In the treatment of asthma and chronic obstructive pulmonary disease (COPD), errors in handling and wrong techniques in using inhalation devices are associated with poor disease control. The aim of this study was to evaluate the number of instructions that are necessary to minimize errors in using pressurized metered-dose inhaler (pMDI), soft mist inhaler (SMI), and dry powder inhaler (DPI).

Among 216 patients with asthma (n = 135) and COPD (n = 81), we studied 245 cases that used different types of inhalation devices. After initial guidance, 145 of 245 cases (59%) made at least one error that could affect efficacy. For every device, at least three instructions were required to achieve entirely no errors or less than 10% errors in total. The most common error on the use of pMDI was device handling, whereas that of DPI was inhalation manner. Both errors were associated with low peak flow rate. In both patients with asthma and in patients with COPD, the most common error was inhalation manner.

We concluded that it is necessary to repeat at least three times of instructions to achieve effective inhalation skills in both asthma and COPD patients.