Yes or No to Nitrox????

[fisherdvm]

So I've dove with Nitrox alot, and am also a Nitrox instructor.
I don't believe that Nitrox makes you feel less tired (personally I think it's a sales generated placebo effect) and have never felt different after a Nitrox dive as a opposed to an air dive. I think it's time for a blind study to determine if some people receive some sort of physical benefit from diving Nitrox (as opposed to psychological).
If you find yourself at the NDL on a dive with plenty of extra air in your tank, Nitrox is worth it. If you are ending dives because of a low air supply, Nitrox is just money thrown into the ocean.
If you decide that Nitrox will benefit you, check with the operator you plan to dive with. Some operations will not give you extra bottom time when diving Nitrox. If they don't allow you to use more time, then it's not worth the cost.

There are actually 2 studies (do the Rubicon foundation search) - one on firemen, and one on construction worker) that was double blinded, and did show a benefit of nitrox iin reducing fatigue.

The only 1 study done on divers was a poor study - small sample size, and the divers were not pushed to much of a limit.

A study was done on rats, and shown a direct correlation between nitrogen concentration of a gas and lesions of DCS. Indirectly this will support that nitrox decrease the incidence of DCS. Too bad we can't do a study on humans.

 

[skynscuba]

I did 20 dives my week at CCV. At the time I was not EANx certified, so I dove air. I was close to the NDL on occasion, but NDL never really limited my diving. I now dive enriched air on pretty much every dive where it is available. I don't dive enough that the difference in cost means much, it is warmer when diving dry (air-activated hand and toe warmers cook better on 36%), I get a little more NDL on boat dives, and I may benefit some day if I suddenly need to make a faster ascent.

 

[bperrybap]

Back on Topic.

I dove CCV for a week back in June '06.
The compressors were all new then.
The current price for Nitrox is $6/tank or $100/week.
You can do the math to figure out which is cheaper for you
depending on your number of dives.

Most of my dives were about an hour and average depths
in the 40-45 ft range. Max depths were typically between 60-80ft.
but you could easily average alot deeper if you wanted to cruise
the walls lower. Along some of the walls, especially CCV wall,
you could even stay up as shallow as 10-15ft, but you may
experience some surge depending on the tides.

Now beyond any "it makes me feel better" reasons for using
nitrox at CCV, you have to consider how the boat diving is done there.
There are 2 boat trips per day. 1 in the morning, 1 in the afternoon.
You can do 1 or 2 tank dives on each boat.
The first dive is guided by DM and the second dive of the boat
is a "Drop Off" dive. That is on the way back to the resort
they will drop off divers (no DM) along one of the walls or over the
Prince Albert as they are returning. So while you depart
by boat, if you choose to do the 2nd dive, you will swim in
through the "front yard" and exit the water by shore.
Because of this drop off method for the 2nd dive, the SIT time is
typically only around 30 minutes between the 1st and 2nd tank dive on the boat.
Some longer some shorter, depending on how far the dive
site was from the resort.

Me, I chose to dive nitrox all week and did about 22 dives during
my stay.
Others dove only air. Some people dove every dive, some didn't.

If you aren't sure about it, you could always do it per tank
and see if you notice a difference.

--- bill

 

[scubadobadoo]

I'm looking into CCV. They bank 32%. Most of the good diving seems to be shallow (<50'). I personally dive Nitrox mainly for increased NDLs. At shallow depths on 32%, you aren't seeing much of an NDL advantage over air, espeically as I'd get bored before I ever hit NDLs or ran low on gas at 30'. $100 is also a lot for the week (we paid half of that for Nitrox in Bonaire). In this particular case, I'd probably pass.

I agree...CCV equals shallow dives for the most part...nothing below 40-50ft to see to make it worth going deep in the Bay Islands. Dive 4 times a day on air at shallow depths and you will not have any SIGNIFICANT advantage using nitrox over air. The word PADI uses to describe the nitrox advantage is INSIGNIFICANT actually when comparing the number of people who get bent while using nitrox vs. air. In other words, nitrox use hasn't lead to fewer cases of the bends according to DAN's research although we all know that nitrox is a useful and safe tool.

A diver can show you that they stayed at a certain depth longer than they could have stayed while using air. That's really the number one advantage of nitrox. As for the feeling less tired thing, most doctors and DAN research agree that it doesn't, however if you believe in a good luck charm, then it certainly doesn't hurt to do so. A placebo effect can be a very real thing to some people. In the end, diving in a controlled manner and within limits has done more to decrease DCS than nitrox has.

Now, is taking the class for 75 bucks worth it? YES! It's a great class and you will learn some very good theory. Take it if only for what you will learn. Plus, you may find yourself doing dives in the future where using nitrox will be more worth it.

Many will argue that a diver shouldn't put a price on safety and what's another 175 for the class and the nitrox for the week. In the context of the OP's original post, I think this argument becomes a moot point.

While it may seem like I am bashing Nitrox, I am actually a big fan. I use it frequently. It is my opinion that it should be taught with the open water class. I just think that MANY people like to push it as a miracle gas that will make you a SIGNIFICANTLY safer diver instead of as a tool to increase your bottom time. Again, in the end, DAN's research hasn't shown (yet) fewer DCS cases using nitrox vs. air and that goes for using nitrox within air limits too.

 

[rakkis]

It seems though that increasing bottom time is a main reason for going nitrox. I think with the way I suck air "Certified Hoover" I would drown in most situation before getting close to the NDL.

Do not automatically associate a bigger NDL with more bottom time.

If you're going through your tank before you hit air NDL, nitrox won't matter in that respect. It is not as though you breathe less because each breath has a higher concentration of O2. Nitrox makes your NLD bigger. But you can only take advantage of a bigger NDL if you have the air to get to it.

 

[HowardE]

I did 25 dives in my 6 day stay at CCV - I did the unlimited nitrox which was only $80 when I was there (there was a special) which brought my charge down to $3.20 for the nitrox.

I do often push the NDL's on air, so nitrox is beneficial to me... longer bottom times (Because of extended NDL's), and shorter surface intervals required (usually)

 

[fisherdvm]

Here is an animal study to explain why old geezers (DAN reported that the majority of nitrox users are over 45) uses nitrox:

Summary: 4 of 15 goats using air, and only 2 of 16 goats using 40% nitrox got DCS.

Title: The effect of breathing hyperoxic gas during simulated submarine escape on venous gas emboli and decompression illness.
Authors: Blogg, SL
Gennser, M
Loveman, GAM
Seddon, FM
Thacker, JC
White, MG
Keywords: Barotrauma/etiology
Animal
goat
Decompression
Decompression Sickness/*etiology/prevention & control
Embolism, Air/*etiology/prevention & control
High Pressure Neurological Syndrome/etiology
Models, Animal
Oxygen/*administration & dosage/adverse effects
Statistics, Nonparametric
Submarine Medicine
Time Factors
Issue Date: 2003
Publisher: Undersea and Hyperbaric Medical Society, Inc.
Citation: Undersea Hyperb Med. 2003 Fall;30(3):163-74.
Abstract: Raised internal pressure in a distressed submarine rapidly increases the risk of decompression sickness (DCS) following submarine escape. The hypothesis that breathing a hyperoxic gas during escape may reduce the risk of DCS was tested using goats. Shallow air saturation and simulated submarine escape dives were carried out either singularly or in combination (saturation, escape, or saturation followed by escape) using air or 60% / 40% oxygen (O2) / nitrogen (N2) mixture as breathing gas during the escapes. Post-surfacing, animals were observed for signs of DCI and O2 toxicity. Precordial Doppler ultrasound was used to score venous gas emboli (VGE) using the Kisman Masurel (KM) scale. Following escape from 2.5 MPa, the rate at which VGE disappeared in the hyperoxic group (n = 8) was significantly faster(p < 0.05) than the air group (n = 7). One case of pulmonary barotrauma with arterial gas embolism occurred in the air group, but no cases of DCS were observed. After saturation at 0.18 MPa followed by escape from 2.5 MPa, DCS occurred in four of 15 animals in the air group and in two of 16 animals in the hyperoxic group. The rate of disappearance of VGE was significantly faster (p < 0.01) in the hyperoxic group. O2 toxicity was not discernible in any of the animals

 

[fisherdvm]

SCUBA LABS statement on Nitrox support the use of the air table with nitrox to decrease the risk of DCS:

http://www.electropc.co.za/WWSubAqua/nitrox.htm

The Advantages of Nitrox

Clearly the most important reason for using nitrox is the decrease in nitrogen content. But the possibility of longer bottom times as a result is far from the only advantage. By using nitrox instead of air at the same depth, you can also:

· Have shorter surface intervals between dives.

· Decrease time before flying.

· Shorten decompression stops.

· Reduce the risk of decompression sickness (DCS) when nitrox is used with air tables or with an air dive computer.

 

[fisherdvm]

Study to support a higher incidence of DCS in diabetics and those with vascular diseases (indirectly related to hypertension and smokers):



Title: A HIGH INCIDENCE OF DECOMPRESSION SICKNESS IN COMPRESSED-AIR WORKERS IN TAIWAN R.O.C.: AN EPIDEMIOLOGIC STUDY
Authors: Institute of Undersea Medicine, National Defense Medical Center, Taipei, Taiwan, R.O.C., University of Hawaii at Manoa, USA#
K.C. Niu
S.S. Liu
D.F. Lin
K.L. Huang
Y.C. Lin#
L.H. Chen
Keywords: decompression
decompression
neurological
diabetic
Issue Date: 1996
Abstract: BACKGROUND: During the last five years, the number of decompression sickness (DCS) patients has continuously increased from four hundred cases to one thousand cases per year. Therefore, the Council of Labor Affairs is deeply concerned about the safety and public health of the occupational dives. METHODS: A team of researchers interviewed the basic information: types of work, diving location, training and working record, health and DCS treatment history, using a well-designed chart. The results of analysis would be invaluable for verifying factors leading to the high incidence of DCS in Taiwan and for providing policy recommendations for legislation governing diving industries. RESULTS: In the first year, we obtained the names of 450 compressed-air workers from different resources such as insurance companies, hospitals, National Underwater Technology Association, Council of Labor Affairs, and labor union of the harbors. Of those divers 231 were interviewed. Results revealed that the incidence of DCS during the last year was as high as 19.9percent (46/231 cases); 34 cases were diagnosed as type I DCS and 12 cases were type II DCS. Of the possible risk factors leading to the high incidence of DCS, using logistic regression analysis, whether divers knew the step decompression concept was the most important (p less than 0.000). Divers who did not receive annual physical examinations have significantly higher incidence of DCS than those who took annual physical examinations (p = 0.033). Furthermore, the reviewing of past illness history has shown that the incidence of DCS in unhealthy divers (cardiovascular problems, diabetes mellitus, gout, and neurological disorders) was significantly higher than healthy divers (15.3percent versus 10.9percent, p less than 0.01). CONCLUSION: From the results, Council of Labor Affairs has launched a series of teaching programs to re-educate the professional divers. A plan of physical examination is now being carried out in an attempt to further investigate the possible health problems possibly relating to the occurrence of DCS in these divers.
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )

 

[String]

Until someone shows that using nitrox on air tables vs air on air tables actually reduces the chance of someone getting DCS giving any such advice is at best ill informed.

Still none of the above show any statistically significant reduction in the rates of DCS for air vs nitrox group.