Presenters at 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.

The misuse is of concern because it can result in improper dosage, said study author Siegfried Wieshammer, MD, Klinikum Offenburg, Offenburg, Germany.

Wieshammer and colleagues from the University of Heidelberg observed 224 patients with asthma or COPD using one of four common DPIs—Aerolizer, Diskus, HandiHaler, and Turbuhaler. 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 inhaler use had a significantly positive effect on error rate. For patients who received no 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. Researchers speculate that decreased cognitive and psychomotor skills make it difficult for older patients to properly use DPIs.

“Regardless of inhaler type, clinicians should provide instruction on the correct use of inhalers and have patients demonstrate proper usage before leaving the office,” said Alvin V. Thomas, Jr, MD, FCCP, president of the American College of Chest Physicians.