Are some divers more prone to bubble formation than others?+

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DocVikingo

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It has long been suspected that some otherwise normal & healthy divers are more prone to bubble formation than others. Seems they may be.

"Aviat Space Environ Med. 2014 Oct;85(10):993-8. doi: 10.3357/ASEM.3805.2014.

Flying after diving: in-flight echocardiography after a scuba diving week.
Cialoni D, Pieri M, Balestra C, Marroni A.

INTRODUCTION:
Flying after diving may increase decompression sickness risk (DCS), but strong evidence indicating minimum preflight surface intervals (PFSI) is missing.

METHODS:
On return flights after a diving week on a live-aboard, 32 divers were examined by in-flight echocardiography with the following protocol: 1) outgoing flight, no previous dive; 2) during the diving week; 3) before the return flight after a 24-h PFSI; and 4) during the return flight.

RESULTS:
All divers completed similar multiple repetitive dives during the diving week. All dives were equivalent as to inert gas load and gradient factor upon surfacing. No bubbles in the right heart were found in any diver during the outgoing flight or at the preflight control after a 24-h PFSI following the diving week. A significant increase in the number and grade of bubbles was observed during the return flight. However, bubbles were only observed in 6 of the 32 divers. These six divers were the same ones who developed bubbles after every dive.

CONCLUSIONS:
Having observed a 24-h preflight interval, the majority of divers did not develop bubbles during altitude exposure; however, it is intriguing to note that the same subjects who developed significant amounts of bubbles after every dive showed equally significant bubble grades during in-flight echocardiography notwithstanding a correct PFSI. This indicates a possible higher susceptibility to bubble formation in certain individuals, who may need longer PFSI before altitude exposure after scuba diving."
 
It has long been suspected that some otherwise normal & healthy divers are more prone to bubble formation than others. Seems they may be.

"Aviat Space Environ Med. 2014 Oct;85(10):993-8. doi: 10.3357/ASEM.3805.2014.

Flying after diving: in-flight echocardiography after a scuba diving week.
Cialoni D, Pieri M, Balestra C, Marroni A.

INTRODUCTION:
Flying after diving may increase decompression sickness risk (DCS), but strong evidence indicating minimum preflight surface intervals (PFSI) is missing.

METHODS:
On return flights after a diving week on a live-aboard, 32 divers were examined by in-flight echocardiography with the following protocol: 1) outgoing flight, no previous dive; 2) during the diving week; 3) before the return flight after a 24-h PFSI; and 4) during the return flight.

RESULTS:
All divers completed similar multiple repetitive dives during the diving week. All dives were equivalent as to inert gas load and gradient factor upon surfacing. No bubbles in the right heart were found in any diver during the outgoing flight or at the preflight control after a 24-h PFSI following the diving week. A significant increase in the number and grade of bubbles was observed during the return flight. However, bubbles were only observed in 6 of the 32 divers. These six divers were the same ones who developed bubbles after every dive.

CONCLUSIONS:
Having observed a 24-h preflight interval, the majority of divers did not develop bubbles during altitude exposure; however, it is intriguing to note that the same subjects who developed significant amounts of bubbles after every dive showed equally significant bubble grades during in-flight echocardiography notwithstanding a correct PFSI. This indicates a possible higher susceptibility to bubble formation in certain individuals, who may need longer PFSI before altitude exposure after scuba diving."

Was the presence/absence of a PFO collected as part of this study?
 
Not sure how the laws of physics could vary from one diver to another.
 
Nobody really understands the process of nucleation for bubble formation, but it has been documented in the past that, with the same nitrogen exposure, some people will bubble and others will not, no matter what you do to them. So there is something about plasma proteins or perfusion that can encourage bubble formation in some people, where others will tolerate higher overpressure gradients without forming bubbles.
 
This is really interesting. I'd love to have a study of those same divers charted over the next several months, once per month. I'd love to see variance from day-to-day on all of that. If that's the case, I'd love to get myself checked out.

Another interesting twist to this, if day-to-day variance was within acceptable limits, would be to progressively push their NDLs to see at which point some get bubbly and others don't. Of those that didn't have bubbles present, was one verging on having bubbles present? Would another minute of bottom time added a seventh diver?
 
Not sure how the laws of physics could vary from one diver to another.

Physics doesn’t. But blood chemistry, body mass to lung area ratios, body tissue ratios, and a myriad of other factors that influence the physics of bubble formation do vary... day-to day-and between individuals.
 
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Interesting study. I had thought that s 24 hour interval was sufficient. Given my age and aggressive diving habits, maybe I need to allow a 36 hour interval?
 
Probably is completely dependent on where you would lay on the study. :wink:

Some rarely bubble no matter what they do. 20 years of fairly aggressive diving as a traveller has given me skin bends twice and complete exhaustion once. Years of no recognizable problems and then skin bends twice within a two year period.

What is one to speculate. I'm fascinated by this study. Do do wish it was a larger longer sampling, with more known specifics and protocols.
 
Physics doesn’t. But blood chemistry, body mass to lung area ratios, body tissue ratios, and a myriad of other factors that influence the physics of bubble formation do vary... day-to day-and between individuals.

So I'm assuming that the study didn't control or adjust for, at minimum, things like diver size/BMI, etc? Did everyone dive the same profile for every dive? The abstract says "similar" dives, but that's pretty vague. You and I could dive "similar" dives, but one of us ascends more rapidly than the other, etc. Were things like diet, caffeine, alcohol consumption, sleep, physical fitness, pre/post-dive activity level, etc controlled for? What about SAC rates, pulmonary function, respiration rate, etc? Did they have the same beginning and ending tank pressures? Without these things being held equal, the finding could be purely artifactual.

It's certainly interesting (or intriguing as the author suggests) but seems that the study regarding PFSI was neither designed nor controlled to adequately detect intersubject differences in nucleation susceptibility in any meaningful way.

That's not to say that the intuitive hypothesis that "different people are likely to be different" isn't true relative to bubble formation... just that it's a pretty good stretch to use this study as significant support for the idea.
 
RJP

A lot of small-scale studies are conducted primarily to justify funding for large scale studies. A statistical study of the number of diagnosed DCS cases would probably be more useful to the industry. People need a simple number of hours to avoid flying rather than an algorithm that factors in every environmental and biomedical variable.
 

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