@ggribble , even though this is beyond the question(s) posed , please check with your airline before renting as airlines have their own rules as to which particular brand/ model they will allow -- my wife needed 24 hour oxygen and I have been through this. From your statements it seems that your wife uses Oxygen only while sleeping or only limited usage ( not 24 hrs) ---- please consult your doctor to make sure that the equipment allowed and rented is one that can support the travel conditions and duration -- charging facilities on the planes are often non-existent and seat facility in cattle class is even more limited. Wish you luck with this .
pk
