Elsevier

Heart & Lung

Volume 47, Issue 5, September–October 2018, Pages 497-501
Heart & Lung

The minimal important difference of the ICU mobility scale

https://doi.org/10.1016/j.hrtlng.2018.07.009Get rights and content

Abstract

Background

The intensive care unit mobility scale (IMS) is reliable, valid and responsive. Establishing the minimal important difference (MID) of the IMS is important in order to detect clinically significant changes in mobilization.

Objective

To calculate the MID of the IMS in intensive care unit patients.

Methods

Prospective multi center observational study. The IMS was collected from admission and discharge physiotherapy assessments. To calculate the MID we used; anchor based methods (global rating of change) and two distribution-based methods (standard error of the mean and effect size).

Results

We enrolled 184 adult patients; mean age 62.0 years, surgical, trauma, and medical. Anchor based methods gave a MID of 3 with area under the curve 0.94 (95% CI 0.89-0.97). The two distribution based methods gave a MID between 0.89 and 1.40.

Conclusion

These data increase our understanding of the clinimetric properties of the IMS, improving its utility for clinical practice and research.

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, 89 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.

References (28)

  • C.J. Tipping et al.

    The effects of active mobilisation and rehabilitation in ICU on mortality and function: a systematic review

    Intensive Care Med

    (2017)
  • C.L. Hodgson et al.

    A binational multicenter pilot feasibility randomized controlled trial of early goal-directed mobilization in the ICU

    Crit Care Med

    (2016)
  • E.J. Ridley et al.

    Supplemental parenteral nutrition in critically ill patients: a study protocol for a phase II randomised controlled trial

    Trials

    (2015)
  • K. Hayes et al.

    Physical function in subjects requiring extracorporeal membrane oxygenation before or after lung transplantation

    Respir Care

    (2018)
  • Cited by (16)

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    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.

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