Realistic evaluation of metered dose inhalers alone or in association with add-on devices

Abstract

A pressurized metered dose inhaler (MDI) is a type of medical device designed to deliver multiple, individually precise doses of finely dispersed drugs to the lungs via the oral inhalation route. As documented by numerous studies, a significant drawback of MDIs is the use of incorrect techniques by patients. The effects of improper use and subsequent inadequate dosing can lead to a host of clinical problems ranging from sub-optimal therapeutic outcomes to emergency room admissions or mortality. All these outcomes also place a financial burden on society due to increased medical costs and decreased productivity from missed days at school or work. In an attempt to improve therapeutic outcome, MDIs were instrumented with a differential pressure transducer, load cell and accelerometer to facilitate simultaneous capture and display of inhaled flow rate, applied finger-force on canister, and shaking in real-time plots. A biofeedback function for inhaled flow rate was also included. Once developed, the instrumented MDI was used to train pediatric patient volunteers recruited from a predefined high risk population for asthma-related complications. The instrumented MDI was shown to be an effective training aid for significantly improving inhaler techniques. Improving inhaler techniques, as demonstrated by real-time collection of shaking, actuation, and inhalation profiles based on actual patient use, is an important step to reducing incidences of preventable therapeutic deficiencies or failures due to inhaler misuse. In addition to training alone, another way to facilitate correct MDI use is to deploy add-on devices such as dose counters, valved holding chambers, and facemasks. However, there is no generally acceptable or agreed upon methodology for evaluating these products. To that end, test methods were developed which consisted of using a force-instrumented MDI to evaluate dose counter accuracy, and using a novel soft anatomical model face-based test fixture with adjustable settings to evaluate valved holding chambers with facemasks under realistic simulated use conditions.