BACKGROUND:  Cross-sectional observational studies suggest that between 50% and 60% of patients misuse a dry powder inhaler, whereas studies with electronic monitors indicate that patients sometimes overuse/underuse their inhalers. It is not known what impact errors and erratic use have on inhaler adherence.

OBJECTIVES: The purpose of this study was to longitudinally quantify when and how patients adhered to a twice-daily preventer treatment by using a novel acoustic recording device attached to an inhaler (INhaler Compliance Assessment).

METHODS: Patients with a history of asthma or chronic obstructive pulmonary disease (n = 123) from primary care and community pharmacies were given an INhaler Compliance Assessment-adapted inhaler for 1 month. Analysis of the audio files provided quantitative information on time and technique of inhaler use.

RESULTS: Data were available for 103 patients. Twenty-one patients (20%) used their inhaler in the correct manner at the correct interval. There were 5045 audio files with attempted inhalations, of which 1204 had technique errors (24%). Errors included inadequate flow (27%), drug priming without inhalation (19%), exhalation into the inhaler (18%), and multiple inhalations (25%). On average, participants made errors 20% of the time. Of 60 doses expected to be taken in a month per person, on average 49 doses (82%) were attempted and when errors were accounted for, the average number of actual doses taken was 34 doses (57%; P < .01) comparing attempted to actual doses.

DISCUSSION: These data highlight that ineffective and irregular inhaler use is common and when combined in a single calculation indicate that only 20% of participants used their inhaler correctly and on time.