Verification of CPAx-Chi

This was a cross-sectional observational study, and the flow chart is shown in figure 1. We took the MRC-Score which is the most widely used diagnostic tool for ICU-AW as the comparator to test CPAx-Chi, and a manual dynamometer was used to assess grip strength (WCS-100). Meanwhile, researcher A and researcher B simultaneously and independently assessed eligible patients using the MRC-Score and CPAx-Chi.

The flow diagram of the research. CPAx, Chelsea Critical Care Physical Assessment Tool; CPAx-Chi, Chinese version of Chelsea Critical Care Physical Assessment Tool; ICU-AW, intensive care unit-acquired weakness.

Adult critically ill patients were recruited from the general ICU of five third-grade class-A hospitals in western China from September 2019 to June 2020. The recruiter explained the purpose and significance of the study to participants who meet the eligibility criteria, and then serial numbered.

The inclusion criteria were the following: (1) critically ill patients eligible for ICU admission; (2) age ≥18 years; (3) duration of ICU stay ≥48 hours; (4) Glasgow Coma Scale (GCS) score ≥11; (5) volunteered to participate in our study.

Patients were excluded if they may be misdiagnosed as ICU-AW just like: (1) unstable fracture, limb deformity or limb dysfunction; (2) myasthenia gravis or Guillain-Barre syndrome.

The sample size was calculated by the principles of scale development. In general, the sample size was 10–15 times the number of scale items and add taking into 20% account loss to follow-up and participant attrition.¹⁹ The sample size of this study was 120–180. However, there are some studies that introduced that a sample size of 200 is reasonably good for ordinary factor-analytical work with 40 or fewer variables.^19–21 Therefore, we finally took 200 cases as the sample size of this study.

In the pretesting study, we found that there were significant differences between patients with informed consent and the patients with no informed consent, especially in the items respiratory function, grip strength and transferring from bed to a chair. In order to ensure data validity and quality, the Ethics Committee provided a waiver of informed consent which was uploaded as supplemental information (online supplemental material). In addition, it was routine work that researchers assessed eligible patients using the MRC-Score and CPAx-Chi.

bmjopen-2020-045550supp001.pdf