Less than half of the sample performed the inhalation technique correctly. Incorrect inhalation technique was related to lower number of evaluations of the use of the inhalation device and uncontrolled asthma.

Objective: To demonstrate the most frequent errors in inhalation technique in patients with asthma undergoing treatment at a tertiary care hospital. Methods: A cross-sectional study with a convenience sample of asthma patients aged 18 years or over, treated at a pulmonology outpatient clinic of a tertiary care hospital. The assessment of inhalation technique of users of the dry powder inhalers Aerolizer ® , Aerocaps and Diskus ® , or metered-dose inhalers was based on the manufacturer's instructions for use of each inhaler device. Patients demonstrated the inhalation technique with empty inhaler devices, and it was considered correct when all stages were performed properly, or when errors probably did not interfere with the treatment outcome. Results: Among 71 participants, 43 (60.5%) performed inhalation technique incorrectly. Among metered-dose inhalers and dry powder inhalers users, inhalation technique errors were found in 84.2% and 51.9%, respectively (p=0.013). Errors were more frequent at the exhalation stage (67.4%), followed by breathing in (58.1%) and apnea (51.2%). In the group using dry powder inhalers, the most common errors occurred during exhalation and, for those using metered-dose inhalers, the most compromised stage was aspiration. Conclusion: Errors were more frequent among those using metered-dose inhalers compared with dry powder inhalers. Misconceptions are more common at the expiration stage among users of dry powder inhalers and in aspiration among those on metered-dose inhalers.