Pre-breathing O2 before a dive?

[gcbryan]

Do any divers (tech/commercial/military) pre-breath O2 before a dive to shorten decompression schedules or is the small reduction not worth the effort?

 

[SteveAD]

Between dives to accelerate nitrogen washout, yes. I've never heard of prebreathing O2 before the first dive of the day.

 

[vintagediver]

Might cause ICD.

 

[TSandM]

If you think about it, it seems likely that it would be of little benefit. You're going to wash nitrogen out of the fast compartments, but they equilibrate quickly and will saturate on recreational length dives anyway, even if they start low. You won't wash much nitrogen out of long half-life compartments unless you sit on O2 for hours. You might see a little benefit in the middle compartments, which could be beneficial if you are going to do moderate depth but long time dives. But it's probably not worth the effort.

 

[Gene_Hobbs]

Well, we did look at surface interval O2 to lengthen available bottom time on repetitive dives.

Gerth, Vann, and Southerland. NO-STOP REPETITIVE N2/02 DIVING WITH SURFACE INTERVAL 02 (SI02): CALCULATION OF SCHEDULES. UHMS Abstract 1992.
RRR ID:3616

Vann and Gerth. SURFACE INTERVAL OXYGEN REPETITIVE DIVE TABLES: A SUMMARY REPORT. Final Grant Report to NOAA/NURP at UNC-W: NA88AA-D-UR004.
RRR ID:3620

 

[G~Diver]

According to a research that was done recently on rats, breathing oxygen before the dive might reduce the number of bubbles evolving during decompression by replacing the inert gas in the micronuclei with oxygen which later will be consumed by the cells.
Link to the research: http://img2.tapuz.co.il/CommunaFiles/26184735.pdf

 

[Dr Deco]

Hello Readers:

PreOxygen

As others have already indicated, there is not a great advantage to inert gas washout prior to a dive. The “driving pressure” is less than one ATA during the oxygen prebreathe (washout), but it is at least 2 or 3 ATA for the inert uptake during the dive.

I would guess that it is better to save the oxygen for an emergency. If you wish safety, shorted the bottom times, lengthen the surface interval, and avoid stressful physical activity.

Research

Below are a couple of recent research studies involving preoxygenation [I was involved with ref 1.]. Both administered the oxygen hours before the dive, and the authors indicated that biochemical mechanisms were playing a role [ref. 1] or nuclei reduction was involved [ref. 1 and 2]

Dr Deco :doctor:


References :book:

[1.] Butler BD, Little T, Cogan V, Powell M. Hyperbaric oxygen pre-breathe modifies the outcome of decompression sickness. Undersea Hyperb Med. 2006 Nov-Dec;33(6):407-17.

[2.] Katsenelson K, Arieli Y, Abramovich A, Feinsod M, Arieli R. Hyperbaric oxygen pretreatment reduces the incidence of decompression sickness in rats. Eur J Appl Physiol. 2007 Nov;101(5):571-6. Epub 2007 Aug 3.

 

[BarryNL]

According to a research that was done recently on rats, breathing oxygen before the dive might reduce the number of bubbles evolving during decompression by replacing the inert gas in the micronuclei with oxygen which later will be consumed by the cells.
Link to the research: http://img2.tapuz.co.il/CommunaFiles/26184735.pdf

Interesting paper - but it only talks about hyperbaric oxygen, at pressures up to 5 bar!! Breathing O₂ at 1 bar for any practical time period before the first dive is unlikely to have any clinically significant effect and will also provide significant OTU and CNS clock penalties.