size of decompression bubbles

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anton115

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Hi Dr Deco,

I was wondering if there was any literature you knew of looking into the size of bubbles produced on decompression say on dives at the NDL of common tables. The only information I have seen was in the article "Echo imaging techniques determine the size of intravascular bubbles in decompression sickness." by Robert M Olson which suggests bubble diameters between 50 to 300 microns? Do you have an opinion on the matter?

Thanks
Anton
 
Hi anton115:
I suspect that lower limits are determined by the difference in pressure between the bubble inside [determined by srface tension] and the pressure change with ascent. This could mean bubbles of less than a few microns and tens of microns. Thus, it depends on the dive.
 
Thanks Dr Deco,
I was wondering if you had and information on the upper size limits of bubbles produced on dives to say 30-40 meters when diving to the no deco limit. The reason I ask is that looking at DAN Project's Project safe dive It claims that 37.4% of divers tend to get IV bubbles on a single dive but on repetitive dives 85% of divers get bubbles with 67% of divers having high grade bubbles. It also states that bubbles are more common and of a higher grade in dives deeper than 30m.
Now it seems general consensus for there to be no need for PFO screening and PFOs are present in 25-30% of the population. However 4-5% of people have a PFO with a large right to left shunt at rest. Members of this population would have a signifiant number of bubbles passing to the arterial side after a repetitive dive to 30m which is common. Even though neurological DCS is much more common in this group it seems that most cases of decompression with arterialisation of many bubbles in this group produces no symptoms.

I was wondering if decompression bubbles, when arterialised, tend to be small enough to simply pass through the arterioles and capillaries and is it a rare occurrence when these bubbles coalesce to form a large bubble the cerebral DCS manifests or are the decompression bubbles ofter large enough to produce damage but are ofter just causing silent lesions hence there being no symptoms?

Thanks Anton
 
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