The minimal important difference of the ICU mobility scale
Introduction
Significant muscle weakness and decreased functional status are common after critical illness,1 and in some cases patients do not fully recover.2 Early mobilization in the intensive care unit (ICU) is a potential treatment to improve muscle strength, mobilization and function, decrease complications and potentially increase the long-term quality of life and functional outcomes of patients.3 Therefore it is necessary for functional outcome measures to have strong clinimetric properties for use in the ICU.4
The ICU mobility scale (IMS) is an 11-point scale, used to record a patient's highest level of mobilization (Table 1).5 A multidisciplinary team of researchers and clinicians developed the IMS for use in the ICU. The IMS is being increasingly used in research,6, 7, 8–9 however a minimal important difference (MID) has yet to be established.
The MID is defined as “the smallest difference in score in the outcome of interest that informed patients or proxies perceive as important and which would lead the patient or clinician to consider a change in management”.10 There are two key methods for establishing a MID; anchor based and distribution based.10 Anchor based methods involve using an external indicator or anchor to separate patients into groups that show the direction and magnitude of change over time. This is the most valid way to determine the MID as it includes the patient's or clinicians perspective of what constitutes important change.11 Distribution based methods use statistics and psychometric properties of the measure to estimate the MID.12, 13 Many studies have recommended the concurrent use of both anchor and distribution based methods to most accurately determine the MID.11, 14 The aim of this study is to establish the MID of the IMS.
Section snippets
Design, participating centers and patients
This study was a prospective multi-center observational study of adult patients admitted to ICU and high dependency unit's (HDU) across Victoria, Australia. The study received ethical approval with waiver of consent, from the Alfred Hospital Human Research and Ethics Committee. The individual ethics boards for each participating site provided research governance. Study sites were, the Alfred Hospital, Ballarat Base Hospital and The University Hospital Geelong. Patients were included in the
Results
We enrolled 184 patients, with a mean age of 62.0 years and a mix of surgical, medical and trauma cohorts (Table 2). The consort diagram in Fig. 2 outlines the number of patients screened and enrolled in the study.
Discussion
This multi-center prospective observational study demonstrated that in a general ICU population, the MID of the IMS is between 0.89 and 3. This is the first study, as far as we know, to prospectively determine the MID of the IMS using both anchor and distribution based methods. We believe it is the first time an outcome measure designed to assess mobilization in ICU has had a MID determined in this way.
This study calculating the MID of the IMS allows clinicians and researchers to determine the
Conclusion
The IMS is a quick, multi –disciplinary, reliable and valid tool and a change of 1.4–3 on the IMS is clinically significant. Increasing the use of the IMS across clinical and research practices allows for improved understanding of the mobilization levels in certain ICU cohorts and the ability to compare between different cohorts.
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2021, Enfermeria IntensivaClinimetrics: The Intensive Care Unit Mobility Scale
2020, Journal of PhysiotherapyAdaptation and validation of the ICU Mobility Scale in Spain
2020, Enfermeria IntensivaEarly Mobilization for a Patient with a Right Ventricular Assist Device with an Oxygenator: A Case Report
2023, Journal of Acute Care Physical Therapy
Authorship: C.J.T., A.H., M.H. and C.H. contributed to conception; all authors contributed to design and drafting the article; C.J.T., N.H. and T.C. collected data, C.J.T. and A.H. completed data analysis and all authors had final approval of the version to be published.
Ethics approval: HREC-17-Alfred-57.
Conflict of interests: None.
Funding: None.
Registration of protocol number: ACTRN12617000536369p.