First rebreather Dive uncomfortable

[Rbdive]

Hello all,

Pleasure to be on scubaboard.

So I recently decided to switch from diving OC tec to CCR. I had a “try rebreather” experience but was underwhelmed afterwards honestly. My buoyancy was relatively fine for a first RB dive, but what I found uncomfortable is how hard it is to draw a breath compared to an open circuit regulator. I obviously was trying to maintain the minimum loop volume as much as possible but whenever it actually got comfortable to breathe I would start floating up even though my wing was fully deflated. I had a bailout drill where I got to compare breathing on OC vs CCR directly and drawing breath from OC was infinitely easier.

two questions:

(a) Is that normal? Is an OC regulator easier to breathe?

(b) is ease of breathing related to the “work of breathing” concept I keep reading about in RB forums? If so, I note that different types of CCRs have different WOB rates. Any recommendations for a RB that breathes easy when staying in good trim?

Newbie questions I know, but please help me get the excitement back towards my CCR journey

Cheers

 

[dsp]

a lot of people will give you great advice here. My small input is that it's natural to feel crappy in the beginning, you were probably shallow (pool?) which made everything harder.
You were trying to compensate for boyancy using your lung volume.
Don't try to keep minimal loop volume, at least for the first 10s of dives. Breath comfortably. What you will find out is that rebreathers breath absolutely amazingly, like breathing right now. you don't think about it. that's what you want to get on the unit too. The only problem to that would be a lung configuration that is very susceptible to pressure changes in the water column but that's a technicality and the effect is compared to what you were propably experiencing by underbreathing for a whole dive, negligible.

So for now IMO just add a bit more weight and breath normal, but your instructor should make that call.
you want to be able to get a full breath like, FULL out of those CLs

Edit: and don't underbreath. Shallow breathing for prolonged periods can result in a CO2 hit. don't ask me how i know ;p

 

[JonG1]

The units configuration, subtleties in terms of trim, harness adjustment, lung position, loop volume all play their part.

As important though is your level of comfort or relaxation, I still have dives where if I am not chilled or things are getting stressy my breathing reflects it.

As you get more comfortable though it improves

 

[jfe]

I'm no expert and very new to RB diving but would not trade it back for OC. You should not have difficulty breathing at all, minimal loop volume is just that, minimal air to breath comfortable and not so little that you get in trouble should you suddenly take a deep breath. Don't understand why on a try-dive you want to get into the refined side of RB diving already, get confortable and enjoy the feeling first, there is more important aspects to focus on like PPO2, maintaining setpoint etc than minimal loop volume that is what keeps you breathing and alive. I think counter lung orientation might also played a role in your try-dive, front mount especially I've found to be very sensative on the orientation of the breathing hoses, if they are too low on you chest you'll struggle. I have no experience on BMCL so cannot comment.

 

[taimen]

(a) Is that normal? Is an OC regulator easier to breathe?

No, rebreathers breath well enough to be very comfortable. An OC reg does provide you gas with slight overpressure so in the end it may be "easier" to breathe. But what you experienced is not normal.

(b) is ease of breathing related to the “work of breathing” concept I keep reading about in RB forums? If so, I note that different types of CCRs have different WOB rates. Any recommendations for a RB that breathes easy when staying in good trim?

Yes, to some extent. But what you just experienced probably doesn't have anything to do with the small differences between units. It was due to diving technique and that will get better with hours. This is why personally I have found try dives to compare different units before buying useless, until you really know how to dive a rebreather.

I obviously was trying to maintain the minimum loop volume as much as possible but whenever it actually got comfortable to breathe I would start floating up even though my wing was fully deflated.

To me (as a recent beginner) it seems that you were actually breathing with less than minimum loop volume, and that can be really unpleasant. In addition, you may have been underweight, as you were not able to stay neutral with a loop volume comfortable to breath.
Minimum loop volume is something you approach later on, in the beginning aim for comfortable loop volume.

 

[AdamSa]

When I first did a try dive, I experienced something very similar to what you explained but i think to a lesser extent. The thing is though, i got to the dive centre, had a briefing and got strapped into a unit. The unit was not correctly setup for me.

When I eventually got my own unit, I spent a couple of hours setting it all up and doing a proper weight check during the first course. The feeling and general experience was very very different. I could breath much easier and it was way more comfortable.

This might not have been all to do with the harness, counter lung etc.. setting, but I feel that it hada large impact for me. Bottom line is, once you dial it all down, breathing effort becomes amazing. The first time i realised how amazing it is was when I had to do a bailout ascent drill which had me on OC for 10 mins following an hour on CC...I would never switch back to OC diving by choice!

Hang in there, it will get better. Which unit did you try?

 

[michael-fisch]

Had buddys diving RBs so I was familiar with them. Bought a used ECCR, and dived it for 8 weeks (15-20 dives), usually with a buddy also diving the same model untill I felt that I had enough experience to take a course.
My instructor kicked my butt for several weekends in a local lake, ditching and donning stages, plugging the stages in to my backgas and O2, switching between CC and OC and back to CC but the hardest experience was going to 40M and floating 1M off the ground without any hand or fin motion or touching the controlls doing nothing for 5 minutes. Then ascending 5M and doing the same thing every 5 meters all the way to a depth of 5M. Then it was a 1M ascent and do nothing for 2 minutes before ascending another 1 meter step all the way to the surface. The dive was only a bit longer than an hour but I was exhaused after that dive, the stress of trying to maintain perfect trim while doing absolutely nothing was hard.

Michael

 

[Rbdive]

When I first did a try dive, I experienced something very similar to what you explained but i think to a lesser extent. The thing is though, i got to the dive centre, had a briefing and got strapped into a unit. The unit was not correctly setup for me.

When I eventually got my own unit, I spent a couple of hours setting it all up and doing a proper weight check during the first course. The feeling and general experience was very very different. I could breath much easier and it was way more comfortable.

This might not have been all to do with the harness, counter lung etc.. setting, but I feel that it hada large impact for me. Bottom line is, once you dial it all down, breathing effort becomes amazing. The first time i realised how amazing it is was when I had to do a bailout ascent drill which had me on OC for 10 mins following an hour on CC...I would never switch back to OC diving by choice!

Hang in there, it will get better. Which unit did you try?

AP inspiration. For weighting, what is the closest OC analog to a rebreather (I know different units differ in buoyancy, but generally speaking?) I know my weights with AL and steel 80s and AL 100s.

 

[Rbdive]

Had buddys diving RBs so I was familiar with them. Bought a used ECCR, and dived it for 8 weeks (15-20 dives), usually with a buddy also diving the same model untill I felt that I had enough experience to take a course.
My instructor kicked my butt for several weekends in a local lake, ditching and donning stages, plugging the stages in to my backgas and O2, switching between CC and OC and back to CC but the hardest experience was going to 40M and floating 1M off the ground without any hand or fin motion or touching the controlls doing nothing for 5 minutes. Then ascending 5M and doing the same thing every 5 meters all the way to a depth of 5M. Then it was a 1M ascent and do nothing for 2 minutes before ascending another 1 meter step all the way to the surface. The dive was only a bit longer than an hour but I was exhaused after that dive, the stress of trying to maintain perfect trim while doing absolutely nothing was hard.

Michael

So the question becomes, is it worth it?

 

[rjack321]

sounds like you were underweighted