So there I was, having breakfast with my good friend Dr Nick at the usual hotel before the Our World Underwater show in Chicago a few months ago. Nick is one of the most knowledgeable guys I know on the subject of decompression theory and physiology, and if he is talking then I am definitely listening. Anyway, we are talking about divers doing stupid stuff, and then he starts to talk about something serious, an unnamed diver who suffered an "unearned hit". An "unearned hit" is one of those politically correct terms now used to describe a decompression sickness (DCS) event where the diver has supposedly followed all the rules, and done absolutely nothing wrong, but still ends up bent for reasons that remain a total mystery??? "Unearned hit" really means unexplained hit to me.
Just to be clear, we are not talking about divers with serious medical problems that end their diving careers until the medical issue(s) is resolved, like PFO's or any medical condition that affects diving and decompression. Events like these are truly unearned by the diver, but explainable. We are also not talking about divers who get caught doing stupid things that end them in the chamber, and hopefully they then learn a lesson. What we are talking about here are divers who are healthy, have a DCS event, and then claim a mysterious unexplained, "unearned hit", and then return to diving, of course after a stint in the chamber and a short rehab on the beach, having learned nothing.
Just the use of the term, "unearned hit", is enough to get me going, so I had to stop Nick in mid-sentence. I asked him if he meant unexplained hit, as opposed to unearned hit, and he thought for a second, and responded positively. I told him that so long as there was not a medical background to this particular case, I was able to explain it completely, entirely, without even knowing all of the dive particulars. The reason I was able to explain it was because there is one, and only one reason for DCS in a healthy diver.
Every single case of DCS in a healthy diver, without exception, has been caused by the diver..... not doing enough decompression!!! That is it. I just assumed that science guys know this, but apparently not?
It is not really that complex is it? The cause of DCS, is coming to the surface too soon, without having done enough deco. Now the causes for coming to the surface too soon are almost infinite, and there are divers who take responsibility for their mistakes, and learn from them. But "unearned hit" is really a lot of, "let me tell you my story of how I am too smart to get bent, and I did nothing wrong, and blah, blah, blah, blah, blah."
When I first arrived in London to dive the Lusitania, in 1994, the expedition leader had just been treated for a pretty serious Type II DCS hit involving some paralysis. I was not only worried about her, but sympathetic to her situation, and none of us were sure how this would impact our expedition? When she was finally released from hospital, she told our group what had happened.
She went down to the tabled depth, but the grapnel was a little deeper, so she went down and secured it, she did her dive and she was right on time coming back, but after she had started up the line she remembered the hook, and went back down to free it, and she did not understand why she got bent....... it was a totally "unearned hit". I mentioned something to the effect that it was totally "unearned", except for going over on time... AND depth!!! My comments were not well received, but I am experienced at saying the wrong thing.
A few years ago, a friend of mine got himself in trouble in the Pacific. When I saw him after he returned, he sheepishly told me how even the chamber operator had agreed with him that it was a totally "unearned hit"! However, I had already spoken to another friend of mine who was there. I do not mean to be unkind, but this guy was overweight and out of shape at the time. It was his first dive of the trip, it was deep, he was jet-lagged, and stayed up into the wee hours drinking with friends the night before the dive. So, he was claiming the hit was "unearned", except for his lack of fitness, the lack of sleep, the abundance of alcohol, the dehydration, and the stress of travel. Aside from that, it was totally "unearned", because his rebreather computer told him to surface? Seriously?
This is the deal, it does not matter whether you use a computer, or tables, or just remember your dive plan in your little head, you are the only one responsible for when you come to the surface. Come up too soon and you will get bent. I have made thousands and thousands of dives, and understanding this simple premise is the only thing that has kept me from being bent.
Is there a check box on your dive planner, or a button to press on your dive computer for any of the following?
- Are you seasick, or did you start out feeling not too good to begin with?
- Are you tired, sleep deprived, or jet lagged?
- Are you dehydrated?
- Is your individual cardio-pulmonary efficiency poor for any reason?
- Are you out of shape or carrying too much weight around your middle?
- Are you stressed out at work, or are you stressed out at home?
- Did you do a lot of swimming or hard work on the dive?
- Did you get cold, or wish you had worn your drysuit?
- Did you scare yourself?
- Were you lost?
- Is that 12' shark a bull or a white?
- Are you going to get your butt kicked on the surface because the environmental conditions are a tad challenging this afternoon?
- Did you breathe more gas than usual today, for any of the many possible reasons?
I love my dive computers, but mine doesn't have an "I am seasick" button, and I would imagine yours probably doesn't either? Computers and tables give us mathematical predictions, based on time and depth only. They provide information, which is just a bunch of numbers based on an algorithm estimating typical human physiology at a molecular level. If this stuff was an exact science no one would ever get bent, but that is not the case, is it?
When we look at the information from our computer or table, it is only numeric data for a baseline dive based on time and depth. Then........ and I know this is hard to believe, but the diver needs to get personally involved, and interpret this data as it applies to himself/herself on that particular day, and that particular dive. You may need to buffer the calculated hang, safety stop, or ascent. Just because the computer, and/or tables say it is okay to surface, does not mean that it is absolutely safe to do so. There is a lot that the computer and/or tables simply don't know about your dive. You should know more than the magic box!
I hope none of you are ever in this situation, however if you do not interpret the data correctly, and you don't do enough decompression, and you get yourself bent, please do not call it an "unearned hit", simply because it is totally, unabashedly, "earned" by you. Utilizing politically correct and wholly inaccurate terminology to hide the fact that you are a jackass is not going to make you a better diver. Nor will this earn the respect of anyone who knows anything. DCS of this kind is not a mystery, it is not caused by the hand of god, and it is not all complicated like brain surgery. The cause of DCS is not doing enough deco.