Nitrox in Cozumel

[nimoh]

I sold my computer and turned my brain on. In a team a computer is an issue because two or even three will never be on the same page. One guy will have 3min deco another 5 min and another will have different stops. Then mix in some funky gasses and your all messed up. Diving a plan removes these issues but does require more work. For vacation reef diving with a buddy I still use a bottom timer, navy tables, and sometimes v-planner on my iPhone. Tracking my load over a week is not very hard.

I dive a computer as do my dive buddies, if I end up with a 3 min safety stop and a buddy gets a 5, then I do a 5, no big deal.

 

[macado]

I don't particularly feel there is an added benefit of using Nitrox if you're only diving 2x a day, based on some of the profiles and surface intervals that many dive shops use in Cozumel. That is not to say however that using Nitrox is a bad thing; it will give you an increased safety margin, less nitrogen loading. This is always a good thing. I just feel that most profiles can be done in Cozumel using air (if, and I mean if you're diving with a group that shares that same profile). If you're diving with a group of divers who are all using air, AL80s and diving the same profile then you may not see the full benefits of using Nitrox.

The resistance that some DMs and Dive Ops have to divers using Nitrox on the first dive is, the risk of having to chase them down a wall at 130ft+ if they're not paying attention to their depth and/or computer/bottom timer. Of course you know this can end up being particularly dangerous but if you're comfortable with your skills and can stick to an MOD then it's not an issue.

I can't tell you how many times I've been diving in a Cozumel and looked down and see divers unaware that they were well past 100ft chasing a turtle or something else. It DOES happen, I can tell you.

That being said, if you're planning on diving 3x or more a day or doing more aggressive profiles then Nitrox will benefit you. If you're diving with an op such as Aldora, generally the entire boat will be diving the same mixture and using HP100s/HP120s which allows much more aggressive profiles than a typical AL80 and divers using a mixture of air and Nitrox.

For the record, I do use Nitrox if i'm doing a 3rd/4th tank with a typical dive op using AL80s or if i'm diving with Aldora as everyone on the boat would be using Nitrox. I can tell you based on my last trip that my last 5 dives would have been decompression dives based on my backup (air only computer used as a bottom timer) if I had not been using Nitrox.

 

[boulderjohn]

We do some fun workout dives above 50 feet of water but cover a mile or so. We run at a very fast pace with doubles, dry suit , and deco gas. I mean after the dive younthink your suit was leaking pace. Lots of drag even in a clean kit. Some divers have found they feel better on 21% then any enriched mixes. Pushing hard o2 became and issue for them. Theses divers were far beyond my abilities with over 10,000 dives. Makes me always keep in mind how hard I'm working at depth. Is it worth passing out?

I need to apologize because my reading skills are apparently a bit weak here. Could you help me understand how this post relates to the contention that increased workload leads to increased nitrogen absorption?

 

[Mayor]

If you don't train for issues then how will you know what you can really do. Fighting current is never a good idea but if you have to I know how much I can push it.

 

[Mayor]

That's not how i was trained.

 

[boulderjohn]

If you don't train for issues then how will you know what you can really do. Fighting current is never a good idea but if you have to I know how much I can push it.

That's not how i trained.

I really have to confess once again that your point in relation to this thread has eluded me. I could use more of an explanation, please.

 

[Mayor]

Sorry off topic! Your show my friend........

 

[boulderjohn]

It is simple > workload means >Nitrogen. Do you believe it is true?

No..... If you want me to go into detail, I will be happy to.

Not having gotten a reply and not wanting to leave this issue untended, I will attempt a simplified answer.

All gases move randomly to enter and leave the body through a process called diffusion. When you inhale air into the lungs, some N2 molecules move randomly from the lungs into the blood and some move randomly from the blood to the lungs. As the blood goes through the tissues (perfusion), the same thing happens. When you have been hanging around at the same altitude for a while, things even out, so by pure chance just as many molecules go into the body from the lungs as from the body into the lungs. That is called being at equilibrium. That is our normal condition at the beginning of the first dive of the day.

When we descend to 99 feet of sea water (fsw), though, things change. In order to inflate our lungs, we must breathe in 4 times as many gas molecules as we did on the surface. That means that by random motion, 4 times as many N2 molecules are entering our body as are leaving it. That is called a pressure gradient. Our bodies begin to absorb N2. The longer we stay at 99 feet, the more N2 will be in our tissues, and the lower the pressure gradient between lungs and tissues. Our bodies are approaching equilibrium, and the exchange slows down. As we ascend, each lungful has fewer N2 molecules, the gradient becomes even less, and the rate of absorption slows even more. At some point in our ascent our body has more N2 than our lungs, and there is now a gradient going the other direction. Our body begins to release N2 into the lungs and out into the sea when we exhale. When our tissue N2 is low enough to be safe, we go to the surface and continue to release N2 into the air during our surface interval.

The advantage of nitrox is in the fact that it has fewer N2 molecules than air, so the gradient is less at depth and on the ascent. We take on N2 more slowly during the dive, and we release it more quickly on ascent.

So what does workload have to do with it?

Some people assume that an increased rate of breathing caused by an increased workload means more N2 in the lungs and thus more into the body, but that is not true. Each breath has the same number of N2 molecules, and the fact that you get rid of one breath and take in another doesn't matter--it's still the same number of molecules in the lungs each time. There is a miniscule loss during the time the gas is in the lungs, but that makes little difference, and even if the same breath were impossibly held throughout the dive, the same lungful would still take the diver to the same level of equilibrium.

The other possible issue is with perfusion, and there is some theoretical basis for a difference here. On a very long dive in which the diver is working, the diver will stay warm and the blood will flow efficiently through the body during the working portion of the dive. This will make the intake of N2 most efficient. If the diver then spends a long time holding still on ascent and gets cold, the blood flow will not be as efficient during the offgassing. That should only be a factor during very long dives. For example, I recently had to fight a very stiff current on the surface and on descent, so my heart was racing during much of the 20 minutes of bottom time. My ascent required a series of stops lasting an hour, during which I was calm and relaxed. In theory, this may have made a minor difference in offgassing for me. In a normal recreational dive, though, it shouldn't matter much at all.

Anyway, that's why I don't think workload is a factor in N2 loading or a reason to use nitrox.

 

[beaverdivers]

Not having gotten a reply and not wanting to leave this issue untended, I will attempt a simplified answer.

Nice theory!

I'm preparing our divers for a very important dive.

They will be using Galileo Sols that are Air-Integrared ( AI ) and that have a heart rate
monitor to take into account their workload.

We go to great efforts to provide our students with the Best Scubapro gear. I will reply when I surface.

Why do you think AI dive computers incorporate workload and use it in their decompression algorithm?

It sounds like you should have used a heart rate monitor on your last dive.

Have you ever used an AI computer? or Heart rate monitor?

 

[Texas Torpedo]

When I am doing multiple day, 2 tank + dives per day, I will always go with Nitrox on the second dive if available, and if I have my choice it'll be as rich as possible (36% or more), limited only by the dive profile & MOD... The majority of first dives in Cozumel are going to be deep(er), followed by a more shallow dive for the second. If they are both shallow reef dives, no need unless it really works for you.

When I first started diving EAN / Nitrox I couldn't really tell the difference physically; however, once I started diving heavily = multiple dive days that were either two or four dives total, I quickly realized the benefits of Nitrox..
For me, it removed a considerable amount of fatigue starting on day 2/3, and even more important to me = it decreases the chances of taking a nitrogen DCS hit.. Secondary to me (but more important to most others) is giving you more bottom time by reducing the NDL.

Of course, if you really want to get rid of the n2 fatigue (and you are willing to go through the appropriate training) try breathing 50/50 and 100% on your way up and @ your safety stop on repetitive NDL'ish dives.. Then you will understand the benefits of enriched air "nitrox"..