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Thread: What happened?

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    RBW Member BiOS is an unknown quantity at this point BiOS's Avatar
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    Unhappy What happened?

    Hi all guys, I'm an extremely new member here :) That's my first post and I hope I picked the right section! Anyway... Something really strange happened to me when I tried the Meg for the first time...



    Here I am :D The first 6 minutes were.. great! I felt that breathing was so easy and it was so gorgeous at all! The instructor who was guiding me said to me that when ascending you need to blow through your nose to expell the expanding gas which would otherwise inflate the bag till it pushes air into my mouth... Well, as i said it was going great apart a bailout tank I fixed to my left which was making my buoyancy hard to control... Well It was my first try, the reb wasn't tight as i wanted... so my buoyancy was a mess but my question is another... I was ascending and I felt something pushing through my mouth so I thought it was time to blow through the nose but for some strange reason it didn't help! The air I was breathing was probably the same I had just exhaled! I felt headache and I tried to solve that situation (blowing through the nose) until the pressure towards my mouth was so hard that I couldn't do anything... It took like 5 seconds to use my bailout tank, which I thought was just boring me but it actually saved my life. I was only 14 meters deep, they were the longest 5 seconds of my life and I was about to give up and inhale water... i thought i would have died. We ended the dive and after I went out of the water I felt a strong headache and a feeling of disorientation. Was it my CO2? What happened down there? Please guys help me! Id really like to don't make that happen again, Im a little bit scared to don't be able of solving that just by myself so Im asking you guys and I'm sure you'll find out something! The instructor also offered me a private lesson as a... "payback" against this strange story... I will accept, but I have to know what happened. Could it be that I just wasn't used to rebs so I didn't blow through the nose properly? Im thinking... Could setting 1.3 while on the surface to make the reb inflate the bag be an acceptable way to practice on how to blow the expanding air properly? Thank you very much guys, I hope you'll reply soon!

  2. #2
    RBW Member Delios is an unknown quantity at this point Delios's Avatar
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    Re: What happened?

    1.3 on surface you will never get. I will go on injecting O2 and get overpressure in your lungs.

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    Re: What happened?

    I would suspect that you did not release enough gas through your nose to offset the expansion of the gases in your lungs and loop. A couple of suggestions which may help with you pinpointing the problem to gas expansion, prior too ascending drop your set point to .7 and maintain your ppo manually this will keep the solenoid from firing when unwanted during ascent.
    I would also as soon as you find the same symptoms vent off the loop a complete full breath to the point where when resuming normal breathing you will find that you need to let the adv open.
    Hope this is of help as far as buoyancy do not discourage it will come easier with experience (shallow dives are the most difficult).
    Gabe

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    What happened?

    Reinforcing what Gabe said, it sounds like you had too much volume in the loop. Maintaining minimum loop volume at all times, even during ascent, is an important skill to learn. It is better to vent too much volume so that you feel the lungs bottom out on your next breath, then add accordingly. Otherwise you end up with the chipmunk cheeks you experienced. And I keep my pO2 at setpoint until I'm ready to leave my last stop for the surface, then change it to 0.7. But I'm still controlling manually on ascent anyway.

    As for the possible CO2 issue, I would guess you just weren't breathing deeply enough because of the increased WOB from the excess lung volume. But that's a complete WAG.


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  5. #5
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    Re: What happened?

    Take this private cession with the instructor. Fully open the OPV. You'll make an easy short and shallow dive, so keep your SP @ 0.7.
    Your goal for this dive is to get comfortable and enjoy, no to fumble with the rig.
    But your instructor will make sure of that.

  6. #6
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    Re: What happened?

    Quote Originally Posted by divingabe  View Original Post
    I would suspect that you did not release enough gas through your nose to offset the expansion of the gases in your lungs and loop. A couple of suggestions which may help with you pinpointing the problem to gas expansion, prior too ascending drop your set point to .7 and maintain your ppo manually this will keep the solenoid from firing when unwanted during ascent.
    I would also as soon as you find the same symptoms vent off the loop a complete full breath to the point where when resuming normal breathing you will find that you need to let the adv open.
    Hope this is of help as far as buoyancy do not discourage it will come easier with experience (shallow dives are the most difficult).
    Gabe
    Thank you very much for your help, Gabe, you really helped me understanding the problem... I got a few questions for you if this doesn't bother you :D

    1) Could have I manually ejected the expanding gases through the bag's valve instead of instinctively use my bailout tank?

    2) Should have I set .7 just after I started my ascent? You are right... I didn't set back to .7 after I started the ascent and the solenoid kept pumping gas in... Could this be one of the causes that made difficult expanding gas? The problem is that my instructor said to keep SP 1.3 until my safestop at 6m ends, then get out of the water ascending 1meter per minute, is it right? Im getting confused... sorry I'm such a newbie!

    3) Can auto-injecting on the surface be a possible way to practice on how to get out of this situation?

    Thank you very much i really appreciated your help.

    Quote Originally Posted by kwinter
    Reinforcing what Gabe said, it sounds like you had too much volume in the loop. Maintaining minimum loop volume at all times, even during ascent, is an important skill to learn. It is better to vent too much volume so that you feel the lungs bottom out on your next breath, then add accordingly. Otherwise you end up with the chipmunk cheeks you experienced. And I keep my pO2 at setpoint until I'm ready to leave my last stop for the surface, then change it to 0.7. But I'm still controlling manually on ascent anyway.

    As for the possible CO2 issue, I would guess you just weren't breathing deeply enough because of the increased WOB from the excess lung volume. But that's a complete WAG
    Got it! Will I just breath deeply and kick everything through the nose even if it causes the bag's collapse? And... after that I will just inject some diluent in to restore the loop, right? How much will it take, in your opinion, to learn how to constantly keep the minimum loop volume? Now as now I just don't want to get those chipmunk cheeks ahahah :D Thanks for your help, I appreciate it!

    Quote Originally Posted by Delios
    1.3 on surface you will never get. I will go on injecting O2 and get overpressure in your lungs.
    Well, thank you very much for your help, I didn't realise that... Should I just manually inject some diluent to get that?

    Quote Originally Posted by Philippe GERIN
    Take this private cession with the instructor. Fully open the OPV. You'll make an easy short and shallow dive, so keep your SP @ 0.7.
    Your goal for this dive is to get comfortable and enjoy, no to fumble with the rig.
    But your instructor will make sure of that.
    I will :D Thank you very much for your suggestion >D

  7. #7
    So many CCR So little etc Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase's Avatar
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    Re: What happened?

    From the text there are two separate issues you experienced but they may be related

    Issue 1

    You need to vent through the nose / mouth regularly on ascent. Until you get used to it I'd say you need to stop every three m and regain minimum loop by fully venting the counter lungs until you feel the tension of the ADV. So as you ascend you vent as much as you think you should be venting but litraly stop every 3m and regain minimum loop fulley in order to teach your self if your venting enough.

    It doesn't matter if you vent too much because the ADV will provide gas and I am assuming your not on hypoxic trimix yet so it will be breathable air.

    Getting minimum loop this way will demonstrate how much the gas expands and how much venting you should be doing on ascent. For most people id say it's a LOT more than you think it should be.


    Issue 2

    Let's assume for a moment your instructor carefully inspected the unit so there's no possibility of assembly issues.

    The headache could possibly be C02 related in so much as your breathing was impaired and as a result you were working too hard to breath and this can result in C02 retention. If your feeling gas filling your mouth that meens that when trying to breath out your having to force the gas out with your lungs and they wernt designed to do that.

    However the headache could also just simply be stress related from the mental strain of diving the CCR and the issues you experienced. Stress is something that causes bad breathing patterns which can and do result in headaches


    The final issue is the position of the unit in relation to your diving. On OC it doesn't matter if the harness is a bit loos. It does on CCE you need to ensure the counter lungs are in the correct position and that they are not floating up over the shoulders too much. I had this on an Inspo Classic and it makes the unit hard to breath. It may be the way the shot was posed but your counterlungs look to need strapping down in that pic.

    Also sea horse diving positions (i.e. head up chest vertical) are not great for work of breathing on a CCR. Being for the most part horizontal in the water is the lowest breathing resistance position. If you have front lungs and are diving heads up it will increase your breathing work load and force air into your mouth.


    Finally the set point issue.

    I personally never sit at 6m on 1.3 on a ECCR. (been diving one for 10 years) I have had too many incidents of lost buoyancy where the gas injecting has made things worse so I switch to 0.7 set point at 9m (as I leave my 9m stop) and I run my PP02 manually from 6m an up.

    I believe Meg divers are taught to run their units manually for X hours before reliance on the ECCR. I am a strong believer in this approach to CCR diving and maintaining your set point manually will teach you a lot about how when and how much 02 a CCR needs and when its critical to be on the ball monitoring it.


    PS you cant get 1.3 on the surface. Pure 02 is 1.0 on the surface so you need to switch to low set as you ascend from 6m to avoid the unit constantly injection 02 to try and acheive an impossable set point.

    IMHO good pracice fo ALL CCR divers is to vent fulley the countelungs and fll with pure 02 prior to ascending from 6m

    Once on the surface I vent again and manualy fill with pure 02

    I usualy do this again before I climb the ladder on to the boat

    Its impossable to have too much 02 on the surface but its very easy to have too little as its very hard to read your handsets and or HUD on the surface.


    From the surface and down to 6m its pure 02 manualy injected. From 6m and up its pure 02 every dive.

    I dont step off the boat unless my PP02 is showing above 0.98 on my display.


    HTH

    ATB

    Mark
    Last edited by Mark Chase; 10th June 2014 at 06:24.

  8. #8
    RBW Member Delios is an unknown quantity at this point Delios's Avatar
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    Re: What happened?

    Agree with what Mark say's +1

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    Talking Re: What happened?

    Quote Originally Posted by Mark Chase  View Original Post
    From the text there are two separate issues you experienced but they may be related

    Issue 1

    You need to vent through the nose / mouth regularly on ascent. Until you get used to it I'd say you need to stop every three m and regain minimum loop by fully venting the counter lungs until you feel the tension of the ADV. So as you ascend you vent as much as you think you should be venting but litraly stop every 3m and regain minimum loop fulley in order to teach your self if your venting enough.

    It doesn't matter if you vent too much because the ADV will provide gas and I am assuming your not on hypoxic trimix yet so it will be breathable air.

    Getting minimum loop this way will demonstrate how much the gas expands and how much venting you should be doing on ascent. For most people id say it's a LOT more than you think it should be.


    Issue 2

    Let's assume for a moment your instructor carefully inspected the unit so there's no possibility of assembly issues.

    The headache could possibly be C02 related in so much as your breathing was impaired and as a result you were working too hard to breath and this can result in C02 retention.

    However the headache could also just simply be stress related from the mental strain of diving the CCR and the issues you experienced. Stress is something that causes bad breathing patterns which can and do result in headaches


    The final issue is the position of the unit in relation to your diving. On OC it doesn't matter if the harness is a bit loos. It does on CCE you need to ensure the counter lungs are in the correct position and that they are not floating up over the shoulders too much. I had this on an Inspo Classic and it makes the unit hard to breath. It may be the way the shot was posed but your counterlungs look to need strapping down in that pic.

    Also sea horse diving positions (i.e. head up chest vertical) are not great for work of breathing on a CCR. Being for the most part horizontal in the water is the lowest breathing resistance position. If you have front lungs and are diving heads up it will increase your breathing work load and force air into your mouth.


    Finally the set point issue.

    I personally never sit at 6m on 1.3 on a ECCR. (been diving one for 10 years) I have had too many incidents of lost buoyancy where the gas injecting has made things worse so I switch to 0.7 set point at 9m (as I leave my 9m stop) and I run my PP02 manually from 6m an up.

    I believe Meg divers are taught to run their units manually for X hours before reliance on the ECCR. I am a strong believer in this approach to CCR diving and maintaining your set point manually will teach you a lot about how when and how much 02 a CCR needs and when its critical to be on the ball monitoring it.


    PS you cant get 1.3 on the surface. Pure 02 is 1.0 on the surface so you need to switch to low set as you ascend from 6m to avoid the unit constantly injection 02 to try and acheive an impossable set point.

    IMHO good pracice fo ALL CCR divers is to vent fulley the countelungs and fll with pure 02 prior to ascending from 6m

    Once on the surface I vent again and manualy fill with pure 02

    I usualy do this again before I climb the ladder on to the boat

    Its impossable to have too much 02 on the surface but its very easy to have too little as its very hard to read your handsets and or HUD on the surface.


    From the surface and down to 6m its pure 02 manualy injected. From 6m and up its pure 02 every dive.

    I dont step off the boat unless my PP02 is showing above 0.98 on my display.


    HTH

    ATB

    Mark
    THANK YOU SOOO MUCH for your message, dear Mark: It was a great source of helpful informations! Exactly the starting tips and advices I needed to dive rebs with less difficulties! Just a question: How do I, precisely, manually control the PPO2 of my loop? Thank you very much :D

  10. #10
    Hammermeg, Copis2, Kiss divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe's Avatar
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    Re: What happened?

    To maintain proper ppo in your loop. Reference your controller and add O2 as needed with your manual add on the counterlung. Forgive this observation but are you not taking a certification course with an approved instructor to whom you are entrusting your life. These questions should be addressed to him or her to provide you with the understanding of the functions of your life support equipment.
    As Mark stated ISC recommends that a student be thought to maintain ppo manually during the course this is intended to familiarize you to the mechanics of the rebreather and instill the habit of checking your readout and to be aware of your PPO.
    Gabe

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