DCS Type II in Cozumel

[drapap]

I have been certified for about 10 years (having done recreational resort diving for the previous 30 years) and have done over 60 dives in the Caribbean, Mexico, and Key West. I just returned from Cozumel where I suffered DCS Type II after my my second dive on my second consecutive day of diving. My symptoms, which started about 30 minutes after surfacing, were partial numbness of my left hand and forearm, blurry vision, loss of balance, abdominal pain and edema on most of my upper body. I initially thought I was having a heart attack, and was taken by ambulance to Dr. Piccolo's clinic, where he as a double person hyberbaric chamber. Dr. Piccolo took one look at me and told me my heart attack was DCS Type II. My heart rate was at 51. I was in the Chamber within about 30 minutes of arrival at the clinic for the first of two treatments, one for 5.5 hours and the next morning for 2.5 hours. By the time I arrived at the clinic the hand and arm numbness has stopped. As soon as the chamber was pressurized to 60 feet, the abdominal pain went away and never returned. Upon completion of the first session, my heart rate was 101. After the second session the following day my heart rate was down to about 84 and it remained at or below that level for the next 48 hours, allowing me to fly home a little more than 48 hours after the second treatment. Dr. Piccolo, who has a incredible knowledge of DCS theorize that since I dived on a very conservative profile, with 5 other divers, all of us using at least one computer, the cause was "most likely" dehydration. While I did not drink heavily the night before the dive, I did not drink very much water, and most critically, did not drink any water between my first and second dives on the day of the accident. I am "grounded" for six months, but certainly intend to keep diving. I am probably going to get Nitrox certified before my next dives, and was told that using Nitrox, but following an "air" protocol could somewhat reduce the change of a re occurrence. I am also about 20 lbs overweight, and will try my best to lose this weight.

 

[Ayisha]

Thank you for sharing. Glad everything seems ok now.

Yes, using nitrox while following conservative air No Decompression Limits (and without going over the Maximum Operating Depth for the percentage of O2) can reduce the amount of nitrogen in your body and reduce the chance of DCS. I normally keep my computer set to the nitrox mix I'm using, let's say 32%, and don't go to the MOD or the NDL, leaving a buffer.

Being properly hydrated is important too, especially in hot climates like Coz. I'm not much of a water drinker, but I make sure I drink water before and in-between diving.

 

[MXGratefulDiver]

Thank you for posting, and I'm very happy to hear that you're recovering well.

Looking at your report, I'd like to ask about your dive ... what was your dive profile, and how fast was your ascent rate?

I think the most common cause for this type of hit is a too-fast ascent rate. This is because on a typical recreational dive, where you do not go real deep or stay long enough to exceed no-decompression limits, the tissues that absorb the most nitrogen are usually the "fast" tissues ... notably your blood and nerves. These are the tissues that would also result in the symptoms you reported. These tissues take on nitrogen rather quickly as you go deeper ... and also offgas nitrogen rather quickly as you ascend. And coming up too fast can easily result in a DCS hit as you describe even though you remained well within your no-decompression limits.

So although good hydration, physical fitness and using nitrox can reduce the potential for this type of hit to occur, watching your ascent rate and keeping it at or below the recommended rate of 30 feet per minute is the most critical factor to pay attention to. This is particularly true after the safety stop ... and that's where I've most often seen ascent rate violations ... particularly among people who don't dive very often, because after the safety stop people have a tendency to consider the dive over and surface rather quickly at the very time when watching your ascent rate is most important.

Watch that ascent rate, and stay within the limits all the way to the surface ... it should take a minimum of 30 seconds after ending your safety stop. That seems glacially slow, but keep in mind that the closer to the surface you get, the greater the rate of change in pressure for each foot that you ascend.

Best wishes for a full recovery, and may you enjoy many years of diving into the future ...

... Bob (Grateful Diver)

 

[Ayisha]

Perhaps a deep stop and a graduated ascent can help as well. Here is one of the many articles on Deep Stops by DAN:

Alert Diver | Deep Stops

Here is an online seminar. I believe you have to be a DAN member to watch it:

DAN | News

 

[johnsona1503]

I may have misread the Alert Diver article on deep stops but it appeared to me to not recommend a deep stop for a NDL recreational dive. I assumed a slow ascent rate is the best practice combined with the shallow safety stop and once again a slow ascent to the surface. On my first ocean dive my private DM worked with me deploying my DSMB. He told me the trick he used to time his ascent rate after the saftey stop was to casually roll in my finger spool and go the last 15' as if I was reeling myself up. This slows me down without thinking about it and has my spool ready to clip off by the time I'm at the surface.

As complicated as nitrogen loading can be to the OW recreational diver (ie. me) I assumed if I made a 3 minute stop at 60' or 40' after I made a NDL depth of 116' I would be continuing to load nitrogen while doing this deep stop and would be better off continuing my slow ascent to my 15' safety stop.

 

[MXGratefulDiver]

I may have misread the Alert Diver article on deep stops but it appeared to me to not recommend a deep stop for a NDL recreational dive. I assumed a slow ascent rate is the best practice combined with the shallow safety stop and once again a slow ascent to the surface. On my first ocean dive my private DM worked with me deploying my DSMB. He told me the trick he used to time his ascent rate after the saftey stop was to casually roll in my finger spool and go the last 15' as if I was reeling myself up. This slows me down without thinking about it and has my spool ready to clip off by the time I'm at the surface.

As complicated as nitrogen loading can be to the OW recreational diver (ie. me) I assumed if I made a 3 minute stop at 60' or 40' after I made a NDL depth of 116' I would be continuing to load nitrogen while doing this deep stop and would be better off continuing my slow ascent to my 15' safety stop.

For recreational diving the advantage of a deep stop has less to do with offgassing than it does with ascent rate control. For a lot of recreational divers, making a short deep stop prevents them from inadvertently exceeding maximum recommended ascent rates. But it has additional benefits if used properly.

Deep stops should not be made for three minutes ... they should be made for one minute. And a stop of one minute at half your deepest depth ... as NAUI has been recommending since about 2004 ... won't do anything measureable to your nitrogen loading. What little additional loading will occur will be to the slowest tissues ... which, in the event of a DCS event, are the most easily treatable.

What it gives you in return is a reduced rate of offgassing in your fastest tissues ... which in return nets a reduced potential for a more serious Type II hit. You really WANT to take care of those fast tissues, because they can result in a far more serious condition which is not as easily treated.

To my concern, the benefits far outweigh the disadvantages.

Now, keep in mind that the amount of benefit vs additional loading will depend on maximum depth, time at depth, and your body's ability on any given day to deal with offgassing ... which is a rather significant variable.

But the argument that deep stops contribute to nitrogen loading is far less significant than most people using that argument make it out to be. If you were staying for 10 minutes ... or even 5 ... at half your deepest depth, I might be more inclined to give it credence. But honestly, a one-minute stop at 50 or 60 feet isn't going to increase nitrogen loading even enough to measure. And the benefits of slowing down the offgassing rate of your fast tissues by making that stop far outweigh the potential drawbacks ...

... Bob (Grateful Diver)

 

[Ayisha]

I may have misread the Alert Diver article on deep stops but it appeared to me to not recommend a deep stop for a NDL recreational dive. I assumed a slow ascent rate is the best practice combined with the shallow safety stop and once again a slow ascent to the surface. On my first ocean dive my private DM worked with me deploying my DSMB. He told me the trick he used to time his ascent rate after the saftey stop was to casually roll in my finger spool and go the last 15' as if I was reeling myself up. This slows me down without thinking about it and has my spool ready to clip off by the time I'm at the surface.

As complicated as nitrogen loading can be to the OW recreational diver (ie. me) I assumed if I made a 3 minute stop at 60' or 40' after I made a NDL depth of 116' I would be continuing to load nitrogen while doing this deep stop and would be better off continuing my slow ascent to my 15' safety stop.

There are many articles on Deep Stops by DAN over the years and they do vary a bit in their recommendations, but mostly they do recommend a deep stop. There is debate about whether it should be one minute or 2 1/2 minutes as started being advocated a few years ago. One minute at half-depth doesn't do you any harm and it could help. Some computers have a built-in deep stop and many divers do it routinely for deep dives. I still do one minute at just shallower than half-depth and then do a slow, graduated ascent and an extended safety stop (at least 5 minutes) at about 20 feet, then very slow, sometimes stopping again at 10 feet, and then slowly to the surface. Whether I do all the stops and for how long depends on if my buddy has the same mind-set as me, but the deep stop, extended safety stop and slow ascent are a must for me.

Think of the deep stop sort of like a multilevel dive. What's the difference, really? In the Caribbean, we tend to follow models that help us off-gas efficiently, since the typical dive tends to be a multi-level dive. We spend a fairly short time at depth, and then spend a fair amount of time at mid-depth, and then spend quite a bit of time fairly shallow, and the last 10 or more minutes are often one big safety stop. This profile is what allows the DG to do multiple dives over multiple days for extended periods and *usually* not get bent.

Now if you look at typical dives on a wreck, you could easily go to depth, stay pretty much at depth for most of the dive, and then start ascending - a very square profile that does not allow you to offgas very well if the only stop you're making is once between 15-20 feet. Instead of that square profile, most of us will do the bottom of the wreck, spend some time exploring at mid-depth, maybe go around the top of the wreck, then slowly start ascending and maybe put in some short stops along the way. That multilevel dive will make it much easier to offgas and be in the "green" on a computer when we exit the water. This is all assuming that one is within the NDL's at all times.

A deep stop really isn't much different than doing a multi-level dive, and we all routinely do those.

 

[drapap]

Bob - Thanks for your reply to my post. The dive profile was relatively conservative. First AM dive was to about 90 feet with a gradual ascent to about 40 feet and then slowly to a 15 feet dc stop. After a one hour plus surface interval, second dive was about to 80 feet, again with gradual rise to about 40 feet, with dc stop at 15 feet. It is very lilely I may have exceeded safe ascent rate (although not according to two dive computers) since this is the first time I have done repetitive dives along deep reefs without a safety rope or anchor chain to hold on to while ascending. I need to download the actual dive profiles for the 4 dives I did from my computer to check this.

 

[johnsona1503]

NWGratefulDiver and Ayisha, thanks. Your explanations helped me make sense of a recrational deep stop. I have a few deeper dives in Cozumel and typically my buddy and I are alone on the ascent. Some reefs we can follow it up to shallower depths, others we are in the blue. We just make sure its slow and check our gas.

 

[Parsons]

Last year I started diving with a Aladin 2G and down loading my dives. I'm not sure about other setups but this software you can drag the cursor along the your dive profile and at the same time watch the tissue loading bars. It really opened my eyes after the safty stop how fast the bars loaded up on that last 15' of accent. It slowed me down.