Deco For Divers, Ed 2, And Speed Of Helium Off-gas

[archer1960]

You'd need a few dozen volunteers to get anywhere near statistically meaningful numbers and I very much doubt a chamber big enough even exists.

You don't have to run them all at the same time...

 

[huzenhagen]

So David doolette has done some other work looking at the number needed and depending on the control profile you may only need 100 people (50 in each arm) to have a meaningful difference in VGE (a surrogate for DCS) which is the only way you'd be able to conduct these studies outside of the military as it isn't going to get past a normal ethics committee.

 

[dmaziuk]

You don't have to run them all at the same time...

That's debatable, ideally you do. But once you multiply the dive times required, plus the chamber time, by the number of groups, you'll realise there's just not enough hours in the day to do this two-three divers at a time. Ethics, shmethics: getting that many people bent/unbent is simply a logistical nightmare.

 

[archer1960]

That's debatable, ideally you do. But once you multiply the dive times required, plus the chamber time, by the number of groups, you'll realise there's just not enough hours in the day to do this two-three divers at a time. Ethics, shmethics: getting that many people bent/unbent is simply a logistical nightmare.

You don't have to do it all in one day, and hopefully the number of people who get bent is relatively small. When DAN does research at Duke University, chambers, they spread it over several weeks. As long as the various environmental conditions (temperature, dive profile, workload, etc) that affect DCS are well controlled, it doesn't matter how long it takes to do the study. However, I'm sure you're correct about getting the study past an ethics committee; it will never happen.

 

[KevinNM]

This is why deco studies are hugely costly. Only the big commercial interests and the military have the need and money for these, and the migration to ROVs and atmosphere suits has greatly reduced the commercial willingness to fund these.

 

[dmaziuk]

You don't have to do it all in one day, and hopefully the number of people who get bent is relatively small. When DAN does research at Duke University, chambers, they spread it over several weeks. As long as the various environmental conditions (temperature, dive profile, workload, etc) that affect DCS are well controlled, it doesn't matter how long it takes to do the study.

Ah, but that's the point: they're not. E.g. our various vitals change throughout the day, if I do the same dive now or five hours later, my pulse rate & BP won't be the same. So you have to factor in that and add still more dives to compensate and weeks turn into enough months you've to factor in your subjects' ageing...