go for LTV 1000 - from Pulmonetics
It doesn't require any external high pressure air to drive the pneumatics inside as it uses turbine (built in) technology.
Itlooks and weigh as laptop computer.
It can be used both on high /low (flowmeter)pressure oxygen source to achieve the set O2 %. Modes available are Assist/control, SIMV, CPAP, non-invasive, on both pressure and volume cycled.
tidal vol 50 - 2000ml, pressure support, pressure controled flow termination, has internal battery and can use external battery as well.