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The following only applies to semiclosed circuit constant mass flow rebreathers. >> I wrote: >> >> Bennet&Elliot quote 3 l/m with a potential maximum of 6 l/m. I personaly have >> done over 2 l/m on a land test. >Peter wrote: > >This seems an extraordinary number. The usual computation is around 300cc >*O2* per meter2 body surface at rest. Even allowing that you can raise you >use with excercise, are you sure this isn't a total gas flow rate i.e., >Qs? The 3-6 liters/minute represents metabolic O2 consumption not flow rate. Bennet & Elliot recommend the use of the 3 l/m figure when computing FiO2 for a semiclosed constant mass flow rebreather. From memory Drager recommends 2 l/m for it's military rebreathers. I think the US Navy used 3 l/m for the old Emerson Mark VI semiclosed units. I'm not sure but doesn't the Fieno use 2 l/m? Anyone know the figure for the Atlantis I? The 6 l/m figure is an exteem. I can't remember the conditions maybe cross country skiing while being chased by a polar bear. >Peter also wrote: > >3. The MOD of the unit is the MOD of the gas (nitrox) supply, using a >maximal pPO2 of 1.4 ATA. Interesting Drager seems to have no problem with exceeding the MOD of the supply gas for both their military and recreation breathers. I have US Navy documentation recommending both exceeding the MOD of the supply gas and not exceeding the MOD of the supply gas. The more conservative limit is the newest. >4. The EAD is calculated by assuming the FiO2 the at the MOD is >calculated by subtracting *maximal* O2 consumption (2L O2/min) >from the operational FiO2 (i.e., not including the contribution of any >override) at the MOD, with all remaining gas considered nitrogen. The cool thing is if you have a Bridge II and are running 8 l/m and 50% you can use the Bridge idiot mode for both O2 and deco calculations. >11. The effort of work breathing should not result in a positive end >expiratory pressure (PEEP) of greater than 3 cms of water. I wonder what happens with the Drager LAR V. I would expect the front mounted counter lung has a lot more than 3 cms of water PEEP. >However PEEP will tire the heck out of you and does weird >things to gas exchange and may (consequently) significantly increase O2 >lung toxicity. Do you have references to the lung toxicity effects of elevated PEEP? Barrie
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