Diving and Altitude

As a Colorado resident who dives frequently in New Mexico, issues related to diving at altitude are important to me. Not only is most of my diving done at a relatively high altitude, I frequently have to drive to even higher altitudes to get home. Unfortunately, altitude and diving has not been as thoroughly studied as I would like, so there are not many definitive studies to answer burning questions. At the same time, there are many people who have personal opinions they are not afraid to share, opinions that are often well at odds with whatever research is available.

When Swiss military divers suffered decompression sickness diving at 1,800 meters (6,000 feet), Dr. Albert Bühlmann incorporated altitude adjustments into his design, and his adjusted ZH-L 16 algorithm was successfully tested at Lake Titicaca (3,800 meters/12,500 feet) in 1987. That is good news for me and many divers I know who use the adjusted ZH-L 16 algorithm for dive planning.

But there is more to diving at altitude than simply setting a computer with a Bühlmann algorithm to altitude and jumping in the water. For example, my first altitude dives occurred at the Blue Hole in Santa Rosa, New Mexico, and we were using Nitrox. This was long before I became an instructor. I suddenly wondered about how altitude affected a maximum operating depth (MOD). An instructor in our group got a blank look that told me he had never given that a second thought before. He got out the table used to adjust decompression tables to altitude and used them to advise us to use a much Shallower MOD. I think many and perhaps most people would have either done the same or simply professed ignorance. I now know he was dead wrong in doing that.

Another issue is just driving away from a dive and heading for a higher elevation. I asked a couple true experts on decompression theory to offer advice on that, and they politely refused. It simply hasn’t been studied, and with their reputations as decompression experts on the line, they were quite understandably averse to putting their names on anything resembling advice that was not based upon solid science. Every year, though, thousands of divers around the world drive to higher elevations after diving, and they do so with nearly no guidance whatsoever.

In an attempt to be helpful to divers like me who are concerned about altitude when they dive (or after they dive), I have written two articles that appear in the resources section of this web site. Diving at Altitude is a summary of what we know about the issues related to altitude diving, including why we need to make adjustments and how to computer MODs properly. Ascent to Altitude After Diving presents some of the existing theories and recommendations as well as presenting some of the controversial and unstudied considerations for planning such a trip.

I hope people who dive at altitude or who drive to altitude after diving will find these reticles helpful


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