2 tanks: Nitrox and Air - Which one do you use first?

[cummings66]

There are several things wrong with his post, for one he's telling people to skip breathe, and that will cause CO2 buildup in itself.

I'm assuming his Nitrox instructor tried to do a good thing and repeated things he's heard of. In many cases we agree that it's fine for an instructor to go beyond the basics of the class outline, however as this one shows if you go beyond it it's best to do so with correct material.

I absolutely can not believe a competent instructor would have taught all the things stormbringer posted. IMO that's grounds to lose his instructor's certificate.

I can see where the instructor got the idea it slowed breathing rates, if you assume that more O2 means less need to breathe you'd be right, unfortunately O2 is not what drives a healthy person to take a breath.

What's scarry is this instructor that taught stormbringer is teaching skip breathing.

 

[NW_TechDiver]

The high partial pressures of O2 and depth tends to reduce one's breathing rate. One way to avoid the buildup and retention of CO2 is to consciously regulate your breathing to a constant rate: fully inhalling for 6 secs holding for 2 secs then fully exhalling for 6 secs and repeating each breath cycle can help to reduce the buildup and retention of CO2 while diving EANx over 21%. I learned this technique from my NITROX Instructor. CO2 retention on EANx is a concern and should be a subject discussed in one's NITROX class and the various methods avail for reducing its buildup and retention. I would be concerned if its not a subject discussed in current NITROX classes as more and more evidence and clinical tests show how EANx effects the breathing rate at depth. Even in the latest Military Channel SEAL TEAM training program shown on TV had a Navy SEAL trainee experience CO2 problems on the Drager 100% O2 rebreather unit at the shallow pool depths they were practicing in.

:no
On top of promoting breath-holding, there is also an ignorance of rebreathers too! Unless the SEAL was hyperventilating or not breathing fully (I do not suggest that Stormbringer's method is breathing fully) OR a whole plethora of things that can go wrong on top of just being in the water with traditional SCUBA.

:shakehead

It's people like this that hurt our statistics...

 

[Stormbringer]

Even DAN mentions the problem some divers have with slower breathing rates on EANx http://www.diversalertnetwork.org/medical/articles/article.asp?articleid=35

"CO2 Retention

Why would carbon dioxide (CO2) retention become a problem at increased gas densities? There have been many studies showing that as depth increases while breathing air, the high oxygen and increased gas density will normally slow the rate at which we breathe and thereby the rate at which we eliminate carbon dioxide. This will raise the blood levels of carbon dioxide. On top of this, however, is the fact that, because of individual variations, not all divers will slow their breathing in the same amounts.

Dr. Lanphier investigated the problem of divers who tended to breathe more slowly during diving than would normally be expected - so-called "carbon dioxide retainers." He felt that these individuals would be at an especially high risk of CNS oxygen toxicity when breathing high oxygen in nitrogen gas mixtures. Should a nitrox diver be concerned about whether he is a carbon dioxide retainer? Unfortunately, there is no good test to reliably identify carbon dioxide retainers. The best strategy at present is to use conservative oxygen exposure limits."


No one is talking about skip breathing (Holding ones breath for extended conservation of air - which is very bad) merely maintaining a constant and consistant breathing rate. Full, regular and consistant inhalation and exhalation may help reduce such retention of CO2 (the pause is just a normal pause between inhalation and exhalation-no one is remotely suggesting to skip breathe). CO2 buildup and retention on EANx is the result of a reduced breathing rate. Its logical to conclude a normal regular breathing rate maintained on EANx will reduce the likelihood of CO2 retention. Not everyone is effected the same way. But there is a growing body of evidence to suggest that many divers experience a significant slowing down of their breathing rate while on EANx and its not good science or diving to pretend it doesn't exist.

 

[Thalassamania]

Make your deeper dive (real or EAD) first.

 

[Wilson]

I used a breath count technique at one point, but got away from it. Now, I have an aerobic workout I do several times a week and I just breathe normally when I dive. My air consumption is as good as ever and I focus on enjoying the dive.

 

[in_cavediver]

[From DAN]Why would carbon dioxide (CO2) retention become a problem at increased gas densities? There have been many studies showing that as depth increases while breathing air, the high oxygen and increased gas density will normally slow the rate at which we breathe and thereby the rate at which we eliminate carbon dioxide.

One note, this study was concerned with gas DENSITY not O2 concentration. The references about increased O2 levels came from the depth increasing the ambient pressure and hence the P02, not from nitrox's own inherent increased PO2's. O2 and N2 are very close in density such that 21% and 36% nitrox have the same gas density at recreational dive depths and therefore one would not be suppeor to the other for density related breathing rate effects.

Trimix, or adding He does modify the gas density and therefore has been shown to reduce CO2 retention. He is a much less dense gas than O2 or N2.

 

[NW_TechDiver]

Earlier, Stormbringer wrote:
The high partial pressures of O2 and depth tends to reduce one's breathing rate. One way to avoid the buildup and retention of CO2 is to consciously regulate your breathing to a constant rate: fully inhalling for 6 secs holding for 2 secs then fully exhalling for 6 secs and repeating each breath cycle can help to reduce the buildup and retention of CO2 while diving EANx over 21%. I learned this technique from my NITROX Instructor. CO2 retention on EANx is a concern and should be a subject discussed in one's NITROX class and the various methods avail for reducing its buildup and retention. I would be concerned if its not a subject discussed in current NITROX classes as more and more evidence and clinical tests show how EANx effects the breathing rate at depth. Even in the latest Military Channel SEAL TEAM training program shown on TV had a Navy SEAL trainee experience CO2 problems on the Drager 100% O2 rebreather unit at the shallow pool depths they were practicing in.

And recently, Stormbringer wrote:
No one is talking about skip breathing (Holding ones breath for extended conservation of air - which is very bad) merely maintaining a constant and consistant breathing rate. Full, regular and consistant inhalation and exhalation may help reduce such retention of CO2 (the pause is just a normal pause between inhalation and exhalation-no one is remotely suggesting to skip breathe). CO2 buildup and retention on EANx is the result of a reduced breathing rate. Its logical to conclude a normal regular breathing rate maintained on EANx will reduce the likelihood of CO2 retention. Not everyone is effected the same way. But there is a growing body of evidence to suggest that many divers experience a significant slowing down of their breathing rate while on EANx and its not good science or diving to pretend it doesn't exist.

Are you suggesting that divers use this method all the time? From submerge to surface? I think what your DAN article was trying to point out was the potential for Helium to interfere with C02 circulation. According to your post earlier, you sounded like you want all divers on air or nitrox to follow the same standards. I think you are basing your argument on a trimix article, not a nitrox article. Although there are a lot of similarities between trimix and nitrox, the mere fact that Helium is in trimix makes breathing techniques different.
The mere fact that you wrote "holding for 2 secs then fully exhalling for 6 secs and repeating" makes us dive instructors cringe at the thought that there are students out there who HOLD THEIR BREATH. IMHO...
Not trying to rag on you Stormbringer, but when i saw your post I broke out into a cold sweat because I have seen people who have been told by their instructor to hold their breath between cycles, and they have all ended up in the hospital.