Nitrox and DCI "Safety" question...

[scubadobadoo]

A little clarification please. I just finished my nitrox course and believe I read in the PADI manual that "the primary reason for using nitrox is to extend the no stop limits beyond the normal air no stop limits" and that "simply reducing nitrogen is unlikely to produce a meaningful safety improvement" and that "It's inaccurate to suggest that enriched air is safer than air." My favorite is "...but probably not a realistic, significant, safety improvement from a practical point of view." What the? I could continue with many other direct quotes from the nitrox manual that suggest that using nitrox is a theoretical crock of bull. Someone help my confused brain. I understand that less nitrogen is good but that's only theoretical right? So why do many people suggest that diving nitrox is and or will be safer than air and sometimes suggest diving it within air limits too? Clearly the PADI manual agrees and disagrees with itself? HELP? I hope this is the right place for this post. I just finished reading many posts where people suggest nitrox to help with future DCS problems so here it is. Thanks in advance.

 

[MikeFerrara]

A little clarification please. I just finished my nitrox course and believe I read in the PADI manual that "the primary reason for using nitrox is to extend the no stop limits beyond the normal air no stop limits" and that "simply reducing nitrogen is unlikely to produce a meaningful safety improvement"

Lets just apply a little common sense. ok? If Nitrox extends no-stop bottom time then using nitrox without spending more time on the bottom must mean less DCS risk right? Reference the END equation...yes?

and that "It's inaccurate to suggest that enriched air is safer than air." My favorite is "...but probably not a realistic, significant, safety improvement from a practical point of view." What the?

Theeir points are that 1, while there is an decresed chance of DCS there is an incresed chance of O2 tox (or other O2 handling problems) and 2, that since diving (oops here is the kicker) air tables is statistically safe that an improvement on safe doesn''t mean much. A misapplication od statistics for the history books!

however, all else being equal, less N2 is less risk of DCS. Period! And...within recreational limits O2 tox is really unlikely.

I could continue with many other direct quotes from the nitrox manual that suggest that using nitrox is a theoretical crock of bull. Someone help my confused brain. I understand that less nitrogen is good but that's only theoretical right?

No it's not theoretical. Less N2 is less DCS risk.

So why do many people suggest that diving nitrox is and or will be safer than air and sometimes suggest diving it within air limits too? Clearly the PADI manual agrees and disagrees with itself? HELP? I hope this is the right place for this post. I just finished reading many posts where people suggest nitrox to help with future DCS problems so here it is. Thanks in advance.

I've taught that class for years. I understand what they are trying to say and I still say that they're full of sheep dip.

 

[scubadobadoo]

Thanks for your time. I followed all of it clearly but the last part. Nonetheless, I may be wrong but I don't recall anywhere in the manual where it just comes right out and says that nitrox is safer than air from a DCI point of view, forgetting about oxygen toxicity. That also might be why one can't say nitrox is "safer" because oxygen toxicity comes into play. I guess they are just covering the old but a little too huh? And like you said, how do you easily explain safer than safe? I think I understand why they put it the way they do.

 

[TDunbar]

Try think of it this way....

If your chance of being hit by a bus is 1 in 20,000
and your chance of being hit by the same bus while jumping up and down on one foot is 1 in 20,500 , are you significantly safer by jumping up & down? Either way, you're not likely to be hit by the bus.

Todd

 

[Tim Ingersoll]

Having been hit by the bus I will be seen hopping up and down on one foot at the bus stop!

 

[Rick Inman]

Having been hit by the bus I will be seen hopping up and down on one foot at the bus stop!

FUNNY!!
You'll be exhausted when the bus finally arrives on Jan.6.

 

[scubadobadoo]

Very funny and very clear. LOL!

 

[Atticus]

This mixed message from the training agencies annoys me too. Other weird messages about nitrox are that you will feel better after a dive and that you will be warmer during the dive

1. Safety - as Mike F explained, the message is that diving air is pretty darned safe as long as you follow the rules, so the slight safety benefit of nitrox is minimal.

2. Feeling better after a dive - this ties into the same thing. If you feel like you have mild flu symptoms after a dive then you may be experiencing subclinical dcs. Nitrox will help here (by reducing the amount of nitrogen in your system), but learning proper ascent procedures will help more and is the right answer.

3. Warmer - I have no idea where this comes from. If we were talking rebreathers, yeah, but nitrox?!??!? I've had students come to me with this one and I can only answer that I don't know of or understand any such affect.

 

[scubadobadoo]

Oh boy. "Subclinical DCS." I have read a bit about this but still not clear on it. Before I lost 30 pounds and improved my cardio health I got tired when diving a lot. Obviuosly just a case of being out of shape right? However, the sun and diving cold water with more weight and a dry suit and the extra bulk can make me tired too. How is one to tell the dif. between being warn out and "Subclinical DCS." And, does having Subclinical DCS mean you need a trip to the chamber or is it just the idea that you have done a bit too much to your body, stuff that normally wouldn't happen when not diving, and that your body is saying, "Okay enough, I'm tired and stressed from the nitrogen and the pressure but I don't really have actual DCS." Is that clear? Thanks again folks for your time and knowledge.

 

[Atticus]

Subclinical DCS is best described as post dive fatigue resulting from some mild bubbling. It does not warrant a chamber trip. If it did it wouldn't be "sub" clinical. This is also called deco flu by some, though I'd reserve that term for the more serious cases.

Basically if you feel more pooped after your dive than you should based on your activity level, cold exposure, etc, and you think you may have had some rapid ascents or were pushing the limits then it may be subclinical dcs.

The term sub-clinical means that this is not clinically recognized and/or treated (at least that's my interpretation).

To be clear, I'm not a medical professional. These are my opinions only.