CPAx: Responsiveness and Minimal Clinically Important Difference

Chelsea Critical Care Physical Assessment tool (CPAx) change score

Intensive care unit (ICU) acquired weakness is a common complication associated with
 long-term physical impairments in survivors of a critical illness. The Chelsea Critical Care
 Physical Assessment tool (CPAx) is a valid and reliable instrument for physical function and
 activity in critically ill patients at risk for muscle weakness. However, its ability to
 measure change over time (responsiveness) and the minimal clinically important difference
 (MCID) have not yet been rigorously investigated. This multi-centre, mixed-methods,
 longitudinal cohort study therefore aims to establish responsiveness and the MCID of the CPAx
 in the target population from ICU baseline to ICU and hospital discharge. The study uses
 routine data from standard physiotherapy sessions like mobility, function and activity with
 no additional burden for critically ill adults. The investigators expect the CPAx to be
 responsive allowing its use as a primary outcome in future effectiveness trials for the
 treatment of ICU-acquired weakness using the newly established MCID for sample size
 calculation. A high quality, rigorously tested measurement tool for physical function and
 activity in the ICU should benefit researchers, clinicians and patients.