My hypoxic incident

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nadwidny

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Scuba Instructor
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Location
Cranbrook, BC
# of dives
I just don't log dives
I said I would someday get this out there so here it is. I'm putting it here in the RB forum and not the near misses forum as it is more for RB people to learn from than the general diving community.

In November 2020 I was doing a shore dive near Nanaimo, BC. First day of a 5 day trip. It was the 2nd shore dive of the day. Compared to most of my dives (deco, deepish, etc) this was a very unremarkable profile. An "easy" dive. 80' for 50 minutes. No deco. Look at fish, take some pictures. I was on my KISS Classic (diving it since 2008 so 12 years experience on the rig). Dil was air or 18/35. I forget. On the first dive I thought something was off with my leaky valve. It seemed that I had to manually add O2 more often than normal. "I'll look at that tonight" I said to myself.

At the end of the 2nd dive we were coming back to shore. I was in about 10' of water. I was in a team of 3 and I was lagging behind the other 2. All was well except my NERD was not staying in place and I had to adjust it for the whole dive as it kept moving. "I need to fix that tonight" I said to myself. I was just below the surface and started to fold up my camera arms while swimming in. All of a sudden I had a couple of visual aberrations. My thought was cardiac event (I'm in that demographic). Through my mouthpiece I yelled a couple of times to get attention. This all took place in seconds .Basically I was there, then I wasn't. It was that quick. Then I woke up in the back of an ambulance.

I sort of remember talking to the paramedic on my way to the hospital. I sort of remember being told I was in A-Fib. I sort of remember being in emerg. Lots of people in masks, gowns, blood being drawn, electrodes hooked up. I definitely remember a tech coming in to draw arterial blood from my wrists and it taking him 6 goes, 3 on each wrist which were extremely painful ('ve since learned it usually takes one go. I must have had a rookie) I remember being quite spacey for about 4 or 5 hours. I didn't have the strength or coordination to walk until the next morning. I ended up staying 2 nights at the Nanaimo hospital, mostly because I was on IV antibiotics as I had aspirated some sea water. My roommates were both elderly addicts so that was interesting. I was coughing up blood for a day after probably due to the CPR that I was given on the beach. The A-fib spontaneously resolved itself after a few hours so I didn't' need to get shocked.

I was told after that the 2nd buddy in our team heard me yell something unintelligible (I was yelling into a rebreather so that's not a huge surprise) and turned to see what's up. She saw me drop my camera and sink to the bottom. She came and hauled my dead a$s up to the surface and yelled for help ( I was about 20 yards off shore). The group got me to shore, cut me out of my harness, cut me out of my suit and another bystander (volunteer Firefighter) started CPR.

Afterwards I looked at the dive data from my Shearwater. My PO2 had dropped from .21 to 0.00 in around one minute.

There's more but here's what made me dead-

My leaky valve was partially or fully plugged ( I found out after when I took it apart) causing the O2 flow to slow.

I wasn't diving my usual profile which involves deco where I'm paying rapt attention to my PO2 and spiking the O2 at the end of my dives to try and keep as high a PO2 as possible.

My NERD strap was acting up so I was constantly messing with it during the dive so I could see its' display (yes I had a wrist mount Petrel but I failed to look at that at the end). I wasn't too worried at the time about my PO2 since I was going to be on shore in a couple of minutes and stopped futzing with it . As far as I was concerned the dive was done.

But the biggest thing is on me. I broke the number one rule of CCR diving -Always know your PO2. I failed to do that and it almost cost me. If I had done that, I wouldn't have this story to tell. Always know your PO2.

Here's what kept me alive-

A last second coherent thought that made me call out for help.

An attentive buddy who heard me, saw me sink, pulled my butt up and got others to help. Never underestimate the power of buddys.
 
Excellent writeup, thank you for sharing it. It's wonderful to have your lucky outcome (and therefor some analysis) that we can all learn from rather than another tragic and mysterious CCR death. Glad you made it out.

These things NEED to have PO2 alarms. "Always know your PO2" is a nice mantra but not realistic enough to be safe given the high cost of lapses and natural tendencies of human nature as illustrated in your post. There's a reason alarms are the norm in aviation, medicine, and other safety-critical pursuits. I would hope that all future rebreathers include haptic or audible alarms like the newer shearwater controller.

What PO2 were you intending to maintain? You mention 0.21; was that your setpoint (or whatever you call your intention on an MCCR) or did you just mention 0.21 - 0.00 to indicate the time it took your loop to loose life-supporting ability? Was the rapid decrease partially due to ascent?
 
Excellent writeup, thank you for sharing it. It's wonderful to have your lucky outcome (and therefor some analysis) that we can all learn from rather than another tragic and mysterious CCR death. Glad you made it out.

These things NEED to have PO2 alarms. "Always know your PO2" is a nice mantra but not realistic enough to be safe given the high cost of lapses and natural tendencies of human nature as illustrated in your post. There's a reason alarms are the norm in aviation, medicine, and other safety-critical pursuits. I would hope that all future rebreathers include haptic or audible alarms like the newer shearwater controller.

What PO2 were you intending to maintain? You mention 0.21; was that your setpoint (or whatever you call your intention on an MCCR) or did you just mention 0.21 - 0.00 to indicate the time it took your loop to loose life-supporting ability? Was the rapid decrease partially due to ascent?
I suppose the Petrel could have some sort of haptic alarm. Given my state I probably wouldn't have known what it was saying. I should have kept my visual display in view right until the end as there are alarms on the NERD. But I didn't. That's on me.

On my KISS I always tried to maintain something around 1.0 as a minimum. 1.2 on the bottom. 1.4 or higher on deco. I mentioned the .21 to indicate how fast the PO2 went down which was mostly due to the ascent (not a particularly rapid ascent. )

FWIW I now dive an ISC Tiburon. Not because of the incident. I actually had it on order before all this.
 
The Petrel 3 does have a powerful haptic alarm that can warn of low/high PPO2 (and depth, ndl, etc). I upgraded from a Petrel 2 -> 3 for this feature alone.

Always know you ppo2, abort the dive if your ccr isn't working.
 
The Petrel 3 does have a powerful haptic alarm that can warn of low/high PPO2 (and depth, ndl, etc). I upgraded from a Petrel 2 -> 3 for this feature alone.

Always know you ppo2, abort the dive if your ccr isn't working.
Does the Petrel 3 have a CANbus or Fisher connector version? I am not sure I understand how it can warn about pO2 without...
 
Does the Petrel 3 have a CANbus or Fisher connector version? I am not sure I understand how it can warn about pO2 without..
Yes, it is a connected computer. Both interfaces are available.
 
Have you

Have you ever triggered the alarm yet (unintentionally)? :D
Sure. It is not that unusual to occasionally spike your ppo2 past 1.6 for a few seconds which triggers the haptic alarm. I did it the other day when i did a flush at 90ft after kicking against current for a few minutes. The low alarm defaults to .4 or something and I don't think i have triggered that during a dive.
 
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Thanks for sharing. Did you measure the flow rate through the cmf after the dive?
 
Who are you asking?

Nadwidny was in the hospital after the dive.
Thanks for sharing. Did you measure the flow rate through the cmf after the dive?
 

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