Fatality Western Australia & Sat divers injured

[kaerius]

I think some of your numbers are a little mixed. Six months decompression can't be right, even 6 weeks for decompression would be too long. Six weeks for the total dive including decompression is reasonable.

You're right, my memory totally mixed up everything there, oops. 6 weeks total indeed, decompression was 24 days and the depth was 701m not 1700m.

Sidenote: for a 0.3 ATA of O2 at that pressure, the gas mix would be 0.42% oxygen, I'd call that extremely hypoxic, wouldn't you?

 

[Akimbo]

Sidenote: for a 0.3 ATA of O2 at that pressure, the gas mix would be 0.42% oxygen, I'd call that extremely hypoxic, wouldn't you?

Only if you try to breathe it when you are too shallow... like I have.

It is amazing how fast you lose consciousness on essentially anoxic mixes. Part of the pre-dive checklist is to test breathe each BIBS (Built-In Breathing System) masks. Unfortunately, all the bottom mix wasn't purged from this chamber's BIBS lines because it was surfaced unmanned. Normally the mix would be adjusted as the divers decompress. Anyway, all I remember is taking about half a breath and waking up flat on the deck plates with a knot on my head.

 

[Miyaru]

Elite diver Chris Tanti recalls waking up to his own private hell 272m under water

"Saturation diving experts and the Maritime Union of Australia said that dives to equivalent depths elsewhere in the world usually involve 24-hour or longer periods of compression, with rests — known as holds — along the way.
The first three diving teams were allegedly “blown down” in eight hours, while the fourth and fifth teams were allegedly “blown down” in five hours and 20 minutes."​

Haven't heard about this case for quite some time now, as it happened back in June 2017. All divers complained about HPNS symptoms on two different descents/blowdowns.

Why did different divers suffer from HPNS during different events? And why can OC/CC divers descend faster to similar depths? @Akimbo might be able to enlighten me?

In this case however, the problem was that they were descending faster than the helium could be added to the bell, they essentially got an extreme case of oxygen poisoning, think CNS oxygen toxicity on a massive scale, extreme PP02, and probably likewise of nitrogen narcosis.

Was this reported? It sounds like a mechanical shortcoming which would have injured the 2nd group of divers even worse.

 

[Akimbo]

Why did different divers suffer from HPNS during different events? And why can OC/CC divers descend faster to similar depths? @Akimbo might be able to enlighten me?

I speculate that several factors are at play. Divers in a chamber are not as distracted by the environment and time constraints, resulting in greater awareness of symptoms. They also have much more demanding performance requirements for exertion and complex work where HPNS symptoms would be restricting.

Additionally, saturation divers are almost exclusively on HeO2 instead of Trimix. Trimix was used as early as the early 1960s to alleviate (or mask?) HPNS symptoms (and save money). See Hannes Keller's 1,000' Dive

Non-saturated divers (bounce dives in the commercial diving world) must descend as fast a possible to optimize working/bottom time. Saturation divers aren't subject to these time constraints. For all practical purposes, sat divers are committed to sat decompression schedules by the time the reach bottom at "normal" compression rates. See What is Saturation Diving? for a detailed discussion on this subject.

@Duke Dive Medicine probably has more insight into your question. The "formula" to avoid HPNS and compression neuralgia was well established by the time I made my first sat dive.

 

[Wingy]

There was a two page article in Friday's (print) news regarding where the case is at now. Will try and scan it if anyone is interested.

 

[Duke Dive Medicine]

Elite diver Chris Tanti recalls waking up to his own private hell 272m under water

"Saturation diving experts and the Maritime Union of Australia said that dives to equivalent depths elsewhere in the world usually involve 24-hour or longer periods of compression, with rests — known as holds — along the way.
The first three diving teams were allegedly “blown down” in eight hours, while the fourth and fifth teams were allegedly “blown down” in five hours and 20 minutes."​

Haven't heard about this case for quite some time now, as it happened back in June 2017. All divers complained about HPNS symptoms on two different descents/blowdowns.

Why did different divers suffer from HPNS during different events? And why can OC/CC divers descend faster to similar depths? @Akimbo might be able to enlighten me?


Was this reported? It sounds like a mechanical shortcoming which would have injured the 2nd group of divers even worse.

HPNS could be one explanation for the fatalities that sometimes happen on world record attempts. It's a poorly understood phenomenon and can affect different people in different ways.

Best regards,
DDM