Airflometer: new toy or worthwhile advance?

The Airflometer provides a useful index of expiratory flow rate and as such it is a worthwhile advance. It can provide an accurate index of FEV1 provided it is individually calibrated. Perhaps the only limitation is the lack of response of the instrument at low flow rates, for example, with an FEV1 of less than one litre. It is remarkably inexpensive.