125 feet air dive DCS risk?

[Duke Dive Medicine]

Thanks for the link, good read.
That makes total sense to me, I imagine the original testing by Buhlmann et al was conducted in a range far shallower than the dives being conducted now. Any algorithm shaped to experimental data is going to lose a lot of utility as you move out of that range.

However for 30 ish metre dives there must be a gajillion dives performed on any number of DCs with all kinds of algorithms without people getting bent all outta shape.

I think that in this particular case, the gas mix and even the water temps to a certain degree are of secondary concern.

As @Diver0001 said, these are dives any Rec diver would be pretty happy to do on any mix with any algorithm and be quite confident of success. I really think the issue here is an individual susceptibility which means the only valid advice would be to go see a good hyperbaric physician and see what's what.

You're welcome!

The probability of DCS at that depth is still not zero. If the same diver experienced repeated similar unexplained hits it would be time to talk about carefully controlling risk factors like temperature (which at 39-40 F could well have played a role here IMO), diving more conservatively, not pushing the edge of the algorithm as you already alluded to, and getting trained to decompress using hyperoxic mixes. There's not much else a hyperbaric physician could say.

Best regards,
DDM

 

[Kevrumbo]

@Into the Water :

Actually rounding conservatively the diver's multi-level profiles to 21m ave depth for 40min (an acceptable compensatory protocol motivated by the cold 4 deg C water temp), the diver was over the NoStop time into mandatory deco based on UTD's Air NDL/Min Deco Table:

Depth : NoStop Time
40'/12m 170min
50'/15m 60min
60'/18m 50min
70'/21m 35min
80'/24m 30min
90'/27m 25min
100'/30m 20min
110'/33m 15min
120'/36m 10min
130'/39m 5min

So a Ratio Deco profile with Oxygen switch at 6m would have looked like this:

9 meters/min ascent rate from 21m to 12m depth (1min);
12m: Stop for 30sec;
9m: Stop for 1min;
6m: 100% O2 gas switch, and slow 1meter/min ascent rate to surface (6min);
or alternatively, O2 Stop at 6m depth for 6min, if the surface conditions are rough.

 

[Rred]

Warm water: Well, even the USN noted many years ago that diving in cold water (assuming your dry suit wasn't perfectly toasty) "should" require going up one depth/time group to compensate for the effects of the cold. (And I know one of the major dive certification groups here finally makes a similar note on their dive tables.) So warm water definitely should help.

Have been poking around today including the DAN web site, where one article mentioned that the typical rate of DCS in sport divers (~4:10,000) can be cut in half or better if the divers only use 1/2 of the recommended normal no-decompression times. Bearing in mind that the "safe" limits are only "safe most of the time" and that all of the anatomical processes involved with DCS are not fully known or understood, and most of the new algorithms (including the top secret custom ones in every computer) have not been studied in any actual large population of divers...

Some divers are supposed to get bent, when using the normal safe tables/computers. Ugly truth. So you might want to bump the safety factor up to "2" even in warm water. Less bottom time, yes, inconvenient. DCS? More inconvenient.