Important to understand...pulse flow portable oximeters may have setting up to 6 liters per minute...but THEY DO NOT DELIVER THAT ...pulse rate is not the same as continuous flow. Mayo rehabilitation pointed that out to me. Look at capacity of the portable.
For night sleep I have a stable oxygen concentrator that delivers continuous flow not a portable one . For higher portable concentrator it is necesssary to go with bigger one, tank I believe.
I have a portable Inogen Rov 6 - latest model, they stopped making the One 5. I bought it but my Medicare provider gave me a Inogen One 5 under Medicare. They are very very similiar and same batteries work on both. My prescription is for 2 lm but I set my Inogen at 4-6 when exercising to keep my O2 at safe level.