One out of three patients with asthma or COPD use inhalers incorrectly

One out of three patients with asthma or chronic obstructive pulmonary disease (COPD) use their inhalers incorrectly, a new study shows.

The study, presented at CHEST 2007, the 73rd annual international scientific assembly of the American College of Chest Physicians (ACCP), found that 32.1% of patients made at least one essential error while using a dry powder inhaler (DPI) and that the error rate increased with age and severity of airway obstruction.

DPIs rely on the force of patients' inhalation to activate, deliver, and manage the flow of medication to the lungs, compared with pressurized metered-dose inhalers (pMDIs), that use propellents to deliver a measured dose of medication to the patient. Although MDIs are more commonly used in the United States, the use of DPIs has grown substantially in the last 5 years.

“The frequent misuse of dry powder inhalers can lead to the inappropriate dosage of medication, which can result in increased morbidity and mortality for patients,” said study author Siegfried Wieshammer, MD, Klinikum Offenburg, Offenburg, Germany. “Our results suggest that inhaler type, age, severity of lung obstruction, and prior training can determine the risk of inhalation errors. These factors should be considered before prescribing an inhaler for a patient.”

Dr. Wieshammer and colleagues from the University of Heidelberg in Germany observed 224 patients with asthma or COPD using one of four common DPIs - Aerolizer, Diskus, HandiHaler, and Turbuhaler. Patients were asked about the instruction they received on using their inhaler and to demonstrate their inhalation technique. The overall error rate (the percent of patients making at least one error) was 32%. Regarding inhaler-specific error rates, Aerolizer has the lowest error rate at 9.1%, followed by Discus at 26.7%, Turbuhaler at 34%, and HandiHaler at 53.1%. Previous instruction by medical personnel on how to use the inhaler had a major impact on the error rate. In patients who had not received instruction, the error rate was 52.6%, whereas only 23.1% of the trained patients made essential errors.

Error rate also increased with age and severity of lung obstruction. Patients under age 60 had a 20.0% error rate, while those 60-years and over had an error rate of 41.6%. Patients with normal lung function had an error rate of 25.0%, while patients with severe obstruction had an error rate of 63.6%.

“Matching the appropriate device for an individual patient is as important as selecting the drug to be delivered because the best drug remains ineffective if it is not deposited to the lung,” said Dr. Wieshammer.” “Our data suggest that DPIs are useful tools in the management of younger patients with normal lung function or mild airway obstruction provided that instruction in inhalational technique is given by medical personnel.”

Researchers speculate that decreased cognitive and psychomotor skills, as well as a COPD-specific cognitive impairment, may make it difficult for older patients to properly use DPIs. Although the study authors do not advise against the use of DPIs in older patients, they recommend checking older patients' inhalational technique at every health-care encounter in order to ensure the efficacy of treatment. Because DPIs rely on the force of a person's inhalation to propel medication into the lungs, DPIs are not recommended for children under age 5, people with severe asthma or those suffering a severe attack.

“With the increasing use of dry powder inhalers for asthma and COPD, it is critical for patients to understand the appropriate use of their inhalers in order to minimize inhalation errors,” said Alvin V. Thomas, Jr., MD, FCCP, President of the American College of Chest Physicians. “Regardless of inhaler type, clinicians should provide instruction on the correct use of inhalers and have patients demonstrate proper usage before leaving the office.”