Inogen One G5 portable oxygen concentrator that is what the new and improved Inogen for Sale will be called. Inogen is sending out post cards to patients on oxygen therapy boasting about their new travel oxygen concentrator. Most important features of a portable oxygen machine for patients are size, weight, and battery life. The second generation Inogen One G5 is supposed to have it all. Features of Inogen: The original unit was about 2,2 kg. (4.7 lbs.) (includes single battery). The second generation is going to be 7 pounds. Not…