I've never seen one that is.  I have two bipap machines, one which runs
a compression fan continuously, and one when you breath.  Neither would
probably run long on batteries, they use a lot of power.
the newer machines are a lot like my second machine, but still probably
draw enough to need a pretty substantial supply to run for very long.
Jim
On 1/21/2012 3:11 AM, Alexandre Souza - Listas wrote:
     Eeeeeek!  I
am on CPAP as well; power failures are VERY
 disconcerting.  I run mine on a small UPS now.  I strongly recommend
 it.  In the event of a power failure, the beeping of the UPS will
 likely wake you up, but without that oh-so-wonderful suffocating
 feeling. 
    Shoudn't these toys be battery-backed from factory? :oO