Easiest breathing CCR.

[padiscubapro]

Hi Joe, yes I'm aware that comparisons are difficult, given the 2 differing test protocols, that's why I qualified what I said by referencing the USN tests specifically. I'm not trying to give any impression other than the facts as they are documented in the NEDU test data, as I said. So please stop giving the impression that I'm trying to give some impression other than what I posted.

But since you brought up the subject of cross test comparisons, please remember that Alex Deas bothered to include the Prism in a WOB chart on an RBW thread, after making adjustments for internal diver WOB and the deeper NEDU test depth in the calculations and the unit still came out with lower WOB than all except Boris. I don't take it as fact, but those were Alex's calculations not mine and he is a stickler for detail of the highest order. The NEDU Prism tests also include a hydrostatic load measurement for both prone(.47kpa average) and upright(-.09kpa average), both of which exceed their 1.0kpa test criteria. And if I understand the figures correctly, the hydrostatic load is actually higher in the prone position, the opposite of Boris and which might be another reason why the NEDU WOB tests are done in the prone position, other than divers typically working hardest while swimming... -Andy

The hydrostatic imbalance peak depends on the design.. some are optimized for vertical some for horizntal.. This is different from resistive breathing.. The latest chart that alex put out doesn't have the prism on it.. Correcting for the diver's wob is easy.. you just have to add a bit to the prism (or subtract from all the others), the difficulty comes in is that there is no direct way to compare verticle vs prone position.. All sorts of otehr things come into play. especially the way lungs or hoses can collapse.. at low ventillation rates these do not make a huge difference but at high rates they do...

The standard testing these days for wob in the ce tests is at 40m.. this point is listed in the nedu tests, in the past 50m was frequently used..
I am not saying I agree with the CE liimits and protocol just thats why people have been using to do the tests..

Take a rig like the rEvo in the vertical position the breathing is significantly higher than the prone position, this is especially true on the exhale.. Paul used a few tricks to optimize the breathing when in the prone position.. 2 key tricks he used is that the inhale and exhale lungs are different sizes, and that the inhale lung is at a lower point than the exhale lung.., This uses the fact that our lungs are more efficient blowing than sucking, so the inhale is very easy on the rEvo, and we don;t notice the exhale.. Paul once gave me the numbers for a single test in this position on a rig without all the upgrades, and the numbers were lower than any other test number I heard.. He wount publish these results as first they are a single test and second it was done without all the recent upgrades..

on ots rigs the changes will be less drastic but will still be influenced on how well the gas path stays open or is collapsed..

The trick of 2 different sized lungs also has another benefit.. when 2 counterlungs are used a smaller exhale helps increase scrubber efficiency as the gas is not allowed to cool as much.. a design using a signle lung, that immediately passes the gas through the scrubber before capturing it should in theory have the best efficiency (as long as flow is not too fast).

as to me implying what you imply.. I understand you being passionate, but for those that really are new to this thing, the way the messages come across implies they can just look at the numbers to see relative ease of breathing, but this is not the case..

 

[silent running]

The hydrostatic imbalance peak depends on the design.. some are optimized for vertical some for horizntal.. This is different from resistive breathing.. The latest chart that alex put out doesn't have the prism on it.. Correcting for the diver's wob is easy.. you just have to add a bit to the prism (or subtract from all the others), the difficulty comes in is that there is no direct way to compare verticle vs prone position.. All sorts of otehr things come into play. especially the way lungs or hoses can collapse.. at low ventillation rates these do not make a huge difference but at high rates they do...

The standard testing these days for wob in the ce tests is at 40m.. this point is listed in the nedu tests, in the past 50m was frequently used..
I am not saying I agree with the CE liimits and protocol just thats why people have been using to do the tests..

Take a rig like the rEvo in the vertical position the breathing is significantly higher than the prone position, this is especially true on the exhale.. Paul used a few tricks to optimize the breathing when in the prone position.. 2 key tricks he used is that the inhale and exhale lungs are different sizes, and that the inhale lung is at a lower point than the exhale lung.., This uses the fact that our lungs are more efficient blowing than sucking, so the inhale is very easy on the rEvo, and we don;t notice the exhale.. Paul once gave me the numbers for a single test in this position on a rig without all the upgrades, and the numbers were lower than any other test number I heard.. He wount publish these results as first they are a single test and second it was done without all the recent upgrades..

on ots rigs the changes will be less drastic but will still be influenced on how well the gas path stays open or is collapsed..

The trick of 2 different sized lungs also has another benefit.. when 2 counterlungs are used a smaller exhale helps increase scrubber efficiency as the gas is not allowed to cool as much.. a design using a signle lung, that immediately passes the gas through the scrubber before capturing it should in theory have the best efficiency (as long as flow is not too fast).

Thanks for all the interesting info, Joe. I have never experienced a collapsed or restricted gas path, that I know of, other than a kinked hose. When my RMV goes up, I tend to add gas, which makes a collapsed gas path that much less likely. Another reason I prefer OTS CLs is the imediate loop volume feedback I get from having CLs on my chest where I can feel them moving, how much volume there is and whether the lungs have collapsed or bunched up.

as to me implying what you imply.. I understand you being passionate, but for those that really are new to this thing, the way the messages come across implies they can just look at the numbers to see relative ease of breathing, but this is not the case..

Passionate I am, but I was merely quoting the NEDU test data, which I think is relevent enough. The Prism is one of the few CCRs to make it through 3 stages of rigurous NEDU testing designed around using CCRs in demanding conditions beyond those seen in typical recreational use. These standards have served me well diving in demanding conditions, especially regarding WOB and working hard in high current for extended periods.

For the record, I recomend prospective CCR buyers familiarize themselves with the different testing protocols and sort through the fine print to decide which tests/standards are most important for their particular use. For myself, I'm more concerned with a unit's WOB in the prone position as that's where I spent most of my time working hard and not in the upright position, which I pressume one would only find themselves working hard in while making an ascent, which means WOB and PPCO2 would be decreasing as the diver fins upward. IMHO, it's more important to know the WOB in the prone position in order to prevent retaining CO2 in the first place.

I think most divers contemplating buying an expensive CCR will take the time
to see which units have been tested and by who and then sort things out for themselves. I doubt anybody reading here will take one person's word for it, considering all the info on the subject of WOB and they will quickly realize they have lots of homework to do... -Andy

 

[padiscubapro]

Thanks for all the interesting info, Joe. I have never experienced a collapsed or restricted gas path, that I know of, other than a kinked hose. When my RMV goes up, I tend to add gas, which makes a collapsed gas path that much less likely. Another reason I prefer OTS CLs is the imediate loop volume feedback I get from having CLs on my chest where I can feel them moving, how much volume there is and whether the lungs have collapsed or bunched up.



Passionate I am, but I was merely quoting the NEDU test data, which I think is relevent enough. The Prism is one of the few CCRs to make it through 3 stages of rigurous NEDU testing designed around using CCRs in demanding conditions beyond those seen in typical recreational use. These standards have served me well diving in demanding conditions, especially regarding WOB and working hard in high current for extended periods.

For the record, I recomend prospective CCR buyers familiarize themselves with the different testing protocols and sort through the fine print to decide which tests/standards are most important for their particular use. For myself, I'm more concerned with a unit's WOB in the prone position as that's where I spent most of my time working hard and not in the upright position, which I pressume one would only find themselves working hard in while making an ascent, which means WOB and PPCO2 would be decreasing as the diver fins upward. IMHO, it's more important to know the WOB in the prone position in order to prevent retaining CO2 in the first place.

I think most divers contemplating buying an expensive CCR will take the time
to see which units have been tested and by who and then sort things out for themselves. I doubt anybody reading here will take one person's word for it, considering all the info on the subject of WOB and they will quickly realize they have lots of homework to do... -Andy

Some of the tests are quite interesting on how the data changes.. a "collapsed or restricted" gas patch doenst mean a blockage but rather any change in the diameter of the hoses and or gas path within the C-l...

at normal venillation rates something like a rt angled fitting does not have alot of impact, but on high ventillation rates the resistance can be quite surprising.. There are alot of little gotchas like this..

The reason tests are done in the vertcial position is that thid is usually the worse breathing position and its the position most divers fall bak to in an emergency..

If you can come out good in this position you should be really good in the proe position..