Decompression Models

[DepartureDiver]

Doc, since I haven't looked at all decompression tables I could only make a guess at their differences, or lack thereof. I suspected that differences were more in the snake oil regime than that of science.

I have to disagree, the "models" are based on science ... even Buehlmann's. The offshoots were of course just manipulation of Haldanian/Buehlmann's principals. Dr. Hills' thermodynamic approach was also grounded in sceince and dives were perfomed with it as well as actual measurements of inherent unsaturation (oxygen window) being performed (on lab animals of course). The bubble models (including mine) are also completely different models and are well grounded in science. This of course does not mean that there has been testing satisfactory to all. But they are still grounded in science without just manipulating a number from another theory. In the PDF file I attached to a post of mine below, the differences (and similarities) in the models are clear. But the work from different individuals in the creation of these different more modern apporaches came from scientific experiments, studies, physiological knowledge, observations, etc. This does not mean that the models will not continue to evolve or that the testing has been done to everyone's satisfaction. But the results are in - deep stops are better and work (or we would be bending) and this started back with Dr. Hills work that showed stops could be started much deeper and that the decompression obligation could be reduced. Based upon Dr. Hills work, I believe the US Navy even came up with a new procedure (many years ago) that allowed the 10' stop to be performed at 20' without adding to the decompression obilgation. Deep stops are not new and should be considered the way to do deco dives.

 

[Dr Deco]

Hello Readers:

Models

It is true that the models are based on science – to some degree. I would definitely agree that the models are formulated in a sufficient manner that parameters can be adjusted to result in a satisfactory answer (i.e., a useful table).

However, when I read the basic assumptions of many of the table designers, I must shake my head. The assumptions do not match reality as I have observed it in animal subjects. If one wishes to make an algorithm that describes a safe decompression, then I am pleased with that result. If one offers that the model actually describes what is occurring in all of its significant points, than I am less than impressed. Some ideas are certainly better than others, no argument there.

Gas Loading

There is more to decompression than gas loading. We learned that at NASA with our decompressions for EVA. These are the simplest processes possible in the world of decompression. They involve no gas loading assumptions and the decompressions in only one step. Gas loading analysis did not yield the correct results in space as on the ground. the procedure that we use today, and tested in several hundred manned-decompressions, is based on several factors:

• The concentration of tissue micronuclei must be adjusted or the decompression process will not work;
• the halftimes of the tissues are not a constant, but rather they vary with the work load in a very regular fashion, and
• There are yet-undetermined parameters that make some individuals DCS-prone and others resistant.

Dr Deco :doctor: