Hypoxia, Stoney Cove, 3rd March 2007

[The Purist]

Date:
3.3.07

Location:
Stoney Cove

Details:
I've already posted this on RBW & it's drawn a fair amount of comment, but I'm posting it here too for the benefit of those who may not yet dive a RB, in the hope that my experience informs their decisions some day.

--------------------

(sorry folks, this goes on a bit!)

A bit of background before we start - I've been diving the KISS since 2001. I've had a fairly well documented manufacturing problem with my KISS which meant that water could enter the stack even after a successful +/- test, so I quickly learned about the fun of CO2. Before finally diagnosing the problem (which Gordon helped me with & then supplied spares FOC) I was getting my buddies to check my pre-dive prep, then still getting flooding so I became suitably paranoid about my rebreather and was always fastidious in prepping it and doing my pre dive checks.

The real time story of what happened

We arrived at Stoney Cove at about 11.30 and were able to park just under the bridge in the upper car park. We hit the on site shop as my buddy wanted a new thermal top then ran through all our pre-dive tests & kitted up for our first dive. Into the water from the bus stop at about 12.15, pootled off to the right along the wall at about 20m, got bored, came up to about 10m, pootled back, my buddy did a couple of drills and we got out. My neckseal had been a bit loose on entry so I'd got some water down my neck & I was a bit chilled, but nothing too bad. I was also keen to get used to my Shearwater HUD on this dive, it was only my 2nd dive using this and I was pretty pleased with its operation.

We had an hour for lunch - I was a bit chilly as the sun decided to hide behind a cloud on an otherwise glorious day, then we kitted up again just after 2.

We were on the quayside part of Stoney so we shifted our kit to the side of the water, then sat down & got into it - I went onto the loop to do a pre-breathe and had the PO2 steady at around 0.3-0.4ish. That's a bit lower than I normally do, but we were only planning another pootle so I wasn't too stressed. I dropped into the water just ahead of my buddy and was disappointed to feel my neck seal leaking again, then we submerged & did our bubble check. My buddy had spotted a small leak from the turret on my dil 1st stage on the 1st dive and confirmed it was still there, I checked his kit (new shiny Inspo stuff with no leaks at all, pah!). I had a quick scan of my displays then we turned to head off on our dive. After a few fin strokes I realised all was not well and signalled to my buddy that we should head back to the exit, he gave me an OK - it then gets a bit hazy - I remember going for my DSV switch and seeing some bubbles coming out of the reg, but I'm not sure why I even went for the switch in the first place.

The next thing I know, I'm feeling warm and fuzzy, everything's dark and all I can feel is my heart beating in my chest. I start to hear voices then faces start to come into view and the voices start making sense. I start telling them I'm OK and they can leave me alone (I got a bit stroppy apparently) then they start trying to dekit me, which is when I got proper stroppy as I could get my arms out OK. I stood up rather shakily (somehow I was at the slipway) and was walked over to the wall and sat back down. One of the group who'd assisted was a trained chamber operator and he gave me a good DCI check - I was mentally coherent by then but physically feeling poorly, but there was no sign of DCI. A paramedic was already on the scene and an ambulance arrived at some point - my assessor then told them that they could stand down the helicopter which was en route as I wasn't showing symptoms.

Stepping back a bit, my buddy's side of the story is that after I signalled to head for the exit I turned, stopped, went for the DSV and then slumped/shook/spasmed in some way - he got to me, realised something was up (eyes open but no response), lifted me to the surface then towed me to the slipway exit, calling for help. On the surface I was apparently blue, not breathing and one chap checked for my pulse, couldn't find it and started giving CPR, another brought an O2 kit down. The Stoney rescue boat arrived with further O2 and it seems that once I was on O2 I started to come round. Several people I've heard from since the incident (including my buddy) said they were convinced I was dead, another has said I was the bluest person they've ever seen.

I was stuck into the ambulance, hooked up to a machine that goes ping and then they said they were going to try to 'canulate' me - ie. stick in a drip (no jokes required). I was too cold and they couldn't find a vein, by this time I was mentally sharp but still felt wiped out and was occasionally nauseous. I was also feeling a chest pain when I inhaled deeply - this was due to the CPR as it now turns out, but I was unaware of that and my thoughts were towards DCI or lung injury so I was careful to explain this to the ambulance crew.

The ambulance took me to Leicester Infirmary where I was hooked up to more machines that go ping, still on O2, and another doc had a go at finding a vein - he eventually got a bit of blood out on the 3rd attempt and took it off for a test. I must have been there for about 45mins to an hour when my buddy arrived, and he was good enough to phone my Mrs to let her know the score and get me some chocolate!

I was in the resuss bit of the A&E ward until about 5.30ish (I think) by now I was changed & sat up in the bed, off O2 and feeling more together. I was transferred down to another ward where we waited for the head doc to come around & discharge me - at about 7pm we got bored and asked to see him, and were out the door about 7.45. At the time we thought that was that, and I'd had a lucky escape - but it's not that simple...

What went wrong?

I've downloaded the profile from my Sensus (attached) & the log from my HS Explorer is:

(time) (depth) (temp)
000015 CC 00 0000.0 18
000030 CC 00 0000.0 18
000045 CC 00 0001.5 18
000060 CC 00 0001.8 17
000075 CC 00 0002.4 17
000090 CC 00 0003.0 17
000105 CC 00 0003.6 16
000120 CC 00 0004.2 16
000135 CC 00 0004.5 16
000150 CC 00 0004.8 16
000165 CC 00 0004.2 15


I was in the water for no more than 2 minutes before blacking out. It's about 70 seconds into the Sensus log when everything goes flat, which I'm guessing is the time when I slumped. The only apparent defect with the KISS is a free flow of the ADV - I'm guessing the (old Mk 1) valve was knocked by some rough handling when I was beached - this was categorically not present in the pre breathe or the 1st dive otherwise the PO2 wouldn't have been stable and the loop pressure would have been noticeable. Crucially, while underwater I didn't notice any constriction of the loop volume as you'd expect from having gas entering the loop, and a KISS diver was part of the resuss team and he also confirmed there were no gas leaks evident. Somehow I must've got dil (10/50) flooding my loop, failed to notice it, made the wrong decision when I did notice it (going for the DSV switch) and then went hypoxic - basically I failed to diagnose and manage an equipment malfunction. I haven't yet stripped the unit down to take a more detailed look at any of the components.

My current theory of what happened does however involve the ADV. I was in the water about 30 seconds before my buddy, and noticed what I thought were bubbles from my neck seal after it leaked on the 1st dive. I now think that my vertical position in the water with the ADV just below/breaking the surface may have caused the ADV to leak gas into the loop, with the bubbling coming from the OPV. Because there was already hydrostatic pressure on the loop from my in-water position I didn't notice the extra WOB, so was probably breathing neat 10/50 at this time and dropping my loop PO2. Once properly submerged the ADV got a more static load on the diaphragm and so behaved itself.

What about the display scan after the bubble check? Well, this would be around 60+ seconds into breathing a hypoxic mix - and crucially I can't remember the readings I saw. It's possible I was already confused and either mis read the displays or, since we were at 2 or 3m at this time I may have mis-read 0.13 as 0.3, or maybe I just looked at them as a reflex action and didn't take in what I saw - similar to those deep air days.

What about the HUD? Well, first off I knew it would be flashing red LEDs at me anyway as I hadn't tried to hit a set point yet, secondly we were in bright, shallow water so it wasn't particularly obvious and finally it was only my third dive with this so it wasn't an intuitive monitoring system. Basically it's so new to me that we can discount it as an effective warning system.

Whatever the cause, the bottom line is that complacency and laziness nearly got me killed. 10/50 is the wrong diluent to use at a site with a 35m max depth - I used it because I've only got 1 dil cylinder and it had 10/50 in it, and I was too lazy/tight to think about ditching that for air. 10/50 is one thing that will have to change if & when I get back to deep diving.

What next?

It took a while for events to really sink in - just how close I'd come to being another statistic or thread in the memorial forum - and now I'm realising just how really deeply it's affected me. Two days after the incident I was feeling tired, had a raging headache and was feeling disconnected from my legs so I did the sensible thing and called the duty diving doc in Portsmouth. We had a long chat where DCI was all but eliminated as a cause, with physical and mental shock were suggested but he did recommend a visit to my GP to get a full check up & eliminate other possible causes such as fits or a "heart attack".

My GP is currently talking to other specialists to see if we can organise tests to eliminate other causes, even though I now think they are tenuous possibilities at best. Mentally I've been totally preoccupied with this, and still have occasional bad moments where things trigger the wrong memories/thoughts. My GP is helping me sort this out too. A few days after the incident I tried to get into a 4m deep pool, just for a swim - I made it but it took 5 minutes of psyching myself up to get in, and I nearly walked away. The thought of being 30 miles offshore and leaping into 70m+ is just a non starter right now.

So why post this?

First off, to highlight how just a few seconds of complacency can kill. My OC breathing rate was around 6 breaths a minute, so we're talking no more than 12-15 breaths between a happy, well person on the surface and total blackout. I know what I should have done now, but hindsight is always 20/20.

Also to highlight that laziness in choosing a diluent, going for the easy 10/50 option, adds risk to any diving in shallow water. I'll have to have a rethink about how to approach dil selection and encourage anyone diving 10/50 to make sure their approach is squeaky clean.

Thirdly, to ask for help. If anyone was at Stoney that day and saw anything of my incident I would really like to hear their story - I'm keen to get as much information as possible about what happened. Also, I know there are other divers who have been through similarly unsettling incidents and have 'got back on the horse'. At the moment I don't even know how to start working out where I go from here, so any feedback from those guys would be really welcome.

And finally...

I obviously owe a massive debt to my buddy, plus the bystanders who brought down O2 and assisted with the rescue and also to the rescue crew from Stoney Cove. A public thank you to them, and thanks also to those who have been in touch so far and filled in their side of my story.

Cheers for now

Keith

[GLOC]

Keith I am glad you are alive to relate this story. I hope you manage to get over the head games soon and get in the water to get back on that horse.

There are some very salient points in there for all to read and understand, even those who don't operate a RB.

Keith, can I ask that I move this thread to the 'I Learned About Diving from That' forum as I believe that more people would frequent that, than the incidents forum?

Regards and well done to all involved.

[GLOC]

New addition to sub-forum from Incident Reports

[BJ]

Originally Posted by The Purist

Date:
3.3.07

and I was too lazy/tight to think about ditching that for air.

Keith

I'm sorry to say that this is one of the telling things for me from this very important story. Many people who use rebreathers seem to place too much reliance on OC bail-out. I know from my own experience that when things go REALLY wrong - CO2 hit, hypoxia etc - people are in no fit mental state to switch to a different rig. You may disagree and you may have bailed out to OC in less stressful circumstances - but there are now too many cases of fatalities where this did not happen.
It is my (well informed) belief that OC bail-out is insisted upon by training agencies as a condition of their Product Liability Insurance. I know that some high profile CCR users do not use bail-out but they always make sure their unit is absolutely 100percent OK immediately before using it.
This subject has been a well subscribed thread on RBW titled "Who is this idiot John Bantin?". It's only my opinion but I am in some very good company. I have been in at the beginning of the renaissance of rebreathers and originally trained by Peter Readey. I am Draeger SCR diver No004 (trained by Rob Palmer) and APD Inspiration diver No004 (trained by Martin Parker). But I sometimes get scared to death with what I see going on nowadays.

[Mark Chase]

Originally Posted by BJ

I'm sorry to say that this is one of the telling things for me from this very important story. Many people who use rebreathers seem to place too much reliance on OC bail-out. I know from my own experience that when things go REALLY wrong - CO2 hit, hypoxia etc - people are in no fit mental state to switch to a different rig. You may disagree and you may have bailed out to OC in less stressful circumstances - but there are now too many cases of fatalities where this did not happen.
It is my (well informed) belief that OC bail-out is insisted upon by training agencies as a condition of their Product Liability Insurance. I know that some high profile CCR users do not use bail-out but they always make sure their unit is absolutely 100percent OK immediately before using it.
This subject has been a well subscribed thread on RBW titled "Who is this idiot John Bantin?". It's only my opinion but I am in some very good company. I have been in at the beginning of the renaissance of rebreathers and originally trained by Peter Readey. I am Draeger SCR diver No004 (trained by Rob Palmer) and APD Inspiration diver No004 (trained by Martin Parker). But I sometimes get scared to death with what I see going on nowadays.

Its quite simple john. If i didn't carry OC bailout Id be dead about now and so would a lot of other CCR divers. As a result Alpinist will never get a lot of support.

My unit past a perfect neg test last week then flooded during the dive for reasons we cant yet figure out. It passed a neg test for over an hour when trusted after the dive as well.

Had this been a deep dive with a lot of deco Id have needed to bailout to OC As it was it was 30m no deco so I just went up gurgling a lot.

I totally agree about the difficulty of getting off the loop which is why it is essential to have a Bailout Valve (BOV) plumbed into breathable gas. Turn a lever and your OC. I hear AP have finally accepted this fact as well and are pro ducting one.

ATB

Mark Chase

[BJ]

Carry as much OC bail-out as you like - but please make sure your CCR is working perfectly before the dive. There is no such thing as a mysterious loop flood only a potential for a flood that was not seen in advance. Keep the witchcraft for Pipin!

[The Purist]

John, with respect, you've played this game before on an the 'pre breathe' thread and never answered the questions about how you can guarantee a perfectly working loop on the surface. I've had similar problems to Mark - to the point of getting other people to watch and verify that my RB passed all pre-dive tests only to have a flood. There are also reported cases of Inspo canisters being improperly assembled & the diver not discovering this until they were under water.

Please don't sideline what could be a potentially educational debate on this thread by dragging it off on your personal crusade.

[wilbo]

Originally Posted by The Purist

John, with respect, you've played this game before on an the 'pre breathe' thread and never answered the questions about how you can guarantee a perfectly working loop on the surface. I've had similar problems to Mark - to the point of getting other people to watch and verify that my RB passed all pre-dive tests only to have a flood. There are also reported cases of Inspo canisters being improperly assembled & the diver not discovering this until they were under water.

Please don't sideline what could be a potentially educational debate on this thread by dragging it off on your personal crusade.

Keith,

Its BJ. Ignore him and he has no power..


Just read through your incident (not a CCR diver myself) and it really struck home how fragile we really are and how dangerous our sport (to varying degrees) really is. Thankyou for being up front and posting this.

I hope you route out the failure and either get it fixed - whether it is man or machine - and get back to doing something you love again.

[BJ]

Originally Posted by The Purist

There are also reported cases of Inspo canisters being improperly assembled & the diver not discovering this until they were under water.
.

In my case it was a PRISM Topaz scrubber canister, now redesigned because of my mistake! In that case I knew something was wrong before I hit the water but I only just made it.

People like to misunderstand my 'personal crusade". It is NOT that people should not carry OC bail-out. It IS that people should be aware that there will be circumstances when it will NOT help them. CO2 hits and hypoxia being the first that I can think of. I regularly see people being cavalier (I am not saying you were) with preparation BECAUSE they have OC bail-out. That is my beef. I hate hearing about people dying unnecessarily - especially when they have recently had a go at me on this subject on a forum. Your experience seems very serious to me. Than God you were not in different circumstances.

Keith does not appear to be able to explain why he did not bail out on to OC. That's my point.

[GLOC]

As I transferred this thread across from Incidents to ILADFT... and set up this forum, I reaffirm that this thread is not for stone throwing but for others to learn from.

The quote which John lifted from Keith's post is a learning point; don't use hypoxic mixes near the surface (which Keith admits is a failing). The rest of the post is not truely relevant to the thread.

Please keep the thread on subject.