although decreasing annually, still nearly 20% of Britons smoke, and that percentage is roughly the same among divers. The increased risks for decompression sickness and nitrogen narcosis, not to mention the potentially fatal cardiovascular malfunctions, are often cited as reasons why divers are discouraged from tobacco use.
The UK is famous around Europe for its obese populace, and waistlines are continuing to expand. One in three British children and two in three adults are considered overweight (BMI >26) or obese (BMI >30), and there are certainly lots of ‘cuddly divers’ out there too. Given the relationship between obesity and cardio and many other disorders, it’s no wonder that HSE medical examinations make fitness such a top concern. If a person is a danger to him/herself underwater, how could s/he possibly be expected rescue another diver? The concern for safety certainly seems valid.
Why the controversy?
Blogs and online forums have revealed a great deal of disgruntled divers since the medical policy change. A large part of the uproar has to do with the way in which limits are drawn across the board, and how those limits reflect, or do not, the reality of a person’s physical fitness.
The two most controversial measurements are BMI and VO2max. As indicated above, BMI, or body-mass index, is a common way of measuring body fat calculated by height against weight (more advanced calculators factor in age and sex as well). But just because it’s common doesn’t mean it’s accurate, and according to HSE’s new standards, professional divers cannot have a BMI above 30, the supposed threshold for obesity. There is some leeway there, if a diver’s BMI is 30-35 and depending on the waistline. But there has to be some leeway because BMI does not factor in such essential determinants as where fat is stored (especially important for women) and muscle mass, which weighs more than fat and can easily skew BMI results.
Indicating the maximal volume of oxygen (oxygen consumption), VO2max quantifies fitness levels by analysing breathing and heartbeat rates incrementally before and after exercise. For the HSE dive medical, the Chester step test is used to calculate VO2max, even though the validity of this test has been found “questionable”:
“The Chester step test can be used confidently as a reliable assessment of aerobic fitness in healthy young adults but its validity in predicting VO2max is questionable. Heart rate and ratings of perceived exertion data taken during the CST are valid and reliable representations of relative exercise intensity (%VO2max), but only when intensities are >65% HRmax or >50% VO2max and when a practice trial of the Chester step test is first performed.“
While reliant on the Chester step test, or the examining doctor’s variation thereof, HSE has declared that a VO2max of less than 45 is a failing grade for professional divers. By comparison, for UK firefighters, the pass/fail threshold is only 42.
Who you calling ‘couch potato’?
I have a friend, a fellow scientific diver, who just took this test as part of her required medical for the coming field season. She’s a healthy, non-smoking thirty-something, and her BMI is low-normal, if one puts any credit in that sort of thing (as HSE does). Between cycling, trail running, and various forms of yoga, she spends a low-estimated average of 10 hours per week working out. Her VO2max was 42, a failing fitness grade for a professional diver (although she could fight fires). Fortunately, HSE offers some leeway here too, and after a consultation with the doctor, she was declared fit to dive for the next 12 months. When it’s a matter of your career though, that’s an awfully close call. And besides, how could someone that fit be at the border of fit/unfit to dive?
There are many factors that affect VO2max, even beyond the “questionable” accuracy and reliability of the Chester step test. Genetics is one of them, but there are other things too: how nervous is the patient whose career rests on the results of the test? how hot and cramped is the room, and is the patient aware that her Listerine may have worn off? How fast did the patient cycle to the doctor’s office to keep from being late? How much coffee did the patient drink that Saturday morning before the medical, thereby increasing heart rate (and nervousness)? For a first-time step-tester, these are especially important factors, as the Buckley et al. 2004 paper cited above demonstrates.
When we divers were first introduced to the physiology of diving, the one thing that gets drilled into our minds perhaps more than any other is that the causes for decompression illness and nitrogen narcosis are shrouded in mystery. While we are aware of some factors (e.g., hydration level, carbon monoxide exposure, etc.) that can make us predisposed to diving illnesses, it all varies from person to person. What we walk away with is the reminder that people do not fit into boxes. Individual physiology is complex, and these complexities should be taken fully into account before declaring that an individual is ‘unfit’ to do his or her job.
For scientific divers, the HSE system of medical testing may be especially problematic. Most of us spend a relatively small amount of time doing underwater fieldwork. The rest of the scientific activity is spent analysing our data, collating and interpreting results, and finally disseminating them. And most of this takes place, sadly, behind the computer. Add to that desk-based research, seeking funding, administration, teaching responsibilities, and the ever-growing push for public service, and the time left to train for a triathlon can only be found if you have no friends or family and you dislike sleep.
In the words of my friend with the deplorable VO2max of 42, if I’m already spending 10 hours a week working out and that’s not enough, what do I have to sacrifice next to be able to pass this test and keep doing my job?
But perhaps a more crucial question for the Health and Safety Executive is: how can the stress associated with making personal sacrifices like that be considered healthy?
Dr. Sara Rich works with old wood from submerged landscapes and shipwrecks at Maritime Archaeology Trust / Maritime Archaeology Ltd. in Southampton, UK. She is the Experienced Researcher in Nautical Archaeology for ForSEAdiscovery.