Does anyone know what is the smallest, lightest portable oxygen concentrator available? The Inogen One and Invacare XPO2 seem to be the most popular. They are small but at around 7 lbs., they're not very light.
Then there are LifeChoice by Inovalabs and FreeStyle by AirSep which are under 5 lbs. each. I never heard of these before. Has anyone had any experience with these? Are there others as light as these?