Effects of Helium content on O2 Toxicity suceptibility

Padowan · 15th February 2007, 06:53

As the title says - does anyone know if there is any research into the susceptibility of a diver to an O2 hit with regards to anything other than just the PPO2 of the breathing gas?

Was thinking about bailout gasses, and in particular if there is any difference in tox liklihood if you switch to a particular PPO2 gas, depending on if it is a Nitrox, Trimix or Heliox blend.

Was wondering if perhaps the narcosis/numbing effects of a higher PPN2 might delay the onset of a hit, and that you might be better switching to a He lean mix if it is a bit hot, rather than a He rich one? Obviously there's the issue of IBCD if the He is too lean (the N2 spike is too high), but I'd like to keep that out of this discussion for now...

Any thoughts?

jaap · 15th February 2007, 09:11

Effects of nitrogen and helium on CNS oxygen toxicity in the rat -- Arieli et al. 98 (1): 144 -- Journal of Applied Physiology

Entrez PubMed

bletso · 15th February 2007, 10:36

If you will notice, this study appears to be irrelevant to the question. The temperatures were elevated and the times were long.

There was a similar thread about a month or so ago in which the Israelis did which to some degree was more appropriate. It did show a very slight increase in onset symptoms of CNS if I recall. It too, was not directly related to what normal divers do and was not conclusive.

Dale

jaap · 15th February 2007, 11:02

Quote: (Originally Posted by bletso)

If you will notice, this study appears to be irrelevant to the question. The temperatures were elevated and the times were long.

There was a similar thread about a month or so ago in which the Israelis did which to some degree was more appropriate. It did show a very slight increase in onset symptoms of CNS if I recall. It too, was not directly related to what normal divers do and was not conclusive.

Dale

Is 27 Celsius considered an elevated temperature? Times were long?

Sure its not conclusive and far from a real diving situation. But at least its something. I found the abstract and discussion interesting. Especially the trends in fig 6.

bletso · 15th February 2007, 21:10

Quote: (Originally Posted by jaap)

Is 27 Celsius considered an elevated temperature? Times were long?

Sure its not conclusive and far from a real diving situation. But at least its something. I found the abstract and discussion interesting. Especially the trends in fig 6.

Sometimes I forget that some divers actually get to dive in hot water. I am pretty much dry suit year round.

Three day exposure is loong. Especially for a mouse.

Dale

**nigelh** · 15th February 2007, 21:21

Quote: (Originally Posted by bletso)

Three day exposure is loong. Especially for a mouse.

At 5 to 6.5 bar ppO2?

Rats must be tough kiddies. I suspect the mechanism is sufficiently different in rats to render extrapolating to humans dicey.

jaap · 15th February 2007, 22:16

Quote: (Originally Posted by bletso)

Sometimes I forget that some divers actually get to dive in hot water. I am pretty much dry suit year round.

Three day exposure is loong. Especially for a mouse.

Dale

Sure, its all snow and ice here. Its kind of hard to outfit a rat in an insulating drysuit to simulate diving in cold water, eh?

Three days?

Experimental procedure
When the first electrical discharge (FED) in the EEG, which precedes clinical convulsions, was seen on the recorder, the time was noted and decompression was commenced according to a computer-generated decompression table, whereas the PO2 was maintained at 300 kPa. If the FED did not appear within 60 min of exposure, the hyperoxic exposure was terminated to prevent the development of pulmonary oxygen toxicity.

15th February 2007, 06:53	#1 (permalink)
Padowan Proper Boffin Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: Kent, UK. Posts: 501	Effects of Helium content on O2 Toxicity suceptibility As the title says - does anyone know if there is any research into the susceptibility of a diver to an O2 hit with regards to anything other than just the PPO2 of the breathing gas? Was thinking about bailout gasses, and in particular if there is any difference in tox liklihood if you switch to a particular PPO2 gas, depending on if it is a Nitrox, Trimix or Heliox blend. Was wondering if perhaps the narcosis/numbing effects of a higher PPN2 might delay the onset of a hit, and that you might be better switching to a He lean mix if it is a bit hot, rather than a He rich one? Obviously there's the issue of IBCD if the He is too lean (the N2 spike is too high), but I'd like to keep that out of this discussion for now... Any thoughts? __________________ Padowan The future's bright, the future's Yellow .....for now padowan.net - Latest Video: Scapa Flow Rebreather Diving
(Online)

15th February 2007, 09:11	#2 (permalink)
jaap Normal people worry me Current Rebreather/s: Classic Kiss Other CCR RB80 / Clone Ray Other SCR Home Build Other Rebreather/s: Other CCR RB80 / Clone Ray Other SCR Home Build Join Date: Jun 2005 Location: Stockholm Sweden Posts: 438	Re: Effects of Helium content on O2 Toxicity suceptibility Effects of nitrogen and helium on CNS oxygen toxicity in the rat -- Arieli et al. 98 (1): 144 -- Journal of Applied Physiology Entrez PubMed __________________ My initials: JAAP
(Offline)

15th February 2007, 10:36	#3 (permalink)
bletso An independent diver. Current Rebreather/s: Dolphin Home Build Other Rebreather/s: Dolphin Home Build Join Date: May 2006 Location: Louisville, KY, USA Posts: 220	Re: Effects of Helium content on O2 Toxicity suceptibility If you will notice, this study appears to be irrelevant to the question. The temperatures were elevated and the times were long. There was a similar thread about a month or so ago in which the Israelis did which to some degree was more appropriate. It did show a very slight increase in onset symptoms of CNS if I recall. It too, was not directly related to what normal divers do and was not conclusive. Dale
(Online)

15th February 2007, 11:02	#4 (permalink)
jaap Normal people worry me Current Rebreather/s: Classic Kiss Other CCR RB80 / Clone Ray Other SCR Home Build Other Rebreather/s: Other CCR RB80 / Clone Ray Other SCR Home Build Join Date: Jun 2005 Location: Stockholm Sweden Posts: 438	Re: Effects of Helium content on O2 Toxicity suceptibility Quote: (Originally Posted by bletso) If you will notice, this study appears to be irrelevant to the question. The temperatures were elevated and the times were long. There was a similar thread about a month or so ago in which the Israelis did which to some degree was more appropriate. It did show a very slight increase in onset symptoms of CNS if I recall. It too, was not directly related to what normal divers do and was not conclusive. Dale Is 27 Celsius considered an elevated temperature? Times were long? Sure its not conclusive and far from a real diving situation. But at least its something. I found the abstract and discussion interesting. Especially the trends in fig 6. __________________ My initials: JAAP
(Offline)

15th February 2007, 21:10	#5 (permalink)
bletso An independent diver. Current Rebreather/s: Dolphin Home Build Other Rebreather/s: Dolphin Home Build Join Date: May 2006 Location: Louisville, KY, USA Posts: 220	Re: Effects of Helium content on O2 Toxicity suceptibility Quote: (Originally Posted by jaap) Is 27 Celsius considered an elevated temperature? Times were long? Sure its not conclusive and far from a real diving situation. But at least its something. I found the abstract and discussion interesting. Especially the trends in fig 6. Sometimes I forget that some divers actually get to dive in hot water. I am pretty much dry suit year round. Three day exposure is loong. Especially for a mouse. Dale
(Online)

15th February 2007, 21:21	#6 (permalink)
nigelh New Member Current Rebreather/s: Inspiration Vision Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Mar 2005 Location: Brighton, Sussex, UK Posts: 787	Re: Effects of Helium content on O2 Toxicity suceptibility Quote: (Originally Posted by bletso) Three day exposure is loong. Especially for a mouse. At 5 to 6.5 bar ppO2? Rats must be tough kiddies. I suspect the mechanism is sufficiently different in rats to render extrapolating to humans dicey. __________________ nigelh Last edited by nigelh : 15th February 2007 at 21:25.
(Online)

15th February 2007, 22:16	#7 (permalink)
jaap Normal people worry me Current Rebreather/s: Classic Kiss Other CCR RB80 / Clone Ray Other SCR Home Build Other Rebreather/s: Other CCR RB80 / Clone Ray Other SCR Home Build Join Date: Jun 2005 Location: Stockholm Sweden Posts: 438	Re: Effects of Helium content on O2 Toxicity suceptibility Quote: (Originally Posted by bletso) Sometimes I forget that some divers actually get to dive in hot water. I am pretty much dry suit year round. Three day exposure is loong. Especially for a mouse. Dale Sure, its all snow and ice here. Its kind of hard to outfit a rat in an insulating drysuit to simulate diving in cold water, eh? Three days? Experimental procedure When the first electrical discharge (FED) in the EEG, which precedes clinical convulsions, was seen on the recorder, the time was noted and decompression was commenced according to a computer-generated decompression table, whereas the PO2 was maintained at 300 kPa. If the FED did not appear within 60 min of exposure, the hyperoxic exposure was terminated to prevent the development of pulmonary oxygen toxicity. __________________ My initials: JAAP
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode