Odd pain in my knee

[headsqueeze]

Hi headsqueeze,

I entirely agree, sir.

Now, if could answer my specific questions I'd be most grateful.

Thanks,

DocVikingo

yes, I will, but not without discussion of some important concepts that the original post alluded and did not fully express. You are asking me to simplify concepts into black and white, which I will not do. The first question is a matter of semantics. decomp or safety? The underpinning offgassing concept is the same no matter what you name it. As to the later questions and additional concepts raised by the original post, those will come later, perhaps over the weekend.

 

[Dr Deco]

Hello Skipperjohn and Readers:

I was out of town Friday and missed this. Here is what I know about the topic.


Underreported/ Missed DCS Cases

As reported by divers in the field, the incidence rate of pain-only DCS is much higher than is typically found in laboratory trials. This might be from (a) a lack of recognition of DCS, (b) the belief that “you will definitely know it when you see it,” (c) the short-term nature of many cases [they are gone by the time the boat reaches shore], or (d) a “test-of-pressure” is not performed since a chamber is not available to recreational divers.

In laboratory studies, a “test-of-pressure “ is always performed to clarify a DCS case. In altitude cases, this is always done since the test subject must be returned immediately to atmospheric pressure.

Many recreational cases might well be missed except for those appearing during the flight home.

Old Pain in the Knee

There was the case of two divers who were “hit” during an experiment from a deep dive at Ocean Systems. They were treated [decompression stopped and oxygen breathed] and both exited the chamber symptom free. Three days later, on a flight home, one (maybe both) experienced pain in the knee. (This incident occurred in 1967before I joined the company in1969. I am relating what was told to me.)

Late “Hits”

Divers should know that a problem with DCS that is several days old is past the time window for hyperbaric therapy. The situation is a bit different for neurological problems. Here one is treating edema and injured nerve cells. Hours after the appearance of neurological DCS is really a bit late to decide one needs hyperbaric therapy. You are trying for an in-the-park home run and the odds are bad. Do not delay!

At a UHMS workshop comparing treatment with helium or nitrogen, they concluded that earlier than five hours post, both treatment gases work fine. Post five hours, neither gas works. Bummer! :depressed:


Dr Deco :doctor:

 

[headsqueeze]

I have been reluctant to ask this but it has been nagging me for a few weeks. Reluctant because some know where I did my OW diving and I don't want them to be judged.
Anyway, I did my OW cert a few weeks ago. The organization I used scheduled my 4 dives 1 on one day and the last 3 dives 2 days later. I thought it odd diving 3 dives in one day (after all my book learning) but the instructor answered: "we do it all the time". So I was in their hands.
The first dive was shallow, 25 feet so I had no worries.
2 days later we repeated the first dive, then 2 hours later dove 55 feet for 45 minutes (plus a 3 minute safety stop), then after a 1 hour SI Dove 45 feet for I believe close to 1 hour (I didn't time this dive but I burned significantly more air on this last dive-came up with only 500 pounds left).
But here is where things got weird. This being my OW certification, my assent on this final dive was my Controlled Emergency Swimming Assent. I will admit I was not watching my rate of assent but my instructor was at my side.
Anyway, by 4:00 I was done. That night some time in my sleep I noticed a pain in or slightly above my left knee.....

'we do it all the time' - as I mentioned in a prior post, your gut feeling about the dive profiles was correct. If your OW test was similar to mine, you spent a great deal of time and expense preparing for certification. When the checkout dives finally arrive, they weren't perfect by the book and a bit on the cavalier side. The emergent ascent worried me too because it was not what the book taught about safe ascents. The instructor missed the rest stop altogether, but my family was the last in line of the others, so it worked out anyway and the later part of the dive was in the shallows. To make a long story short, I am now more confident and won't think twice about bucking a dive operation in a hurry, even if chided by them that "I'm too slow getting back on the boat". My other option is to rent the equipment and shore dive - we had a blast diving around 20 feet on our own time.

If you could post the SIT times, then I would like to look at the dive profile a little closer, but from what I can tell, the second day appears to violate the NAUI and NAVY tables @ 56 min on the second dive, not even considering the nitrogen load from the 25 foot dive.

If you slept w/ a bent knee after your diving, then that knee could certainly be DCS prone.

 

[Wayan]

Terminology can be a confusing thing for all of us. However quite rightly a 3-5 minute stop at 3-5 meters (15-20 feet) is just that a safety stop and is recommended practice to do. A decompression stop is one we have to do to stayed with in the non decompression limits. This all can become confusing with the nature that we dive today with the acceptance of dive computers as in more temperate waters more and more people are actually multi level diving rather that old square profile we all had to do before computers became common place.

And I agree there is no one profile that can guarantee that a diver will not get a DCS hit there are just many factors to consider. But we all should understand that is an risk and a acceptable risk since the latest DAN figures suggest a probability 3 or 4 cases for every 10,000 dives. of the cases reported to DAN. There was an article in the DANAP diver alert magazine by Dr Andrew Flock that suggested that In excess of 75% of divers presenting with symptoms of decompression illness have dived within the limits of their tables / computers.

Certainly from the people I have seen (at the various Hyperbaric Units I have worked) the fair majority all have apparently dived within the limits of the computers they were were using (some of these stupidly did not have anything and relied on their dive guide - go figure - this certainly is a training and education issue).

Denial still seems to be the biggest problem and there would be many unreported cases out there which goes to getting complete data impossible.

3 Open water training dives in a day whilst acceptable to some training agency's is acceptable is IMO to much for the new diver. Diving is tiring, I know that when I did my NAUI course many years ago whilst on to max 35 feet after the 2 dives (shore) I was very very tired.

I also believe that the methodology behind the CESA needs to be reviewed. As an EX Submariner we did these from 100 feet in a specialized tank with constant supervision. I am not suggesting we train divers to do it from 100 feet, but am suggesting that if a we were to again examine they way divers do this divers very few could do it safely. And certainly not practiced again until instructor level.

Certainly after a few days the window for Hyperbarics to achieve results is passed.

There seems to be the thought amongst a far majority that if the present to a diving medicine Dr
with some signs and symptoms which could be DCS/DCI that they are going to have to undergoing treatment. This fortunately in most reputable centers is not the case.

There are numerous medical conditions which display similar symptoms to DCS and in some cases may require only normabaric oxygen. This, however, should not negate that fact that anyone with has minor symptoms and or doubt should not seek advice from a Diving Medical Professional as soon as possible. As has been rightly pointed out there could be other predisposing medical conditions which may increase the risk.

It is even even harder to determine the problem without a complete medical history and examination. However, in this case it is IMO that it is not possible to rule out that there could have been a DCS incident, however as well past the window for Hyperbaric to have any meaningful results.