Is UTD still a "fringe" organization?

[CAPTAIN SINBAD]

The TDI manual appears to be mischaracterizing Haldane's work. Nowhere does he (and his fellow authors) state that the 50% reduction in pressure that they found to be safe is due to a complete avoidance of bubbles. Instead the number was based on a review of previous diving and tunneling incidents. No severe symptoms had been recorded from a pressure less than 2.25 atmospheres absolute (1.25 above sea level or 41 fsw). He simply rounded that down to 2.0 to give a safety margin and, no doubt, to simplify calculations. He then performed experiments to check the validity of this assumption.

I've attached the actual paper. It's fascinating, if somewhat gruesome if you read the experimental section. The authors introduce all the bases of modern decompression theory, including tissue compartments, staged decompression and saturation curves. It's also surprisingly readable. Perhaps because it was meant to be a practical rather than a purely theoretical work.

So I browsed through this and I am not seeing any proof or awareness of presence of bubbles prior to critical limits being exceeded. On the contrary I am reading this ...

"The formation of gas bubbles during or shortly after decompression evidently depends on the fact that the partial pressure of the gas or gases dissolved in the blood and tissues is in excess of external pressure." (Page 344)

This is the flawed assumption which TDI manual refers to that body stores gas in dissolved gas state until a certain pressure difference is reached between the partial pressure of gas inside the tissue and outside. TDI Manual is not the only one that asserts that. Mark Powell in "Deco for Divers" also states exactly what TDI manual writes:

"Traditional decompression models were based on the assumption that inert gases are held in the body until they form bubbles and it is the bubbles that cause decompression sickness. These models are known as dissolved gas models due to the assumption that the gas is held in solution or dissolved in the body." (Mark Powell, Deco for Diver page 118)

 

[lowwall]

So I browsed through this and I am not seeing any proof or awareness of presence of bubbles prior to critical limits being exceeded. On the contrary I am reading this ...

"The formation of gas bubbles during or shortly after decompression evidently depends on the fact that the partial pressure of the gas or gases dissolved in the blood and tissues is in excess of external pressure." (Page 344)

This is the flawed assumption which TDI manual refers to that body stores gas in dissolved gas state until a certain pressure difference is reached between the partial pressure of gas inside the tissue and outside. TDI Manual is not the only one that asserts that. Mark Powell in "Deco for Divers" also states exactly what TDI manual writes:

"Traditional decompression models were based on the assumption that inert gases are held in the body until they form bubbles and it is the bubbles that cause decompression sickness. These models are known as dissolved gas models due to the assumption that the gas is held in solution or dissolved in the body." (Mark Powell, Deco for Diver page 118)

Are you saying that inert gases are not held in the body until they form bubbles? Or that something other than the bubbles cause decompression sickness? The first question is a simple matter of physics. The second isn't really debated, current questions revolve around the various contributions of factors such as the amount of bubbles, the size of bubbles, how bubbles interact with various tissue and substances within the tissues, and how the bubbles move throughout the body.

TDI's mischaracterization is their claim that Haldane stated that bubbles could not be created below his critical limit. He never said that. The critical limit was not based on a theoretical bubble formation model. It was an empirical attempt to set a safe limit based on experience and experimentation.

 

[rjack321]

So I browsed through this and I am not seeing any proof or awareness of presence of bubbles prior to critical limits being exceeded. On the contrary I am reading this ...

"The formation of gas bubbles during or shortly after decompression evidently depends on the fact that the partial pressure of the gas or gases dissolved in the blood and tissues is in excess of external pressure." (Page 344)

This is the flawed assumption which TDI manual refers to that body stores gas in dissolved gas state until a certain pressure difference is reached between the partial pressure of gas inside the tissue and outside. TDI Manual is not the only one that asserts that. Mark Powell in "Deco for Divers" also states exactly what TDI manual writes:

"Traditional decompression models were based on the assumption that inert gases are held in the body until they form bubbles and it is the bubbles that cause decompression sickness. These models are known as dissolved gas models due to the assumption that the gas is held in solution or dissolved in the body." (Mark Powell, Deco for Diver page 118)

Dude, it was published in 1908

Haldane had no way to generate bubble scores, or guess at how much gas might be in the dissolved state vs circulating as asymptomatic bubbles. And the body does store gas in the dissolved state - you aren't going to have any measurable bubbles at all after arriving on the bottom. I doubt he really cared about asymptomatic bubbles anyway although he would probably have been fascinated. He was trying to empirically derive safe decompression practices and considering he was 35 years before the SCUBA gear was even invented, his work absolutely stands the test of time.

 

[rjack321]

Just to remind you of the state of medicine in 1908... This was 3 years before the first antibiotic that actually worked - arsphenamine which is an organic arsenic that was used to treat syphilis - although it was pretty darn toxic, syphilis progressing to your brain was a worse fate.

It would be another 25 years before sulpha antibiotics were released in the 1930s and penicillin coming along in the 1940s.

 

[CAPTAIN SINBAD]

Dude, it was published in 1908

Haldane had no way to generate bubble scores, or guess at how much gas might be in the dissolved state vs circulating as asymptomatic bubbles. And the body does store gas in the dissolved state - you aren't going to have any measurable bubbles at all after arriving on the bottom. I doubt he really cared about asymptomatic bubbles anyway although he would probably have been fascinated. He was trying to empirically derive safe decompression practices and considering he was 35 years before the SCUBA gear was even invented, his work absolutely stands the test of time.

Oh my God! That was my point exactly was it not? People here stated that silent bubbles were something Haldane discovered and his research was about how much of bubble formation causes symptoms. To show that to be wrong I quoted from TDI manual and then I was told that TDI manual is "mischaracterizing" Haldane. Then I quoted from the 1908 Haldane study itself and then from Deco for Divers by Mark Powell.

 

[CAPTAIN SINBAD]

I was responding to the following statement.

From the very beginning of deco theories (Haldane) the assumption was that after every dive, bubbles are present in the body. The question was about what amount of bubbles can be tolerated before having noticeable DCS symptoms.