DPIs depend on the patients' force of inhalation to activate, deliver, and manage the flow of medication to the lungs, compared with pressurized metered-dose inhalers (pMDIs), which uses propellants to deliver a measured dose of medication to the patient.
"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," Wieshammer said. "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," he said.
In the study the team examined 224 patients with asthma or COPD using one of four common DPIs - Aerolizer, Diskus, HandiHaler, and Turbuhaler. The patients were asked to demonstrate their inhalation technique in accordance with the instructions they received on using their inhaler.
The overall error rate, i.e. the percent of patients making at least one error was 32percent. In regard to the inhaler-specific error rates, Aerolizer had the lowest error rate at 9.1 percent followed by Discus at 26.7 percent, Turbuhaler at 34 percent and HandiHaler at 53.1 percent.
Major impact on the error rate was by the previous instructions given by medical personnel on how to use the inhaler. In patients who had not received instruction, the error rate was 52.6 percent, whereas only 23.1 percent of the trained patients made essential errors. The error rate also increased with age and severity of lung obstruction.
Patients under age 60 had a 20.0 percent error rate, while those 60-years and over had an error rate of 41.6 percent. Patients with normal lung function had an error rate of 25.0 percent, while patients with severe obstruction had an error rate of 63.6 percent.
"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," 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," he said.
Researchers noted that the decreased cognitive and psychomotor skills, as well as a COPD-specific cognitive impairment, might have made it difficult for older patients to properly use DPIs.
However, they did not counselled against the use of DPIs in older patients, and recommended 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, and 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," Alvin V. Thomas, Jr., MD, FCCP, President of the American College of Chest Physicians said.
"Regardless of inhaler type, clinicians should provide instruction on the correct use of inhalers and have patients demonstrate proper usage before leaving the office," he said.