Gas bubbles may not be the underlying cause of decompression illness

[atdotde]

As a cause of decompression sickness, this hypothesis has a hole so large you could drive a Mack Truck though it. Specifically, every day, all over the world, thousands of patients undergo hyperbaric oxygen therapy during which they are exposed to far higher doses of oxygen than divers are. If oxygen exposure and oxidative stress (rather than inert gas bubbles) were the cause of decompression sickness, then we would expect it to be a common event among patients treated with hyperbaric oxygen.... but I don't believe there has been a single case of DCS, EVER, in millions of hyperbaric oxygen treatments.

In particular the opposite would be quite absurd: If true, you would be 100% safe from DCS if you did all your dives with a CCR rebreather and a set point of 200mbar O2 (no increased oxygen level at all).

Best
Robert

 

[uncfnp]

Thank you Dr Mitchell.

 

[duke dive medicine]

The paper gets a couple of things right. First, hyperoxia does lead to vasoconstriction. The reactive oxygen species produced in conditions of hyperoxia will effectively scavenge circulating nitric oxide (NO). Nitric oxide is an endogenous vasodilator, so less NO leads to net vasoconstriction. Second, vascular endothelial dysfunction is thought to be one of the mechanisms behind DCS symptoms.

They go on to seemingly contradict themselves: "Importantly, hyperbaric oxygen (HBO) has been shown to attenuate the tethering of neutrophils to the endothelium possibly via a reduction in CD18 expression" and "HBO inhibits neutrophil adherence [9] and platelet activation has been observed post-decompression which was found to be reduced with oxygen pre-treatment before a dive [10]." Adhesion of neutrophils to the vascular endothelium is a key component of vascular endothelial dysfunction. So, they appear to claim that pre-treatment with oxygen is protective, HBO2 has anti-inflammatory properties, but breathing the same oxygen (with the same concomitant effects) under water can lead to DCS.

Also, their casual dismissal of gas bubbles seems to reflect a poor understanding of exactly what bubbles they're talking about. They probably are referring to post-dive Doppler bubbles, which indeed aren't sensitive or specific for detection of DCS, but nobody I know of is blaming Doppler-detected venous gas emboli for DCS anyway.

Best regards,
DDM

 

[Kharon]

No computer algorithm has ever prevented DCI.

Well, I assume you are being snide and really understood what I was trying to say. Yes I mis-stated and took a shortcut expecting that anyone not being pedantic would understand what I was getting at..

I should have said if the computer algorithm allows you to monitor your dive and helps prevent DCI in most cases, if followed properly, does it really matter if it's bubbles or microparticles? Happy?

 

[Storker]

you have to be careful about things published in "Medical Hypotheses". This is a journal dedicated to the promulgation of blue sky ideas that have some sort of provenance in logic, but don't need to be proven.

After ruminating a bit, I have to admit that I'm rather astonished that a reputable publisher like Elsevier publishes a journal like this. I'm not a medical scientist, so it might well be that a journal where more or less far-fetched ideas hypotheses with no experimental backing are published is a good thing to have, but just the concept is really weird to me.

I mean, I wouldn't have thought twice if one of the numerous predatory journals were doing this kind of stuff, but Elsevier? Srsly?

 

[StefinSB]

After ruminating a bit, I have to admit that I'm rather astonished that a reputable publisher like Elsevier publishes a journal like this. I'm not a medical scientist, so it might well be that a journal where more or less far-fetched ideas hypotheses with no experimental backing are published is a good thing to have, but just the concept is really weird to me.

I mean, I wouldn't have thought twice if one of the numerous predatory journals were doing this kind of stuff, but Elsevier? Srsly?

“Cold fusion” got published and was bogus. Paper of future novel price winners got rejected by some journals only to be published by other as groundbreaking discoveries. Science is not black and white but always corrects itself. Maybe the authors apply for grants and needed a paper to strengthen their case? In any case, if true we will see certainly see other in the field investigating this tangent.

 

[Storker]

“Cold fusion” got published and was bogus. Paper of future novel price winners got rejected by some journals only to be published by other as groundbreaking discoveries. Science is not black and white but always corrects itself. Maybe the authors apply for grants and needed a paper to strengthen their case? In any case, if true we will see certainly see other in the field investigating this tangent.

Science is often wrong, and the peer review process is far from perfect. However, as in the case of cold fusion, science is self-correcting, and bogus papers are more often than not purged over time. Case in point: Jacques Benveniste's notorious paper in Nature back in '88. Or Andrew Wakefield's paper in The Lancet in '98.

However, the concept of one of the world's most reputable publishers publishing a journal whose sole task is to disseminate poorly documented ideas with little experimental backing just boggles my mind.

 

[Dr Simon Mitchell]

I just wanted to say that I literally laughed out loud when reading this.

Actually, I forgot to mention the second "hole" that would accommodate a similar truck: altitude decompression sickness. No hyperoxia or oxidative stress there, but clear cut decompression sickness still occurs.

I agree with some of your points about the Medical Hypotheses journal. A few points in their defence.

First, most of the papers are not quite as flawed as this one. Quite often the hypothesis is fairly sound and well argued.... it just lacks proof.

Second, it serves a purpose for people who have a great idea and want to get their name on it, but it is going to take a long time to actually acquire the proof.

Third, it relies on the reader having some knowledge of the journal's context. The articles are not intended to be interpreted as truth as sometimes happens (unfortunately).

There are probably other points I could make but those will do for now.

Simon M

 

[Dr Simon Mitchell]

nobody I know of is blaming Doppler-detected venous gas emboli for DCS anyway.

Hello DDM,

Just to clarify this comment before "certain others" latch onto it. I presume you are not dismissing the importance of VGE that cross a right to left shunt in the pathophysiology of PFO-related DCS?

Simon

 

[Storker]

Second, it serves a purpose for people who have a great idea and want to get their name on it, but it is going to take a long time to actually acquire the proof.

As I said, I'm not a medical scientist. So the journal might well serve a purpose in a science I'm not familiar with, but the concept just boggles my mind