Narcosis

[ghosch]

Reading through some old posts I noticed a comment that was kind of intriguing. In a discussion on deco and bailout, someone mentioned that Nitrox didn't make any difference from a narcosis standpoint, as (I'm paraphrasing) O2 is just as narcotic as nitrogen.

Has there been any research on the effects of nitrox on narcosis (granted as you go deeper, and the narcotic effect becomes more pronounced, you are also diving a leaner mix)?

If there hasn't been any research, what is everyone's opinion based on their diving experience?

I know personally I start to "feel" narced (i.e. noticable) at around 135' with a PO2 of 1.3 (rebreather). I know I am being impared before that, but 135 is where it becomes apparent. It would be interesting to see if changing the PO2 in the loop changed the narcotic effect.

[LKunze]

I think it would be tough to determine because narcosis does not affect everyone to the same degree. I can say for me personally I might feel real narced on one dive and not at all on another dive even when they are to similar depths. I have felt narced on dives using air and nitrox. It's kind of a crapshoot. For instance last week at Wazee the first dive I did Friday was down to the crystal ball which was 150 feet. I felt pretty dang narced on that dive. On Saturday I did a dive to 143 feet and didn't feel narced at all really. It really can vary. I dove the cystal ball again Sunday and didn't feel narced really at all on that dive either. I also have felt narced on dives to 90 feet on nitrox. Now obviously you are impaired whether you feel narced or not but it can really vary from person to person, day to day or dive to dive from my experience and I haven't noticed any difference or pattern that suggests there is any difference between air and nitrox.

[scott]

I've been down to 105 feet on air and I was feeling a little narced. I didn't feel to impaired, but I was definitely a little paranoid, I was probably checking my gauges every 30 seconds or so.
It would also be interesting to study the effects of drinking on getting narcosis. I have a friend who went to commercial diving school in Seattle. On a fun dive with a couple other divers, one of them got narced and somehow passed out and spit the regulator out of his mouth (I don't remember the whole story). They made it up to the surface fine as soon as they saw him. When they talked to an instructor, he told the guy that he should go out drinking more (not right before diving, but just in general). Since being drunk feels much like narcosis, you can at least learn to function impaired. I'm sure drinking isn't going to help avoid narcosis, but at least you'ld have some idea of what it's like and how to function under it.

[Chris]

Hmmm, I see a whole new avenue for Budweiser commercials now... Two frogs at the bottom of a lake trying to say Bud-Weis-Er with bubbles coming out of their mouths...

[tcjtn0]

My experience (as most of you know!!) with deep diving is fairly limited. I got pretty anxious at 110 on air this spring.
Almost exactly the same way Scott felt (paraniod etc...). So I know I am not alone on this...Makes me feel a little bit better. Maybe with more experience I might not feel so "jittery". I noticed I felt a little better when I locked my eyes/gaze on my 'puter. Gave me something to concentrate on , I guess.

Jean

[mixelpix]

Isn't focusing on a single task also a sign of being narc'd. I've done a few dives in the 90 - 130 ft range, all on Nitrox. The first time or two I was a little anxious but it seemed to pass relatively quickly. It may have helped that I was diving with a physician and a master dive instructor at the time. I' know water temp really impacts the effects of being narc'd. It'd be interesting to compare my tropical water experience with a dive to the sames depths in Wazee. Jean... Chris.... 150ft at Wazee on air :-\

[DanL]

Did deep dive specialty - went to 130ft drifting along a wall in Cozumel. Felt just great, same as on most other dives. But the instructor had me do three tests - math, memory and dexterity. Ouch - performance definitely impaired.
Point he made is that you can't really judge for yourself how impaired you actually are - it's not just about how you "feel".

[Inspirationdiver]

On the Inspiration there are two setpoints, one low and one high. The default values are .7 and 1.3 PO2. You use the low setpoint for the initial descent and then use the high setpoint at depth and then during the ascent. I've made descents to 100 ft at .7 PO2 and then switched to 1.3 when I got there. There is a big difference in narcosis between these two setpoints. Assuming I am not diving trimix, which means whatever is not oxygen is nitrogen, at 100 ft at .7 PO2 the breathing gas is 17.5 % oxygen and 82.5 % nitrogen. When I switch to the high setpoint it changes it to 32.5 % oxygen and 67.5 % nitrogen. This is a direct comparison between the narcotic effects of oxygen versus nitrogen. I can instantly tell when I change the setpoint.

[ghosch]

So, in summary, you feel that decreased nitrogen will decrease narcotic effect, and that the narcotic effects, if any, of oxygen, are minimal and certainly less than nitrogen?

Do you ever run your inspiration with a high setpoint greater than 1.3?

Couple of weeks ago, while diving the north shore, it seemed to me that running on a 1.4 would make sense, as we were doing just two relatively short (45 min) dives per day.

[Inspirationdiver]

So did you run a 1.4 on those dives? I don't see any problem with running a 1.4 for short dives. Especially if you are only going to be doing 2 dives. Just make sure you track your CNS loading. Many OC nitrox divers will plan their gas so that they have a 1.4 at depth but this is only for the short time they are actually at their max depth. 1.4 PO2 has a maximum single exposure time of 150 minutes, compared to 180 minutes at 1.3 PO2. Doing 45 minute dives is well within these limits.