Got vertebral degenerative changes? Your risk for spinal cord DCS may be elevated.+

[Duke Dive Medicine]

Another interesting study:

MRI findings and clinical outcome in... [Aviat Space Environ Med. 2008] - PubMed - NCBI

These authors found that spinal cord lesions were more common in divers with severe spinal DCS, but no mention of spinal stenosis. So, is it spinal stenosis that increases the likelihood of spinal cord DCS, or is it spinal cord DCS that increases the likelihood of spinal lesions?

Best regards,
DDM

 

[boulderjohn]

Another interesting study:

MRI findings and clinical outcome in... [Aviat Space Environ Med. 2008] - PubMed - NCBI

These authors found that spinal cord lesions were more common in divers with severe spinal DCS, but no mention of spinal stenosis. So, is it spinal stenosis that increases the likelihood of spinal cord DCS, or is it spinal cord DCS that increases the likelihood of spinal lesions?

Best regards,
DDM

I think this is somewhat the reason I wanted to see the full study, even though my lack of a medical background may make it difficult for me to understand it. It is sometimes hard to tell the difference between a cause and an association. As I said, I don't fully understand the nature of the methodologies from this abstract, partly because of my lack of of medical knowledge. I am really wondering what was actually proven.

I have a history that makes me suspicious. That history includes reading long and complex studies that came to a conclusion that I found suspect. One was a study that found a high amount of bone necrosis in dive instructors, and they were tying it to practices associated with instruction. The abstract was convincing, but when I read the full report, I found some of it to be borderline ridiculous. I can't recall the exact numbers, but their "average" OW instructor had supposedly made an absurd number of dives per year while instructing, with average dive depths approaching 100 feet. Anyone who knows that an instructor is not allowed to do more than 3 training dives a day to maximum depths of 40 feet for half the dives and 60 feet for the rest had to question their data. Another such study was the one upon which GUE and later UTD based their S-curve decompression profile due to the supposed magic of the oxygen window, magic that dispensed with Dalton's Law. I read the study carefully, finding nothing wrong with it until the paragraph in which the magic oxygen window was explained, and I said "Huh? Where did this come from?" It seemed to leap in out of nowhere, unconnected in any way to the data that preceded it. I challenged the S-curve community on it, and got some responses that indicated to me that they were simply accepting it on faith. Since then, both GUE and UTD have admitted that the study was flawed, and although they still use the S-curve, they have both come up with different reasons for it.

I have dismissed other studies as well from consideration. I would enjoy the chance to examine this one, but not so much that I am willing to spend $32 for the privilege.

 

[herbdb]

I purchased a non printable copy of the full report. Through a little computer magic, I have a readable copy in MS Word format. For those who may be interested, send me an email address via PM and I will share a copy.

Having read the report, I have the same misgivings expressed by Boulderjohn as to cause and effect.

 

[boulderjohn]

OK, I read the study, but as I feared, a lot of it was over my non-medical head. From what I could understand, though, the results are certainly interesting, and I see nothing that leaps out at me as a reason to question the study. The study ends with a well-stated sentence indicating that the results are not conclusive enough for new policy decisions, and further study is warranted. I concur. Given the fact that DCS is extremely rare in the general diving population now, to what extent will this condition affect one's chances? Does this suggest that divers with cervical stenosis should stop diving, dive more conservatively (how much so?), or avoid certain kinds of dives?

 

[herbdb]

John,

I came away with the opposite feeling. They started the study by selecting a group of divers who had experienced DCS hits and compared them to divers of similar age and similar number of dives.

They did not look at the type of diving for either group. The divers without problems may or may not have done the same type of diving. Its difficult to have a problem doing two 40' reef dives with a hour SI.

Did the control group dive as deep, as long and use similar ascent profiles? Were the DCS hits on dives outside of or near accepted recreational standards.

The "control" group and their experience may or may not be similar to the divers with problems.

I don't see how they can draw any conclusions from this study. Their concluding sentence seems like a plea for research funds?


Unfortunately, as I see it, the rare incidence of DCS makes it unlikely that anyone will be able to develop a study on the scale required to draw statistical conclusions.

Hopefully, someone with medical training will wade in. Am I being too critical?

 

[boulderjohn]

I see those same flaws, and I especially see that the now number of participants is problematic. On the other hand, I think it bears further study.

 

[DocVikingo]

.Hopefully, someone with medical training will wade in. Am I being too critical?

Hey Herb,

I, too, have now read the full text article.

The flaws you present certainly constitute possible significant confounds. Because the subject population was a retrospective one over the period 2009-2012, it likely wasn't possible to pin down the recreational profiles of each diver even in those who were using a downloadable dive computer at the time of the incident. If the info wasn't charted in the medical records at the time of evaluation & treatment, it very probably was lost forever.

I'm guessing that the researchers were aware of this deficit in their work and I do find it dismaying that they didn't even allude to it as being a possible validity issue.

In any event, it is surely the case that the tiny incidence of spinal cord DCS in rec divers makes it extremely unlikely that it would be possible to develop a study involving humans on the scale & methodological quality required to draw truly meaningful statistical conclusions.

The above notwithstanding, for any number of reasons, funding & ethics high among them, published research on many, many medical aspects of scuba is small to non-existent, and likely will remain so for a very long while. As such, IMHO we shouldn't be too quick to harshly criticize or dismiss out-of-hand what little may appear. I believe that based on this study, warts & all, the diver with known degenerative changes in the cervical or thoracic vertebral column would be prudent to consider the wisdom of conservative dive profiles.

Regards,

DocVikingo

This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual and should not be construed as such.

 

[herbdb]

No argument here about conservative profiles given a possible increase in risk factors. My age alone already has me diving nitrox, using conservative factors in my computers and making longer safety stops on every dive.

On first reading, the abstract had me thinking I might have to give up diving; now I think I will just add this to the list of risk factors and continue to be cautious with my profiles.

Thanks for giving us your conclusions.

Herb

 

[DocVikingo]

On first reading, the abstract had me thinking I might have to give up diving; now I think I will just add this to the list of risk factors and continue to be cautious with my profiles.

Hey Herb,

Thank you for getting the interested parties to read the full text piece.

Even on my reading of the abstract I wouldn't have discouraged affected divers from continuing with their beloved recreation, but taking a few steps toward conservative profiles probably is smart.

Cheers,

DocV

 

[TSandM]

I read the study, and it appears to be as well done as such a study can be. The results are very intriguing, and fairly consistent with a vascular model of DCS. If I knew I had a cervical cord compression, I would be very careful with my nitrogen loading and profiles.