For individuals with asthma using a metered-dose inhaler (MDI) to prevent or relieve symptoms, there is a good chance that they are not using their inhaler correctly, and subsequently they are not experiencing lung exposure to the pressurized medication needed to ward off asthma attacks.
Experts from Rice University and Baylor College of Medicine, in their paper recently published in the Journal of Aerosol Medicine and Pulmonary Drug Delivery, point out several flaws in the usage of MDIs that limits the amount of medicine received by more than 50 percent.
Asthma is a common, chronic inflammatory disease that occurs in a range of severity among patients. It is caused by an accumulation of immune cells like eosinophils, mast cells, and others in the various lung tissues that activate, cause inflammation, and lead to the narrowing of the airwaves, and it is exacerbated by a plethora of environmental allergies.
An MDI is a device for delivering bronchodilator drugs to constricted lungs. The most common “rescue medication” is albuterol, a short-acting beta-2 antagonist that causes bronchodilation, which can be used to both prevent and treat acute asthma attacks. The Centers for Disease Control and Prevention (CDC) estimates that over eight percent of the United States population has asthma.
"Metered-dose inhalers are used every day by people with asthma, COPD and other chronic lung diseases, and the vast majority of the time, between 70 and 90 percent, patients make mistakes that keep some of the medicine from making it to their lungs," said study co-author Ashutosh Sabharwal from Rice University. "While inhalers are the most efficient delivery mechanism for many patients, these devices require deft maneuvers on the part of patients. The common errors are well-known, but fixing them continues to be a challenge."
Over six years, a PhD student from Rice University and the other co-author on the paper, Rajoshi Biswas, collected information on common user errors made during inhaler usage and how user errors affect the amount of medicine reaching an individual’s lungs. Biswas also designed an experimental setup to mimic how people use inhalers.
"The thing that matters the most is coordination," Biswas said. "It's vital to start breathing just before or at the exact same time the inhaler is activated. A delay of just a half second between pressing the inhaler and breathing in was enough to limit lung deposition to about 20 percent.”
The work done by Biswas and her team of experts represent a need for health officials to revisit the research and update outdated inhaler user guidelines. "The propellant used in inhalers has changed in recent years, and the current guidelines were developed based on studies of the old inhalers,” Sabharwal explained. “Our findings, coupled with the recent changes in inhaler propellants, suggest it is time to revisit these guidelines."