CO2 production results

diverrob · 19th July 2006, 23:30

I thought I would post this in hopes of getting some more info on CO2 production and the efficiencies of the scrubbers that are out there. First I will give you a little background on how this all came around. I am a Canadian Navy Diver and was able to take part in a study to help develop a Physical Test that will be given to all Navy Divers on a annual basis to ensure that a proper standard of physical fitness is maintained. I was involved in three tests which helped create a baseline for the group to use when developing the standard.

The first test was the standard treadmill test where I was told to run on a treadmill until I was unable to run anymore. I must also explain that when doing this test I was started at a level that was well above my normal running pace! (that is why the test only lasted 9:50)

The second and third tests were held in a pool where I was wearing O/C gear and hooked up to a pulley system that was around my waist and prevented me from swimming away. I had a reference point which I kept in front of me and as the time increased so did the weight pulling me backwards. We were told to keep the reference point in front of us until we could no longer swim against the weight. One of the tests was completed at the surface and the other was at 6’ under water.

The main reason I put this all together is from what I have read in various posts is that the testing on the Evo scrubber is far beyond what the normal production of CO2 is for most people (2 hours @ 1.6L/min @ 6C). As you can see the results of the test I did showed a CO2 production well in excess of that. I know that the tests I was involved in were a maximal test and one would not be able to maintain that level for a extended time but the numbers are quite interesting. I have to admit that I really do not understand all of the data that is shown here but maybe someone out there does and can comment on the info. So here it is and I apologies if it is hard to read. They are posted in the following order……. Treadmill, surface swim and the 6’ underwater swim.

Underwaterbear · 20th July 2006, 00:02

Hi Rob,

Thanks for the data. I sure the doc's and various experts around here will be able to appraise the results and answer any questions you have.

Firstly, I can see you are a pretty fit guy from the VO2 figures!

The second observation I would make is that the results consistently indicate that at about 3-4 mins into the test is when CO2 production starts to overtake Oxygen consumption. This would suggest that CO2 is being retained for some reason. By the end of each of the tests the VCO2 figure is around 20% greater than the VO2.

These sort of tests have been done by the US NEDU to evaluate the Prism (and maybe other CCRS?). At least the prism results can be found by linking from SMIs website.

I'm sure you'll generate some interest - nice post.
Cheers
AB

***ScubaDadMiami*** · 20th July 2006, 01:20

I'd sure like to have an interpretation (for idiots) on what each column means and what the figures represent.

teksimple · 20th July 2006, 05:18

I will spout out what should be important here to us closed circuit divers: the VCO2 column which indicates the volume of CO2 produced in liters per minute.

For most of the VCO2 columns in these exercises, Rob's CO2 production does exceed 1.6L/min. But of course, the stuff that they make Rob do are significantly above the typical physiological exertions rates encountered by an average diver on an average dive. Rob, too bad there is no heart rate column, or did I not know which one that was?

A little thread hijack here...

How is this: want to increase your scrubber duration up to an additional 30%? Easy. Go on a low carb diet before diving. I am not sure if I would need to worry about that with my large scrubber, but I would think that others with smaller scrubbers might find that useful.

Metabolism of protein produces 15 percent less CO2 than carbohydrates do, and fat produces about 30% less CO2 per liter of oxygen consumed.

Reference 1.
Reference 2.

In the second reference, it indicates that the metabolism of alcohol produces even less CO2 than fat. As far as scrubber time, then, a good pre-dive meal would be steak cooked in butter and a sour cream omelette chased with a nice cold glass of vodka.

diverrob · 20th July 2006, 06:13

I am looking into the description of the acronyms the ones I do know are as follows........ RR=respiratory rate, BPM=Breaths per min, VCO2=volume of CO2 in L/min and the same for the VO2 as for the rest I am sure that someone out there knows and if not I will try to hunt down the answers.To answer Tecsimple's question, yes I did have my heart rate monitored but for some reason I did not get that info, I will have to inquire about it. Thanks for the input so far

Rob

iain-hsm · 20th July 2006, 11:14

Quote: (Originally Posted by diverrob)

I am looking into the description of the acronyms the ones I do know are as follows........ RR=respiratory rate, BPM=Breaths per min, VCO2=volume of CO2 in L/min and the same for the VO2 as for the rest I am sure that someone out there knows and if not I will try to hunt down the answers.To answer Tecsimple's question, yes I did have my heart rate monitored but for some reason I did not get that info, I will have to inquire about it. Thanks for the input so far
Rob

Rob
Great post. This level of information deserves its own heading and not get lost in the general posing. Just to comment on the terms used. These are standard terms used to express the input gas and expired gas with water vapour but referenced to avoid differences in ambient temperature and barometric pressure. Pretty much back to basic diving teaching on Charlie Boyles laws
STPD Standard Temperature Pressure Dry
BTPS is Body Temperature Pressure Saturated
RR BTM is Respiration Rate, Breath Per Minute
METS is a metabolic rate of consumed oxygen based on 3.5 ml of 02 per kg of subject weight per minute of RR respiration rate
VE Ventilation Rate usually described in BPM Breath Per Min referenced to BTPS. iain

iain-hsm · 20th July 2006, 11:51

Just a couple of other quick points from the results above.
The diver listed in the test results Rob Deproy is 36 year old male. From the figures you can deduct a high level of conditioning say with an aerobic capacity 25 – 50% over the average sports diver. The height and weight given in the figures allow assumption that body fats are low with lean body mass. Age 37 is upper end when you allow for a 1% decline in maximum V02 per year over the age of 25.

There is a formula for assessing your Maximum V02 I will dig this out later, talking into consideration height, weight, age, sex (gender not duration) against heart rate measured on a one mile walk (treadmill) Also women divers are included by reducing around 75-80% performance against men.

I also would welcome the forums comments on these C02 production rates, look especially at the (VC02 STPD) of this diver shown from this post and answer why some of us keep banging on about the importance of C02 and performance testing at levels of 1.6 l/min or 1.3 (USN) level as the MINIMUM rate of production in rebrether trials for duration claims. Iain Middlebrook

iain-hsm · 20th July 2006, 12:34

That too Tek. Fully agree C02 is the single most important killer against the diver. Being over weight, over 30 and unfit is also pretty good way to die while diving. Re the 1.6 L/min level. Look again at the charts the diver in question never went BELOW a C02 production level of 1.6 l/min. Hijack away on the low carbs 100% on that.

In my diving training during 1979 over 50% of the pre selected fitness tested suitable for diving trainees failed during the first 6 weeks of a 12 week diver training course due to fitness. While not wishing to encourage “mud runs” as part of open water training the physiological differences between OC and CC should not preclude an additional level of required respiratory fitness for CC diving.
On the other hand bugger the diving a good steak and vodka at my age works better. However as hard I think about this I can’t quite see the day when steak and vodka overtakes Lithium Hydroxide Monohydrate as the next best long endurance chemical scrubber design. Iain Middlebrook

diverrob · 26th July 2006, 01:09

Well I tried to get more info on this report but the person who administered the test in on summer leave so it will have to wait for a while. If anyone out there can give us any more info it would be a big help. I also would like to know how AP determined CO2 production value of 1.6l/min as a bench mark?

From what I see in this report 1.6 seems low, I was able to produce 1.6 early on in the test. now I don't think I could have maintained the level of exertion at that point for 2hr (Evo scrubber) but I could certainly over breath the scrubber for short sessions throughout a long dive. Last weekend I was working at 150' with a .5-.75 knot current and at the highest level of work I know I was producing more that 1.6l/min, more like 3-4l/min based on how I felt I exerted myself compared to the test day. My temp stick never came close to the end of the segments and in fact according to the readings I still had over 3/4 of the scrubber left (74 min dive). I will continue to monitor the temp stick but use it conservatively

babar · 26th July 2006, 01:47

this should give an idea of how easy it is too breakthrough a scrubber with exertion, even with a fresh scrubber. I've done it myself. On my first dive on my sk crossover, with a fresh scrubber. Also look at the FeCO2, at some points, his exhaled CO2 is 5-6%! Some of that is going to be scrubbed, but some won't, and will continue to build up.

During the test, how was your WOB? Any increase would also tend to drive the co2 up. I don't know what all the measurements are, but I think the co2 measurements bear some consideration.

20th July 2006, 00:02	#2 (permalink)
Underwaterbear A Prismer in Megland Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: May 2005 Location: Seattle, WA Posts: 164	Re: CO2 production results Hi Rob, Thanks for the data. I sure the doc's and various experts around here will be able to appraise the results and answer any questions you have. Firstly, I can see you are a pretty fit guy from the VO2 figures! The second observation I would make is that the results consistently indicate that at about 3-4 mins into the test is when CO2 production starts to overtake Oxygen consumption. This would suggest that CO2 is being retained for some reason. By the end of each of the tests the VCO2 figure is around 20% greater than the VO2. These sort of tests have been done by the US NEDU to evaluate the Prism (and maybe other CCRS?). At least the prism results can be found by linking from SMIs website. I'm sure you'll generate some interest - nice post. Cheers AB Last edited by Underwaterbear : 20th July 2006 at 00:06.
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20th July 2006, 01:20	#3 (permalink)
*ScubaDadMiami* Moderator Current Rebreather/s: Optima Other Rebreather/s: Join Date: Sep 2005 Location: Florida, USA Posts: 1,890	Re: CO2 production results I'd sure like to have an interpretation (for idiots) on what each column means and what the figures represent. __________________ Howard Packer IANTD CCR Instructor Miami Beach, Florida CCRDiveTraining.com
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20th July 2006, 05:18	#4 (permalink)
teksimple Enlightened Alpinist Current Rebreather/s: Sport Kiss MK 15.X Other Rebreather/s: Classic Kiss Join Date: Apr 2005 Location: Back in Hawaii Posts: 477	Re: CO2 production results I will spout out what should be important here to us closed circuit divers: the VCO2 column which indicates the volume of CO2 produced in liters per minute. For most of the VCO2 columns in these exercises, Rob's CO2 production does exceed 1.6L/min. But of course, the stuff that they make Rob do are significantly above the typical physiological exertions rates encountered by an average diver on an average dive. Rob, too bad there is no heart rate column, or did I not know which one that was? A little thread hijack here... How is this: want to increase your scrubber duration up to an additional 30%? Easy. Go on a low carb diet before diving. I am not sure if I would need to worry about that with my large scrubber, but I would think that others with smaller scrubbers might find that useful. Metabolism of protein produces 15 percent less CO2 than carbohydrates do, and fat produces about 30% less CO2 per liter of oxygen consumed. Reference 1. Reference 2. In the second reference, it indicates that the metabolism of alcohol produces even less CO2 than fat. As far as scrubber time, then, a good pre-dive meal would be steak cooked in butter and a sour cream omelette chased with a nice cold glass of vodka.
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20th July 2006, 06:13	#5 (permalink)
diverrob The Evolution of Diving Current Rebreather/s: Evolution Other SCR Other Rebreather/s: Not Bought Yet Other SCR Join Date: May 2005 Location: Victoria BC Canada Posts: 315	Re: CO2 production results I am looking into the description of the acronyms the ones I do know are as follows........ RR=respiratory rate, BPM=Breaths per min, VCO2=volume of CO2 in L/min and the same for the VO2 as for the rest I am sure that someone out there knows and if not I will try to hunt down the answers.To answer Tecsimple's question, yes I did have my heart rate monitored but for some reason I did not get that info, I will have to inquire about it. Thanks for the input so far Rob
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20th July 2006, 11:14	#6 (permalink)
iain-hsm Custom Title Allowed! Current Rebreather/s: MK 15.X Other CCR Other SCR Other Rebreather/s: Other CCR Other SCR Join Date: Mar 2005 Location: Loughborough England uk Posts: 345	Re: CO2 production results Quote: (Originally Posted by diverrob) I am looking into the description of the acronyms the ones I do know are as follows........ RR=respiratory rate, BPM=Breaths per min, VCO2=volume of CO2 in L/min and the same for the VO2 as for the rest I am sure that someone out there knows and if not I will try to hunt down the answers.To answer Tecsimple's question, yes I did have my heart rate monitored but for some reason I did not get that info, I will have to inquire about it. Thanks for the input so far Rob Rob Great post. This level of information deserves its own heading and not get lost in the general posing. Just to comment on the terms used. These are standard terms used to express the input gas and expired gas with water vapour but referenced to avoid differences in ambient temperature and barometric pressure. Pretty much back to basic diving teaching on Charlie Boyles laws STPD Standard Temperature Pressure Dry BTPS is Body Temperature Pressure Saturated RR BTM is Respiration Rate, Breath Per Minute METS is a metabolic rate of consumed oxygen based on 3.5 ml of 02 per kg of subject weight per minute of RR respiration rate VE Ventilation Rate usually described in BPM Breath Per Min referenced to BTPS. iain
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20th July 2006, 11:51	#7 (permalink)
iain-hsm Custom Title Allowed! Current Rebreather/s: MK 15.X Other CCR Other SCR Other Rebreather/s: Other CCR Other SCR Join Date: Mar 2005 Location: Loughborough England uk Posts: 345	Re: CO2 production results Just a couple of other quick points from the results above. The diver listed in the test results Rob Deproy is 36 year old male. From the figures you can deduct a high level of conditioning say with an aerobic capacity 25 – 50% over the average sports diver. The height and weight given in the figures allow assumption that body fats are low with lean body mass. Age 37 is upper end when you allow for a 1% decline in maximum V02 per year over the age of 25. There is a formula for assessing your Maximum V02 I will dig this out later, talking into consideration height, weight, age, sex (gender not duration) against heart rate measured on a one mile walk (treadmill) Also women divers are included by reducing around 75-80% performance against men. I also would welcome the forums comments on these C02 production rates, look especially at the (VC02 STPD) of this diver shown from this post and answer why some of us keep banging on about the importance of C02 and performance testing at levels of 1.6 l/min or 1.3 (USN) level as the MINIMUM rate of production in rebrether trials for duration claims. Iain Middlebrook
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20th July 2006, 12:34	#8 (permalink)
iain-hsm Custom Title Allowed! Current Rebreather/s: MK 15.X Other CCR Other SCR Other Rebreather/s: Other CCR Other SCR Join Date: Mar 2005 Location: Loughborough England uk Posts: 345	Re: CO2 production results That too Tek. Fully agree C02 is the single most important killer against the diver. Being over weight, over 30 and unfit is also pretty good way to die while diving. Re the 1.6 L/min level. Look again at the charts the diver in question never went BELOW a C02 production level of 1.6 l/min. Hijack away on the low carbs 100% on that. In my diving training during 1979 over 50% of the pre selected fitness tested suitable for diving trainees failed during the first 6 weeks of a 12 week diver training course due to fitness. While not wishing to encourage “mud runs” as part of open water training the physiological differences between OC and CC should not preclude an additional level of required respiratory fitness for CC diving. On the other hand bugger the diving a good steak and vodka at my age works better. However as hard I think about this I can’t quite see the day when steak and vodka overtakes Lithium Hydroxide Monohydrate as the next best long endurance chemical scrubber design. Iain Middlebrook
(Offline)

26th July 2006, 01:09	#9 (permalink)
diverrob The Evolution of Diving Current Rebreather/s: Evolution Other SCR Other Rebreather/s: Not Bought Yet Other SCR Join Date: May 2005 Location: Victoria BC Canada Posts: 315	Re: CO2 production results Well I tried to get more info on this report but the person who administered the test in on summer leave so it will have to wait for a while. If anyone out there can give us any more info it would be a big help. I also would like to know how AP determined CO2 production value of 1.6l/min as a bench mark? From what I see in this report 1.6 seems low, I was able to produce 1.6 early on in the test. now I don't think I could have maintained the level of exertion at that point for 2hr (Evo scrubber) but I could certainly over breath the scrubber for short sessions throughout a long dive. Last weekend I was working at 150' with a .5-.75 knot current and at the highest level of work I know I was producing more that 1.6l/min, more like 3-4l/min based on how I felt I exerted myself compared to the test day. My temp stick never came close to the end of the segments and in fact according to the readings I still had over 3/4 of the scrubber left (74 min dive). I will continue to monitor the temp stick but use it conservatively
(Online)

26th July 2006, 01:47	#10 (permalink)
babar Curmudgeon Current Rebreather/s: Evolution Sport Kiss Other CCR Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Other CCR Join Date: Apr 2005 Location: Southern California Posts: 415	Re: CO2 production results this should give an idea of how easy it is too breakthrough a scrubber with exertion, even with a fresh scrubber. I've done it myself. On my first dive on my sk crossover, with a fresh scrubber. Also look at the FeCO2, at some points, his exhaled CO2 is 5-6%! Some of that is going to be scrubbed, but some won't, and will continue to build up. During the test, how was your WOB? Any increase would also tend to drive the co2 up. I don't know what all the measurements are, but I think the co2 measurements bear some consideration. __________________ Babar Evolution Plus Sport kiss
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