Hello
I find that I cannot post in relevant thread in the DIR forum, so I thought I might put a post here. I don't want this to turn into a deep stops debate. We have been through enough of that already.
I have read the article by Jarrod Jablonski linked to in that thread and I just wanted to share an important perspective. My concern is that the article title puts the question "are deep stops dangerous"? Although the article is typically (for Jarrod) well written and thoughtful, I firmly believe that this title frames the issue in a way that risks inferring that there is a right or wrong answer to the question. It is far more nuanced than that.
The truth is that every decompression needs a deepest stop. The real question is "how deep should that deepest stop be"? Throughout the debate on deep stops, the position I and my colleagues have taken revolves entirely around the concept of decompression "efficiency". If you have X amount of time that you are going to spend decompressing, then what is the optimal distribution of decompression stop depths and times that will give you the safest outcome? Succinctly, the safest decompression for X amount of decompression time.
We have imperfect answers to that question of course, but the fact is that the only human evidence available at this time suggests that bubble models such s VPM and RGBM impose stops that are too deep for the most efficient decompression. In other words, if you spent the same time decompressing as proposed by those algorithms for a particular dive, but de-emphasized the deepest stops and spent more time shallow stopping (I reiterate, for the same total decompression time), then you would probably reduce the risk associated with the dive. This, of course, unveils the potential flaw in the argument that you can do bubble model style deeper stops but do longer shallower stops as well to make up for the extra uptake of gas during the deeper stops. Maybe, but it may also be that if you took this now longer decompression, did the same decompression time but less deep stops and decompressed shallower for longer, then that might be more efficient too.
But this does not mean that "deep stops" per se are bad (I reiterate every decompression has to have its deepest stop), or by inference that decompression plans should be moved shallower and shallower (eg if you believe the answer to "are deep stops dangerous" is yes). Indeed, if you progress too far down the latter path, then efficiency will start to fall and decompressions will become less safe. Unfortunately, the bitter nature of the debates on this matter, and the need to defend the human data against irrational attack, has tended to make the issue seem more polarized than it really. It has risked creating a belief that endlessly shallower is better. No one has ever said that, and the position that I and my colleagues have taken should not be interpreted that way.
Simon M
I find that I cannot post in relevant thread in the DIR forum, so I thought I might put a post here. I don't want this to turn into a deep stops debate. We have been through enough of that already.
I have read the article by Jarrod Jablonski linked to in that thread and I just wanted to share an important perspective. My concern is that the article title puts the question "are deep stops dangerous"? Although the article is typically (for Jarrod) well written and thoughtful, I firmly believe that this title frames the issue in a way that risks inferring that there is a right or wrong answer to the question. It is far more nuanced than that.
The truth is that every decompression needs a deepest stop. The real question is "how deep should that deepest stop be"? Throughout the debate on deep stops, the position I and my colleagues have taken revolves entirely around the concept of decompression "efficiency". If you have X amount of time that you are going to spend decompressing, then what is the optimal distribution of decompression stop depths and times that will give you the safest outcome? Succinctly, the safest decompression for X amount of decompression time.
We have imperfect answers to that question of course, but the fact is that the only human evidence available at this time suggests that bubble models such s VPM and RGBM impose stops that are too deep for the most efficient decompression. In other words, if you spent the same time decompressing as proposed by those algorithms for a particular dive, but de-emphasized the deepest stops and spent more time shallow stopping (I reiterate, for the same total decompression time), then you would probably reduce the risk associated with the dive. This, of course, unveils the potential flaw in the argument that you can do bubble model style deeper stops but do longer shallower stops as well to make up for the extra uptake of gas during the deeper stops. Maybe, but it may also be that if you took this now longer decompression, did the same decompression time but less deep stops and decompressed shallower for longer, then that might be more efficient too.
But this does not mean that "deep stops" per se are bad (I reiterate every decompression has to have its deepest stop), or by inference that decompression plans should be moved shallower and shallower (eg if you believe the answer to "are deep stops dangerous" is yes). Indeed, if you progress too far down the latter path, then efficiency will start to fall and decompressions will become less safe. Unfortunately, the bitter nature of the debates on this matter, and the need to defend the human data against irrational attack, has tended to make the issue seem more polarized than it really. It has risked creating a belief that endlessly shallower is better. No one has ever said that, and the position that I and my colleagues have taken should not be interpreted that way.
Simon M
