Skin Bends - Lessons learned

[TSandM]

I did some searching this morning, because I had never heard of a need to adjust antihypertensive doses by altitude. I was unable to find anything that supports this. Some people with hypertension get worse with altitude, others get better; I could find no recommendation that dose be routinely adjusted for people who move from one place to another, and this certainly would be unlikely to be true for acute changes to lower altitude. (Acute changes to significant higher altitude can cause altitude sickness, including pulmonary and cerebral edema, and it appears that people with hypertension may be more susceptible to this, but that doesn't apply to people living at altitude who come to sea level to dive.)

If anyone has a reference that supports this, I'd sure like to read it.

 

[sharksdelight]

Maybe someone should run this by DAN and see what they have to say.
Steve

 

[BubbleBlocker]

Interesting thread. One note regarding the notion that excess hydration is not a problem. I'd like to point to a DAN article re: Immersion Pulmonary Edema (IPE) (Alert Diver | Immersion Pulmonary Edema) where a potential link between excess hydration and IPE is discussed. I've learned to not go to the extreme either way in terms of hydration. Everything in moderation ...

Also, as a diver who had an extreme PFO and ASD, I can relate with Koyote trying to learn to dive with a heart defect. I dived for years on air profiles with Nitrox in my tanks as symptoms became more frequent, but found that was no longer sufficient as I got older (the holes become larger as you age). If I had known the degree to with I was playing Russian roulette with my life, I would have opted for closure years earlier or made a decision to stop diving (not an option as far as I was concerned). I'm now 3 years and 300+ dives post-closure and have no symptoms whatsoever any longer despite diving more aggressively and more often than I ever have in over 23 years of diving.

 

[E-diver]

Thanks for sharing folks, great info. I agree with the concept of always surfacing in the green on my PD2. Seems the only times this becomes a challenge is after multiple days of repetitive dives (most recently Bonair) but it really is a dramatic difference when diving Nitrox vs air for a similar profile. Not sure how the diving world got by so well without it for all those years. That's why, if your staying at manageable depths and planning for multiple days of repetitive diving, you owe it to yourself to go get the cert. It's well worth it.

Thanks again for sharing.

-E

 

[Ken Kurtis]

Not sure how the diving world got by so well without it for all those years.

I think the answer is fairly simple: Don't push the limits of whatever gas you're diving.

It's not about picking a "better" gas. It's about safely and smartly diving the gas you pick. You can dive safely on air. You can get bent on nitrox. Saturation on air and saturation on nitrox (to an EAD) is still saturation. Your body has no idea where the nitrogen load came from. It will simply get rid of it when it can.

To me, the lesson in all of this is - regardless of what you're diving and how "safe" you think it is - build in some factors in terms of extra safety stop time, etc. Better to do some over-kill on the safety end than to be over-saturated on the nitrogen end. Because diving (in terms of the bends) is pretty much pass/fail. Either you is or you isn't bent. Personally, I'd prefer "isn't bent" and will do whatever I can to maintain that condition.

- Ken

 

[Hatul]

Excellent information. I was bent in Coz (unprovoked ) and dehydration was probably a contributing factor. I also take medication for hypertension, one of which is a diuretic. I live in Utah at about 5,000 feet above sea level. I also had a pfo which has since been corrected but your comments are instructive. I will talk to my doctor about dosages at sea level when I am off on one of my diving adventures. Thanks for the information.

While I don't think there's any dosage adjustment to BP meds with altitude change, it's not a bad idea for someone on these meds to take a BP monitor on diving vacations. With all the stresses of diving and fluid shifts, you want to know that your blood pressure with within reasonable range of normal before you dive.

 

[E-diver]

I think the answer is fairly simple: Don't push the limits of whatever gas you're diving.

It's not about picking a "better" gas. It's about safely and smartly diving the gas you pick. You can dive safely on air. You can get bent on nitrox. Saturation on air and saturation on nitrox (to an EAD) is still saturation. Your body has no idea where the nitrogen load came from. It will simply get rid of it when it can.

To me, the lesson in all of this is - regardless of what you're diving and how "safe" you think it is - build in some factors in terms of extra safety stop time, etc. Better to do some over-kill on the safety end than to be over-saturated on the nitrogen end. Because diving (in terms of the bends) is pretty much pass/fail. Either you is or you isn't bent. Personally, I'd prefer "isn't bent" and will do whatever I can to maintain that condition.

- Ken

Wow, seriously? I think the first thing that comes to mind after reading this is, lighten up. I'm sorry if you took my comments as a serious question, it was a purely rhetorical comment, kinda like wow how did we ever get by without email or cell phones or this whole fancy Interweb thingy we're all enjoying at the moment.

Of course it's possible to get bent on Nitrox. My point was that since much of what we're talking about here is NOT pushing the limits when conduction multiple repetitive dives over the course of several days, that Nitrox is one tool that allows a properly trained diver, at recreational depth, more bottom time with less Nitrogen loading. The benefits of which are noticeable on a single dive but which really start to shine in the repetitive scenario we've been discussing. Yes, if you push the limits with Nitrox you're at just as much risk of being bent, but my point was that if you're interested in surfacing with your computer in the green, as many of us are, Nitrox can make this significantly easier to accomplish.


Again appreciate the fact that you where willing to share this story so others can benefit from a sense of shared hind sight and avoid a repeat of this or something more serious.

-E

 

[Ken Kurtis]

Wow, seriously? I think the first thing that comes to mind after reading this is, lighten up.

Uh, yes, seriously. Though you may have meant it somewhat tongue-in-cheek, in my travels around the world, you might be amazed at the number of people I've heard say "You can't get bent on nitrox" and they absolutely believe that to be true.

. . . but my point was that if you're interested in surfacing with your computer in the green, as many of us are, Nitrox can make this significantly easier to accomplish.

Being devil's advocate here again, not necessarily. This is the old "dive longer, dive safer" slogan which was first used to sell nitrox to the recreational public.

Many people think of nitrox as less nitrogen, regardless of what they do. They have no concept of the fact that you could do a dive on air to recreational limits, and a dive on nitrox to the nitrox limit, at an equivalent air depth, and surface with the same nitrogen load. "Safer" has now gone out the window. I'm not disputing what you say, especially if you dive nitrrox on air tables, but am simply saying that what you're sasying is not the end-all-be-all of the nitrogen dicsussion if you truly want to understand it, and many people don't understand the physics and physiology behind all of it.

I frequently see nitrox either used to mitigate bad diving behavior ("My computer went into deco but it's OK because I'm on nitrox") or to justify more agressive diving practices because they feel the nitrox will lessen the added risk.

To bring it full circle to this discussion, would our skin bends diver have been helped by nitrox? I don't know because she wasn't diving it and you're can't prove that something she didn't do would have made a difference. Will she dive it in the future? Probably every chance she gets because, as you said, it's one more tool that helps when used with an understanding of what it does.

- Ken

- Ken


Again appreciate the fact that you where willing to share this story so others can benefit from a sense of shared hind sight and avoid a repeat of this or something more serious.

-E[/QUOTE]

 

[redacted]

Sure, the body does not really care about where the nitrogen comes from (nitrox vs air). When you hit 90% on the controlling compartment, you are "in the yellow" and will need to do some off-gassing before you surface "in the green". But two points. If you are diving nitrox, your off-gassing will be more efficient (accelerated) due to the lower PP of nitrogen in your gas. So, although the air and nitrox diver may find themselves with the same N2 load, the nitrox diver still has an advantage when off-gassing. If the plan is to SS until "green", the nitrox diver (assuming the same controlling compartment) will require less time to reach the objective. But the idea of multiple days of multiple dives does bring up another consideration. On the first day, first dive, taking it into the yellow will usually mean that one of the faster compartment is controlling the dive. These faster compartment start off-gassing at deeper depths than slower compartment and you will often find yourself back in the "green" before you even reach a SS. Later in the day continuing with similar dives, the controlling compartment tends to move towards slower compartments. So off-gassing of the controlling compartment will be delayed to a shallower depth than earlier dives and will be slower. So, you will probably find yourself arriving at the SS still in the yellow and may well have to extend that SS to reach the "green". Now continue with the 2nd and 3rd day of such diving and the controlling compartment that you need to deal with will be a much slower compartment than on the first day. If you run yourself into the "yellow" at depth, you may well pick up another tick as off-gassing for those slower compartments will not begin until a mujch shallower depth than on the first day. And, when you arrive at the SS, the time to drop back into the "green" may be quite long. I'm not sure how much longer but I find I need to be thinking 10 minutes or more rather than the 3 to 5 minutes I could plan on the first day.

At least this is my observations based on running DiveNav's simulation up to its dive/day limits and my own experience at the Flower Gardens doing 12 dive in 2.5 days all in the 80 to 100 foot range.

 

[Ken Kurtis]

I agree with what you say and your comments illustrate the problems of taking a three-dimensional event (on-gassing here, off-gassing there, on-gassing/off-gassing over multiple tissue groups simultaneously) and trying to discuss it in a two-dimensional format (the written word) let alone trying to simplify things for the sake of the discussion. But I want to clarify one thing you said. (And I don't want to turn this into a nitrox thread. Been there, done that. If anyone's interested in that dicussion, let's start a new thread so this one doesn't become a jumble.) However . . .

Sure, the body does not really care about where the nitrogen comes from (nitrox vs air) . . . If you are diving nitrox, your off-gassing will be more efficient (accelerated) due to the lower PP of nitrogen in your gas. So, although the air and nitrox diver may find themselves with the same N2 load, the nitrox diver still has an advantage when off-gassing.

Strictly in terms of the safety stop, yes. But in my example, I was meaning that they arrive at the surface with the exact same nitrogen load. My point is that once you're on the surface, nitrogen is nitrogen and it's the amount you have in you, not the gas from whence it came, that determines outgassing. In that regard, on the surface with the same N2 load, an air diver and a nitrox diver will outgas the same. On a repetivie dive, the advantage in bottom time to the nitrox diver comes from the fact that he's subsequently loading up the N2 more slowly by breathing nitrox instead of air, not that he off-gassed better during the surface intervfal.

(And the disclaimer is that I'm simply pretending that it's a single-tissue model here simply to make a point. Yes, in the real world of multiple-tissue models, there's no way the two of them surface with exactly the same load in all the tissue groups.)

- Ken