Nitrox instead of air for lower DCS risk?

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Derek S:
Tom -

Don't you think that telling a diver with less than 50 logged dives to go Trimix is a bit premature? :D
Skeeter1097:
Here is one for all of you. I was told that in time as you age. People that dive nitrox has less boine and hip problems later in years thin some one whome did not dive nitrox. a study by the U S NAVY.
Yeah, while altho possibly true, neither seem practical in this thread.

Although I'm nowhere near mature (just ask my wife ), it is great to know that I will still be able to enjoy this sport I love for decades to come.
Maturity has nothing to do with it. My body is 58. :D
 
H2Andy:
ah.... so.... diving Nitrox on air NDL's is dangerous because some people don't
follow proper Nitrox training?

ok.... well... then all Nitrox diving is dangerous, since those people are not
going to follow proper Nitrox training

by this logic, since divers won't follow proper Nitrox training, we should
eliminate Nitrox and dive only air.

That is convoluted reasoning, or lack thereof, that bears no resemblance to anything I've said.

H2Andy:
the issue which you continue to try to complicate, is that if you dive Nitrox
with air tables and otherwise follow Nitrox training, your dives will be safer
DCS-wise, since you will be diving at a "shallower" depth and will have
a bigger margin of safety.

Nope, not complicated at all. My statement is very simple: Use the dive algorithm that matches the breathing gas you have selected. If it is Air, use the Air Table/Algorithm. If it is Nitrox, use a Nitrox table or set your computer to the correct nitrox percentage. Failure to do this results in not tracking all the pertinent factors that can affect your safety and health.

.
 
ok... well.... i guess we disagree

eyebrow
 
http://www.mindspring.com/~divegeek/oxyconcern.htm

For the "average" recreational diver its sure seems pretty safe...:D


The "Numbers"
Larry “Harris” Taylor, Ph.D.


I believe the relative concerns are about oxygen toxicity can be best expressed by looking at some computer-generated numbers, with the understanding that different computer programs may give slightly different absolute values for the numbers quoted. The exact numerical value is NOT as important as the relative magnitude of the number and its comparison to the accepted tolerance limits. Besides, in the clinical situation, even though numbers are important tracking devices and guidelines, therapeutic protocols (time/depth/breathing gas) are evaluated and determined by the medical staff based on individual patient behavior and needs. Lastly, while 1440 OTU's is the allowed daily dose of oxygen, under physician's care in a hyperbaric procedure, doses in excess of 1700 OTU's may be acceptable.



A diver breathing 100% Oxygen at sea level (1 ata pressure) accumulates 1 OTU per minute. An injured diver breathing from a demand inhalator mask typically consumes a DAN jumbo D cylinder in approximately 50 minutes. So, each DAN cylinder consumed represents about 50 OTU 's delivered to the patient. Thus, a diver would need to consume (1440 0TU allowed per day / 50 OTU per cylinder) 28.8 DAN jumbo D cylinders in a continuous 24-hour session to reach the allowed whole body daily dose. Most divers do NOT carry this quantity of oxygen with them AND, more importantly, transfer of the patient to the emergency medical chain of response occurs long before oxygen toxicity becomes a critical factor.



Now, let's address accumulation of OTU's during recreational diving on typical recreational diving breathing gases.



Table One examines the % CNS toxicity (as a measure of CNS toxicity risk) and accumulated OTU's (as a measure of whole body or pulmonary toxicity risk) for dives on air to the no decompression limits of the US Navy tables. These numbers are well below the daily-allowed dose of 1440 OTU.

Table 1: Oxygen Toxicity Values While Breathing Air

Depth (fsw) Time (min) % CNS OTU's

40 200 0 0.00
50 100 12 9.10
60 60 8 14.67
70 50 8 19.04
80 40 7 20.40
90 30 7 19.11
100 25 6 19.07
110 20 6 17.85
120 15 5 15.51
130 10 4 12.10
140 10 5 13.50


There has been some discussion in the recreational diving literature, especially in the early 1990's, about withholding oxygen to divers who have made dives using a breathing mix of oxygen-enriched air. So, let's look at "the numbers" for oxygen-enriched air. Table Two is a compilation of oxygen toxicity values for dives to the no decompression limits while breathing NOAA Mix 1 (32 % oxygen). Again, these values are far below thresholds of concern.

Table 2: Oxygen Toxicity Values While Breathing NOAA Mix 1 (32 % Oxygen)

Depth (fsw) Time (min) % CNS OTU's
40 310 55 149.19
50 200 45 133.17
60 100 29 84.16
70 60 20 60.80
80 50 22 59.42
90 40 20 54.38
100 30 18 46.32
110 25 18 43.55
120 25 22 47.71
130 20 36 42.15


In addition, Table Three is a compilation of oxygen toxicity values for dives to the no decompression limits while breathing NOAA Mix 2 (36 % oxygen). As with Mix 1, these values are below thresholds of concern.

Table 3: Oxygen Toxicity Values While Breathing NOAA Mix 2 (36 % Oxygen)

Depth (fsw) Time (min) % CNS OTU's
40 310 68 200.48
50 200 56 166.46
60 100 35 103.36
70 60 26 73.35
80 60 31 85.01
90 50 31 80.43
100 40 31 72.39
110 30 42 60.36

To help put this is a bit more of a proper perspective, consider (only for the purposes of examining the "numbers" for oxygen toxicity: this is certainly not a suggested mission profile. The "numbers" here are taken to absurdity only for purposes of illustration) making three consecutive dives, with no surface interval, to 60 fsw for 60 minutes. The accumulated % CNS and OTU's for this series of decompression dives is shown below in Table Four.

Table 4: Oxygen Toxicity Values For Three Consecutive Dives of 60 fsw for 60 minutes

Mix % CNS OTU's
Air 25 43.90
Mix1 (32 % O2) 54 152.40
Mix 2 (36 % O2) 64 188.49


It should be obvious that even after three consecutive 60 fsw dives for 60 minutes, a diver would be well below the allowed OTU accumulation of 1440. I also suggest that, especially in cold waters, thermal considerations have more control of the dive durations than whole body oxygen toxicity while diving conventional mixes to traditional recreational diving depths.
 
ArcticDiver:
Nope, not complicated at all. My statement is very simple: Use the dive algorithm that matches the breathing gas you have selected. If it is Air, use the Air Table/Algorithm. If it is Nitrox, use a Nitrox table or set your computer to the correct nitrox percentage. Failure to do this results in not tracking all the pertinent factors that can affect your safety and health.

Paul,

Thank you for posting Larry Taylors comments on the subject. Anyone reading through the numbers can pretty well make up his or her own mind on whether or not the oxygen toxicity concerns are kept within limits.


Artic,

You are not disagreeing with me, sir. You are directly contradicting Dick Rutkowski. Since he and Morgan Wells brought Nitrox to the civilian world, you do not have either the academic or experiential credits to do so.
 
PaulChristenson:
http://www.mindspring.com/~divegeek/oxyconcern.htm

For the "average" recreational diver its sure seems pretty safe...:D

Thanks for your post. I appreciate someone who chooses to discuss facts and understanding rather than engage in The Authority Says Therefore It Must Be True type of emotional argument.

Your point is well made that for the "average" diver not tracking oxygen toxicity levels is probably not a major gaffe. I've reread my posts and I don't think I've ever disagreed with that statement. But, and there is always a but, the diver who has excellent gas consumption and who dives high oxygen concentrations 5 -6 dives a day for a week(as I've observed) is another matter. Depending on individual tolerance there could or could not be a problem. Probably not for "most" divers but all? Why take any unneccesary risk in what is supposed to be a recreational sport?

Even so, why not early on establish the protocol the diver will have to adopt sooner or later anyway as they upgrade that each dive is planned using the information for the specific gas that is selected for that dive? Sound educational practice would dictate that each piece of knowledge is a building block for subsequent learning.

Then there is the matter of the best tool for the job. If I am building a house and need to pound a nail why would I use a rock instead of a hammer? Sure, most of the time the rock will get the job done, and I may not even smash my fingers too badly. But the correct tool for the job is a hammer. Most of the counter arguments in this thread have missed this point entirely. There is no reason to teach a person to use a rock when they should be taught to use a hammer.

So, as has been stated and restated the best way to use any breathing gas is to use the dive planning information for that gas.

Now it is up to the cyber divers to decide what they will do for themselves.
 
ArcticDiver:
So, as has been stated and restated the best way to use any
breathing gas is to use the dive planning information for that gas.

lol... not so fast

i think YOU think that, and everybody else thinks otherwise, as far
as Nitrox is concerned...

so... just because you say so doesn't make it so eyebrow

(not sure if you missed that, but Paul wasn't exactly agreeing with you)
 
Derek S:
Tom -

Don't you think that telling a diver with less than 50 logged dives to go Trimix is a bit premature? :D
If a diver is at the point where they understand how nitrox works and how it can kill you, what's different about the helium component? I'm not telling the guy, "Oh, by the way, when you mix your own gas, use 15/35 and go 275' deep, and make sure you figure out how to factor in a little decompression somewhere along the way."
Now in my previous post, I made a few assumptions - that he is a recreational diver using recreational tanks - single AL80's or a single steel and sticking to depths less than 130'.
If he's using 30% nitrox or 30/30 trimix, what really changes?
Nitrogen is like aggravation - after a certain age, you can do with less of it in your everyday endeavors.
 
ArcticDiver:
I appreciate someone who chooses to discuss facts and understanding rather than engage in The Authority Says Therefore It Must Be True type of emotional argument.

Now it is up to the cyber divers to decide what they will do for themselves.

Artic,

I missed the point where you wind up knowing more about the subject than Mr. Rutkowski, who started this whole deal with Nitrox in the recreational community in the first place.

I have taken his courses, (from him personally), and read his books. I do not find notice in the literature that he gives credit to you for setting him straight, or for teaching him the error of his ways in one of your courses, but maybe I missed that too. If so, I humbly ask the pardon of my readers for the error of my ways as well.

Somehow, I just can't help but thinking that this is not the case, however. :D
 
H2Andy:
lol... not so fast

i think YOU think that, and everybody else thinks otherwise, as far
as Nitrox is concerned...

Actually, not everybody. This was the postion of my original nitrox instructor. Experience and research since then has validated his point.


H2Andy:
(not sure if you missed that, but Paul wasn't exactly agreeing with you)

I read and accurately quoted his post. I'm not sure you did. He restricted his comments to a certain group of divers and did not extend to all divers. He was intellectually honest in his presentation. He also restricted his comments to only one part of my argument, oxygen toxicity.

As a side note I'm told you are a fantastic diver and that we'll be meeting in the near future. So, until then, when we can substitute the real world for this cage rattling cyber world, adieu.
 
https://www.shearwater.com/products/teric/

Back
Top Bottom