Narcosis Properties of Different Gases

[syntaxerrorsix]

I just added the DAN report as well to my original post.

 

[gianaameri]

maybe you should read them again?

"We determined psychomotor and mental performance impairments during exposures to air and to normoxic N2-O2 mixtures at 6, 8.5 and 11 bar ambient pressure in 10 subjects. In this pilot study 3, 3 and 4 subjects were studied at 6, 8.5 and 11 bar respectively, and N2-O2 and air exposures were not randomized."

"A rise in O2 pressure to 1.65 ATA, or in N2 pressure to 6.3 ATA at a constant high PO2 level, caused a significant decrement of 10% in mental function but no consistent effect on psychomotor function."

What am I missing?

There is no study which shows that at our typical exposures in the 20 to 30 meter range (i.e. N32) O2 is narcotic.

Reason: O2 is NOT narcotic in N32 up to 30 meters.

The proof is in the pudding though.

Take a rebreather with Air diluent and use a Setpoint of 0.7.

Go in a cave at 23 meters keeping the Setpoint to 0.7 pPO2 and start to perform some exercises. Put a few short jumps, cut a few lines, take the cutter out, put it back, do things you normally do in a cave where you are task loaded (scooter, silt, light, have to be careful how you move...).

It takes a few minutes for the narcosis to set in.

Then raise the rebreather Setpoint to 1.1 pPO2 and feel the difference. It takes a couple of minutes for the narcosis to clear up.

The above is the typical ranges and values which have worked for me to sense the difference between one gas mix or another.

 

[syntaxerrorsix]

 

[Dr. Lecter]

"We determined psychomotor and mental performance impairments during exposures to air and to normoxic N2-O2 mixtures at 6, 8.5 and 11 bar ambient pressure in 10 subjects. In this pilot study 3, 3 and 4 subjects were studied at 6, 8.5 and 11 bar respectively, and N2-O2 and air exposures were not randomized."

"A rise in O2 pressure to 1.65 ATA, or in N2 pressure to 6.3 ATA at a constant high PO2 level, caused a significant decrement of 10% in mental function but no consistent effect on psychomotor function."

What am I missing?

There is no study which shows that at our typical exposures in the 20 to 30 meter range (i.e. N32) O2 is narcotic.

The quoted N2 partial pressure (6.3ATA) is about the same as air at 230', so I suppose it doesn't provide any support for the idea that nitrogen is narcotic within recreational depths either.

More correctly, it shows that O2 is much more narcotic than N2, with the former producing a 10% impariment in mental function at only a fourth of the partial pressure as that required for the same level of impairment from N2.

 

[PfcAJ]

Self assessment is not science. Try harder. What YOU feel isn't the issue, its all about the data.

I suggest you actually read the studies. But you haven't. And you probably won't.

 

[nimoh]

normally people cite publications to prove points, rather than citing a lack of publications to prove them, but your way seems much easier since it doesn't require any research.

In an attempt to determine the roles of nitrogen, oxygen, and carbon dioxide in compressed-air narcosis, the effects on performance (mental function and manual dexterity) of adding CO2 in various concentrations to the inspired gas under three different conditions were studied in eight healthy male volunteers. The three conditions were: (1) air breathing at 1.3 ATA; (2) oxygen breathing at 1.7 ATA; and (3) air breathing at 8.0 ATA (same inspired O2 pressure as in (2)). By relating performance to the changes induced in end-tidal (alveolar) gas pressures, and comparing the data from the three conditions, we arrived at the following results and conclusions. A rise in O2 pressure to 1.65 ATA, or in N2 pressure to 6.3 ATA at a constant high PO2 level, caused a significant decrement of 10percent in mental function but no consistent effect on psychomotor function. A rise in end-tidal PCO2 of 10 mmHg caused an impairment of approximately 10percent in both mental and psychomotor functions. The results suggest that, at raised partial pressures, all three gases have narcotic properties, and that the mechanism of CO2 narcosis differs fundamentally from that of N2 and O2 narcosis. Adult Atmospheric Pressure Carbon Dioxide/*adverse effects Human Inert Gas Narcosis/*etiology/physiopathology Male Middle Aged Nitrogen/*adverse effects Oxygen/*adverse effects Respiration

 

[gianaameri]

The quoted N2 partial pressure is about the same as air at 230', so I suppose it doesn't provide any support for the idea that nitrogen is narcotic within recreational depths either.

That is a fair comment (but we do know from personal experience we get narced shallower than that).

I never thought I could get narced at 21 meters till the first time I got narced at 21 meters and that I only noted the first time in a cave when I became task loaded in an unfamiliar area (Setpoint of 0.7 pPO2 on rebreather).

I do not think we would notice/perceive narcosis in a recreational dive Open Water and OC unless we were asked to perform some task and the environment is demanding (low vis., bit of current, light, use different tools, store them, take them...).

 

[Dr. Lecter]

(but we do know from personal experience we get narced shallower than that).

As someone who enjoys complex wreck penetrations on air well past 200', all I can say is: speak for yourself. But I'm not disputing you (or even me) may be narced at 100' on air; I'm just saying that doing the same dive on 30% O2 won't be any less narced and will probably be more narced.

Were you planning to address the fact that the study clearly showed that the same impariment occured with a much lower PP O2 than N2, or would that be inconvenient for you?

 

[syntaxerrorsix]

That is a fair comment (but we do know from personal experience we get narced shallower than that).

I never thought I could get narced at 21 meters till the first time I got narced at 21 meters and that I only noted the first time in a cave when I became task loaded in an unfamiliar area (Setpoint of 0.7 pPO2 on rebreather).

I do not think we would notice/perceive narcosis in a recreational dive Open Water and OC unless we were asked to perform some task and the environment is demanding (low vis., bit of current, light, use different tools, store them, take them...).

That's where CO2 narcosis becomes involved. That's why adding a little O2 and reducing a little bit of N does nothing to fix narcosis experienced when working.

 

[gianaameri]

normally people cite publications to prove points, rather than citing a lack of publications to prove them, but your way seems much easier since it doesn't require any research.

It is the scientist who set out to prove O2 is narcotic and it was their choice to design their experiment that way.

I remember another experiment where they compress a mouse fast in 100% O2 at I think 11 bar. The mouse looses consciousness first, and then regains consciousness when it is decompressed. That is how the scientist proves O2 is narcotic (i.e. the mouse narcs out before it convulses... or mice simply do not convulse...).

I think it would be difficult for a scientist to show that O2 is narcotic at 30 meters in N32, when there is no sign of narcosis in humans in a chamber in 100% O2 at 18 meters.

They could try though!

---------- Post added August 27th, 2013 at 04:39 PM ----------

That's where CO2 narcosis becomes involved. That's why adding a little O2 and reducing a little bit of N does nothing to fix narcosis experienced when working.

Not working hard at all when performing the tasks I described in a cave. If anything, the metabolic rate slows down because you are moving as little as possible, but you have to be accurate when working on lines (accuracy you lose when you are narced). CO2 (or CO2 retention and CO2 narcosis) would not be at play in my experience (as I described it)

Raising the Setpoint from 0.7 to 1.1 pPO2 and all other things being equal the narcosis goes away.

No point talking about it. It is something which people can try (we are a bit off topic I think).