Abstract
Background: Outcome measures can assess the change in the health status of a patient in an intensive care unit (ICU). The Chelsea Critical Care Physical Assessment (CPAx) tool is used to assess the functional outcomes to monitor patient progression or regression in an ICU.
Objectives: Our study aimed to identify studies that assess the functional outcomes of patients nursed in ICUs that use the CPAx tool.
Method: An integrative review framework was used. Data were analysed in five steps to formulate a conclusion that aligned with the objective of our study. Data were extracted from peer-reviewed articles published online between 2013 and 2022. Databases that were used include Google Scholar, Directory of Open Access Journals (DOAJ) and PubMed for reviewed articles. Keywords were used in the search strategy, and screening of abstracts was done to extract studies that met the inclusion criteria.
Results: We retrieved 41 studies, of which 11 matched the inclusion criteria. Data were thematically arranged into studies measuring the validity and reliability of the CPAx tool, using the CPAx tool to measure outcomes in the ICU, the tool used at ICU and hospital discharge.
Conclusion: The use of the CPAx tool has no impact on measuring the hospital length of stay or quality of life.
Clinical implications: The tool is comprehensive and enhances the accuracy of patient assessment.
Keywords: critically ill patients; functional outcomes; intensive care unit; Chelsea Critical Care Physical Assessment tool; physiotherapy; outcome measures; physical functions.
Introduction
Patients admitted to intensive care units (ICUs) have severe or life-threatening injuries and illnesses (Vincent 2019). Patients in ICUs require constant care, close supervision by ICU clinicians, life support equipment and medication to restore bodily functions. These patients are usually immobile or sedated to prevent pain and anxiety (Griffiths & Hall 2010). Complications acquired in the ICU include intensive care unit-acquired weakness (ICU-AW), which may slow recovery and limit the patient from returning to their previous highest functional status (Griffiths & Hall 2010). Physiotherapists play a key role to prevent and manage complications acquired in the ICUs. Physiotherapy interventions include promoting lung function, early mobilisation and activity-focused rehabilitation (Holdar et al. 2019). Adequate tools are therefore needed to evaluate patients’ functional outcomes and the effect of the physiotherapy interventions.
In the ICU, various tools have been proposed to measure physical outcomes, and these data can then be used to assess and plan patient-specific rehabilitation programmes (Denehy et al. 2013). These include the Physical Function in Intensive Care Unit Test-scored (PFIT-s), the Perme Mobility Scale, the Surgical intensive care unit Optimal Mobilisation Score (SOMS), the ICU Mobility Scale (IMS), the Functional Status Score for the ICU (FSS ICU) and the Chelsea Critical Care Physical Assessment (CPAx) (Parry et al. 2015).
The CPAx tool was developed by Corner et al. in 2013. The CPAx tool is a non-invasive bedside measure used to holistically measure physical morbidity in the ICU (Corner et al. 2013). The CPAx tool assesses 10 items that include respiratory function, cough effect, movement in bed, supine to sitting on the edge of the bed, dynamic sitting balance, standing balance, sit to stand, transferring from the bed to the chair, stepping and hand grip strength. Each item is measured on a six‐point scale from level zero, representing total dependency, to level five, representing total independence. The CPAx tool can evaluate patients who are sedated, as well as those who are fully awake (Corner et al. 2013). In comparison with other tools used in the ICU, the CPAx tool can measure respiratory function in addition to strength and physical functions.
According to the evidence, the CPAx tool is more responsive in surgical patients. The objective of our study was to identify studies that used the CPAx tool to measure the physical function of adult patients nursed in an ICU. Our study also reviewed the validity and reliability of the CPAx tool.
Method
An integrative review provided a summary of studies with various research designs to provide a comprehensive understanding of the use of the CPAx tool in an ICU. We followed Whittemore and Knafl’s (2005) framework for integrative reviews to conduct our review. To date, there are limited options available to holistically measure the physical function in ICUs in South Africa (Whelan, Van Aswegen & Corner 2018). The available tools generally assess only the patients’ function and muscle strength and do not track progression. The CPAx tool can monitor both the respiratory and physical functions as well as the progression thereof. This integrative review aims to identify studies that used the CPAx tool to measure the physical function of adult patients in an ICU.
Literature search
We searched Google Scholar, Directory of Open Access Journals (DOAJ) and PubMed for articles. Keywords in the titles were used to identify articles. The search strategy included the use of Boolean operators such as ‘OR’ and ‘AND’ between keywords. Peer-reviewed articles included were published between 2013 and 2023. The CPAx tool was developed and first published in 2013. We included observational studies, quasi-experimental studies, an experimental study and clinometric studies. Keywords or search terms included the following: ‘Chelsea Critical Care Physical Assessment Tool’, ‘physiotherapy outcome measures in critically ill patients’ and ‘ICU outcome measures’. The first author screened the abstracts of the identified articles to identify studies that fit the inclusion criteria.
The inclusion criteria were as follows:
- Peer-reviewed articles published from 2013 to 2022.
- Evidence on functional outcomes measured in ICUs using the CPAx tool.
Quality control
Data were collated using an integrative review approach to motivate the use of the CPAx tool to measure the physical functions in ICUs. The first author and a librarian searched for articles. We screened the titles and abstracts to identify articles that met the inclusion criteria. Included studies were appraised using the CASP Guidelines (Long, French & Brooks 2020). This tool has checklists designed for use with systemic reviews, randomised control trials, cohort studies, case-control studies, economic evaluations, diagnostic studies, qualitative studies and clinical predictions. Our review included observational studies as well as experimental studies as other studies did not fit the inclusion criteria.
Data screening and extraction
From the included studies, the following data were extracted: the study title, the study method, the aim and setting of the study, the patient sample, the procedure and the results of the study. The information included in the review was analysed thematically.
Findings
Figure 1 illustrates the selection of studies. The search yielded 41 studies, 2 articles from the DOAJ, 18 from Google Scholar and 21 from PubMed. We screened 34 articles for eligibility. Nineteen studies remained after duplicates were removed. Eight of these studies did not fit the inclusion criteria. Eleven studies were included in the integrative review. The studies are summarised in Table 1.
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FIGURE 1: Flow diagram showing the selection of articles used in the integrative review Chelsea Critical Care Physical Assessment to measure the physical functions of patients in the intensive care unit. |
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| TABLE 1: Data extracted from reviewed articles. |
Themes
Theme 1: Validity
The validity of a scoring tool refers to the tool measuring what it is intended to measure. In the case of the CPAx, it was tested against different tools used and validated in ICU, to measure the functional outcomes (Corner et al. 2013). The CPAx assesses muscle strength, level of consciousness, cough effectiveness, and respiratory and physical functions (Corner et al. 2013). It was found to have a moderate to strong correlation with existing tools (Corner et al. 2013). The tool has been tested in critically ill patients who have sustained burns and traumatic injuries and in surgical populations showing improvements in physical function. The CPAx tool has also been translated into four other languages: Chinese, German, Swedish and Danish (Astrup et al. 2018; Eggmann et al. 2022; Holdar et al. 2019; Zhang et al. 2021). Construct and cross-sectional validity of the German version of the CPAx (CPAx-GE) are excellent with 86%, and the acceptance rate of the cross-cultural hypotheses based on the original CPAx is 83% (Griffiths & Hall 2010). Furthermore, the Chinese-translated CPAx also showed good content validity. The authors used nine ICU multidisciplinary experts with an expert authority coefficient that ranged between 0.75 and 0.95 (Zhang et al. 2021). Item-level index content validity (I-CVI) was from 0.889 to 1, and scale-level index content validity (S-CVI) was 0.955 (Zhang et al. 2021).
Construct validity shows the median and interquartile range of CPAx scores for patients when grouped by their discharge locations from the hospital (Corner et al. 2014). The analysis of variance shows statistically significant differences in the median CPAx scores among the seven discharge groups (H [2] = 311.4, p < 0.0001) (Whelan et al. 2018).
Predictive validity of the CPAx tool as an indicator of the functional prognosis of critically ill patients is found to be good (Corner et al. 2015). The criterion validity shows that the correlation coefficient between the MRC-Score and the CPAx-Chi ranges between 0.60 and 0.65 (Zhang et al. 2021) which is similar to what Corner et al. (2015) had found. The CPAx tool therefore has been shown to have good content validity.
Theme 2: Reliability
The next theme reviewed was the ability of the CPAx tool to produce consistent results, that is, reliability. The CPAx is found to be reliable by the original authors as well as in the translated versions. The tool proves to have internal consistency and inter-rater reliability with a κ = 0.988 and α = 0.798 (Corner et al. 2013). Cronbach’s α for CPAx-Chi is 0.939, and the inter-rater reliability is 0.902 when the original CPAx is translated (Zhang et al. 2021). The inter-rater correlation coefficient is > 0.8 for the items of respiratory function, transfer from bed to chair and grip strength. The inter-rater correlation coefficients of other items of CPAx-Chi are all > 0.7 (Zhang et al. 2021). The inter-rater reliability of the CPAx tool is moderate to almost perfect for most of the components in relation to other outcome measures with the strongest elements being lying to sitting and mobility, from the bed to the chair, with cough having the weakest inter-rater reliability (Wilson-Barry et al. 2018).
Inter-rater reliability by observation is excellent with intraclass correlation coefficient (ICC) > 0.8 including 95% confidence interval (CI) on patient assessment with the translation of the German CPAx (Eggmann et al. 2021). The constructed Bland–Altman’s plots confirm the high agreement of the CPAx-GE with a mean difference of 0.13 ± 0.15 (95% limit of agreement: −2.04 to 1.79) (Eggmann et al. 2021). The inter-rater reliability of the Swedish CPAx tool (CPAx-Swe) is found to be satisfactory and applicable for use within the clinical setting (Holdar et al. 2019). Reliability of the aggregated scores and the individual items is found to be good (Holdar et al. 2019). The ICC of 0.97 and the quadratic weighted kappa values range from 0.88 to 0.98 (Holdar et al. 2019).
Theme 3: An outcome measure in the intensive care unit
Various studies reported that the CPAx tool is useful for assessing the physical function of critically ill patients in an ICU (Astrup et al. 2018; Holdar et al. 2019; Whelan 2017). The tool shows a high consistency with measuring respiratory and functional outcomes in different ICUs. The CPAx is shown to be a good measure of clinical progress in the patient’s functional status after they sustained burn injuries (Corner et al. 2015). Corner et al. (2015) reported that a change in CPAx score of six or more can be considered a clinically meaningful change in physical function.
The length of stay (LOS) in ICU and in hospital is not significantly influenced by the addition of the CPAx tool to standard physiotherapy patient management although physical function improves (Whelan et al. 2018). Whelan and colleagues noted that therapists find that the CPAx tool enhances their accuracy of patient assessment in the ICU setting. They reported that the CPAx assists with patient care and planning, assists with the evaluation of patient progression, serves as motivation for patients to participate in treatment, enhances communication with patients and motivates them regarding patient response to treatment (Whelan et al. 2018).
Theme 4: Measurement at discharge from the intensive care unit and hospital
The CPAx scores correspond well with the discharge destination of patients. Patients with higher CPAx scores can go home post-discharge (Corner et al. 2014). Importantly, CPAx scores measured at baseline are found to correlate with the LOS in critical care units (Eggmann et al. 2022).
As far as changes in the score during ICU stay, the difference in median CPAx scores between ICU admission and discharge is 4.5 (Whelan et al. 2018). From ICU admission to discharge, the median CPAx scores changed by 3.2 points for the surgical group and by 7.5 points for the trauma group in terms of functionality.
In terms of correlation of the CPAx scores on ICU admission to hospital LOS, a moderate negative correlation is shown (r = −0.58, p = 0.001, n = 23). There is, however, no correlation between CPAx at admission and ICU LOS (r = −0.19, p = 0.38, n = 23) or between CPAx at ICU discharge and ICU LOS (r = −0.58, p = 0.13, n = 8) or hospital LOS (r = −0.11, p = 0.78, n = 8) (Whelan et al. 2018).
Discussion
The CPAx tool is shown to be a good measure of physical function for patients admitted in the ICU presenting with different conditions. The tool can assess physical limitations upon discharge from the ICUs to discharge locations. The tool also assists in planning patient-specific rehabilitation (Whelan et al. 2018). The CPAx tool, however, does not predict the LOS of a patient in the hospital. The CPAx tool is shown to have good internal consistency and inter-rater reliability. The tool has high consistency with assessing functional outcomes as well as respiratory functions in patients nursed in the critical care setting.
Clinicians agree that the tool assists with assessing patients in an ICU and that the CPAx tool could be used to plan patient-specific rehabilitation goals. In the identified studies, the physical function of patients improves between admission and discharge from the ICU. The CPAx tool identifies improved functional outcomes in both surgical and trauma patients. The tool assists with developing patient-specific treatment plans that indeed improve physical functions (Whelan et al. 2018). Participants in the surgical group have significantly better physical function at ICU discharge in comparison to trauma patients. Even though physical function improves, there is no impact on the LOS in both ICUs and hospitals (Whelan et al. 2018).
Schaller et al. (2016) noted that improvement in functional outcome may be quicker for patients who are more awake and alert and respond favourably to medical care and rehabilitation care provided to them while in the ICU and hospital. As their cooperation improves and their condition stabilises, patients are more likely to participate in functional activities (Whelan et al. 2018). Indeed, the German CPAx (CPAx-GE) at ICU baseline is mainly determined by respiratory function and movement, while at ICU discharge, basic activities start to emerge, and at hospital discharge, standing, transferring and stepping became more practised for patients (Eggmann et al. 2021).
Assessments done using the tool assist in identifying the impairments and patient activity limitations. The CPAx tool as an outcome measure assists physiotherapists in planning individual patient-specific rehabilitation programmes to better serve patients. The supporting studies were limited to trauma and surgical ICUs. The tool is a supported measure of physical morbidity in patients admitted to an ICU setting with further research recommended in different ICUs and with a bigger study population.
Conclusion
The CPAx tool is a good measure of physical function and respiratory function for patients admitted to an ICU. The CPAx tool, however, does not have an impact on the LOS within the ICU and the hospital, nor does it predict health-related quality of life. Studies have only assessed patients in ICUs and not in a high-care setting that forms part of the critical care setting. The CPAx tool is comprehensive, enhances the accuracy of patient assessment and assists physiotherapists to draw up patient-specific treatment plans to address the identified impairments.
Acknowledgements
Competing interests
We declare that we have no financial or personal relationships that may have inappropriately influenced us in writing this article.
Authors’ contributions
L.C.T., S.G.H. and N.M. designed the study. L.C.T., N.M. and S.G.H. interpreted the data, and drafted and edited the article. All authors approved the final version of the article to be published.
Ethical considerations
Our study was conducted as part of a master’s degree. The Faculty of Health Sciences Ethics Committee, University of Pretoria, approved our study with reference number 303/2022.
Funding information
This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Data availability
All the data that support the findings of our study can be made available by the corresponding author, L.C.T., upon reasonable request.
Disclaimer
The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of any affiliated agency of the authors.
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