Background: Chest physiotherapy is a treatment option for ventilated children. Evidence supporting treatment effectiveness is limited and the safety profile is unknown. This study aimed to identify and understand risk factors for physiological instability and adverse events associated with chest physiotherapy in ventilated children. /

Methods: This was a convergent mixed methods study.
Work package 1: Explanatory sequential study to describe current physiotherapy practice and explore decision making, utilising an anonymous questionnaire, semi-structured interviews, focus groups, and document analysis.
Work package 2: Retrospective single-centre study, using high-resolution data and electronic patient records. Mechanically ventilated children, aged 0-4 years, receiving chest physiotherapy were included. The primary outcome was oxygen saturation index (OSI). Incidence of adverse events (change ≥0.3) in the 60 minutes post-physiotherapy was investigated. /

Results: The questionnaire was sent to 26/27 (96%) UK paediatric intensive care units, with a response rate of 61% (72/118). Sixteen physiotherapist interviews and two focus groups (n=7) were completed. Twenty-nine organisational documents were analysed. The most frequently used techniques were position changes, saline instillation, manual hyperinflations and chest wall vibrations. Variation in practice included the personnel involved in treatments. Clinical decision making was described as complex, iterative, and collaborative, with experience and expertise important factors.
OSI data were available for 247 patients. OSI adverse event rates were between 7.4%-9.3%. The highest rate was recorded in the 5 minutes immediately post-physiotherapy. A higher proportion of patients with an adverse event were emergency admissions (p