The May/June issue of the Pulmonary Paper is a must read reference. All Issues regarding POC' are covered. While most deliver about 1-lpm, and weigh about 5#. Some deliver as much as 3-lpm, but weigh 3-4 times that.
An alternative to consider is the O2 cylinder, at 2 to 3 lpm you can get 6 to 4 hours use, and at about the same weight as a POC.
Sorry for being so late, on noting this, the issue got set aside.