Two new studies

[Dr Simon Mitchell]

Hello,

I have recently alluded to two new studies of high relevance to technical divers on other old threads, but the fact that these threads were old and had largely run their course may have reduced visibility.

These studies relating to topics that have been discussed here and elsewhere have recently been published and are available to the general public.

The first is a review of the very controversial topic of in water recompression. The review includes some new data of high relevance to the question of whether in water recompression is likely to be of benefit. I have uploaded the pdf of that study to this post.

DOOLETTE DJ, MITCHELL SJ. In water recompression. Diving Hyperbaric Med. 48, 84-95, 2018. doi: 10.28920/dhm48.2.84-95.

The second is a study of the effect of storage modality on partly used CO2 absorbent canisters from rebreathers. It addresses the question of whether you need to store a partly used canister in a sealed container (or not) in order to best preserve its absorbent capacity for the next dive. You can download it here.

POLLOCK NW, GANT N, HARVEY D, MESLEY P, HART J, MITCHELL SJ. Storage of partly used closed-circuit rebreather carbon dioxide absorbent canisters. Diving Hyperbaric Med. 48, 96-101, 2018. doi: 10.28920/dhm48.2.96-101.

I am happy to discuss either of these studies here.

A third study containing new data on the efficacy of temp sticks on warning of CO2 break through in rebreathers will be presented at Eurotek at Birmingham in the first weekend of December. Eurotek is an awesome meeting and I commend it to any tech divers who can make it.

Simon M

 

[Sam Miller III]

Thank you for you for your very informative post.
Very interested reading

Please continue posting

Sam Miller, III

 

[stuartv]

Question: If one were to remove the absorbent canister from a CCR, dry out the counterlungs, loop, etc, then put the absorbent canister back into the CCR for storage, would that qualify as a "sealed container" as defined in this study?

IOW, instead of removing a scrubber pack and storing it in doubled Ziploc bags, is it equally fine to dry out the CCR and store the scrubber pack in the CCR for 28 days?

 

[Dirty-Dog]

Thank you for a very interesting read.
I don't dive rebreathers, but I found the IWR paper fascinating.

 

[rjack321]

Question: If one were to remove the absorbent canister from a CCR, dry out the counterlungs, loop, etc, then put the absorbent canister back into the CCR for storage, would that qualify as a "sealed container" as defined in this study?

IOW, instead of removing a scrubber pack and storing it in doubled Ziploc bags, is it equally fine to dry out the CCR and store the scrubber pack in the CCR for 28 days?

Really? Since this study didn't examine either one of the questions what are you expecting here?

Although humidity is the likely culprit for the slightly reduced runtime after open air storage, without knowing the mechanism of degradation its a bit of a stretch to ask if unstudied conditions are relevant (or not). While a vacuum sealed bag is a much smaller air volume than a CCR, on the other hand the open air degradation was not that dramatic anyway.

 

[Johnoly]

...I am happy to discuss either of these studies here.....

As always, an excellent report on IWR with great insight on what happens in the real world of spearfishing & harvesting that some of us live in.

The cost of dive computer components is dropping rapidly every year and this includes embedded WiFi chipsets mounted on internal PCB boards. One of the key topics that D.A.N. needs to have VERY SOON is to agree with manufacturer's on a standardized data set record layout including field names. HOPEFULLY as diver's bring their dive computer near a wireless hotspot, it will automatically download the tiny dataset in a usable format to a central clearing house like DAN has setup manually now. 5G standards next year are going to make even walking past a car vehicle a hotspot. Auto-download should be an 'opt-out' not an 'opt-in' and anonymous unless you chose to put your contact info in the computer. That will give researchers like yourself a huge database without actually talking to the diver, but making educated guesses of why something happened. Like a followup dive to 30 feet just minutes after a deep deco dive and it would be easy to search for that criteria. You may not have outcome, but you'll have data. IMHO, auto upload of WiFi divelogs is the 'holy grail' for DAN research. Some big guy at DAN needs to step up and corral the manufacturers into a DEMA room in November and start the discussion with their DAN proposed data record layout. Get just one to agree and the rest will follow. Provide bagels too, folks will attend any meeting that has food.

 

[rjack321]

As always, an excellent report on IWR with great insight on what happens in the real world of spearfishing & harvesting that some of us live in.

The cost of dive computer components is dropping rapidly every year and this includes embedded WiFi chipsets mounted on internal PCB boards. One of the key topics that D.A.N. needs to have VERY SOON is to agree with manufacturer's on a standardized data set record layout including field names. HOPEFULLY as diver's bring their dive computer near a wireless hotspot, it will automatically download the tiny dataset in a usable format to a central clearing house like DAN has setup manually now. 5G standards next year are going to make even walking past a car vehicle a hotspot. Auto-download should be an 'opt-out' not an 'opt-in' and anonymous unless you chose to put your contact info in the computer. That will give researchers like yourself a huge database without actually talking to the diver, but making educated guesses of why something happened. Like a followup dive to 30 feet just minutes after a deep deco dive and it would be easy to search for that criteria. You may not have outcome, but you'll have data. IMHO, auto upload of WiFi divelogs is the 'holy grail' for DAN research. Some big guy at DAN needs to step up and corral the manufacturers into a DEMA room in November and start the discussion with their DAN proposed data record layout. Get just one to agree and the rest will follow. Provide bagels too, folks will attend any meeting that has food.

1) its already been done before, 2) no thanks and 3) it wouldn't be useful anyway.

Ross Hemingway has touted his "database" of dives for years (derived from VPM uploads). There are no outcomes and no way to derive outcomes of decompression success, failure or iffy. So the whole thing is useless for biomedical epidemiology research. You can't make "educated guesses" on the medical condition or DCS status of anonymous divers walking past wifi hotspots with the dive computers. For all you know the diver died and its their spouse walking around town trying to sell it.

 

[Dr Simon Mitchell]

Question: If one were to remove the absorbent canister from a CCR, dry out the counterlungs, loop, etc, then put the absorbent canister back into the CCR for storage, would that qualify as a "sealed container" as defined in this study?

IOW, instead of removing a scrubber pack and storing it in doubled Ziploc bags, is it equally fine to dry out the CCR and store the scrubber pack in the CCR for 28 days?

Hi Stuart,

This is a perfectly legitimate question. Not the first time we have been asked it and some seen surprised that we did not test that. The problem with studies like this is that there are many potential "things" (subtle variations to the question) that could be investigated, and sometimes people have trouble understanding why we did not go down these various paths. The answer, of course, is that these studies are very labour intensive, time consuming and costly. Our primary goal here was to establish that storage modality actually makes a difference. It may seem obvious in hindsight now that the facts are known, but prior to this study we did not actually know that, and I personally would not have been surprised if leaving the canister just sitting on a shelf for a month would not have made a difference. We now know it does.

Anyway, to answer your specific question, as rjack says, I cannot give you a definitive answer because the conditions you are interested in are slightly outside the conditions of the study. However, in the paper we do cite a Canadian study that suggested that storage inside a sealed rebreather for a week did not make a difference to absorbent capacity, and I suspect (though cannot say for sure) that so long as the rebreather is sealed, storing sorb for longer periods in this way will not degrade its absorbing capacity.

Hope this answers your question.

Simon

 

[Dr Simon Mitchell]

As always, an excellent report on IWR with great insight on what happens in the real world of spearfishing & harvesting that some of us live in.

Hello Johnoly,

Thank you for your positive comments. It is great that people have an awareness of the limitations of the data we currently have access to.

rjack has alluded to the challenges of your suggestion. Primarily, without outcomes and other relevant clinical data, databases of dives are of limited value, and they are subject to significant selection biases. One plainly obvious one is that divers who die will not submit their dives. I accept this is not a common scenario, but injured divers may be less likely to submit also. There are all sorts of potential selection biases. This is what DAN was trying to get around with project dive exploration where observers were actually out on boats; so that the entire process of dive and outcome was prospectively and directly observed. The obvious problem is the logistic difficulty and cost of such endeavours.

In relation to questions about the potential efficacy of in water recompression, David's access to databases of USN test dives and their outcomes has been invaluable as you will have seen in the paper.

Simon M

 

[Remy B.]

Dr Simon, any new studies on ICD ?