A System for Estimating Drug Delivery from a Dry Powder Inhaler by Analysis of Acoustic Recordings of Time-Stamped Inhaler Events

Inhaled medications are the mainstay of therapy in the treatment of chronic respiratory diseases like asthma and COPD because they allow delivery of the active ingredient directly to the site of action. Poor adherence to inhaled controller medications has been estimated to account for up to 60% of asthma-related hospitalizations and increased rates of 30- and 60- day hospital readmissions in patients with COPD. Numerous electronic monitoring devices have been developed over the last four decades to monitor temporal non-adherence; however, many of these devices do not monitor all or most aspects of inhaler technique. Currently used methods for monitoring inhaler technique, including subjective checklists, are suboptimal.

There is a need to study the frequency of temporal and technique non-adherence in the Irish population and to investigate the impact of dosing and technique errors on drug delivery. Moreover, a comprehensive system of tracking the date and time of inhaler use, as well as the presence or absence of technique errors, on a daily basis is essential to not only an epidemiological understanding of inhaler use but to tailoring of inhaler training and clinical care plans to individual patients. This thesis describes the use of the INCA^TM device, a novel acoustic monitor, which provides longitudinal data on the date and time of inhaler use, as well as data on inhaler technique.

Studies showed that inhalation flow rate, exhalation into the inhaler mouthpiece prior to inhalation, breath-hold duration and missed doses had a significant effect on delivered dose. Data on both temporal and technique adherence were combined in an algorithm, which provided a single measure of overall adherence, called “actual adherence”. The dose counter rate correlated poorly with INCA^TM derived adherence rates, highlighting the need to incorporate technologies, like the INCA^TM device, into clinical trials and patient care.