----- Original Message -----
From: Simon Carley >
> What circuit are you using off the Boyles machine? The flow rate above is
an
> insufficient flow rate to prevent rebreathing with many circuits. Most
> anaesthetic machines I encounter come with a Bain coaxial system (mapleson
> D) system which should have at least twice the minute volume flow rate to
> prevent rebreathing (Aitkenhead recommends at least 12L/min in the average
> adult). I have also used the anaesthetic machine in this way but at higher
> total flow rates.
Yes, I'm sure there would be considerable CO2 rebreathing with a Bain's
circuit, but I usually use a Magill's circuit (Mapleson A) which, as you
know, is the most efficient circuit going for spontaneous breathers,
requiring little more than the patient's minute volume to prevent
significant rebreathing. Sometimes I crank up 3 and 9 litres/minute in the
rugby player type who deep-breathes. In any case I don't think transitory
rebreathing of CO2 is harmful to younger folk, and perhaps adds to the
narcosis! Using such a high concentration of nitrous however has the
potential to lead to post-procedure hypoxia so one must be liberal with
oxygen for several minutes afterwards.
Regards
Adrian Fogarty
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