Oxygen and narcosis

[tb]

I don't know if the comment attributed to Dr. Sawatsky about narcosis not being signifcant for recreational divers is accurate since I haven't read the orginal article. However a study published in Undersea Hyperbaric Medicine in 2003 found that even at 2 atmospheres, psychomotor skills are measurably impaired. All the more reason to have a dive plan and perhaps a bit of explanation for why many divers have difficulty with underwater navigation. T

 

[pipedope]

I don't know if the comment attributed to Dr. Sawatsky about narcosis not being signifcant for recreational divers is accurate since I haven't read the orginal article. However a study published in Undersea Hyperbaric Medicine in 2003 found that even at 2 atmospheres, psychomotor skills are measurably impaired. All the more reason to have a dive plan and perhaps a bit of explanation for why many divers have difficulty with underwater navigation. T

To be clear, Sawatsky is talking about the narcosis of O2, NOT the narcosis of N2 or the total narcosis of the breathing gas used.

We are so trained to thinking of N2 narcosis in diving that it is important to specify what gas you are talking about anytime you are talking about the narcosis of something other than N2.

 

[tb]

Ah. That's better.
Thanks.

 

[MikeFerrara]

The narcotic effects of O2 make for a nice discussion but I don't see why all the concern. As a practical matter narcosis isn't much of an issue over the range of depths I use air or nitrox. When I'm diving a helium mix, I assume O2 is narcotic in my END calculations. It's conservative and END only gives us a rederence point anyway. END is not all that telling and our own day to day variation in our reaction to narcosis can probably make more of a difference than a few feet difference in our END calculation due to the way we handled the O2 in the equation. When diving air or nitrox I don't calculate END and niether do most other divers since most nitrox courses don't even teach the concept...though the math would look pretty familiar huh?

 

[WarmWaterDiver]

just do a gas switch from 30/30 to EAN50 at 70 fsw and come to your own conclusions...

Why not switch from air to 50/50 at 60 fsw and take the He effect out of the study? Especially if this is during an ascent from a deeper depth where air was also used at the deeper (than 60 fsw) depth?

I'd be interested in any data from hyperbaric chamber tests. Supposedly such tests declared there's no truth to being "less tired" on using typical Nitrox mixes vs. air in recent times. Why not repeat those tests for objective testing of narcosis?

 

[MonkSeal]

Why not switch from air to 50/50 at 60 fsw and take the He effect out of the study? Especially if this is during an ascent from a deeper depth where air was also used at the deeper (than 60 fsw) depth?

Can you describe the dive where air is used as bottom gas and then you switch to Tx 50/50? I can't imagine.

There are certain issues with switching from nitrogen based mixes to helium based mixes (deep tissue counterdiffusion). I hope Dr Deco will give precise explanation.

 

[padiscubapro]

Ask any rebreather diver this same question. Anyone who has experienced a change in PPO2 at depth a felt an immediate change in perception will support the O2 = less narcosis argument.
When doing SCR bailout drills I was required to shut off my O2 at 100ft and use my diluent (air) to breath my CCR as a semi closed rebreather. After a period of time the drill was over and my PPO2 went from about .6 to 1.3 in a matter of seconds. I noticed an immediate feeling of perception increase, like a fog being lifted. That was enough to convince me.

I have to agree with dave.. I run lots of deep training, when I have the guys do scr drills the po2 drops... I ALWAYS get the same comments that they cant believe the difference in their narcotic perception once they pump the po2 back up... A big drop isnt, even really that necessary when you are deeper and near the person's narcotic limit..

A few% drop in n2 exposure can be a big deal...

 

[DiverBuoy]

I'm not a scientist but I just can't see how this could be true. An inert gas like nitrogen which is not absorbed, sure, but this issue has come up with football players who for the longest time breathed 100% 02 to catch there breath between sideline visits. Extensive medical research indicated that they were actually starving for oxygen due to breathing heavy and exceeding the demand of the supply valve, and from the sides of the mask ended up pulling enough of a dilutant of air as to nearly nullify the 'advantage' ... further tests revealed that proper restful positioning on the bench with directed area fans had nearly exactly identical recovery periods. The "starving" effect at high work load, not the fact that it was 100% O2 was the cause of any 'side effect'. In our bodies we consume, absorb, convert only a portion of the O2 we take in each breath, increasing the total amount of O2 in the source air does not increase absorption. On the other hand not exhaling completely while the CO2 builds up, is very dangerous at higher work-loads and can have a powerfully narcotic effect. I really enjoyed reading all the different angles mentioned in this thread. Personally I'll need to do more research. When I find the reference to the football article i'll hunt down this thread and post it.

 

[Rick Murchison]

In keeping with the KISS principle, I offer the following...

As divers, we need to know what to expect from the gasses we breathe. All the research, theory & anecdotal evidence suggests to me that:

(1) Oxygen is about twice as soluble in lipids as Nitrogen, so I'd expect it to be twice as narcotic at the same titer.

(2) Oxygen is both metabolized by the body and scavenged by hemoglobin; when compared to inert gasses its tissue-level titer is way less, on the order of a sixth or less, so any narcosis contributed by oxygen should be less than 2/6 what you'd expect from nitrogen.

(3) Therefore, while it is likely that Nitrox is a little less narcotic than air, when comparing the two, as SSI says

"It is best not to assume any reduced narcosis from breathing Nitrox."

Rick

 

[webediving]

There has been studies done in the aspects of narcotic efects of therapeutic oxygen. Theoretical calculation shows that yes, O2 has narcotic effects. But practical studies shows little or no significant O2 narcotic effects. Some Deco models ( like VPM) offers you the choice for taking in cosideration the narcotic effects of O2 in the calculation of deco obligations. I (personally) consider the efects of O2 in the decompresion to have no effect in my deco obligation calculations. Having said that, it is my personal choice. I am more concerned in PPN2 spikes and Ox Tox. These two are greater risk factors not the narcotic effects of O2.

There is very little know on the narc effects of O2in the diving world. Research continues and so the debates and opinions...

The bigest problem is not everyone reacts the same to N2 exposures (O2 too) so to try to put everything in a standard table it is not only hard, but to force it it even more ignorant. I teach my basic courses the danger of Ox tox, CO2 and N2 narcosis. To try to mention O2 narcosis is a little too much.

I do teach my Tec Diver to know the fact that O2 has/has not narcotics effects but we are more concerned by the Ox Tox, CO2 and PPn2 spikes (these two will kill you faster).
Anyway you are suposed to read and research and make your own educated guess. Happy Diving!