Nitrox question for Dr. Deco

[ianr33]

Could it also/instead be that the air tables are not conservative enough, but the nitrox tables are?

Another thing to bear in mind is that the tables are designed so that safety stops are "optional" If you do a long safety stop on nitrox that has to be more beneficial than doing it on air. (you will be offgassing faster due to the lower pN2 in the nitrox) A 3 minute safety stop on nitrox might equate to 4 or 5 minutes on air.

 

[fisherdvm]

There's probably quite a bit of placebo effect here.

The placebo effect could go both way. Strong ardent gullable divers are going to buy the conventional wisdom that nitrox has no effect on fatigue, and ignore beneficial effect of nitrox. Or gullable wealthy (nitrox cost $$$) are paying extra just because some dumb dude tell them that nitrox is going to make them feel better.

I don't know, I was extremely dubious of this, until my sister tried to convince me otherwise. I just figured, she has a double major in physics and chemistry, master in metallurgical engineering, and a PhD from MIT in electronic material... She likely also questioned nitrox benefits on her own. I am not a believer yet, but getting close. I will not negate this survey because of 1 singular double blind study of 11 participants.

 

[fisherdvm]

Then again, as far as fatigue goes, I made a post some time ago with an attachment of a report of a double blind controlled test done with firemen breathing air or Nitrox without knowing what they were actually breathing and the conclusion was that at low and normal activity levels there was no difference while at high exertion rates (aerobic level) there was a fatigue reduction.

.

Interesting, do you remember the citation here??

 

[fisherdvm]

Given the very low incidence of DCS cases per thousand dives I find it hard to believe that dive tables are anything other than conservative and your suggestion that they are not conservative enough for 58% of the population does not seem reasonable to me. If we had 58% with sub-clinical effects then on a normal distribution curve we'd expect a lot more serious cases.

I am not questioning the low incidence of clinical DCS.

I am questioning the possibility of subclinical DCS.... Where it might be possible that you have generalized fatigue and weakness rather than neurological symptoms.

 

[skynscuba]

I'm pretty sure that EANx helped me as I climbed 60 steps from the sea to the parking lot after a dive (still breathing it on the surface ). It also keeps me warmer in my drysuit, since I use the chemical toe- and hand-warmers, which generate more heat with 32-36% O2. I'm not so sure about those other placebo/non-placebo benefits, but I do get some added margin in the case of a problem requiring a rapid ascent.

 

[Kendall Raine]

You are getting at my biggest area of interest for research going forward.

I have been very intrigued by idea of neurocognitive function following cardiac surgery for years. That is probably a function of being at Duke and the work on this topic that has occurred here. When I started at Duke I used to go to the Cardiac Anesthesia Rounds every week. It was interesting to me that these guys were seeing the emboli (gas, fat, gunk - my technical term, etc...) after every surgery. The cranial doppler signal on these patients sounded similar to signals I had heard on research subjects after dives. After a while I started seeing the work on neurocognitive function changes that could be teased out of people that showed no outward symptoms and would have gone totally unnoticed in the previous years. Then work seemed to focus on biomarkers to explain these changes. Since that time I have followed this literature intently hoping that one day we would be able to apply some of these techniques to our dives in the field. I think we are getting closer but we are not there yet.

Pulling back to topic, this is an interesting paper that was only ever published as a thesis.
Doppler Detection of Silent Venous Gas Emboli in Non-Decompression Diving Involving Safety Stops.
Uguccioni, D. 1994
RRR ID: 3430
Anyone else think we would see similar results on similar profiles using air vs. nitrox?

If anyone is really interested in what I was talking about above with Biomarkers, I would suggest the a book chapter: Grocott HP, Laskowitz D, Newman MF. Markers of cerebral injury. In: Newman S, Harrison M, eds. The Brain and Cardiac Surgery. London, England: Harwood Academic Press; 1999: 113-141.

Gene;

Has your work taken you into looking at the idea that different inert gasses (e.g. N2 v. He) might have different effects on things like blood components (i. e. RBC rigidity) or complement system activation? There was a three paper series by Cross and Pimlott of DDRC presented at the 1989 EUBS in Isreal which discussed blood filterability testing following exposures using helium versus nitrogen based breathing gasses in sat context. There appeared to be a difference related to the inert gas. If short duration exposures showed similar results, there would be implications for nitrox use as well as hyperoxic trimix.

Few people in hyperbarics seem to have heard of these papers-I asked Vann, Moon, Powell and Huggins-and there also appears to have been no follow-up to these studies in the literature. The original context was implications for North Sea diving protocols in an effort to reduce incidence of dysbaric osteonecrosis so maybe the research went "in house," but I've found nothing before or since these papers on topic.

Irvine and Co. spent some time talking about this stuff on the net but, when asked for the research on this, no one I wrote connected with WKPP seemed willing or able to produce anything on point. George was excited to get a copy of these studies and did not otherwise seem to have known about them. The sources Bill Mee cited as being germane were in fact related to coagulation rather than RBC rigidity.

The papers to which I refer are titled; 1) "Pressure Induced Changes in Blood cell Rigidity: A Mechanism For Causing Asceptic Bone Necrosis," 2) "The Effects of Pressure on Blood Filterability," and 3) "The Effects of White Blood Cells on Blood Filterability at Pressure."

Many thanks,

Kendall

 

[fisherdvm]

Interesting study found:

EVALUATION OF FATIGUES UNDER AIR AND TRIMIXED COMPRESSED AIR WORK
Authors: Tokyo Med. and Dental University, Shiraishi co. Ltd., Kawashima Orthopedic Hospital. Tokyo 113, Ohita 871, Japan
Y. Mano
N. Yamami
M Hatano
M. Shibayama
S. Kasai
M. Ishii
M. Kawashima
Keywords: nitrogen
narcosis
air
Issue Date: 1998
Abstract: BACKGROUND: Compressed air work by Caisson has been carried in Japan since 1902, however there are no detail data about laborers' fatigue. So, fatigue tests by Jpn Society of Industrial Health and the Cumulative Fatigue Symptom Index (CFSI) by Kosugoh had been repeated for 6 months in 1995. This is the first trial to analyze the compressed air workers in Japan. METHODS: Caisson work had been carried until 4.85 ATA in 1995. They used air until 4 ATA. Then, they used tri-mixed gas after that. All of them, including outside workers, had been tested, i.e. 21 caisson group and 15 outside. The test of the Society had been done three times per day during the last week per months, and CFSI at the last day in each month. RESULTS: The incidence of mental and physical fatigues of air breathing caisson group was the highest and that of the same people but the tri-mixed gas breathing group was the lowest among the both inside and outside laborers at the field. (p less than 0.01) CONCLUSION: High contents of oxygen and the helium included into breathing gas would decrease the fatigues by high pressure stress during caisson work and also decrease nitrogen narcosis over than 4 ATA pressure work.
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: http://www.rubicon-foundation.org:8080/dspace/handle/123456789/701
Appears in Collections: UHMS Meeting Abstracts

 

[Gene_Hobbs]

There was a three paper series by Cross and Pimlott of DDRC presented at the 1989 EUBS in Isreal which discussed blood filterability testing following exposures using helium versus nitrogen based breathing gasses in sat context. There appeared to be a difference related to the inert gas. If short duration exposures showed similar results, there would be implications for nitrox use as well as hyperoxic trimix.

These were very good, once we get through the UHMS abstracts, we will be confirming the permission to start with the EUBS collection. There is a TON of gold buried in there.

Few people in hyperbarics seem to have heard of these papers-I asked Vann, Moon, Powell and Huggins-and there also appears to have been no follow-up to these studies in the literature.

This is a major motivation behind all the work we have been doing with the Repository. There number of researchers in Diving Medicine is decreasing and the knowledge of where to find things like this is going with them.

The original context was implications for North Sea diving protocols in an effort to reduce incidence of dysbaric osteonecrosis so maybe the research went "in house," but I've found nothing before or since these papers on topic.

NUI-NUTEC Publications have some really good items but we have not had a chance to follow up with them yet. The UHMS Library collection does have a good portion of the reports. Alf says he will help me with permission from NUI when the time comes but we are still behind on the other collections we have already started to pick up another right now.

Irvine and Co. spent some time talking about this stuff on the net but, when asked for the research on this, no one I wrote connected with WKPP seemed willing or able to produce anything on point. George was excited to get a copy of these studies and did not otherwise seem to have known about them. The sources Bill Mee cited as being germane were in fact related to coagulation rather than RBC rigidity.

RBC rigidity is something you may not EVER be able to find support for. ALL of the guys here laugh at the idea of hemolysis or other changes in recreational depths.

The papers to which I refer are titled; 1) "Pressure Induced Changes in Blood cell Rigidity: A Mechanism For Causing Asceptic Bone Necrosis," 2) "The Effects of Pressure on Blood Filterability," and 3) "The Effects of White Blood Cells on Blood Filterability at Pressure."

I have not read these but we do have some interesting search techniques at our finger tips now so I'll see what I can do. Do you know where you saw these first?

Interesting study found:

Glad someone is getting some use out of the work!

So, any volunteers to help format data? :blinking:

 

[Charlie99]

You know, it's an interesting thought about inflammatory mediators and subjective fatigue. One of the common symptoms of autoimmune diseases like rheumatoid arthritis and lupus is profound and persistent fatigue. If, in fact, small bubbles are activating complement or otherwise exciting an immune response, it's not inconceivable that fatigue could be a manifestation of this.

Andreas Zaferes wrote an article for Immersed magazine (Spring '97??)on this topic. Reviewed by Bill Hamilton, Ph.D., and Karen Van Hoesen, MD. The title was "Rethinking the Hit".

The very first item in the highlight bullets at the beginning is "Bubbles are not the only cause of damage. The immune response and its domino effect on blood ch e m i s t r y
changes may lead to further damage even after the bubbles are gone." It then goes into a fair amount of detail on this, but still written for the layman.

Unfortunately, although I still have the PDF file, Immersed magazine has been bought by Diver magazine and I can no longer find the article posted online.

Charlie Allen


Anybody have a link?

 

[Kendall Raine]

Andreas Zaferes wrote an article for Immersed magazine (Spring '97??)on this topic. Reviewed by Bill Hamilton, Ph.D., and Karen Van Hoesen, MD. The title was "Rethinking the Hit".

The very first item in the highlight bullets at the beginning is "Bubbles are not the only cause of damage. The immune response and its domino effect on blood ch e m i s t r y
changes may lead to further damage even after the bubbles are gone." It then goes into a fair amount of detail on this, but still written for the layman.

Unfortunately, although I still have the PDF file, Immersed magazine has been bought by Diver magazine and I can no longer find the article posted online.

Charlie Allen


Anybody have a link?

There was also an article, I think it was in Immersed, discussing the prospect that the cumulative impact of multi-day diving might have the effect of reducing complement system response on successive dives. The article suggested that the immune response just ran out of gas (my term). Implication was that progressively lowered marginal immune response reduced potential for taking a hit. As such, multi-day diving could allow for progressively more aggressive profiles without commensurate increase in odds of taking a hit. Divers of Mosquito Coast sort of thing. Obviously, for this to hold deco and SIT's would need to provide for residual inert gas washout.

Anybody remember that article?