Mailing List Archive Mailing List Archive
Rich, In reply to: On Wed, 29 May 1996, Richard Pyle wrote: > > There is a much cheaper way to do this: If the student excercises (say on > > a stationary bicycle) at 1.0 ATA wearing/using the SCR as a breathing > > source, the VO2 can be calculated at a worst case scenario. I think this > > would be a useful part of standard rebreather training and would not add > > appreciably to costs. > > I agree that is cheaper and useful, but it only provides data to plug > into a theoretical model. I think real-world testing on an actual unit > would bypass the weakness of the model and cut right to the chase? How > expensive would it be to make a modified unit with an O2 analyzer? > Dennis did it himself on his Fieno. It wouldn't take much more to build > a trianing unit. The advantage of the stationary cycle mehod is that the VO2 can be calculated at a worst case scenario, i.e., at 1.0 ATA. You should also be able to get workload up to a level that is nearly impossible underwater. This is not a theoretical model, if the diver passes out, then you know the capacity of the system was exceeded! Finally no one who "teaches" rebreather courses can claim that they can't afford to do this for *each* student. I agree that an in-water test might be closer to the "real" thing, but again it's a worst case scenario within minimum risk at the surface. I am also not sure that any pPO2 meter is going to be more or as accurate as measuring actual consumption (watching the cylinder gauge) at the surface. > > The CO2 is being absorbed by the canister *after* you get it out of your > > body. If I deliver a pPO2 to you of 1.2 ATA but in a volume of 150cc, you > > wont't run out of O2, but you will become hypercarbic, because I am not > > meeting your minimum minute respiratory volume needs. > > I'm a little confused... What do CO2 levels have to do with > loop/counterlung volumes? Let's assume that the FiCO2 is stable and constant (a really big, effective canister), but the tidal volume falls. Now this shouldn't happen for any given depth as the over-ride should kick in and compensate. But say that the diver is dropping like a (Bill) stone - 100 ft/min. Then the reservoir bag may not deliver the volume of gas required to ventilate the diver. i.e., 500 - 750 cc/breath minimum. Then you retain CO2, because you don't have enough "breath" to blow it off. - ph
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]