@hellopam I tried a pom . .They are over rated. None of them can supply enough oxygen for me . My home consentrator is good . I use 4 ltrs 24/7. I use a tank on a cart to go out . I have no more problems . And yes a person will use more oxygen when moving or walking. Even I , at 4 ltrs, drop to 82 after changing my clothes to go to bed That is the hardest thing on my oxygen . Pulling on clothes& such . It comes back up within a minute and a half. My pulmonologist says if it comes up to 92 in -“1 1/2 min then I am fine. The portable couldn’t do that either . They are advertised with people that either don’t need them. Or they are prescribed less than 3 ltrs. They need advertising rules. They say 2 on pulse is 2 liters . That is not true. Those numbers on the dial are not measuring ltrs .