The New Dive Rite Optima CM - My 30 Hour Review

[silent running]

Disinterested third party here, but intrigued by RB's, so following this thread.

Why the focus on testing? I understand the need for EN testing for EU sales, and why that interests a potentially large number of divers.

Honest question though..I'm not trying to start a personal battle here, but genuinely curious. Why is @Superlyte27 's experience seemingly being ignored? Again, I've never even seen an RB in person..but he sounds pretty well qualified to make subjective comparisons to me?

My mind defaults to firearm suppressors. A lot of people put a LOT of stock in test numbers. Lower dB tests mean it's a quieter silencer, therefore better. But the testing standards don't look at tonality, length of impulse, etc. and so there are numerous cases of a factually "louder" silencer being consistently perceived as being considerably quieter than a factually "quieter" one by subjective observer/user input.

Once again, no clue here and no dog in this fight, but are whatever WOB tests that exist really that much better than subjective, experienced user input? I really am curious, and not trying to suggest anyone here is wrong.

No one is ignoring anyone’s subjective experience. But the word “subjective” is key, especially when it comes to life support equipment. Testing removes subjectivity and establishes limits for safe performance.

As you are unfamiliar with RBs, the main issue with work of breathing (WOB) is what happens during periods of high exertion, and how much CO2 either bypasses the scrubber and/or is retained inside the diver’s body. A high partial pressure of CO2 triggers the respiration cycle to drastically increase, which then causes panic so bad it’s actually paralyzing, enough that most people can’t even bail out to open circuit. Additionally, some people’s bodies are more tolerant of retained CO2 than others, further necessitating baseline standards for scrubber efficiency and WOB. Hypercapnia is a big deal and has been implicated in fatalities.

 

[Schwob]

So, I don‘t know enough yet. I don‘t dive enough (yet). I don’t plan on ever hardcore team tech diving. If I were to get a breather, ever, it would be more for long, silent picture taking dives, maybe with deco, and hence tech... but not hardcore tech or expedition diving. I certainly do not need a rebreather. So, why does this thing appear so appealing. Dang! No need to reply. Just convincing myself: Don‘t need a rebreather. Don‘t want to afford one. Don‘t really need one, Don‘t .... Dang!

 

[Superlyte27]

My last dive on the CM. CO2 not an issue

IMG_20200313_135743

• Superlyte27
• Mar 29, 2020

Bonaire 2020

 

[CuriousRambler]

No one is ignoring anyone’s subjective experience. But the word “subjective” is key, especially when it comes to life support equipment. Testing removes subjectivity and establishes limits for safe performance.

As you are unfamiliar with RBs, the main issue with work of breathing (WOB) is what happens during periods of high exertion, and how much CO2 either bypasses the scrubber and/or is retained inside the diver’s body. A high partial pressure of CO2 triggers the respiration cycle to drastically increase, which then causes panic so bad it’s actually paralyzing, enough that most people can’t even bail out to open circuit. Additionally, some people’s bodies are more tolerant of retained CO2 than others, further necessitating baseline standards for scrubber efficiency and WOB. Hypercapnia is a big deal and has been implicated in fatalities.

So I understand the CO2 issues, and the implications of retained CO2. Maybe I'm just fundamentally misunderstanding the definition of work of breathing in this context. Is WOB not the amount of energy/effort required to complete an inhale-exhale cycle? Whether that's correct or not, can you explain how that effort being more or less can have an impact on retained CO2? I understand if exhalation is difficult, maybe for some reason your scrubber is excessively restrictive (no idea if this is possible, but seems reasonable), you may not "naturally" exhale completely to clear the waste gas from your lungs, and maybe have to consciously "blow" the gas out of your lungs...am I on the right track with that?

In that vein, is that why people are pointing out different dive styles in relation to a WOB conversation? Higher perceived current could potentially impact WOB, as might different diver orientation in the water?

Apologies if I'm the bumbling kid trying to participate in adult conversation.

 

[telemonster]

Seems like a nice compact unit. Shame the price point didn't move down any.

 

[grantctobin]

Seems like a nice compact unit. Shame the price point didn't move down any.

If SuperLyte’s price is accurate, it’s $2500 cheaper than the base O2ptims.

 

[silent running]

My last dive on the CM. CO2 not an issue

IMG_20200313_135743

• Superlyte27
• Mar 29, 2020

Bonaire 2020

It usually isn’t, but without an end tidal CO2 monitor, which has yet to be brought to the CCR market, we will never know for sure. That’s why WOB testing is so important, so we know what kind of risk we are actually taking at any given moment...

 

[Superlyte27]

Most CCR divers wouldn't understand the numbers anyway. But, dive a few units, you'll know which one sucks and which ones don't. I have 5 different units. None of them breathe the same.

 

[stuartv]

I can't really say anything useful about CCR WOB. My only significant experience is with only one unit - my rEvo.

But, I can say something about WOB for OC. Maybe it is relevant. Maybe not.

When I went through ScubaPro Reg Tech school, I trained on the G260 2nd stage, the S620Ti 2nd stage, and a variety of other 2nds and 1sts. At the time, the S620Ti was pretty new and they talked a lot about how the 620 had the lowest WOB of any reg they make (I'm sure they meant - currently make - no idea if they had something better in that past. If they did, I'm sure they wouldn't want to talk about it).

They told us how the 620 had 30% better WOB than the S600. That really sounded impressive!

Meanwhile, the owners and a couple of the other instructors at the shop I worked for had been telling me for ages that the Mk 25/G260 was the best breathing reg set any of them had ever used.

I wanted to see for myself. So, I took advantage of Key Man pricing and bought 4 reg sets. 2 x Mk 25 EVO/G260, and 2 x Mk 25 EVO/S620Ti.

I assembled on 620 and one 260 onto the same Mk 25, so they would have exactly the same IP feeding them both. I used the stock hoses that came on both, so that each 2nd had the same exact hose feeding it.

I dived it like that. To me, I could feel a slight difference between the two - the G260 breathed just a little bit nicer than the S620Ti. I let a friend dive that reg set and she concluded the same thing.

So, I can only speak for myself, but WOB #s are nice, I guess. But, I cannot see myself ever buying a reg or a CCR based on the WOB #s over how it actually breathes when I use it. WOB #s might help suggest to me what reg or what CCR to try. But, in the end, I don't care if the WOB # on the chart says X breathes 50% better than Y. If Y breathes better to me, in my subjective assessment, then I'm going for Y.

@Superlyte27's opinion definitely carries more weight for me that whatever some test data might ultimately show. But, I guess that could be my inexperience talking. Maybe there is some reason to weight test #s more heavily than the experience of somebody who has a lot of experience teaching and diving on a number of different units?

I agree with @Schwob. I don't need (another) CCR. The chest mount deal kind of puts me off at first blush. But, at the same time, I am really intrigued and interested to try one. I tried sidemount (OC) before. It was neat, but was a tool for a job I'm not doing, so I sold my SM rig. Now, I can imagine a sidemount rig, with a dilout on one side, a deco gas on the other side, and a CM CCR and that just seems like it could be pretty cool. Or a backmount setup with independent doubles and travel gas or extra deco gas carried in sidemount style. It seems like it could really be a neat and clean way to do some serious deep wreck diving.

 

[silent running]

Is WOB not the amount of energy/effort required to complete an inhale-exhale cycle? Whether that's correct or not, can you explain how that effort being more or less can have an impact on retained CO2? I understand if exhalation is difficult, maybe for some reason your scrubber is excessively restrictive (no idea if this is possible, but seems reasonable), you may not "naturally" exhale completely to clear the waste gas from your lungs, and maybe have to consciously "blow" the gas out of your lungs...am I on the right track with that?

In that vein, is that why people are pointing out different dive styles in relation to a WOB conversation? Higher perceived current could potentially impact WOB, as might different diver orientation in the water?

Apologies if I'm the bumbling kid trying to participate in adult conversation.

No apologies necessary, this is the place to ask questions and gather info.

Yes, the specific efforts involved in completing the respiratory cycle are directly related to CO2 ventilation. All CCR designs involve trade offs. Chest mounted lungs will be easier on the inhale, back mounted are easier on the exhale, because of the hydrostatic head pressure of having the counter lungs above or below the diver’s lungs. If the WOB is too high, especially on the exhale, it takes more effort to ventilate CO2 from the body, too much CO2 is retained and hypercapnia begins.

I don’t know if “dive styles” is the right way to talk about different types of diving. Most CCR divers actively avoid high workload diving, as most are are trained to do. Most divers rarely or never encounter high workloads, but WOB can still be an issue on moderate workload deep dives where large volumes of gas are being exchanged at depth.

Regardless of one’s diving habits, anybody can find themselves in a short period of high exertion, trying keep from being blown off a wreck during a live drop, or trying to reach the anchor line after a tidal current picks up at the end of a dive.

So, for a variety of reasons WOB can become very important, sometimes unpredictably.