Got bent, preferred IWR to my local chamber

[Julius SCHMIDT]

Interesting question. Yes, my shoulder strap was tighter than usual. I dive a halcyon infinity BC so I adjust before every dive and I must’ve pulled the right side too hard. We considered it as a risk factor especially since the exertion at depth was with the right arm.

What's happened is that you have restricted the vessels in your armpit with your shoulder strap, so a slower ongas and offgas than the rest of your body. Once you took off your "halcyon infinity BC" and released the pressure you got circulation back, and out came the bubbles whoosh!!!!!

 

[AbyssDiver1983]

What's happened is that you have restricted the vessels in your armpit with your shoulder strap, so a slower ongas and offgas than the rest of your body. Once you took off your "halcyon infinity BC" and released the pressure you got circulation back, and out came the bubbles whoosh!!!!!

That sounds quite plausible. Because there’s no chest strap the thing isn’t comfortable underwater unless the shoulder straps are pulled tight, must’ve overdid it. Will keep in mind

 

[AbyssDiver1983]

What's happened is that you have restricted the vessels in your armpit with your shoulder strap, so a slower ongas and offgas than the rest of your body. Once you took off your "halcyon infinity BC" and released the pressure you got circulation back, and out came the bubbles whoosh!!!!!

Don’t get your use of parentheses though, anything you’re trying to “say”?

 

[boulderjohn]

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.

If you read carefully, you will see that at no time did I say that was the cause of his DCS. In fact, when he specifically asked that, I said I had no idea what caused his DCS. I was speaking for the fact that a lower GF number does not make the profile safer.

Are you disputing that?

 

[KenGordon]

If you read carefully, you will see that at no time did I say that was the cause of his DCS. In fact, when he specifically asked that, I said I had no idea what caused his DCS. I was speaking for the fact that a lower GF number does not make the profile safer.

Are you disputing that?

I am saying that his GF low had nothing to do with his profile and so discussing it is irrelevant. Not only did it not make it safer it did not make it less safe and indeed did not make it similarly safe. It is almost, but not quite, as relevant as the price of fish.

You moved the discussion for several posts onto an irrelevance.

Take a look at the profile vs the ceiling. Maybe he was deep too long but since the ceiling (probably actually stop depth) was well above him until the final stop (and then I guess only because of him leaving his final stop setting to 6m) the algorithm paid no part in his bend. He was actually diving free style with a general indication of where not to go. I expect he’d have had an identical, late ascent with 70/70, the only bit of the ascent the computer controlled was the final ascent to the surface.

The interesting bit about this thread is not what caused the bend but the behaviour and thought processes that followed. People get bent, the algorithms assume an allowable rate of bending people. Divers should not be embarrassed when they get bent or suspect they are bent and should take whatever first aid measures are available ASAP. What we have here is dubious judgement regarding first aid O2 and then possibly going for IWR vs a chamber. Denial is a symptom.

 

[Ayisha]

That sounds quite plausible. Because there’s no chest strap the thing isn’t comfortable underwater unless the shoulder straps are pulled tight, must’ve overdid it. Will keep in mind

It sounds like it's unstable and you're tightening the shoulder straps so that it stays on securely. If a bp/w is fitted to you properly, it doesn't need a chest strap to stay securely on you.

Is the crotch strap tight? It might help to tighten the crotch strap as that's what holds the rig securely in place. Then you can loosen the shoulder straps so that they're comfortable. It might need an adjustment of the harness D-rings as well, in case they're digging into your armpits.

Hope that helps?

 

[Peter69_56]

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.

Totally agree with your thoughts. The reality is that about 20-25% of the population has some sort of PFO, and I would suggest that only a small % of that number know that they do. Often for the person there are no or little symptoms that would indicate that medical condition. Its only when they go diving, and start showing indications of potential bends, do they find out. As I said previously, my wife and also a friend of mine both got all the way to Tech extended air range before they both found that they had the condition. Had they stayed as recreational or never dived at all, perhaps they would have been oblivious to the condition.

So just because "technically" you stayed within the dive limits, doesnt mean your body can cope with that and maybe you have actually breached your bodys own limits (which are different for everyone). Perhaps on that particular dive, you were a little dehydrated, a little overweight, cold water etc etc. As n example, my wife and I both dive the same profile and settings. She gets bent (unless we take extra precautions) and I dont get bent. Clearly my body limts are different, as to what they are is an actual guess, but I try not to push my limits just to find out.

I think the only time the computer "technical" limits should be used, is when one clearly has exceeded those limits for some reason, and then one should assume "worst case" that one may be bent and precautions should be taken.

My rule of thumb is if I have breached my deco stops, or I do a normal dive and feel off or suspiscious of body indications, then go onto O2. If I have breached a stop, then I stay down much longer on subsequent stops, in particular at the last 6m stop.

If I am doing multiple dives on multiple days, then as a matter of course, I stay longer at 6m, and then also spend some time at 3m and 1.5m on the way back, simply as a precaution, given often we are diving in a remote place with no help nearby.

 

[Julius SCHMIDT]

 

[fsardone]

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.

The way pressurisation works is:
- high pressure air is taken from the engine compressor, cooled of in a heat exchanger (where it looses most of its humidity) and then sent to a mixing unit where it is reunited with hot air from compressor to achieve the right temp (outside temp can be as low as -55 degrees Celsius);
- this high pressure/temperature regulated air is the sent into the cabin;
- a controlled valve vents off excess pressure to maintain in teh cabin the set cabin altitude.

Quite a "simple" system. The limit is the maximum cabin pressure differential the aircraft can withstand. If the maximum differential was to be 1 bar you could fly in space and keep cabin altitude at sea level. This would have a cost in weight because you need to reinforce the structure (a 300 bar tank weight more than a 232 bar tank). Weight in an aircrafts means fuel consumption hence it costs money to make heavier aircraft and cost money for every flight because you need to produce more lift to sustain that weight and more lift means more drag (I can mathematically prove it for those willing to challenge it).

This said the pilot can set the cabin altitude to minimum not to exceed maximum cabin pressure differential. In a few aircrafts you can maintain sea level up to FL 250 (25000') which is a good fuel economy altitude for most turboprop. Helicopters fly much lower but for those a/c weight is even more critical than for fixed wing.

My 2 c on the matter.

Cheers