CPAx: Responsiveness and Minimal Clinically Important Difference

May 26, 2026 updated by: Insel Gruppe AG, University Hospital Bern

Responsiveness and the Minimal Clinically Important Difference of the Chelsea Critical Care Physical Assessment Tool (CPAx) in Critically Ill, Mechanically Ventilated Adults

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.

Study Overview

Status

Active, not recruiting

Conditions

Detailed Description

The use of invasive life support in critically ill patients clearly saves lives but carries substantial risks, including intensive care unit (ICU) acquired weakness and long-term disability. The investigators urgently need a valid, reliable, and responsive measurement tool for this population to use in clinical practice and trials. The Chelsea Critical Care Physical Assessment tool (CPAx) is a promising measurement instrument to measure change in critically ill patients' physical function and activity. After several studies have confirmed its validity and excellent reliability, it is time to confirm responsiveness and to establish the MCID in a large, international sample of the target population. This multi-centre, mixed-methods, longitudinal cohort study will include critically ill, mechanically ventilated (>72h) adults at risk for muscle weakness and collect their mobility, physical function and activity with the CPAx and other relevant measures at ICU baseline, to ICU and hospital discharge. Responsiveness will be determined by the ability of the CPAx to identify change according to a prespecified anchor (criterion validity) and by testing prospective hypotheses about the expected magnitude of change between the CPAx and other relevant measures (construct validity). The MCID will be established with anchor- and distribution-based methods, whereby a seven-point global rating of change scale obtained from treating ICU physiotherapists will serve as anchor to distinguish improved from unchanged patients.

Study Type

Observational

Enrollment (Estimated)

120

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Australia
      • Clayton, Australia
        • Monash Health
      • Melbourne, Australia
        • Alfred Health
  • Switzerland
      • Bern, Switzerland
        • Inselspital

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Probability Sample

Study Population

The target population are critically ill adults who are mechanically ventilated for a prolonged period (≥ 72 hours) and who have an increased risk for ICUAW and long-term impairment.

Description

Inclusion Criteria:

  • Age ≥ 18 years
  • Mechanical ventilation ≥ 72 hours
  • Expected to remain for ≥ 48 hours in the ICU
  • Physiotherapy referral

Exclusion Criteria:

  • Not expected to survive to hospital discharge (imminent to death)
  • Second or subsequent ICU admission for this hospital stay
  • Transfer from external ICU (with an ICU stay of >72 hours)
  • Primary neurological admission diagnosis (i.e., of the central nervous system including stroke, intracerebral haemorrhage, traumatic brain injury)
  • Known pregnancy
  • Living in a care facility pre-admission (severe pre-existing mental or physical disability)
  • Local regulations (i.e. Switzerland: refusal of general consent)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Chelsea Critical Care Physical Assessment tool (CPAx) change score
Time Frame: Assessed at ICU discharge (within 24 hours before or after ICU discharge)
CPAx change score for ICU period (ICU baseline to ICU discharge); CPAx ranges from 0 (worst score) to 50 (best score)
Assessed at ICU discharge (within 24 hours before or after ICU discharge)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
CPAx change score
Time Frame: Assessed at hospital discharge (last value before discharge)
CPAx change score for hospital period (ICU to hospital discharge); CPAx ranges from 0 (worst score) to 50 (best score)
Assessed at hospital discharge (last value before discharge)
Global rating of change scale
Time Frame: ICU and hospital discharge (change for ICU and hospital period)
Seven-point global rating of change scale (GRC): (1) very much improved; (2) much improved; (3) little improved; (4) no change; (5) little deterioration; (6) much deterioration; (7) very much deterioration for 'physical function and activity' (rated by treating physiotherapist)
ICU and hospital discharge (change for ICU and hospital period)
ICU Mobility Scale
Time Frame: ICU baseline (within 72-144h after ICU admission), ICU and hospital discharge
To evaluate mobility level, the score ranges from 0 (worst) to 10 (best)
ICU baseline (within 72-144h after ICU admission), ICU and hospital discharge
Medical Research Council Sum Score
Time Frame: ICU baseline (within 72-144h after ICU admission), ICU and hospital discharge
To assess muscle strength, the minimal score is 0 (worst), the maximal score 60 (best), ICUAW is defined as <48 points
ICU baseline (within 72-144h after ICU admission), ICU and hospital discharge
Richmond Agitation-Sedation Scale
Time Frame: ICU baseline (within 72-144h after ICU admission), ICU and hospital discharge
To assess the level of sedation and/or cooperation, score ranges from -5 (unarousable) to +4 (combative)
ICU baseline (within 72-144h after ICU admission), ICU and hospital discharge
Modified Iowa Level of Assistance Scale
Time Frame: ICU baseline (within 72-144h after ICU admission), ICU and hospital discharge
To determine assistance in functional tasks, the score ranges from 0 (worst) to 36 (best)
ICU baseline (within 72-144h after ICU admission), ICU and hospital discharge
ICU and discharge destinations
Time Frame: ICU and hospital discharge
Categorical variable (death, external/internal hospital ward, external ICU/hospital, rehabilitation, home, other) to assess the predictive validity of the CPAx score
ICU and hospital discharge

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Insel Gruppe AG, University Hospital Bern

Collaborators

Monash University

Investigators

  • Principal Investigator: Sabrina Eggmann, PhD, Inselspital, Bern University Hospital, Switzerland; Monash University, Australia

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

May 23, 2024

Primary Completion (Estimated)

October 1, 2026

Study Completion (Estimated)

October 1, 2026

Study Registration Dates

First Submitted

May 13, 2024

First Submitted That Met QC Criteria

May 13, 2024

First Posted (Actual)

May 17, 2024

Study Record Updates

Last Update Posted (Actual)

May 27, 2026

Last Update Submitted That Met QC Criteria

May 26, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 5678

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Solely anonymised main outcome data

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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