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

Status

Indicates the current recruitment status or the expanded access status.
Active, not recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

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

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
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 Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Contact Backup

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

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

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
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

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
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

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Insel Gruppe AG, University Hospital Bern

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Monash University

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • 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)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
May 23, 2024

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
October 1, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
October 1, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
May 13, 2024

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 13, 2024

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
May 17, 2024

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 27, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 26, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant 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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