The aerosure is sold as an exercise programme so it's nothing like a flutter device. The measure I use before I purchase anything medica, is this......if the item has been medically tested and approved, as a disabled person I can by it VAT free. The aerosure is not available VAT free. I purchased a Powerbreath, which was vat free and cost me just over £24.... Not only that but I can go on line to various hospitals up and down the country and download more exercise recording sheets. It does help too. If you work your way through all of the exercises, you think..." Finished with that then,".... but you haven't. Keep it handy and if you have an Asthma attack or have an episode of poor breathing, get it back out and start again. I do take the precaution of not using it when I have an infection or my breathing is bad, basically for the same reason you don't take a spirella test..,your lungs have got enough to do without you pushing them further.