Acclimatization to decompression

[scubadada]

What do you know about acclimatization or tolerance to decompression? There is only a very short section in Bove and Davis' Diving Medicine pp138-9.

Thanks, good diving,

Craig

 

[Dr Deco]

Hello scubadada :

It is known that tunnel workers become acclimated and show reduced susceptibility to DCS as do commercial divers. I do not know if recreational divers perform enough dives in a short time period to show this effect.

A DAN study indicated such reduced susceptibility, but there was also a "rest day" for the divers.

Dr Deco :doctor:

 

[crpntr133]

Correct me if I am wrong but DAN also reported that "ramping up" (doing a deco before your trip) also helped with the deco process.

 

[Diver0001]

Dr. Deco,

How significant was the reported effect? This is the first time I've heard of this.

R..

 

[scubadada]

Dr Deco,

Thanks for replying to my query. As a recreational diver, my questions would be is adaptation or acclimatization to decompression relevent to my dive activities and, if yes, to what degree or magnitude?

I went back and read chapters 4 and 7 of Diving Medicine, both written by Richard Vann. It appears acclimatization has been well documented in caisson/tunnel workers. Apparently, it has been more difficult to demonstrate for air diving with some mixed results. A study using chamber dives was not able to demonstrate acclimatization using Doppler-detected precordial bubbles whereas a multiday, repetitive, open-water diving study did show a lower incidence of bubbles on days 3-6 compared to days 1-2 for both 1st dives each day and repetitive dives. Interestingly, acclimatization has been easier to demonstrate for helium-oxygen diving. It is proposed that the faster exchange of helium more closely approaches the caisson exposures than nitrogen does.

Sometimes, the more I learn, the less I really know with any certainly. I was also unaware of this phenomenon until a recent exchange with John Chatterton on ScubaBoard. Any additional information would be greatly appreciated.

Good diving, Craig

 

[Gene_Hobbs]

WOW, TONS of reading available on this topic from the caisson work but a couple of my favorites with recreational type profiles are:

Doolette, DJ. Health outcome following multi-day occupational air diving. Undersea Hyperb Med. 2003 Summer;30(2):127-34. RRR ID: 3965 NOTE: David is a researcher at NEDU so one could use that forum for questions about this paper.

Dunford, RG; Vann, RD; Gerth, WA; Pieper, CF; Huggins, KE; Wacholtz, CJ; Bennett, PB. The incidence of venous gas emboli in recreational diving. Undersea Hyperb Med. 2002 Winter;29(4):247-59. RRR ID: 3773

The old Navy guys around here probably remember thier "work up" dives.

 

[scubadada]

There appears to be modest evidence that adaptation or acclimatization to decompression applies to recreational diving. The study by Doolettte supports an element of acclimatization. The study by Dunford, et al. is the study cited in Bove and Davis' Diving Medicine that was mentioned in my post above. Though the magnitude of the contribution of acclimatization is not clear, it is encouraging to know that multi-day and repetitive dives do not increase the risk of DCS and may actually reduce the risk compared to the first few days and dives.

Good diving, Craig

 

[Gene_Hobbs]

I was just talking to Dawn Kernagis and she thought this paper might also be of interest:

Anders Ersson, Maria Walles, Kjell Ohlsson, and Anders Ekholm. Chronic hyperbaric exposure activates proinflammatory mediators in humans. J Appl Physiol 92: 2375-2380, 2002. First published February 15, 2002; doi:10.1152/japplphysiol.00705.2001



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[TSandM]

I wonder if there's any upregulation of nitric oxide production with repeated exposure to high N2 tensions -- As a potent vasodilator, that could assist tissues in offgassing. (I tried a couple of Rubicon searches to see if I could find anything on it, but either I'm not using the right search terms, or nothing is there.)

 

[cutlass]

I'm not sure if increased receptors of NO would altogether be a good thing. In the body, oxygen drives the reaction to produce NO and I've heard it proposed that excess NO overwhelming the CNS is a mechanism behind oxygen toxicity.