Skin Bends - Lessons learned

[AggieDiver]

Nitrox is one tool that allows a properly trained diver, at recreational depth, more bottom time with less Nitrogen loading.

Ken pretty much covered it, but your comment illustrates why some people who think they are being extra cautious actually aren't. With Nitrox at recreational depths, you can have more bottom time or less nitrogen loading, but generally you can't have both in the same dive.

One thing to keep in mind also about HBP medications is that Altace/Ramipril has a warning that you shouldn't become dehydrated while taking it, because it can cause a big drop in blood pressure. I am sure that reaction would probably have an affect on nitrogen off-gassing as well.

[Hatul]

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.

I also did a quick search and it appears there are some hemodynamic changes in going through large altitude changes. One is the increase in red cell mass with altitude, a change that takes a few weeks and can increase the blood pressure through increase in vascular resistance. I wonder if anyone has done a study on plane passengers who fly at 8000 ft pressure, as there are short term factors at play as well.

Because of the uncertainties if someone is on a number of BP meds it's a good idea to take monitor on vacation whether at a different altitude or not.

[meebs86]

You can easily have both, to a certain extent.

say for a given depth you get X amount of nitrogen load in 5 minutes on air as 8 minutes on nitrox. Say you are at that depth for 6.5 minutes. More bottom time, less nitrogen.

Unless I'm thinking about it the wrong way of course....

[AggieDiver]

I am thinking of it as divers diving on Nitrox for more bottom time usually dive to the nitrox calculations of their computer. Divers wanting to be safer will usually dive an air-type profile using nitrox. Those diving with their computers set to nitrox will get the same nitrogen load, but more bottom time. Those diving air profiles will get the same bottom time as they would on air, but less nitrogen. Yes, there is some minor number in between where you could conceivably get a little of both, but I was really referring to the mindset of the diver when saying you can't have all of both.

Those who use nitrox because they want more bottom time rarely end up getting less nitrogen than they would have on air, because they are diving to the limits either way, and the limits are based on nitrogen load in most cases. Those who use nitrox to be more cautious about DCS generally don't change their profiles, and wind up with less nitrogen because of it.

[FritzCat66]

I had a case of "skin bends" a few years back, although I did not recognize it at the time and only understood what it really was years later after reading about it here on ScubaBoard.

I had dived twice in the morning off Jupiter, Florida, where the depths are typically in the 70'-90' range, diving EAN somewhere around 32%. No problems. I took the afternoon off, went sightseeing at the lighthouse, but mostly relaxed in the shade, had a little lunch, and stayed hydrated. I then returned for their once-monthly two-tanker night dive (the op only does night dives under a full moon). Pretty much the same dive profile. Nothing too extreme, and of course I had 6+ hours SI. My computer did not go into deco, but of course was just one bar shy.

No problems immediately after the dive, or even all the way back to the shop, loading up gear, and hitting the road home - where I was looking at a couple hours' drive.

Then the itching started.

Yeah, that's definitely what I noticed, about 15 minutes into my drive home. Just itching, first just under my arms, towards the front. I just wrote it off as chafing from my BC. I like to take pics completely inverted sometimes, so I can have my head and camera close to the reef while my feet are well away from bumping anything, and back then I had not yet modded my SeaQuest with a crotch strap to keep it from riding up when I flipped over like that. No big deal, I thought.

But then within ten minutes it spread across my chest, and the itching got worse. I started to think there must have been some little stingey things in the water that had lodged up under my wetsuit. So, thinking I was having some sort of histamine reaction, I pulled over at the Interstate rest stop and pulled out my 2% Benadryl cream tube I keep with my gear for just such things.

I remember my surprise when I got to the restroom and unbuttoned my shirt. Not only was my whole upper chest area itching like I had poured fire ants over myself, but it was red and mottled and blotchy as well. While it didn't quite look as severe as the pic someone posted above, it was similar in that there was a kind of marbling going on, with some darker streaks punctuated by lighter pinkish blotches. I was convinced I was having a bad allergic reaction and was looking forward to the relief the Benadryl cream would be giving me as I drove off down the road.

Only the relief never came. Which is unusual for me, as I've always responded well to Benadryl for any kind of local histamine reaction, from mosquito bites to actual fire ant stings to a jellyfish that left red rope-like welts on my leg - but which also mostly disappeared within an hour of applying that wonderful white ambrosian goo.

Yet this time - nothing. And it was a weird itching, too. Hard to describe, except to say that, with most of those other things, yeah they made you itch but at least when you scratched the itch, it at least felt good to scratch it. Even if just for a moment. Even if scratching isn't really the best thing to do, there was still something, well, satisfying about scratching.

But this time, the scratching just didn't really seem to do anything. The itching wasn't localized for one thing, just the whole area was itchy. And scratching did nothing for it - no better, no worse, nothing. Definitely weird.

Anyway, to make a long story short, I got home after a fairly miserable hour and half and the red itchy blotchies were not at all eased by the Benadryl. I popped a Claritin as well and took a cold shower and washed thoroughly (still thinking I had some kind of microscopic sea-lice on me or something). It got no better, and I hardly got any sleep that night - I couldn't get comfortable, and scratching did nothing to alleviate the itchy feeling.

But by morning, it was dramatically reduced, and pretty much entirely gone by evening. Not even a welt like a mosquito bite leaves, just gone. So, I shrugged it off and went about my life.

Only later, here on SB, after seeing pictures of skin bends and reading others' descriptions of it, did I realize that must have been what I had. And then the sobering realization that, no matter how mild, I had taken a DCS hit!

So, maybe by describing my experience someone else can learn. Knowing what I do now, once I realized it was no ordinary rash, I should have called DAN straightaway and gotten myself into a chamber. Because if you're getting skin bends, that means you took a DCS hit; and if those bubbles are coming out of your skin, then where else are they fizzing out of? You really don't want to wait and find out. I was lucky that time, just plain stupid luck. Not something you want to rely on.

Since then, I have never again experienced skin bends. But at least now I know what it is when I see it - or, perhaps better said, when I feel it.

[Ken Kurtis]

Possibly along the same themes as the hit that befell my diver that started this whole thread . . .

A guy I know here in L.A. got a bends hit (not skin bends but the type that required chamber treatment) a week or so ago. Granted, he was doing some deep techy type of dives. But the common thread? He was found to be dehydrated and he's also on blood pressure medication.

Don't know if it's a commonality or not but it's an interesting coincidence.

- Ken

[vladimir]

But the common thread? He was found to be dehydrated and he's also on blood pressure medication.

Don't know if it's a commonality or not but it's an interesting coincidence.

- Ken

Just to give the coincidence some perspective, about 30% of US adults are hypertensive, and at least half of them take medication for it. Were both victims obese? That could be another commonality. I'm sure we could come up with more, with enough data, and our sample size of N=2.

[FritzCat66]

As for me and my skin bends hit, I have always paid lots of attention to staying well-hydrated before diving. However, I was then (and still am) on anti-hypertensives, although not the diuretic kind (mine's telmisartan). And yeah, I don't exactly cut a svelte figure.

[Ken Kurtis]

I'm sure we could come up with more, with enough data, and our sample size of N=2.

Don't you mean our massive statistically-accurate sample size of N=2???



Fully agree it could be nothing more than coincidence.Or simply one more factor to consider, whether or not it's the pirmary driving one. And yes, both overweight.

- Ken