Nitrox problem, is it normal?

[kalidor's8]

ok LOL lots of info and questions so I will try to answer as I can

1 I have been diving for 6 months now, I know it is not that long took my Nitrox in January but this was the first dive.
2 we were diving Lake Travis in Austin
3 mixes were 32.4 and 32.2 verified by us, we are not crazy enough to trust anyone
4 water temp at depth was 54 condition was calm.
5 stage bottle was for our 5@15 stop just incase we came back low and it was standard air
6 my regs are ScubaPro MK2plus and SP R295 Octo, buddies regs were also SP but not sure what model.
7 these were rented tanks.

I just bought my regs a couple of months ago and have not even thought of having them serviced yet. Normaly they breath just fine even at 112ft they were ok so I am puting it as overexertion with a bit of narcing as well. Was just wondering since I did not get a high feeling from it. The tank valve was fully open with 1/4 turn back. I could breath just could not get enough if you know what I mean, so yes more than likely hyperventing.

Hope this helps and ty
Kev

 

[fire_diver]

While your isn't a "top of the line" model, it is decent and shouldn't have been the problem. You were diving cold (depending on who you talk to ) water. Never dove that lake but I would guess that vis was rather murky, and it was probably dark at that depth?

Cold, dark, low-vis dives really tend to crank up the narcosis. Narcosis doesn't always feel "drunk." It can feel dizzy, loopy, or scared. A narced dive can leave you feeling the VERY strong desire get the heck out of that area or depth, even if you've been there before and been fine. Narcosis can even feel like "nothing" and just slow your resposes without you realizing it. A little "scared" narcosis, combined with some over-breathing of the reg, and you may have felt like it wasn't giving any air.

The line about feeling better after ascending 10 feet is the big tell. Narcosis tends to turn off like a switch after getting a little shallower.

The reason I ask all the questions was to rule out a few things. Some cheap regs should never be taken below 60 feet. They don't perform up to par if you start breathing heavier than normal. Verifying the mix is also important (as I'm sure you know). Rental tanks are always suspect in my mind, becuase they are used way more than private tanks and probably abused too. But that's just me, YMMV.

Hanging a safety tank is a good consideration, but be sure you don't include that as part of your dive plan. Since you are new to diving, did you instructor teach you how to REALLY plana dive? Have you calc'ed your SAC (RMV for purists) yet? Do you know how to determine if you have enough air for both you and your buddy if one has a catastrophic reg failure? If not, don't feel bad. Most of us didn't get it either. Do a search for SAC, or ROCK BOTTOM and you'll have enough reading to keep you busy for the next month. You can also PM me any questions, and I'll be glad to answer or direct you to better folks here that can help.

Good luck with your diving, play it safe!

Comrade (OKIE) Stroke

 

[Bobby]

Couple of thoughts I would like to add. 32% has an MOD of 111 feet @ 1.4 PPO2. Planning the dive you should always round to the conservative side which would be 110 feet. Planning your MOD right at 1.4 with added stress such as cold water, heavy exhurtion is not very conservative. You did not state the surface interval between dives but it is likely you could have been pushing CNS a little on the second dive. This alone in recreational diving would not be much of a factor. Combined with the cold, stress and possible CO2 build from working at getting to the dive objective could have all contibuted in the result of the second dive. Pushing to the limits of anything to include NDL's, PPO2's or dive ability can have bad results. For a dive like this I might have set my PPO2 @ 1.0 for my MOD, ended my first dive well before getting close to the NDL's (you did not say how close you were to NDL's just making a point), and if the dive objective caused me to work hard possibly turn the dive early.

Hope this helps.

Bobby

 

[fire_diver]

Couple of thoughts I would like to add. 32% has an MOD of 111 feet @ 1.4 PPO2. Planning the dive you should always round to the conservative side which would be 110 feet. Planning your MOD right at 1.4 with added stress such as cold water, heavy exhurtion is not very conservative. You did not state the surface interval between dives but it is likely you could have been pushing CNS a little on the second dive. This alone in recreational diving would not be much of a factor. Combined with the cold, stress and possible CO2 build from working at getting to the dive objective could have all contibuted in the result of the second dive. Pushing to the limits of anything to include NDL's, PPO2's or dive ability can have bad results. For a dive like this I might have set my PPO2 @ 1.0 for my MOD, ended my first dive well before getting close to the NDL's (you did not say how close you were to NDL's just making a point), and if the dive objective caused me to work hard possibly turn the dive early.

Hope this helps.

Bobby

I'm sorry, but this wrong! For some background, people used to dive PPO2 of 2.0 or more before studies started to show that SOME people were toxing out. The 1.4 limit is set by the agencies becuase that was the safest number they could agree upon. Deco divers routinely use 1.6 PPO2 for deco hangs.

Ox tox limits are based on time, depths, and percentage. There is also a difference between CNS toxing and whole-body toxing.

 

[timle]

Which part are you calling wrong?

I don't see a problem going to 110 with 32% on a nice day. However many people and agencies recommend a pp02 of 1.2 or less on any significant profile. Significant is a relative term - if the water is fairly cold for them, the depth pretty deep, current, visibility, anything - could increase their breathing and stress them. Knowing this planning the bulk of the dive to be spent at 1.2 pp02 seems like a smart thing to do.

I'm a fairly new cavern certified and I know I try to keep my pp02 near 1.2 on my cavern dives. Still learning to control the reel, light, watching my buddy's light, etc - leading to task loading and more stress - why push it? Which means when I drop into the cavern at Orange Grove sink I try to stay around 90'. Will I go to 100' - yup thats 1.3 - will I go beyond that - maybe for a bit - but I'll plan for the bulk of the dive to be between 80-90'.

 

[bubba105]

Over exertion, possibly CO2 retention leading to a bit of narcosis.

If I were a betting man, I'd go with this. Apprehension about nitrox (first time), working hard, CO2 retention causing gasping for air and a splash of narcosis = get me out of here. You did good, you recognized the onset of panic but you didn't let it consume you. The fight or flight mechanism sometimes has a hair trigger. Deciding to end the dive, WITH YOUR BUDDY, and ascending at a rate where you could recognize that breathing became easier, tells me you had it together. Like fire diver pointed out, ascending 10 ft is the tell. Funny thing that narcosis. First dive over 100 ft, second dive 88 ft and things get whacky. Good lesson.

 

[rockjock3]

If both of you had the same problem at approx the same depth and different equipment (except for the tank) I would go with another thing to think about. I know it is a simple and a basic thing, but I have seen it happen before. Did either one of you do a final check on both the tanks before you got in? The reason I ask this is if somebody thought the tanks were off and rolled the valves open then backed off a 1/2 turn so that the valves were actually 1/2 turn or so from closed this would be exactly the kind of problem that you might encounter.

 

[fire_diver]

Which part are you calling wrong?

I don't see a problem going to 110 with 32% on a nice day. However many people and agencies recommend a pp02 of 1.2 or less on any significant profile. Significant is a relative term - if the water is fairly cold for them, the depth pretty deep, current, visibility, anything - could increase their breathing and stress them. Knowing this planning the bulk of the dive to be spent at 1.2 pp02 seems like a smart thing to do.

I'm a fairly new cavern certified and I know I try to keep my pp02 near 1.2 on my cavern dives. Still learning to control the reel, light, watching my buddy's light, etc - leading to task loading and more stress - why push it? Which means when I drop into the cavern at Orange Grove sink I try to stay around 90'. Will I go to 100' - yup thats 1.3 - will I go beyond that - maybe for a bit - but I'll plan for the bulk of the dive to be between 80-90'.

What am I calling wrong? The entire concept being taught that you're going to die if you make a dive to 1.4 PPO2! You're even repeating it. You seem to have been taught that 1.4 is the maximum you should ever be at, and should spend 99% of your dive at less than 1.4. What rubish! The 1.4 max was decided upon as the limit for the entire dive. Read your Nitrox book again. Study your tables again. There is a time limit you can spend at 1.4, but even that is a recommendation. You can get hurt with less, you can be fine with more.

 

[timle]

I never said you would die if you made a dive to 1.4 PP02. I know many spend deco at 1.6 - that being a non-working part of the dive - to maximize o2 exposure to decrease deco times.

I'm well aware of the oxygen clock and calculating you 02 exposure. Everything is scuba is a recommendation, everyone is different, and even what will tox you one day might not tox you the next. I'm also well aware of the PADI Nitrox manual with 1.4 as MOD and 1.6 for contingency. I even said I don't see anything wrong with a nice dive to 110 on 32%, thats what PADI would recommend. However I would say if I knew I was going to be further task loaded or stressed in other ways I would lower my PP02 and aim for 1.2 for the bulk of the working part of the dive.

 

[nereas]

Ok let me start by explaining the situation. A buddy and I did our first Nitrox dive this last weekend, this was our second dive the first going to 112FFW. We made it to 88ft on the nitrox when we both noticed a problem with breathing. We both felt that it was hard to catch a breath and could not draw enough into our lungs.(pressure was at 1100 on my tank at this point) Normaly I am relaxed in the water and have never had a problem with issues but this time I felt myself start to panic. We desided to start heading back to our stage bottle for our safety stop and after going up about 10ft we noticed a big change in breathing ease, but contiued to stop due to gas lvl. We were working a bit to get to our target and we think that had a big part to do with things, but is that all it was? I know when you work harder it gets hard to breath thru the regulator but for us both tobe affected by it at almost the same point it seems strange. What are your thoughts on it and has anyone had te same or simmilar issues?

Thanks

It sounds like you both have really inexpensive regs, and therefore the slightly increased breathing resistance from the higher oxygen mix, which would normally be negligible with a better reg, is causing your problems.