Got bent, preferred IWR to my local chamber

[AbyssDiver1983]

L

I cannot possibly tell that. It might be. It might not be. As I said, I got bent on a dive for which there simply should not have been a problem. In fact, for some reason I had decided to be extra careful that day. I did two NDL dives (admittedly to the edge of NDL) and did extended safety stops while breathing oxygen. I should not have had a problem.

Like you said in your first reply, there’s a lot of guesswork in this sport.

 

[Searcaigh]

@AbyssDiver1983

Sorry to hear that you got a hit, but happy to hear that you managed to resolve it with your dive buddies.

Within my tech group we have two Kirby Morgan FFMs two switch blocks and associated O2 clean regs and QD connectors. We did an IANTD IWR Course a few years ago and your post reminds me that we need to do a refresher.

I was a bit apprehensive of breathing 100% at 9m when we did the course but none of us had any adverse events so proving that it is reasonably safe to do IWR.

Where we normally dive off Fujairah in the UAE involves a drive over an altitude of 600m (IIRC) and there's no chamber on that side of the country.

Prior to our IWR course one of our group had a hit (shoulder pain) after a 70m dive on one of the wrecks. He was put on 100% and on the way to Dubai for a chamber ride he definitely felt some twinges despite breathing 100% during the drive over the mountains. Had we done the IWR courses prior to this we would certainly have had no issues doing the IWR as it was normal for us to carry several AL80 with 100%

I hope you recover with no issues.

 

[AbyssDiver1983]

T

@AbyssDiver1983

Sorry to hear that you got a hit, but happy to hear that you managed to resolve it with your dive buddies.

Within my tech group we have two Kirby Morgan FFMs two switch blocks and associated O2 clean regs and QD connectors. We did an IANTD IWR Course a few years ago and your post reminds me that we need to do a refresher.

I was a bit apprehensive of breathing 100% at 9m when we did the course but none of us had any adverse events so proving that it is reasonably safe to do IWR.

Where we normally dive off Fujairah in the UAE involves a drive over an altitude of 600m (IIRC) and there's no chamber on that side of the country.

Prior to our IWR course one of our group had a hit (shoulder pain) after a 70m dive on one of the wrecks. He was put on 100% and on the way to Dubai for a chamber ride he definitely felt some twinges despite breathing 100% during the drive over the mountains. Had we done the IWR courses prior to this we would certainly have had no issues doing the IWR as it was normal for us to carry several AL80 with 100%

I hope you recover with no issues.

Thanks, appreciate the concern
Your gear makes me feel we’re under-equipped.. I’m buying the damn FFM on Monday

 

[tursiops]

I doubt that they can fly at low altitude for the entire flight. They need to be able to change altitude to deal with varying weather and other conditions in the course of the flight.

From the US's FAA website:

The advantage of air ambulance transportation is that the cabin pressures may be controlled and limited much more closely than on a commercial aircraft, which will typically operate at the equivalent of 7,000-8,000 feet (barometric pressure of ~550 mmHg), although limiting the cabin altitude to 1,000 or 2,000 feet, or even to the altitude of the departure airport can seriously limit the range of most air ambulances with pressurized cabins, sometimes reducing the operating range by 50%, because the aircraft can no longer climb to its fuel efficient cruise altitude. Certain conditions, such as transporting decompression sickness patients to centers for hyperbaric treatment mandate cabin pressure limits.​

So at least in the US, a proper air ambulance can maintain SL cabin pressure if necessary, but with reduced altitudes thus reduced ranges. The quote is unclear on what those operating altitudes are, just that they are reduced.

 

[BoltSnap]

From the US's FAA website:

The advantage of air ambulance transportation is that the cabin pressures may be controlled and limited much more closely than on a commercial aircraft, which will typically operate at the equivalent of 7,000-8,000 feet (barometric pressure of ~550 mmHg), although limiting the cabin altitude to 1,000 or 2,000 feet, or even to the altitude of the departure airport can seriously limit the range of most air ambulances with pressurized cabins, sometimes reducing the operating range by 50%, because the aircraft can no longer climb to its fuel efficient cruise altitude. Certain conditions, such as transporting decompression sickness patients to centers for hyperbaric treatment mandate cabin pressure limits.​

So at least in the US, a proper air ambulance can maintain SL cabin pressure if necessary, but with reduced altitudes thus reduced ranges. The quote is unclear on what those operating altitudes are, just that they are reduced.

I am not an expert and thus I can't give any further opinions. I am relaying information I heard in a dive medicine conference I attended few years ago.

 

[beester]

@AbyssDiver1983
I was a bit apprehensive of breathing 100% at 9m when we did the course but none of us had any adverse events so proving that it is reasonably safe to do IWR.
.

I once was part of a scientific study, examining oxygen toxicity on lungs. Basically they needed guinea pigs. So they had 17 divers spending 120 minutes at 15m breathing a mix of 64% nitrox = 1.6 PPO² in a big indoor pool. Our CNS clocks went through the roof (all above 200%), there were safety divers, and a lot of medical staff in place in case any of us toxed out. Nothing happened.

I wouldn't take these kind of chances in a non controlled environment, and key word here was as well a max PPO² of 1.6 and not pure Oxygen. But if IWR is the only option and you have a team that knows the process and a full face mask to avoid drowning when you do tox out, yes why not. I do include the process and some explanation in most of the deco classes I teach.

 

[johndiver999]

I should’ve taken some surface O2 right after the dive just to be safe. But to be fair, the pain at that point was quite minor, and like I said I’ve had injuries before. My rotator cuff’s been through hell, so the differential diagnosis was not as straightforward as you reckon, that’s why the dive profile was a deciding factor. The truly excruciating pain began 6hrs later. I’m a proponent of IWR for sure, but IWR carries its own risks, so I don’t agree that jumping back in the water on pure O2 is the best thing to do every time you surface with minor discomfort. Thanks for the advice, but I’m keeping my dive buddies, the decision to go back in the water was based on my trust in their abilities.

I think you are getting good advice, but the mindset of assuming that you must not be bent because the computer says so (especially after a deco dive) ... is a bad one. As an earlier poster said, most of the people who get bent have followed the computer.

Checking the computer might have some value, for example if it shows the victim made a significant violation of deco, ascent rate etc. - then that information could reasonably be used to HELP support the findings of a suspected DCI hit. Conversely, unless the dive was completely trivial (with respect to: time, depth and ascent rate) then a computer that shows no violations should NOT be used to rule out a suspected DCI diagnosis. This distinction should be obvious, if you do deco diving.

I pretty much always try to have a scuba bottle of oxygen on the boat and I would not be hesitant to use it even if I did a non-deco dive and the computer says all is well.

 

[AbyssDiver1983]

I think you are getting good advice, but the mindset of assuming that you must not be bent because the computer says so (especially after a deco dive) ... is a bad one. As an earlier poster said, most of the people who get bent have followed the computer.

Checking the computer might have some value, for example if it shows the victim made a significant violation of deco, ascent rate etc. - then that information could reasonably be used to HELP support the findings of a suspected DCI hit. Conversely, unless the dive was completely trivial (with respect to: time, depth and ascent rate) then a computer that shows no violations should NOT be used to rule out a suspected DCI diagnosis. This distinction should be obvious, if you do deco diving.

I pretty much always try to have a scuba bottle of oxygen on the boat and I would not be hesitant to use it even if I did a non-deco dive and the computer says all is well.

You are right for sure. Just saying my previous rotator cuff pain, the low level of pain at that moment and the clean dive profile threw me a curve ball. If I had any other symptoms I would’ve gone straight to O2. Anyway from now on I’m getting on the O2 ASAP if I feel any discomfort after a dive. Like @tursiops said, O2 can be done while discussing other options. And as @beester mentioned, O2 can help determine if it was a hit or not.

 

[AbyssDiver1983]

I once was part of a scientific study, examining oxygen toxicity on lungs. Basically they needed guinea pigs. So they had 17 divers spending 120 minutes at 15m breathing a mix of 64% nitrox = 1.6 PPO² in a big indoor pool. Our CNS clocks went through the roof (all above 200%), there were safety divers, and a lot of medical staff in place in case any of us toxed out. Nothing happened.

I wouldn't take these kind of chances in a non controlled environment, and key word here was as well a max PPO² of 1.6 and not pure Oxygen. But if IWR is the only option and you have a team that knows the process and a full face mask to avoid drowning when you do tox out, yes why not. I do include the process and some explanation in most of the deco classes I teach.

View attachment 682394

What we did was a mix of the Australian (slow ascent rate) and US Navy (9/6/3) tables with 2 airbreaks.

 

[KenGordon]

Is 30/70 "conservative"?

What does "conservative" actually mean? What you describe is how the word is usually used in diving, but if by "conservative" you actually mean "safer," you may be wrong in that belief. There is no doubt that a GF high of 70 is safer than 80+. It is the GF lo of 30 that is of concern. In most modern diving thought, a GF that low is riskier than a higher one.

Evolving Thought on Deep Decompression Stops
Gradient Factors in a Post-Deep Stops World

This is a red herring. The difference between 30/70 and 50/70 or 50/80 is much smaller than his late arrival at stops looking at his screenshot. We are talking a couple of minutes at 18m really and he will have been doing a gas switch then anyway. This isn’t all that long a dive that GF low would have a big impact.

Deco algorithms are about probability. Some of the time a given profile will bend someone, some of the time the same profile will not bend that same person. If you want cause and effect then the cause is diving.