Safe Ascent

[DCBC]

How fast do you ascend and what are the variables? How do you monitor your ascent rate?

[Kevin Carlisle]

I like to go slow. Not always possible due to the high flow spring systems I dive. When I have a place where I do ascend faster then I should, ( fissures, ect. ) once clear I will usually give myself a one or two minute window for a safety stop. Just a peace of mind type thing. I use my computer some but I know the profiles of the places I dive. If the computer died I could tell you my depth at most placse I go.

[TSandM]

On a recreational dive, I do 30 fpm to half my average depth (or the depth I begin my ascent from, whichever is deeper), and then 10 fpm to the surface. I do that by leaving my current depth at "x" minutes and not leaving the next depth until "x+1". That may require a short period of stop, if my actual ascent rate has been faster than the goal. (For example, I leave 30 feet at 3 minutes and arrive at 20 at 3:30, then I stay there until 4:00.)

[vladimir]

I watch my computers. My Suunto has a maximum rate of 10 meters per minute built in, and my Uwatec has a variable rate that is close enough that i never notice the difference. I like the indicator on the Uwatec better--it displays your ascent as a percentage of the maximum rate. I generally ascend much slower than my computers require, especially during the last 5 meters.

[Blackwood]

What Lynne said.

30fpm deep, 10fpm average shallow (where I generally move at 20fpm, with 30 second stops).

[gcbryan]

If you're taking about a minimum safe ascent I would do what many of the others are doing...30 fpm/deep stop/10fpm but unless it was a wreck and I was coming up an anchor line and actually needed to do a minimum ascent I would do more from 30 fsw to the surface.

As far as my normal shore dive profile it would be much more from 30 fsw to the surface...usually around 15 minutes if there is plenty to look at. I would prefer to hit my deepest depth very early in the dive, have most of the dive be a slow decompression in effect (less time spent in the middle depths connecting the deeper and shallower portions) and then the longer optional time spent at 30 fsw and above.

[muddiver]

I still do the 30' per min per the USN. All of my computers have the same ascent rate programed in. Some times I even stop at 20' for :03 to :05.

[boulderjohn]

This DAN article might be interesting:

DAN Divers Alert Network (http://www.diversalertnetwork.org/news/Article.aspx?newsid=514)

[TSandM]

It's an interesting paper, but I wonder where they come up with the idea that it is KNOWN that the spinal cord has a 12.5 minute halftime? As far as I know, the only studies that attempted to measure tissue tensions in real time were done a long time ago by the Navy, and those data are not generally available. And I don't know whether they measured washout.

[Michael_Lambert]

Recreational I ascend at 30 FPM till the shallows then tend to hang out a bit more 1 min @ 30, 20 and 10. I watch my computer and BT for my accent rates.

[DCBC]

It's an interesting paper, but I wonder where they come up with the idea that it is KNOWN that the spinal cord has a 12.5 minute halftime?

I think that DAN took this from the book "Diving and Sub-Aquatic Medicine," by Edmonds, Lowry and Pennefather (I think it was published in the early 90's). I find it interesting that the spinal cord has the same 12.5 minute halftime for both Nitrogen and Helium where other tissues diffuse Nitrogen at a much slower rate.

[rjack321]

This DAN article might be interesting:

DAN Divers Alert Network (http://www.diversalertnetwork.org/news/Article.aspx?newsid=514)

Try the original papers, much better.
2004 paper
Rubicon Research Repository: Item 123456789/1520 (http://archive.rubicon-foundation.org/1520)

2007 paper updating the work and describing how just taking 1 min of a 3min safety stop and moving it deeper (to 50fsw) is inadequate.
Rubicon Research Repository: Item 123456789/7901 (http://archive.rubicon-foundation.org/7901)

Personally, I really start slowing the ascent at about 50% of the depth for recreational dives or about 1.8atas up from the bottom for deco dives.

[boulderjohn]

2007 paper updating the work and describing how just taking 1 min of a 3min safety stop and moving it deeper (to 50fsw) is inadequate.
Rubicon Research Repository: Item 123456789/7901 (http://archive.rubicon-foundation.org/7901)

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The 2007 paper is quite interesting. I was especially interesting in the poor results for one minute stops.

It seems to me that all the papers studied indicate a preference for a relatively fast ascent with more extensive stops at a prescribed depths rather than a very slow ascent. It would seem to me that a slow ascent with 1 minute stops would be pretty similar to a very slow ascent without stops, which they did not see as being as good. This would appear to me to be especially true of protocols that call for a series of one minute stops that include the travel time between stops as a part of the stop time.

[TSandM]

As I recall Marroni's work, though, they used the same ascent rate throughout -- in other words, if they did a 75 foot dive, they did a 10 fpm ascent from 75 feet. I wasn't all that surprised that that slow an ascent rate wasn't optimal from that depth.

The math strongly suggests that ascent rates ought to change as one gets shallower.

[boulderjohn]

The math strongly suggests that ascent rates ought to change as one gets shallower.

I agree.

[AfterDark]

I always used 60fpm or no faster than my smallest bubbles.

[gcbryan]

I think that 1 minute stops are less about the stop and more about making sure you slowed the ascent down.

A 1 minute stop for a deep stop isn't really enough time for any significant offgassing to occur even for the faster compartments.

Slowing the ascent down until you are well shallow of the controlling tissue offgassing point does nothing regarding offgassing.

I don't think these limited studies really showed much one way or the other.

[AfterDark]

I think that 1 minute stops are less about the stop and more about making sure you slowed the ascent down.

A 1 minute stop for a deep stop isn't really enough time for any significant offgassing to occur even for the faster compartments.

Slowing the ascent down until you are well shallow of the controlling tissue offgassing point does nothing regarding offgassing.

I don't think these limited studies really showed much one way or the other.

I've always added time onto the last stop on decom dives. A few minutes more at 10' isn't going to do any harm and could be difference from wondering what that rash is from?:dontknow::confused:

[Blackwood]

I think that 1 minute stops are less about the stop and more about making sure you slowed the ascent down.

Exactly. It makes monitoring and controlling ascent rates easier.

Most of us can count to 10 seconds fairly accurately, but much beyond that we get off beat. (Other of us have seconds on our timing device).

So take the paradigm Lynne suggested: 30fpm to half your Dmax, and 10fpm to the surface.

On a dive from 100 feet, that would mean that every 10 seconds, you move 5 feet until you hit 50FSW.

1...2...3...4...5...6...7...8...9...0

Easy to count, easy to keep track.

Once you make it to 50, you can keep MOVING at the same rate, but add stops which will average out the shallow portion of your ascent to 10fpm. In the above case, move 30fpm (or 5f/10s), and stop for 40 seconds. Lather, rinse, repeat, surface.

[Karel26]

I just use my dive watch and then i keep looking up to keep up with my bubbles so that i know if my watch die then i can still ascent with out it. .

[divengolf]

(Other of us have seconds on our timing device).

Blackwood:

What BT do you use with seconds on it??

I've not seen a UWATEC with seconds.

Harry

[Blackwood]

Blackwood:

What BT do you use with seconds on it??

I've not seen a UWATEC with seconds.

Harry

My Uwatec Tec2g has resettable seconds, though I don't know if the stopwatch function is available unless you are in gauge mode.

[roturner]

How fast do you ascend and what are the variables? How do you monitor your ascent rate?

I'm not saying that this is the best way to do things but this is what I do:

1) on a no-deco dive I ascend to 1/2 of my maximum depth and start counting Fibonacci (rounded to the nearest 3 metres) at that point. For example, if I'm making a dive to 36 metres then my first "stop" is at 18 metres for 1 min. Then I work with 18, 15, 12, 9, 6 and count stops like 1,1,2,3,5. After the 5 minute stop I'm clear to ascend. If I reach a "stop" depth earlier than my clock does then I wait at that depth for my clock to catch up before starting with timing my stop.

For deco dives the strategy depends to a much greater extent on the profile so I won't go into that here.

My "target" ascent rate is 10 metres per min. If I don't achieve that then I sort it out by waiting longer at a deep stop if necessary or by adding the extra ascent time to my bottom time if I ascended too slowly.

R..

[Blackwood]

Yowzers. I'll do quasi-fibonacci sometimes, but not for NDL dives.

[muddiver]

Interesting, all the deep analysis and deco theory that is coming out. I've been diving for approx. 25 years, max. depth of 135 fsw, use a 30 fpm ascent rate with / or without safety stop and I have never been bent, or had any symptoms of DCS.

Why do ascent rates have to be so complicated? :shakehead:

It's recreation for Christ sakes!

[gcbryan]

Interesting, all the deep analysis and deco theory that is coming out. I've been diving for approx. 25 years, max. depth of 135 fsw, use a 30 fpm ascent rate with / or without safety stop and I have never been bent, or had any symptoms of DCS.

Why do ascent rates have to be so complicated? :shakehead:

It's recreation for Christ sakes!

What does recreation have to do with whether something is complicated or not?

I agree fibonacci is complicating things terminology wise!

[roturner]

Yowzers. I'll do quasi-fibonacci sometimes, but not for NDL dives.


It's not as bad as it sounds. We usually ascend over the bottom so it's like riding the computer but with the brain engaged. It's not that complicated.

R..

[Blackwood]

It's not as bad as it sounds. We usually ascend over the bottom so it's like riding the computer but with the brain engaged. It's not that complicated.

R..

I'm not saying it's complicated. I'm saying it's overkill.

But yah, if you have something to look at, go for it!