You look and find the loop hypoxic....

[rjack]

Garth, the design choices have been explained to you several times and its why on the Meg, if you find yourself with a low, but not imminently dangerous ppO2, you hit the O2 MAV instead of doing a dil flush. A stuck open O2 MAV is not the imminent danger you think it is. And the O2 MAV on the Meg CLs is standard sitec suit inflator, they don't stick open much if ever. I have never seen nor heard of a suit valve sticking full on open and there are 10s of thousands in use. When they eventually leak, they dribble.

On the other hand, I ran my Meg manually last weekend for practice (very low 0.7 parachute) and I tell you I twitched every time I hit the MAV. So maybe you are onto something...

 

[Mark Chase]

I thought we were all dive gods on here ????:banana1: What happened to minimum loop volume ? If you are on MIL then you are only one breath away from hitting the ADV ?

Yeah but in the real world

Pete Kemp for a laugh breathed pure Helium to see what would hapen. Aparently one or two inhalations and he just hit the floor like a sack of sand.

Thats always made me look at Hypoxia as a very serious issue.

Id hate to try and hit my ADV on a hypoxic loop and find I couldn't do it in one breath.

And even if I could hit the ADV it takes three good flushes to purge a loop and i might be flushing with 10/50 so its not exactly gonig to rocket the PP02 back up

The more i think about it, it would defo be a big slug of 02 and sort the Hyperoxia out once I am sure I can stay awake

ATB

Mark

 

[Mark Chase]

Our discussion started because you stated the JJ didn't have a dil MAV, but you've evolved it into something both unrelated (KISS) and specific to you (unit mods). The only reason I made a comment was to clarify that the JJ does, in fact, have a dil MAV. If you have trouble reaching it, that doesn't mean it isn't there. Also, the CE unit comes stock with a MAV at the chest. Not trying to argue; just trying to clarify facts in case a potential JJ buyer stumbles across this.

My bailout is on a tight necklace just below my chin. I breathe it uncharged while loading gear and charged in the water to ensure the flappers work and gas is being delivered. A few times during the dive I put my hand on it to make sure it's where I think it is. If I need to bail, there won't be any fumbling around for the reg, as would likely be the case if it were stowed on the bottle. It's as close to BOV response time as you can get, but provides a reg that breathes great for CO2 events. If I am alerted to a hypoxic PO2 by looking at the handset (and not because I'm starting to black out), I'm going to bail because I know exactly what I'm going to get. Given this scenario is most likely caused by an O2 supply or delivery problem (for my eCCR), hitting the O2 seems like the worst thing to do.

The JJ I own doesent have a MAV as standard but it does have a purge button on the ADV

I need to dislocate my left elbow to reach it or try and reach across to it with my right which is also not easy (for me in a dry suit).

The did in the past (and may still do) sell a Diluient add valve for the JJ which was exactly the same as the 02 add valve.

I have never seen a unit with one on but I am sure they exist

My idea of a dill add valve is like the one on an inspo on the counterlung. Back in my inspo days i considerd it part of my dive planning (rightly or wrongly)

I dont on my JJ

ATB

Mark


O2 and Dill buttons on an inspo

Egypt 2004 (Christ wernt video cameras massive back then )

 

[Garth]

Garth, the design choices have been explained to you several times and its why on the Meg, if you find yourself with a low, but not imminently dangerous ppO2, you hit the O2 MAV instead of doing a dil flush. A stuck open O2 MAV is not the imminent danger you think it is. And the O2 MAV on the Meg CLs is standard sitec suit inflator, they don't stick open much if ever. I have never seen nor heard of a suit valve sticking full on open and there are 10s of thousands in use. When they eventually leak, they dribble.

On the other hand, I ran my Meg manually last weekend for practice (very low 0.7 parachute) and I tell you I twitched every time I hit the MAV. So maybe you are onto something...

Haha! Good to know. Hope your MAV treats you well and doesn't dribble. That sounds embarrassing. Hehe


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[matt]

A bit of clarification needed here:

Sounds like a mid-life-crisis. I'd suggest a beer (a proper one, not one of those iffy America lagers).

My passion for understanding comes off the wrong way commonly. I'm really not a dick head in real life,

LOL. Did you KISS and make-up?

Matt.

 

[matt]

I have never seen nor heard of a suit valve sticking full on open and there are 10s of thousands in use. When they eventually leak, they dribble.

I dived with a dude (no longer with us) and his suit inflater did just this. 80m, upside down, suit full of air and holding on for dear-life. Then full of water when we cut his boot off.

Matt.

 

[kwinter]

Much is being made over the different place to add O2 and tempers are flaring. I'm more pragmatic. "It's not a problem" would be good enough for me. This is easy to resolve. Take your Hammerhead and your buddy's Meg and run them both to a setpoint of 0.7 in your kitchen. Then hit the O2 MAV for exactly 1 second and immediately analyze the gas coming out the mouthpiece. Then take a full breath from the loop and analyze again. Do this on each rebreather and report back whether there is a big difference. I strongly suspect there is not. So maybe that will calm you down.

Even a breath of pure O2 at depth will not be instantly fatal. And while even drysuit inflator type valves do occasionally stick open, I don't think that having it on the exhale lung would protect you any better.


iPhone. iTypo. iApologize.

 

[cferrar]

I'm thinking of building a cell holder that I can put in right before the dsv. Then I can see what kind of spike is reaching the diver when the MAV is hit. I suspect that there is a little more of a spike on the meg but when adding o2 normally the spike would be well bellow anything that would be dangerous. I will post my results after I have a chance to try it.

Interestingly I have had a MAV fail full open on the evolution. This happens if the button is not screwed together and the shaft that holds the spring for the button comes unscrewed....operator error. I assure you breathing a high PO2 gas is the least of your problems.

Chris

 

[colinicky]

If you want something even more dangerous :- think there was a KISS DSV that had a lever inside that you used to add dil or O2 ? Might have been called a "Snog" valve ?

 

[Capt Morgan]

If you want something even more dangerous :- think there was a KISS DSV that had a lever inside that you used to add dil or O2 ? Might have been called a "Snog" valve ?

It was called a "Simplified Non-manipulated Oxygen Gate" or SNOG for short :lol:

 

[rjack]

I dived with a dude (no longer with us) and his suit inflater did just this. 80m, upside down, suit full of air and holding on for dear-life. Then full of water when we cut his boot off.

Matt.

Did he die on that dive? Do you recall the suit valve type? This is the first catastrophic failure I've heard about, still seems like a rare event.

Me and everyone I know pretty much universally hate the apeks suit valves. They fail inside of a year around here. The sitec and rebranded versions thereof seem to last a long time (many years) and slowly leak when the orings finally get clogged with junk or just wear out. The stock inflators on the ISC CLs are (thankfully) sitecs.

 

[matt]

Did he die on that dive? Do you recall the suit valve type? This is the first catastrophic failure I've heard about, still seems like a rare event.

Nope, he just got wet, and cold. I don't remember the suit type or valve type I am afraid.

Me and everyone I know pretty much universally hate the apeks suit valves. They fail inside of a year around here. The sitec and rebranded versions thereof seem to last a long time (many years) and slowly leak when the orings finally get clogged with junk or just wear out. The stock inflators on the ISC CLs are (thankfully) sitecs.

I have used both Apeks and SiTec. Currently have SiTec. I've not had a problem with either type.

Matt.

 

[Deep_Six]

Garth, is/was this thread originally about hypoxic loop procedures or about the location of O2 mav injection? Also, which do you view as a more immediate threat to your life a hypoxic loop or a hyperoxic loop?

 

[Garth]

Garth, is/was this thread originally about hypoxic loop procedures or about the location of O2 mav injection? Also, which do you view as a more immediate threat to your life a hypoxic loop or a hyperoxic loop?

Great questions.

First question has to do with both. When I started the thread I was thinking about the diver who has the oxygen in the inhale counterlung and how they handle cells that are reading low nearing Hypoxic loop ppO2. The question originated by hearing time and time again why the inhale counterlung has oxygen designed to be lifesaving if ever in a hypoxic situation.
Is oxygen lifesaving in a hypoxic situation or is proper diluent better to be breathed first? The answer to that for me actually answers your second question.

Second question. I'm concerned about both. By managing a loop that could be hypoxic or could be hyperoxic depending on the cell health I vote for bailout, Diluent flush and determine the problem. For a rebreather to claim that you should just squirt a little oxygen into the loop seems like a bad idea for me and therefore tells me that inhale oxygen is a bad design.

Oxygen doesn't seem safe for breathing at depth so regardless of how much it mixes via some cockamamie ideal gas law Id rather not be guessing how much oxygen is being mixed before breathing especially when my rebreather isn't working properly.

Hope I answered your questions, do you like the oxygen in the inhale counterlung?

Garth


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[Deep_Six]

Although I've run my Meg both ways, I have the manual O2 connected to the MAV in my inhale lung.

If I had to rank the big three, i would say that in order of most to least 'imminent threat to life' would be hypoxia, hypercapnia and hyperoxia. That said, I'd gladly take 10 full, slow breathes at a ppo2 of 3.0 before doing half that many breaths at 0.15.

Answer to your first question is that yes, oxygen is a lifesaver in hypoxic situations. How you go about obtaining that oxygen is what you seem to believe can or should only be done in one manner.

As per my training and studies, my hypoxic display indications response during the meat of a dive and assuming that we're talking about a fairly normal type dive (ie a single non-hypoxic dil dive) is dil flush and go to OC to sort shit out while watching displays and confirming dil ppo2, O2 pressure, etc.

However, if I'm ~40' or shallower, I'd be just as likely to jump on the O2 mav instead, more so hopefully. This response was not part of my formal training but is what I did during my one real-life hypoxic event that occurred in about 10'. I was not on a Meg at the time. I believe most truly hypoxic events are likeliest to occur at or near the surface, in those cases O2 right to your mouth could actually be a lifesaver.

 

[Mark Chase]

Great questions.

First question has to do with both. When I started the thread I was thinking about the diver who has the oxygen in the inhale counterlung and how they handle cells that are reading low nearing Hypoxic loop ppO2. The question originated by hearing time and time again why the inhale counterlung has oxygen designed to be lifesaving if ever in a hypoxic situation.
Is oxygen lifesaving in a hypoxic situation or is proper diluent better to be breathed first? The answer to that for me actually answers your second question.

Second question. I'm concerned about both. By managing a loop that could be hypoxic or could be hyperoxic depending on the cell health I vote for bailout, Diluent flush and determine the problem. For a rebreather to claim that you should just squirt a little oxygen into the loop seems like a bad idea for me and therefore tells me that inhale oxygen is a bad design.

Oxygen doesn't seem safe for breathing at depth so regardless of how much it mixes via some cockamamie ideal gas law Id rather not be guessing how much oxygen is being mixed before breathing especially when my rebreather isn't working properly.

Hope I answered your questions, do you like the oxygen in the inhale counterlung?

Garth


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Why are you concerned about Hyperoxic? Its not a light switch like Hypoxic.


High PP02 is all about long exposure. Pay attention to your unit and its not a drama

Low PP02 you pass out and die without even noticing.


Low PP02 & death you can hit in under 7mins

High PP02 and tox takes several times longer

 

[rjack]

Why are you concerned about Hyperoxic? Its not a light switch like Hypoxic.


High PP02 is all about long exposure. Pay attention to your unit and its not a drama

Low PP02 you pass out and die without even noticing.


Low PP02 & death you can hit in under 7mins

High PP02 and tox takes several times longer

The Fock (2013) paper confirms this too. Hypoxia killed far more recreational divers than hyperoxia. 17% vs 4%
Here you go Garth, see Table 1.
http://www.cpalb.fr/IMG/pdf/fock-rebreather_deaths.pdf

While I am relatively new to CCR myself (6 months, ~60hrs), I've noticed that longtime OC divers seem to focus on hyperoxia and with more and more hours CCR divers tend to worry about hypoxia more. The O2 MAV on the inhale lung does not concern me under normal diving (if it didn't work there many of us would have toxed long ago). And if my loop is hypoxic as the thread title states, then the O2 MAV is in precisely the place I want it.

 

[Garth]

Interesting paper. My favorite part or shall I say the part that intrigued me the most was the 56 divers who perished yet scant data was determined.

The part I find troubling to comprehend is when one or more cells fail. How can someone sit there and say it was a "hypoxic" vs "hyperoxic" event?


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[Garth]

I suppose if the diver dies shallow it's less likely for hyperoxic and although some may disagree I wonder if hypoxia is less likely in deeper water.


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[rjack]

The part I find troubling to comprehend is when one or more cells fail. How can someone sit there and say it was a "hypoxic" vs "hyperoxic" event?

You are assuming that these fatalities were caused by failed cells. At least some of the hypoxic loops were caused by the O2 being off, the ADV leaking, or the batteries dying when the cells were fine.