The Chelsea Critical Care Physical Assessment Tool (CPAx): validation of an innovative new tool to measure physical morbidity in the general adult critical care population; an observational proof-of-concept pilot study
Introduction
Critical illness frequently results in impaired neuromuscular function and hence debilitation [1], [2], [3], [4]. This phenomenon is commonly known as intensive care unit acquired weakness (ICU-AW).
In March 2009, the UK National Institute for Health and Clinical Excellence (NICE) introduced Clinical Guideline 83 (CG83), entitled ‘Rehabilitation after critical illness’, which aims to optimise the management of ICU-AW [5]. It recommends early identification of patients at risk of physical morbidity by regular short clinical assessments at intervals throughout the patient's hospital stay. Once identified as ‘at risk’, a comprehensive physical assessment should be completed, and a structured patient-specific rehabilitation programme commenced. Progress should be monitored using patient-agreed goals and should be reviewed regularly.
NICE CG83 was a long-awaited guideline and a milestone in the management of ICU-AW. However, the document highlights the lack of validated assessment tools and paucity of evidence-based rehabilitation practices in the critically ill population. For example, Section 2.1 (p. 23) of CG83 focuses on identifying screening and assessment tools to assess physical morbidity. Only one research article [6] was considered to be sufficiently scientifically robust for inclusion; this looked at the Rivermead Motor Index and even this ‘should be interpreted with caution due to its ill-defined inclusion criteria and small population’. The lack of a validated assessment tool poses a significant obstacle to the practical application of CG83, preventing its implementation in a standardised manner at a national level. Further implications include the lack of an objective marker for standardisation of patient management and health economic assessment. It also has implications in the research setting.
The most commonly accepted scoring system for the assessment of muscle function is the Medical Research Council (MRC) score for muscle strength [7]. This score looks solely at strength, and as patients may learn to be functional in the absence of strength, its generalisability and validity for measuring physical morbidity is questionable. More importantly, it is time consuming and relies on a degree of co-operation and cognitive function. From the patient perspective, it may be considered relatively abstract and difficult to interpret. Other measures that have been trialled, such as the Barthel Index and the Functional Independence Measure, lack sensitivity in patients with low levels of function, and/or they have not been validated or reliability tested in a critically ill population [8], [9].
The most realistic attempts to address the lack of validated assessment tools in critical care are the Physical Functional ICU Test (PFIT) [10] and the University of Rochester Acute Care Evaluation (URACE) [11]. The PFIT relies on the patient being able to stand up from a chair and march on the spot. These tasks may be difficult for patients in the acute phases of critical illness, and published results only exist for a very small sample size (n = 13). The URACE is a scoring system that grades people's independence with bed mobility, transfers (bed to chair), locomotion and stairs. It has not been tested for reliability and validity, and no patient data have been published to date. It was also developed with input from clinicians at a single hospital site in the USA; thus, its generalisability is questionable.
There is an obvious and urgent need for a practical, holistic and reproducible bedside measure of physical morbidity. This could facilitate patient assessment, highlighting problem areas and guiding rehabilitation; help to monitor progress; and form an objective measurement that is intelligible between clinical specialties and service users.
The aim of this pilot study was to develop a bedside scoring system to grade physical morbidity in the critical care population – the Chelsea Critical Care Physical Assessment Tool (CPAx).
Section snippets
Methods
This study involved several stages. For clarity, this paper is presented with the method followed by the results for each stage in order of completion.
The CPAx was developed using a pragmatic iterative process recommended by Streiner and Norman [12] and mimicking a modified Delphi technique (Fig. 1, see online supplementary material). The final version of the CPAx is shown in Appendix 1.
Discussion
The CPAx score demonstrated moderate to strong significant positive correlations with GCS score, sedation score (−3 to 1), muscle strength, AusTOMs score, SF-36 (physical component) score and peak cough flow. It also demonstrated a significant negative correlation with SOFA score and the number of days of mechanical ventilation. These results combined suggest validity in the assessment of overall physical morbidity.
Equally importantly, the CPAx score has been endorsed by physiotherapists
Conclusion
This preliminary work demonstrates proof of concept of the CPAx. As a pilot study, it provides a cogent argument for investigating this assessment system further in large multicentre studies. Future work should focus on clinician and patient perceptions of the CPAx, further reliability testing, expert review of the CPAx, and predictive validity for hospital outcome.
Acknowledgements
The authors would like to acknowledge the input of those involved in the development of the CPAx: Ms. Bronwen Connolly, Mr. Gareth Jones, Ms. Alex Curtis; and the support of the clinical teams at the Chelsea and Westminster NHS Foundation Trust, the Royal London Hospital and St George's University of London.
Ethical approval: Camden and Islington Research Ethics Committee (Ref. No. 10/H0722/34).
Conflict of interest: None declared.
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