DCS in Cozumel

[Streydog]

Not all ops are for everyone. That is why there are so many in Cozumel. I have never dove with an op that made me remain at a certain depth that would put me at risk.

 

[uncfnp]

Hey Streydog. You are absolutely right that the variety of dive ops in Cozumel is a glorious thing, at least for the divers. But if it is a choice, for me personally, between a dive op known for its long dives and group ascents, where I would have to either end the dive early for everyone or spend the dive floating 30 feet or more over the reef for much of the dive or an op that lets me choose the depth AND the length of the dive with no penalty to anyone else...to me its a no brainer.

 

[scubafanatic]

Because I dive nitrox strictly on air limits - the tracking of the O2 is just in case, although I'm never doing more than 2 dives a day anymore so it really isn't totally necessary. The computer set to actual O2 setting also serves as a back-up. My computer has various settings in re conservatism - and mine are both set to the most conservative profiles already.

I know it's not practical for everyone, but I always recommend having a back-up computer. I can't tell you how many people's computers crap out on them in the middle of a dive week - either battery, flooding or some other problem then they want to rent a computer. Sorry to say folks, but we can't rent you a computer once you've started diving, unless you take a full 24 hours off first - it has no idea what your previous profiles were.

I always dive with 2 computers at a minimum, and sometimes include a 3rd computer if it's an expensive trip as that's the worst time to have to sit out dives for computer failure.

 

[leadduck]

For me, the TYPE of DCS that occurs with this lesion is what makes it scary. Although (for unknown reasons) skin bends is a lot more common in this group, so is neurologic catastrophe.

Seems that neurologic DCS might cause skin bends: https://thedivelab.wordpress.com/20...result-of-brain-lesions-caused-by-gas-bubbles

 

[uncfnp]

Seems that neurologic DCS might cause skin bends: https://thedivelab.wordpress.com/20...result-of-brain-lesions-caused-by-gas-bubbles

Hopefully @Dr Simon Mitchell will not mind my reposting his response to this study from another thread ...

Hello Islanddream.

I agree with DDM that there is no science behind these decisions.

My personal view is that if all you had was the rash, with no other manifestations, then a 6 month wait to dive is excessively conservative. As DDM has implied, the cutis marmorata form of rash is generally viewed as more "serious" but this perception arises because it is more frequently associated with other more serious symptoms (particularly spinal DCS) than the hive-like rash that he mentions. It is not that the cutis marmorata rash per se will harm you. If all you experienced was the rash with no other symptoms, then we would still view this as a mild episode of DCS. Put another way, the significance of cutis marmorata is that when we see it we are more alert to the possibility that more serious symptoms might arise. If no more serious sumptoms arise then the rash itself is essentially harmless.

We would normally advise divers in the latter situation (cutis marmorata rash but no other symptoms) to have a month off diving. This advice is not based on science, but there is a lot of experience with it, and there is no signal in our experience that it is insufficient time. Having said that, even a diver who waits six months or a year could suffer another event the next time they go diving just on the basis of bad luck. So whenever diving physicians give this sort of advice it is always heavily contextualised with a clear statement that there are NEVER any guarantees that there will not be a repeat event, no matter how long you wait. It follows that the decision to dive again, and when to dive, has to be made by you and you must take responsibility for that decision.

DDM mentioned the study which has shown that pigs may exhibit cutis marmorata after brain arterial gas embolism. Unfortunately this study has led to a fairly uncritical acceptance that cutis marmorata is (or may be) caused in this way in human divers. The truth is that a cutis marmorata appearance of the skin may be caused in many ways, and one of them is a significant adrenergic (think of it as an intense fight or flight) response. This can occur in a variety of medical settings. For example we see a cutis marmorata-like rash in illnesses like septic shock, or shock of any cause for that matter. Non diving brain injury can also cause it - we see it sometimes in brain bleeding events. It is not surprising therefore that cutis marmorata may be seen in severe stroke-like events caused by bubbles (as in the pigs in the study).

Two things get overlooked in conversations about this study. First, the pigs in the study were anaesthetised. Second, the doses of air used to elicit the cutis marmorata response would have produced significant stroke like symptoms if the pigs were awake. But in the vast majority of cases of cutis marmorata in human divers we don't see symptoms of brain injury. Indeed, it is very common to see cases like yours with no other symptoms at all. Thus, it seems that the dose of arterial gas required to elicit the response in pigs is simply not encountered in the vast majority of human cases. It certainly cannot be concluded on the basis of this study that human divers with cutis marmorata must have suffered from arterial gas embolism.

A proponent of the brain embolism hypothesis might argue that maybe you don't need such large doses of gas going to the brain to elicit the response in humans. But this reasoning can also be challenged. Humans undergoing strongly positive bubble contrast echo studies for PFO inevitably have their cerebral circulation showered with bubbles of relevant size to those which "often" enter the arterial circulation from the veins after diving. This happens every day in cardiology suites where PFO tests take place. Sometimes we even see transient cerebral symptoms after such studies, but we NEVER see cutis marmorata. If "sub-clinical" cerebral arterial bubble exposure were the cause of cutis marmorata in human divers, we would expect to see it more often in strongly positive PFO tests, but we never do.

I am not dismissing the study out of hand. It seems likely that cutis marmorata could be seen after serious arterial gas embolism in humans, but this would be accompanied by stroke like brain injuries, and the majority of cutis marmorata cases in divers (who do not exhibit such injuries) do not seem to be caused in that way.

Simon M

 

[tarponchik]

Sorry to say folks, but we can't rent you a computer once you've started diving, unless you take a full 24 hours off first - it has no idea what your previous profiles were.

I'd say this is an overkill, as useless as diving air profile while breathing EAN.

 

[BRT]

I'd say this is an overkill, as useless as diving air profile while breathing EAN.

How long would you take off before starting with a fresh computer?

 

[tarponchik]

How long would you take off before starting with a fresh computer?

Zero.

 

[scorpiofish]

To the original poster. You can dive as conservatively as you need. Coz can make it a little harder, but not impossible. My wife has had skin bends 3 times, without ever exceeding any limits. She also doesn't have a PFO. The last event was almost 10 years ago. A friend of mine has a theory that some people are just more bendable than others. Regardless, we consciously dive super conservatively and yet not many people would notice.

1) We dive nitrox always, 36 if available, 32 if not. She dives with computer set on air.
2) We dive shallower. This is actually a preference for shooting video and stills anyway. We will always be 10-20ft above the rest of divers. If there is anything we need to see deeper, we bounce down, film and return. This is also a tip for those not as good on air. It doesn't matter if it's Palancar or Columbia, we still rarely bother going below 60ft. BTW, I have been shooting for almost 20 years and have won/placed in many contests and been published in Scuba Diving Magazine. Every winning shot and purchased image was shot above 60ft., usually well above. My favorite dive site in world consists of diving 3 hours at 5ft.
3) Work your way shallow earlier than normal. If you are doing site like La Francesa, stay off the bottom and side of the reef and stick to the top. Become attuned to the creatures that live shallow, even in the sand. You can spend hours in the shallows looking for them.
4) Long safety stops
5) When you surface, keep breathing through your regulator until you are on the boat. You will be off-gassing on nitrox instead of air. If you can, keep breathing during the SI until it is time for them to switch out your tank.
6) Ridiculous levels of hydration
7) Ask for Columbia Deep and Shallow. Dive Deep at 60-70. Then do Shallow. It's like an hour safety stop.
8) My dive site tastes are different than most. Back when we rent the whole boat, we would do Cedar Pass as the first dive, then Cedar Pass as the second dive. I've been diving Coz for a long time and don't find it necessary to hit Palancar every first dive. I haven't done the Throat since 1999. Don't be afraid to ask for a shallower site for the first dive.

If I kept track I'd guess I'm slowly closing in on 2000 dives. I can't count on 2 hands the number of dives below 100'. I'm just not interested unless there is something specific to see, at which point I go see it and return to my comfort zone. This includes some with doubles and a deco bottle.

There are no guarantees, but you can take lots of precautionary steps to mitigate your risk. None of these will reduce your enjoyment. So far, so good for our team.

 

[tarponchik]

My favorite dive site in world consists of diving 3 hours at 5ft.

Must be some very special place, with zero chances of being run over by a boat