sleepy, scuba makes me very sleepy, zzz

[The Pirate]

Keep in mind that sub-clinical dcs is different than bent dcs. They are different degrees of dcs. I view sub-clinical as "almost bent" kinda like "almost only counts in horse shoes and hand grenades." So it only really counts as far as having to take a ride in a chamber if you have bent dcs.

 

[divemistress]

but my pre-dive rituals and preparations sound about as relaxing as O-ring's description of his NC experiences.

O-ring once bubbled...
...that I was getting occasional subclinical DCS... but it seemed much worse when I was doing dives off of NC. I finally realized it had something to do with waking up at 5:30 am to catch the boat, skipping my morning coffee, and taking a bumpy 3 hour ride out to the dive site.

i can't speak for the other sleepyheads out there, but the first changes i plan to make are pre-dive: plenty of sleep, low stress, light-but-healthy breakfast, and hydrate-hydrate-hydrate.

then add in slower ascents, and longer and more frequent
safety stops. (i already dive nitrox.)

finally, post-dive, instead of tackling the dreaded unpacking-the-gear-bag chore (the prospect of which is enough to make me sleepy!) i'll try mild exercise, as doc v. suggested: perhaps a leisurely walk or lazy swim.

if all THAT doesn't help, then i'll start to worry.

 

[Arnaud]

You may want to try a warmer exposure suit, hood and gloves, too.

 

[gannet]

Sub clinical DCS or just being tired from exersice, this article on deep stops and slow ascent rates makes for interesting reading. http://www.gue.com/dplan/docs/Deco/Deep Stops.pdf

 

[ElectricZombie]

Northeastwrecks once bubbled...

I've also noticed that increasing my safety stop times, doing deep stops and maintaining slow ascent rates eliminates this problem, which suggests to me that there is some basis to this theory.

I completely agree. I used to be fatigued after dives every now and then. I was so fatigued once that I almost fell asleep on the way home and nearly caused a serious accident.

Since I started doing deeps stops, increased safety stop times (At least 7 mins, up to 20 or so - I teach my students 5 - 7 minutes at least...not 3 mins as suggested) and even slower ascent rates, I have felt great after every dive.

Adequate rest and hydration is also very important.

Diving Nitrox or switching to a high O2 mix at your 15' stop helps too.

 

[pufferfish]

DAN estimates that as many as 3% to 4% of recreational dives result in some form of decompression illness - that's scary!

Reefraf, I don't know where you got those numbers but they are way too high. That means that if you do a hundred dives, four of them will have "some form of DCI".

In fact I am looking at the DAN slide from their hyperbaric medicine course and a 1998 DAN-US Navy Survery estimated the incidence of DCI at 1.51/10,000 recreational dives which is a .015% risk.

The problem with these estimates has been determining the denominator or the number of dives done over the time period in question.

So how safe is recreational diving? The Underwater Council of British Colombia set out to find out by tracking in one region all the tank fills (146,291) over a 14 month period and the number of cases of DCI and diving fatalities. This was called Abacus project and low and behold recreational diving is extremely safe.

The incidence of DCI was .01% which is very close to the DAN 1998 estimate. The incidence of fatalities was .002% again very low. The combined incidence of death and DCI was still only .012%.

The message here is our sport is very safe, not "scary" and we now have the evidence to back this claim up. The fact that the DAN estimate and the Abacus Project almost had identical incidences suggests .01- .015% or one to two incidents of DCI per 10,000 dives is pretty close to the real risk.

So let's spread the message that recreational scuba is very safe, not scary

 

[SDAnderson]

The 3% - 4% figures is published on DAN's website at:

Estimated DCI Incidence in a Select Group of Recreational Divers

Excerpted:

"Results: Dives from logs, memory, or both had medians estimated from log normal distributions fitted to cumulative frequency plots by eye. Data are given in table. About 75% of responders were male accounting for 82% of dives, the 25% females accounted for 18% of dives. The median for logged dives was similar for males and females but the male median was slightly higher in the other two categories. Fifty-seven divers reported 67 cases of DCI (4.3% of females, 1.06% of dives; 3.3% of males, 5.3% of dives) (ed.; emphasis added), but only 30 cases were reported as treated. The median number of dives for divers reporting DCI was similar for treated and untreated cases, ~25.2. Whether untreated cases were actually DCI is unknown, but if they aren't, DCI incidence would be only 1.51."

"Conclusion: Total DCI incidence, assuming untreated cases were DCI, is close to Bove's (3.41) for sport divers but above that for military divers (2.65) (Undersea Hyper Med 1998;25:175-178). If the survey population of DAN members is assumed to be representative of the larger population then an average of 1,006 cases of DCI/year, reported to DAN from 1992-1997, at 3.38 DCI/104 dives would represent 2.98 million recreational dives/year. Whether untreated cases represent underreporting or false positives is unknown."

To dismiss or not to dismiss the untreated cases? Hmmm... In their conclusion, the authors indicate that these numbers correlated to another (Bove) study of sport divers. As this thread has shown, even suggesting to the average person that they might be suffering from a mild case of DCI is likely to produce a strong and immediate denial. To systematically dismiss all untreated cases would seem imprudent. At any rate, this information would seem to strongly contradict the .015% number you stated.

One man's "safe" is another man's "scary?" Frankly, I'm not qualified to get into an argument about the relative merits of one study -vs- another. I have just enough of a statistics background to know that all that lies down that road is a headache (sub-clinical DCI?) and wet shoes.

Steven

 

[pufferfish]

Reefraf.

I am no statistician either, but just eyeballing a rate of 3 to 4% DCI in recreational divers tells me something is not kosher.


In fact in that DAN article you point to that number of 1.51 is an incidence which has a denominator of 10,000 dives. In other words that is the same incidence I quoted at .015% and the military incidence reported in the same article is 2.65 DCI per 10,000 military dives. The military tolerates a higher rate as they are often doing things we recreational divers don't do and they have a recompression chamber on site at all times. One can then assume the military data may represent the upper limit of the DCI risk. I guess though Bove's number of 3.41 per 10,000 dives may show that it depends on what group of recreational divers one looks at and likely the kind of diving they might be doing.

The problem with all these previous studies is the number of active divers was estimated and the number of dives was only an estimate as well. That DAN study you refer to used some fancy math to estimate these numbers indirectly.

That is why the Abacus Project was so signifcant as it was the first time the numerator and denominator were actually known not estimated. Their estimate of 1 case of DCI per 10,000 dives is the incidence in a cold water ocean setting in a country where training is to a reasonable standard. As the authors point out what is needed is other regions of the world to do the same study and see if that incidence holds up.

In any case we can say at this point that the incidence of DCI amongst recreational divers is somewhere between 1 to 3.41 cases per 10,000 dives (.01 to .03%). The .01% is a hard number for a particular region and the other numbers are best estimates.

What we can say is that recreational diving is not 'scary' but very
'safe'. Why would we want to promote it otherwise. I don't have the numbers but I would guess things like parachuting or back country skiing are more dangerous. After seeing the Abacus numbers we should be encouraging more people to start diving not telling them it is scary .

Here is the link to the Abacus Project.

Abacus Project

 

[The Iceni]

divemistress once bubbled...
i'm not fatigued, not tired, but sleepy. after a few dives, all i want to do nap. (so i'm not a heck of a lot of fun on dive trips )

does anyone else feel this way?

judy

Yup,

There are three things that spring to mind;

1. Sleep reduces offgassing, so is not such a good thing post-dive.
2. Oxygen does act as a stimulant, thus EAN reduces all soporific effects. 100% oxygen used for deco produces a mild buzz. Although anectdotal, this is certainly widely reported.
3. All inert gasses are narcotic in proportion to their tissue partial pressure. Thus, regardless of whether this is a form of DCI or not and whether bubbles of nitrogen are present or not , all diving increases the quantity of dissolved nitrogen at tissue level in the brain which, by itself, is likely to be soporific.
   [/list=1]There are, of course, other factors mentioned in earlier posts.
   
   Odd anatomy?
   
   At risk of appearing childish and fatuous there is the well known, Post-Coital Hormone Release Valve - located near the hippocampus in the brain. Within 13.5 seconds of coitus or other pleasurable activity, this valve opens, flooding the body with temazepam, inducing sleep:- Male only.
   
   Does diving mimick this anatomical structure?
   
   That was a joke!

 

[diveaustin]

Nitrox helps...But after 3-5 dives for a few days those last dives of the day are hard. If I lived close to blue water I wouldn't push it but Lake Travis just doesnt cut it. I know I have pushed it when I am yawning in my regulator towards the end of my trip. But boy it feels good!!!!!!