A MODEL FOR THE EFFECT OF INHALATION DEVICE FLOW RESISTANCE ON THE PEAK INSPIRATORY FLOW-RATE AND ITS APPLICATION IN PHARMACEUTICAL TESTING

An empirical relation between the peak inspiratory flow through a device and the flow resistance of the device has been developed using results from healthy subjects and verified to a limited extent using data from asthmatic patients. The empirical relation can be used to predict the change in peak inspiratory flow resulting from a change in flow resistance. Matching flow rates, representing equal inspiratory force, may thus be calculated for different inhalation devices. The fine particle dose generated by a variety of commercial powder inhalers was tested in-vitro at flow rates representing, for each device, a weak, a medium and a forceful inspiration. It was found that both the level of the fine particle dose and its flow rate dependence varied for the products.