Your mobile concentrator needs to be able to provide you with the oxygen dosage you need at all times, no matter where you are or what you're doing. Your oxygen needs will be different when you're physically active when you're sleeping and or sitting and watching television. The POC needs to be able to detect the changes in your breath rate and compensate accordingly.
There are two types of oxygen settings that come with portable models – pulse dose, and continuous flow oxygen. All POCs that have continuous flow settings, also have pulse dose settings, as well. As of right now, the highest continuous flow setting in a mobile unit is 3 LPM (liters per minute).
You will need to make sure that whatever concentrated oxygen portable you get has the dosage setting you need, with a high enough breath rate. The maximum breath rate and dosage volume should exceed what you would normally need, to make sure you'll never run short. It should have a good oxygen reserve, so when your breath rate goes up, the dosage will go up to meet it. Breath rate is measured in breaths per minute (BPM). If you need a low dose or a low pulse dose of oxygen, you'll be able to take advantage of the smaller concentrated oxygen portables. If you need 5 LPM of continuous oxygen, you won't be able to use any of the continuous flow portable models that are currently on the market.