This is a cross-sectional study on muscle strength measurement safety using HHD in ICU patients. The participants were patients of both sexes, >18 years of age, admitted to the ICU where the research was conducted, with sufficient cognition to coordinate the muscle strength measurement tests, hemodynamically stable or on minimal dose of vasoactive drugs (dopamine or dobutamine <3 mg/kg/min, adrenaline or noradrenaline <0.05 mg/kg/min, vasopressin <0.01 mg/kg/min), those without intracranial hypertension, arterial dissection or active bleeding, and who agreed (and/or their legal guardian agreed) to participate in the research. We excluded patients if they withdrew consent to participate at any time during the research or if they did not have the minimum force to trigger the device pressure cell, which was graduated at 15 N to avoid cell self-triggering by the weight of the limb or fixation of the device, thus minimizing measurement bias13.
This study was approved by the Ethics Committee (No. 1537948). A sample calculation was performed, estimating a variation of 20% in heart rate (HR) and systolic blood pressure (SBP), with power of 80% and alpha of 5%, totaling 45 volunteers, estimating a sample loss of 5%.
The sociodemographic and functional data were collected from medical records and written informed consent was obtained from the patient or legal guardian. Of the variables studied, the following are nominal variables: sex, outcome, and dominance. Functional status score for the intensive care unit (FSS-ICU) and the ICU mobility scale (IMS) were categorical variables. Discrete or continuous quantitative variables were age, weight, height, acute physiology and chronic health evaluation, second version (APACHE II), peak muscle strength, mean muscle strength, and sum of peak torque. The safety data were monitored pre and post the measuring procedure using a Dixtal multiparameter monitor, model DX 2020 (Phillips, Amsterdam, Netherlands), and variables such as HR, respiratory rate (RR), SBP, diastolic blood pressure (DBP), and peripheral oxygen saturation (SpO2) were continuously monitored. The pre and post measurement of categorical variables were performed using the visual analog scale (VAS) and Borg scale of perceived exertion (Borg). If adverse events, such as loss of the device, hematoma, malaise, cold sweats, accidental extubation, fatigue, or lipothymia occurred, the event was notified.
Isometric muscle strength measurement was performed using the HHD, Lafayette model 01165 (Lafayette, Sagamore, USA), and an ISP goniometer, for adequate determination of the joint position in the test of each muscle group. The evaluation was performed in the ICU bed in the dorsal decubitus position. The peak force torque obtained in isometric contraction was tested for the function of the main muscles bilaterally. Before the measurement, the patient was oriented, trained, and warmed up for each movement. After performing the isometric contraction for three seconds, the equipment sounded a beep signaling the end of the contraction for each movement. Each muscle was tested three times and the highest measure was considered. Patients were constantly encouraged by the examiner, who said “Go, go, go!”.
Before the study, all the measuring instruments were calibrated in order to minimize possible measurement bias. The maximum torque for each muscle group tested was assessed using the HHD positioned with the hands-on segment.
Six large muscle groups were evaluated, same as those used in the MRC scale, adopting the following positioning for measuring the HHD. First, the shoulder abduction – in dorsal decubitus: limb positioned parallel to the trunk, elbow, and wrists 180°, the patient was requested to perform shoulder abduction. Second, the elbow flexors in dorsal decubitus: shoulder in a neutral position, elbow in 90° flexion and wrists in 180°, and forearm supinated. Third, we performed elbow flexion: the wrist extensors – in dorsal decubitus position, forearm supported on the bed, parallel to the body, shoulder positioned with 15° of abduction, elbow in 0° of flexion and wrists 0°, forearm pronated. HHD was supported on the posterior aspect of the carpal bones, with fixation hand supporting the radius and ulna against the bed. Fourth, extend the wrist: hip flexors – in dorsal decubitus, stabilize the pelvis and contralateral lower limb with inelastic tape, hip and knee with 0° of flexion, HHD supported on the anterior face of the thigh, at its distal third (suprapatellar). Fifth, Hip flexion: knee extensors – in dorsal decubitus, stabilized pelvis and contralateral lower limb with inelastic tape, hip and knee with 45° of flexion, supported with the examiner’s fixation hand. HHD was supported on the anterior face of the leg, on its distal third. Sixth, knee extension: ankle dorsiflexors – in dorsal decubitus, stabilized pelvis and contralateral lower limb with inelastic tape, hip and knee with 0° of flexion, HHD supported on the dorsal face of the foot, on its distal third. The ankle fixation hand prevented hip flexion (by synergism). Finally, hip flexion was requested13–19.
The MRC scale was used to measure the same muscle groups in the same positions with free or resisted movement, categorizing the best performance as 0 (no visible contraction), 1 (visible contraction without movement of the segment), 2 (active movement with the elimination of gravity), 3 (active movement against gravity), 4 (active movement against gravity and resistance), and 5 (normal strength)11.
The SPSS 28.0 (Statistical Package for the Social Sciences) software for Mac was used for data analysis. Descriptive statistics were used with data presented in tables and graphs. Qualitative data were expressed as absolute and relative frequency, and quantitative data were expressed as mean and standard deviation. The Kolmogorov–Smirnov test was used to test the normality of the distribution of the variables studied. The means of the pre- and post-HHD-use safety variables were compared after the paired t-test to evaluate the safety, considering a p<0.05 as statistically significant.
The prevalence of muscle imbalance in ICU patients was calculated by the number of individuals affected at a given moment, divided by the total number of individuals studied in the sample.
The added muscle groups’ torque and their mean were correlated with the MRC score using Pearson’s correlation coefficient (r). For didactic purposes, to categorize the correlation magnitude, the classification proposed by Mukaka (2012)20 was used. Values of 0.0–0.3 indicated a negligible correlation, 0.3–0.5 a weak correlation, 0.5–0.7 a moderate correlation, 0.7–0.9 indicated a strong correlation, and values >0.9 indicated a very strong correlation.