TYPE OF STUDY
We conducted a prospective cohort study following the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE)11 guidelines. The study was undertaken in a Surgical ICU in the Federal District Base Hospital between October 2020 and February 2021.
The study protocol was approved by the research ethics committees at the University of Brasilia (CAAE: 31665120.0.0000.8093) and Federal District Strategic Management Institute (CAAE: 31665120.0.3001.8153). All participants signed an informed consent form.
The study participants were recruited using convenience sampling, adopting the following inclusion criteria: patients of both sexes aged over 18 who had been in the ICU for more than 24 hours and were hemodynamically and neurologically stable and able to understand the proposed tests. The following individuals were excluded: hemodynamically unstable patients; pregnant women; patients with neurological and/or neuromotor impairments; patients who had undergone head and neck surgeries or thoracic surgeries involving diaphragm plication; patients with unstable bone fractures; patients who had been hospitalized in the last six months; and patients receiving palliative care.
The assessments were undertaken at ICU admission (24 hours after surgery) and discharge. The patients received physical therapy three times a day during their stay in the ICU in accordance with the ICU protocol.
The following data were collected on the patient’s first day in the ICU: clinical variables (APACHE II, SOFA score and SAPS II); surgical risk; surgery duration; duration of orotracheal intubation (OTI); type of anesthesia; and length of ICU stay. We also assessed mobility, physical functioning, peripheral muscle strength, respiratory muscle strength and pulmonary function.
The assessments were carried out by experienced physiotherapists who received prior training in how to use the scales and assessment tools. The physiotherapists explained the assessment beforehand so that the patient was able to perform the task as independently as possible.
Mobility was measured using the single-domain ICU Mobility Scale – IMS12,13. The scale is scored from 0 to 10, where 0 indicates no mobility (passively rolled or passively exercised by staff) and 10 indicates a high level of mobility (walking independently without a gait aid)12. The IMS has been translated into Portuguese and adapted for use in Brazil13.
Physical functioning in ICU was assessed using the Chelsea Critical Care Physical Assessment (CPAx)15, developed and validated by Corner et al. (2013; 2014)15,16. The CPAx measures key components of physical functioning (respiratory function, cough, moving within the bed, supine to sitting on the edge of the bed, dynamic sitting, standing balance, sit to stand, transferring from bed to chair, stepping and grip strength) and is the only physical functioning in ICU assessment tool that includes aspects of respiratory function. The tool consists of 10 physical function items ranging from complete dependence to independence. The score ranges from 0-50, where the higher the score the greater the level of independence14. The CPAx has been translated into Portuguese and adapted for use in Brazil14.
Muscle strength was assessed according to grip strength (GS), which was measured using a hydraulic hand-held dynamometer (JAMAR®, Saehan Hydraulic Hand Dynamometer)17. GS was measured with patients sitting on a standard chair with feet flat on the floor and the elbow flexed at a 90º angle. When this was not possible, the participant was placed in a supine position with elbows supported on the bed at a 45º angle and the bed raised at a 45º angle. The patient was then instructed to squeeze the dynamometer as hard as possible to measure GS16-18. Three tests were performed on both the dominant and non-dominant hands at one-minute intervals in order to avoid muscle fatigue. The result was taken to be the highest score of the three attempts18,19. The test was performed in accordance with the recommendations of the American Society of Hand Therapists (ASHT)18.
Indirect muscle strength was measured using the Medical Research Council Sum-Score (MRC-SS)20. Participants were considered eligible to participate in the study if they responded at least three of the five commands proposed by De Jonghe21: “open/close your eyes”; “look at me”; “open your mouth and put out your tongue”; “nod your head”; and “raise your eyebrows when I have counted up to five”. The following six muscle groups were graded on a scale of 0 to 5: abduction of the arm, flexion of the forearm, extension of the wrist, flexion of the hip, extension of the knee, and dorsal flexion of the foot22. A maximum score of 60 indicates normal muscle strength, 59 to 48 slight weakness, 47 to 36 significant weakness, and under 36 severe weakness22. The MRC-SS is a simple tool for assessing global muscle strength in intensive care patients and has good inter-rater reliability22. The tool has been translated into Portuguese and adapted for use in Brazil20.
Respiratory muscle strength was tested according to maximal inspiratory pressure (MIP) using a respiratory pressure meter (MicroRPM®, Micro Medical, United Kingdom). The test was done with the participants seated on a chair with a backrest and armrest and undergoing continuous monitoring. Each participant was encouraged to make maximum voluntary expiratory effort at residual volume (RV) and then instructed to make maximum inspiratory effort to measure MIP. In accordance with American Thoracic Society guidelines, three maneuvers with effort maintained for at least 1 second that varied by less than 20% were performed23. The values were recorded and compared with published normal values for the Brazilian population, using Neder et al.’s normalcy prediction equation as a frame of reference24.
Dynamic inspiratory muscle strength was measured based on the S-Index and peak inspiratory flow (PIF), obtained using the POWERbreathe K5 (POWERbreathe International Ltd., Warwickshire, United Kingdom) with disposable filter nozzle and employing the same technique used to measure MIP described above. Ten maneuvers were performed with a 30-second rest between inspiratory maneuvers. The maximum value of the maneuvers was recorded25-27.
The categorical data were presented as absolute (n) and relative (%) frequencies and the continuous variables were described using medians and the interquartile range (IQR). The Kolmogorov-Smirnov test was used to check whether the data followed a normal distribution. All statistical tests were bilateral and adopted a 5% significance level (α = 0.05). The data were divided into two periods: ICU admission (24 hours after surgery) and ICU discharge.
The Shapiro-Wilk test was used to show evidence of the non-normality of the clinical variables, followed by the Wilcoxon test for paired samples to provide evidence of eventual differences. Correlations between the test scores at admission and discharge were determined using Spearman's correlation coefficient. We assessed CPAx, IMS and MRC-SS performance at ICU admission and discharge using the floor and ceiling effects, calculated based on the percentage of patients scoring the lowest and highest values, respectively, for each tool. The statistical analyses were performed using R version 4.02.
The appropriate sample size the CPAx (tested using the Wilcoxon test for paired samples) was calculated based on the means and respective standard deviations reported by Whelan in a pilot study with 85 patients conducted in 201828: 32 and 44.35, respectively, and 11.34 and 9.66, respectively, considering a correlation of 0.48. Based on these measures it was possible to determine effect size using the Cohen method, resulting in 1.1711. Minimal sample size for a bilateral test was calculated using G Power version 184.108.40.206 based on a type I error of 0.05, type II error of 0.8, and effect of 1.1711, resulting in nine patients.