Study Examines Common Misuse of Inhalers by Asthma Patients
Researchers at Rice University and Baylor College of Medicine conducted a study to evaluate common incorrect usage techniques and to determine optimal methods for patients using metered-dose inhalers to ensure the maximum delivery of medication to the lungs.
According to the researchers, current guidelines are based upon clinical studies using chlorofluorocarbon-MDIs and in vitro studies of hydrofluoroalkane-MDIs using idealized techniques of uniformed inhalation and actuation that do not take into account nonuniform techniques used by actual patients.
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“The effectiveness of metered-dose inhalers in delivering medication to the lungs highly depends on its correct usage technique,” the researchers wrote.1
However, it is estimated that between 70% to 90% of asthma and COPD patients do not use their MDI correctly. A study published in 2016 examined the techniques of 23 patients diagnosed with asthma or COPD using a placebo MDI attached to a CapMedic device, finding that 100% of patients made at least 1 error and 74% made at least 3 errors.2
In order to better understand the effects of time-varying MDI usage parameters on the deposits of medication delivered by a HFA-MDI, the researchers conducted an in vitro study modeled on real-life variable inspiratory flow and actuation techniques recorded from 15 asthma and COPD patients The in vitro experiment used a mouth-throat cast, programmable MDI actuator, and breath simulator to evaluate lung deposition according to the MDI techniques used by patients, and to determine the optimal method that delivers the most medication to the lungs.
“High inspiratory flow rates, 60–90 L/min, consistently resulted in high in vitro lung deposition (>40%) of aerosol (albuterol delivered from Ventolin HFA-MDI) compared to 30 L/min when MDI actuation occurred in the first half of inhalation,” the researchers wrote.
In addition, variation in coordination affected lung deposition more significantly (23%) than flow rate or duration of inhalation (≤5%), and positive coordination resulted in higher lung deposition in the in vitro model compared with negative or zero coordination (actuating before or at the start of inspiration).
“Our results differ from the current Global Initiative for Asthma inhaler use guidelines,” said co-author Dr Ashutosh Sabharwal of the Electrical and Computer Engineering Department at Rice University. “The propellant used in inhalers has changed in recent years, and the current guidelines were developed based on studies of the old inhalers. Our findings, coupled with the recent changes in inhaler propellants, suggest it is time to revisit these guidelines.”3
—Melissa Weiss
Reference:
1] Biswas R, Hanania NA, and Sabharwal A. Factors determining in vitro lung deposition of albuterol aerosol delivered by Ventolin metered-dose inhaler [published before print February 3, 2017]. J Aerosol Med Pulm Drug Deliv. doi:10.1089/jamp.2015.1278.
2] Biswas R, Patel G, Mohsin A, Hanania N, and Sabharwal A. Measuring competence in metered dose inhaler use using Capmedic electronic inhaler monitoring tool [published online October 17, 2016]. Chest. doi:10.1016/j.chest.2016.08.017.
3] Boyd J. Inhaler study: how much medicine makes it to lungs? [press release]. Houston, TX: Rice University, February 28, 2017. http://news.rice.edu/2017/02/28/inhaler-study-how-much-medicine-makes-it-to-lungs-2/.