RESUMO
BACKGROUND: Delirium is an underdiagnosed condition and this may be related, among other causes, to the incorrect use of assessment tools due to lack of knowledge about cognitive assessment and lack of training of the care team. The aim of this study was to investigate the difficulties encountered by the nursing team in the application of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) in patients on mechanical ventilation. METHODS: This is descriptive study with a qualitative approach in a private tertiary hospital located in northeast Brazil. Data collection took place from July 2018 to January 2019. We included 32 nurses and used face-to-face semi-structured interviews. The recorded data were analysed using content analysis. This study followed the recommendations of the Standards for Reporting Qualitative Research (SRQR). RESULTS: We identified three major categories: lack of knowledge of professionals, subdivided into deficit in academic formation, difficulty in the differential diagnosis of delirium and delusion, and lack of knowledge about the steps of the CAM-ICU; difficulty in patient cooperation; and lack of adequate training to apply the CAM-ICU. CONCLUSION: Nurses have a deficit in academic formation on delirium and need adequate training for the correct and frequent use of the CAM-ICU.