Probably stupid question from a non-RB person

[Dr. Doug Ebersole]

Lynne:

Kudos for being a good buddy and asking the rebreather diver the appropriate questions.

By the way, did Peter know you were asking about another guy's "unit"???? Sorry, but I couldn't resist.

On a serious note, you can do a "dil flush" a number of ways on the stock Sport Kiss. As was mentioned, if you exhale all of the gas out of the loop and then inhale the ADV will automatically add diluent. Additionally, you can switch the BOV to open circuit mode and take a breath of diluent and then switch back to closed circuit and exhale into the loop. These are the common ways the diver manages a high PO2.

If you were to find yourself in an emergency with a buddy who was on a Sport Kiss and wanted to do an "emergency" dil flush for him or her the proper technique would be to hold the mouthpiece in his mouth and push the ADV button on the right "pod" (it's on the outside just below where the hoses come off) on top of the Sport Kiss.

The Kiss Classic has the same "button" but it is on the back right side of the cannister.

A lot of people have modified thier Kiss units to have manual addition valves. In fact I now dive the Kiss Explorer and one of the reasons I went to that was to have the manual diluent add valve on a hose coming over my left shoulder. That having been said, I don't think I've ever used it in the 70 or so dives I've put on the unit. It just isn't needed for routine day to day diving if you keep minimal loop volume and use the ADV.

Doug

 

[Peter Guy]

Doug, I confess that I was interested in "his unit" also!

 

[Dr. Doug Ebersole]

Tmi !!!!

 

[TSandM]

Doug, thank you. Vlad did point out the "button" on the back of the unit -- I just thought it was very strange that the diver himself didn't have the ability to reach it during a dive.

Since the constant flow O2 is, as I understand it, capable of being set for the diver's metabolic rate, it seems inconsistent to say that it can't oversupply.

I just spent the evening at Mel Clark's, talking about rebreathers, and I have to say my brain is spinning. OC is so simple!

 

[Tienuts]

I would suggest from your perspective as an OC buddy, attempting a dil flush for your CCR buddy is likely to lead to more issues than it solves.

Given that he had a BOV, I think as his buddy, this should be your primary method of intervening if you believe you need to rescue.

Reasons for this are

- good, known gas instantly delivered (at a good PO2 as long as he dives sensible bailout)
- enough known gas to surface (again as long as good planning is done)
- you can easily tell if he is breathing or not
- a simple dil flush might solve the immediate problem but if your buddy is incapacitated or distracted, it might be only a temporary solution.

One other thing. If you do flip the BOV, and need to rescue your buddy, definitely make sure you know how to dump their counterlungs before ascending them as otherwise they act like a second (very unwanted) BC...

For those OC divers who find themselves suddenly paired with a CCR diver 'insta-buddy," it's best to ask that diver (if they have not already explained to you,) what to do in the case of rescue. Read Rebreatherworld threads for 10 minutes, and you'll see that there is no 'common configuration' when it comes to CCR. Just because someone has a BOV does not mean it's plumbed to the correct gas or has an adequate supply.

Some divers plumb their bailout valve to their offboard bailout gas supply, and make that their primary means of bailout. Others might choose to plumb their BOV to their onboard diluent tanks, and use the BOV for sanity breaths only. Onboard tanks are typically 20cf or less, and most likely will not have enough gas to sustain an OC ascent. Other divers might have gas shut-offs, manifolds, or gas switching blocks routed to their BOV. Many ccr divers, like myself, do not use a BOV. (gasp!)

If you have no plan with your ccr buddy, or you should happen to stumble across a ccr diver unconscious underwater, a dil flush is always the best idea. For recreational depths, a dil flush should always provide a breathable gas to the CCR diver, and will correct a hypoxic or hyperoxic loop. Dil flushes are the most basic skill taught to a CCR diver. I even saw one rebreather diver who placed a "press to rescue" label pointing towards his diluent addition button.

Don't worry about trying to figure out how to dump counterlungs. It's too much to ask from a task loaded diver trying to perform a rescue on an unconscious diver with unfamiliar equipment. Dumping the counterlungs incorrectly could result in flooding the loop, and a very negative unconscious diver. Most CCR's have an over-pressure relief valve to vent expanding gas from anyway.

 

[DiveNav]

...... Apparently there is a button you can push to add dil, but it's up behind the diver's head, and apparently not accessible while you're diving....

Other brands/models have the DIL button in a more accessible way....

.....I just spent the evening at Mel Clark's, talking about rebreathers, and I have to say my brain is spinning. .....

I don't agree .... once you write a simulation for an eCCR they become very easy to understand

Alberto (aka eDiver)

 

[sunkmail]

I'll see what I can do to help, but honestly, Mel is probably your best bet for detailed explainations ... I'll aim for a general understanding.

My question is, if you had an O2 spike, would that flush the system fast enough?

If your O2 does 'spike', it probably isn't going to do it suddenly on a KISS, unless you press the O2 add button too much.

I mention this because you will have already been breathing the higher PO2 because of the slow change, and it does take some time for the sensors to register a change.

If you notice the 'spike', breath whatever is in your lungs out your nose. On the KISS, when the counterlungs are empty, and you're still trying to draw a breath, the ADV (Automatic Dil-add Valve) activates, allowing Dil to enter the loop.... Now exhale the breath you just took out your nose, and repeat breathing in.

At this point, you don't have a full dil flush, but you will have significanty reduced your PO2.

This whole proceedure only takes a few seconds.

Well, I think as an OC buddy, I had already decided that if I have ANY questions about what's going on with an RB diver, off loop is the answer.

Thanks for the hint about asking how to dump the counterlungs. I didn't ask that one.

Good answer!

I'm not sure I would want someone messing around trying to vent my counterlungs - I'd rather them just take me to the surface - it's probably faster, and less likely to flood the loop, possibly drowning the person you are trying to save.

Vlad did point out the "button" on the back of the unit -- I just thought it was very strange that the diver himself didn't have the ability to reach it during a dive..

Generally speaking, the diver wouldn't 'need' to reach it, due to the system explained above. Personally, I klike having the ability to add with a button, which is why I have modified my CK with gas add block. (The same one Mel and Curt use on their units)

Since the constant flow O2 is, as I understand it, capable of being set for the diver's metabolic rate, it seems inconsistent to say that it can't oversupply.

The adjustment is made to the first stage by setting the IP. I suppose creep could change it, but that would be over a period of time, and the diver would probably notice that they have been doing a lot of Dil adds to lower PO2.

(It would be similar to you noticing bubbles coming out of your necklaced 2nd stage - you would notice it as being 'not right' and be checking your pressures when you got home.)

The constant flow is literally a very small hole through a plug. Depending on the IP, only a certain amount of gas can physically pass through it. It can be blocked, but the chances of it getting bigger and allowing more gas are virtually zero. (I can't think of a single instance where that COULD happen and the unit still be functional.

I just spent the evening at Mel Clark's, talking about rebreathers, and I have to say my brain is spinning. OC is so simple!

She'll do that to you, but the next time you hear CCR details, you'll probably understand them better!

I don't agree .... once you write a simulation for an eCCR they become very easy to understand

Alberto (aka eDiver)

Theory and practice are not the same, eventhough in theory, they are.

 

[francousteau]

I did a dive yesterday with a fellow on a rebreather. I know very little about them, but I did ask him some questions about his unit before we got in the water. I wanted to know where his O2 add was, whether he had a HUD (which he didn't), what was in his tanks, if he had a BOV (he did) and how to do a dil flush on his unit . . . and that last point baffled me, because apparently there is no way to do that while diving. He told me the unit automatically adds dil, so if he needs to do a flush, he just exhales through his nose and lets the unit add dil by itself. ~snip~

Talk about asking all of the right questions . . . . You're really thinking ahead and as a new RB diver, I'd love to have an OC buddy like you.

BTW- keep talking to Mel and read her book "Rebreathers Simplified"

Franco

 

[down4fun]

Since the constant flow O2 is, as I understand it, capable of being set for the diver's metabolic rate, it seems inconsistent to say that it can't oversupply.

The rate is set by adjusting the IP on the first stage (at least on the rEvo), this is done on land before the dive. So the chance of it climbing during a dive is very slim. When I first bought my rEvo i got it from a guy whose metabolism was obviously bigger than mine. On the first couple of dives I would only add diluent, never O2. On a manual RB if the O2 is adjusted right, you should be adding o2 throughout the dive. I went home adjusted the IP back and test dove it. It is now set to just about hold my PPO2 without any exertion. My partner shoots a lot of photography so there are many portions of a dive where I am sitting still or just muddling around. If I start to exert myself then I have to add o2. It seems cumbersome to the outsider, but really once you get it dialed in, every couple of minutes you add some o2. You should be monitoring your PPo2, so to react to that reading by pushing a button every so often is no big deal. Point being that lying on the ocean floor doing nothing my PPo2 does not climb. That's how i have mine set.

I just spent the evening at Mel Clark's, talking about rebreathers, and I have to say my brain is spinning. OC is so simple!

It's a lot of information at first, but then so was OC when I started. Mel is a great instructor and has a way of breaking things down into a basic layman's terminology that is easy to understand. I did my hypoxic CCR with her and will do CCR cave next week with her.

If i can help at all with any questions let me know.
Kim

 

[Cave Diver]

I did a dive yesterday with a fellow on a rebreather. I know very little about them, but I did ask him some questions about his unit before we got in the water. I wanted to know where his O2 add was, whether he had a HUD (which he didn't), what was in his tanks, if he had a BOV (he did) and how to do a dil flush on his unit . . . and that last point baffled me, because apparently there is no way to do that while diving. He told me the unit automatically adds dil, so if he needs to do a flush, he just exhales through his nose and lets the unit add dil by itself.

My question is, if you had an O2 spike, would that flush the system fast enough?

The unit in question is one of the KISS rebreathers. Apparently there is a button you can push to add dil, but it's up behind the diver's head, and apparently not accessible while you're diving.

Please excuse (and educate me out of) any misconceptions in the post. As I said at the beginning, I know little about these things, and up until recently, I was too uncomfortable to dive with someone using one. (It still makes me kind of nervous.)

I'm unfamiliar with that unit, but I don't like the idea of not being able to do a quick dil flush, or my OC buddy not knowing how to do one for me. That's part of our pre-dive planning. Since I'm too lazy to type it all out again, I'll repost my response from this thread: http://www.scubaboard.com/forums/advanced-scuba-discussions/308080-ccr-oc-buddies.html

Ok, I'm going to go ahead and jump in with the description of a dive I did with an OC Intro diver and my regular CCR Full Cave buddy.

First off, everyone laid out their gear and started the assembly process. Since OC is much faster to assemble than CCR (at least for me) the OC buddy came over and observed some of the process. Among the things that I pointed out was the locations of:

1) My DSV (Dive/Surface Valve on mouthpiece that opens/closes loop)
2) My ADV (Automatic Diluent Valve, used to add diluent to the loop)
3) HUD (Heads Up Display, red/green LED's that show PO2 via blinking color combos)
4) Primary Display (Attached to wrist, shows digital PO2 readout)
5) Bailout bottle/reg on 7' hose.

Dive plan was discussed in relation to who would be team leader and set the reel, where we were going, etc. The OC diver was put in the middle. CCR divers elected to run a PO2 that displayed a single blink of red/green LED to simplify the OC's ability to read it. They were told that a single red or green LED by itself was a problem and they were to signal immediately (it's not necessarily a problem, but this was a simpler way of dealing with the issue than having to explain all the acceptable blink sequences for our HUD's)

If a CCR divers acts "funny" on my team, we have a rule that buddy is to donate OC long hose and the receiving diver must take it. This is a command signal, just like thumbing the dive. We only return to the loop after everyone is sure the issue is sorted to everyone's satisfaction.

If CCR has to donate to OC diver, they will hand off their long hose on bailout bottle. Whether or not CCR hands off entire bottle or not will be sorted after the OOA situation is handled. This is a dive ending situation.

If CCR diver goes unresponsive, OC diver instructed to let other CCR diver handle it, with them on standby to help. In the event of a restriction where other CCR diver can't access, OC diver is to attempt flushing the loop by use of the ADV. If that's unsuccessful, they are to attempt to donate air with long hose, purging lightly and shut loop using DSV. They should also be verifying PO2 via Primary Handset or HUD during this time.

Standard hand signals for turning the dive, pressure checks, etc. were discussed. After dive briefing, all divers geared up, reviewed each others gear placement and equipment checks and entered the water.

In the water, shallow s-drills and bubble checks were done and the team entered the cave and finished the dive by the plan discussed in the briefing.

Post dive, there was a debrief to review the dive and address any issues that occurred.