Who should I listen to?

[DCBC]

There are two correct answers to your question (or could be). In any class that's evaluated by an Instructor, the correct answer (for examination purposes) is what the Instructor has indicated. Sometimes this "correct answer" will change with time (what the current science recommends) and the degree of exposure (depth/duration).

On a deep technical dive I ascend at 60 FPM to my first decompression stop, 30 FPM to 30 FSW (stopping at my required stops) and 10 FPM thereafter. The most dangerous area is the final 30 FSW; why be in a hurray? Keep in-mind that the rates you have mentioned are maximum ascent rates; slow down the ascent, it's worked for me for almost 50 years. Just be sure to plan for this time in your dive plan (gas consumption).

 

[ARDory]

maybe a consolation prize.

 

[Foxfish]

Agreed with what others have said. 30 ft/min is considered the optimal and 60 ft/min the maximum. In the unlikely event you run out of air and your buddy runs low on reserve air, you can ascend at the maximum speed. You increase your chance of getting bent but bent is better than drowned.

 

[danvolker]

Agreed with what others have said. 30 ft/min is considered the optimal and 60 ft/min the maximum. In the unlikely event you run out of air and your buddy runs low on reserve air, you can ascend at the maximum speed. You increase your chance of getting bent but bent is better than drowned.

I know this is how things are taught, so this is a moral way to explain it.....on the other hand, as one of the people that did many thousands of dives between 1972 and 1990--doing the 60 foot per minute ascents--basically just ascending at the speed of the small bubbles---I never had DCS, never had any friends that got DCS, and to this day I DON'T BELIEVE the agency position that 60 fpm is less safe for "Healthy" divers than 30 fpm..... I think we have a much larger population today of un-healthy divers---divers with severe circulation problems, whether from diabetes, PFO's, or worse....and I really don't need to concern myself with how their safe ascent rates have ANYTHING to do with mine.....on the other hand, when divers began doing the slow 30 ft per minute ascents in the 90's, so did I--but I have never forgotten that if I have a reason to come up faster, there os no reason for me not to

 

[DCBC]

I know this is how things are taught, so this is a moral way to explain it.....on the other hand, as one of the people that did many thousands of dives between 1972 and 1990--doing the 60 foot per minute ascents--basically just ascending at the speed of the small bubbles---I never had DCS, never had any friends that got DCS, and to this day I DON'T BELIEVE the agency position that 60 fpm is less safe for "Healthy" divers than 30 fpm..... I think we have a much larger population today of un-healthy divers---divers with severe circulation problems, whether from diabetes, PFO's, or worse....and I really don't need to concern myself with how their safe ascent rates have ANYTHING to do with mine.....on the other hand, when divers began doing the slow 30 ft per minute ascents in the 90's, so did I--but I have never forgotten that if I have a reason to come up faster, there os no reason for me not to

The US Navy Tables of the time period you specified stipulated an ascent rate of 60 FPM. Navy divers at that time (of which I was one) developed DCS in 2.2% of the dives made. In other words, it was considered acceptable for a Diver to develop some form of DCS in one of every 50 dives made.

In the 70's I was the Diving Operations Officer at DCIEM. As such, I was involved in numerous chamber dives that provided doppler testing of Nitrogen build up. These dives helped revise the DCIEM decompression tables of the time and created new Helium Tables that were adopted by the US Navy. Results clearly showed that an ascent rate of 60 FPM (especially above 30 FSW) was too fast and increased the chance of injury.

I would like to clarify your statement "but I have never forgotten that if I have a reason to come up faster, there is no reason for me not to" withstanding that this is posted in the "New Diver and Those Considering Diving Forum." I believe what you are meaning is that attaining the surface (at any ascent rate) is preferable than not attaining the surface at all; or that DCS is preferable to drowning and death...

 

[victorzamora]

I believe what you are meaning is that attaining the surface (at any ascent rate) is preferable than not attaining the surface at all; or that DCS is preferable to drowning and death...

The way I read it was "better bent than dead"

However, reading your post was really interesting. 2.2% DCS is horrifying!!

Sent from my Samsung Galaxy S4 using Tapatalk

 

[maniago]

The way I read it was "better bent than dead"

As a professional diving zombie, I'm offended by this remark!

Haha, just kidding!

 

[danvolker]

The US Navy Tables of the time period you specified stipulated an ascent rate of 60 FPM. Navy divers at that time (of which I was one) developed DCS in 2.2% of the dives made. In other words, it was considered acceptable for a Diver to develop some form of DCS in one of every 50 dives made.

In the 70's I was the Diving Operations Officer at DCIEM. As such, I was involved in numerous chamber dives that provided doppler testing of Nitrogen build up. These dives helped revise the DCIEM decompression tables of the time and created new Helium Tables that were adopted by the US Navy. Results clearly showed that an ascent rate of 60 FPM (especially above 30 FSW) was too fast and increased the chance of injury.

I would like to clarify your statement "but I have never forgotten that if I have a reason to come up faster, there is no reason for me not to" withstanding that this is posted in the "New Diver and Those Considering Diving Forum." I believe what you are meaning is that attaining the surface (at any ascent rate) is preferable than not attaining the surface at all; or that DCS is preferable to drowning and death...

Yes....the reason for posting is that I have seen so many divers that cling tenaciously to the 30 foot ascent speed and 3 minute minimum safety stop--that when they actually have a real problem, say a diaphragm blew on their reg and it's dumping.....and they do this incredibly slow ascent, and think if they don't hang for a few minutes they will die.....

The thing is, they don't have this in perspective..that was my point. For me, I know I could do 1000 dives in the next 2 years and use 60 ft p/m instead of 30...and I'd be fine. So while I will typically use 30, if I see a sailfish on the surface, or a whaleshark, or if my reg blows...( and let's pretend my buddy is no where around)....then I am using the 60 ft per minute ascent rate.


And while I should just drop this here...because "better than drowning" is the real answer for this forum...you know how I can't help myself with some of the agency issues....

Please correct me if I'm wrong, but it was my understanding when we were using the Navy Tables in the 90's, that they were based on pretty "average" Navy volunteers...this is not a population of Navy Seals with VO2 Max that is off the chart, and no medical issues...but it was a population full of average people, including the 25% that would have a PFO.

With this in mind, it occurs to me that the 2.2% of divers developing DCS -- would be more likely to be due to medical issues like the PFO or impaired circulation ( a badly sprained muscle among other issues) --than it would be due to 60 fpm being bad for the healthy divers or those with high VO2Max ( with attendant peripheral adaptations to intense exercise --such as the large increase in capilary beds in muscles and general perfusion--allowing more effective off-gassing ).

I have never liked following a single, general statistical model....I like things that are individualized. I would rather tell a new diver that happens to be a competitive cyclist that they may well be just fine with 60 feet per minute plus a hang at 20.....or...tell someone that is 60 pounds overweight and diabetic, that they ought to do 30 feet per minute, with several stops on the way up ( in other words, find an even more applicable model for them).

 

[DCBC]

...you know how I can't help myself with some of the agency issues....

Yes, in the past we have shared this concern.

Please correct me if I'm wrong, but it was my understanding when we were using the Navy Tables in the 90's, that they were based on pretty "average" Navy volunteers...this is not a population of Navy Seals with VO2 Max that is off the chart, and no medical issues...but it was a population full of average people, including the 25% that would have a PFO.

The Navy Tables (like the DCIEM military tables) have always been specifically designed for Navy Divers; young men with an extreme level of physical fitness and able to pass a Navy Diving Medical. When I was at DCIEM, we wrote a separate set of Tables for Sport Diving which were more liberal.

The 2.2% figure pertains to qualified Navy Divers using the 60 FPM protocol at the limit of the tables, but marginally within them. My point was that it`s relatively easy to get bent by following the older tables that do not employ a slower ascent rate. In any regard, I think that it`s clear that you have a greater chance of DCS at 60 FPM than 30 FPM and above 30FSW your risk is decreased if you ascend at 10FPM.

...I have never liked following a single, general statistical model....I like things that are individualized. I would rather tell a new diver that happens to be a competitive cyclist that they may well be just fine with 60 feet per minute plus a hang at 20.....or...tell someone that is 60 pounds overweight and diabetic, that they ought to do 30 feet per minute, with several stops on the way up ( in other words, find an even more applicable model for them).

Absolutely, when fitness is low or medical conditions are present, the individual must weigh the risk factors and accept them before the dive begins. That said, some people decide to accept dive plans that are not optimal. I`m aware that my risk increases if I`m diving in a cave, wreck, or on deep Heliox. Each of us must be directed by our physical and mental condition-attitude, level of confidence, training and experience. Afterall each of us are the ones that must accept or reject the risk and pay the piper if required.

 

[Foxfish]

According to the PADI deep diver course book (Rev 02/13), the 18 m / 60 ft per minute ascent rate was not based on any test data but rather a compromise between what the US Navy hardhat and frogmen divers wanted (25 and 100 feet per minute respectively). The testing for the US Navy and the current PADI recreational diving tables were based on the 18 m / 60 ft per minute ascent rate. The US Navy changed the rate to 9 m per minute in recent times.