Electric muscle simulator

Electric muscle stimulator   Intensive Care Unit acquired weakness (ICU-AW) is a neuromuscular complication frequently observed in survivors of acute critical illness. It is characterized by profound muscle weakness [1] and is associated with delayed weaning from mechanical ventilation [2]. Risk factors include systemic inflammatory response and sepsis [3, 4], several medications [5], prolonged immobility and bed rest [5], and severity of organ dysfunction [6]. Apart from controlling for potentially reversible risk factors and subsequent adjustment of therapy, no other effective means have been suggested so far for the prevention of ICU-AW. Prevention of ICU-AW is also related to early mobilization and rehabilitation in the ICU. Recent studies have demonstrated that early mobilization can be safe and feasible, with a potential reduction in short-term physical impairment [7, 8]. However, patient’s cooperation is necessary for an essential intervention to be applied. Electrical muscle stimulation (EMS) is a form of exercise and mobilization that does not require active participation and can be applied to immobilized subjects. EMS has been shown to be beneficial in patients with chronic heart failure (CHF) [9] and chronic obstructive pulmonary disease (COPD) [10, 11], as well as ICU and hospital inpatients [12–14]. We have previously shown that EMS in ICU patients induces a systemic acute effect on the microcirculation of muscles not applied [15] and preserves the mass of muscle groups applied [16]. We have also found that EMS prevents ICU-AW, which was diagnosed in 12.5% of the EMS group in comparison to 39.3% of the control group and results in shorter duration of weaning from mechanical ventilation [17]. However, the EMS effects on the strength of individual muscle groups are not known. Therefore, the primary aim was the posthoc analysis of recently published data [17] to investigate the effect of EMS on the strength of various muscle groups in critically ill patients. Secondary aims were to establish the relationship between different tests of muscle strength evaluation and to explore the technical issues in relation to muscle strength assessment in the ICU setting. Go to: 2. Materials and Methods 2.1. Patients All patients consecutively admitted to the multidisciplinary university ICU of Evangelismos Hospital during the study period (September 2007–June 2009) were considered for inclusion. Exclusion criteria were age under 18, pregnancy, obesity (BMI > 35 kg/m2), preexisting neuromuscular disease (e.g., myasthenia gravis, Guillain-Barré), diseases with systemic vascular involvement such as lupus erythematosus, technical restrictions that did not allow the implementation of EMS such as bone fractures or skin lesions (e.g., burns), and end-stage malignancy. Patients with cardiac pacemakers and those with an ICU stay of less than 48 hours were also excluded. Patients with the diagnosis of brain death were not considered for inclusion. The study was approved by the Scientific Council and the Ethics Committee of “Evangelismos” Hospital in accordance with the ethical standards set by the Declaration of Helsinki, and written informed consent was given by family members of all the patients included in the study. 2.2. Study Design and Randomization This was a posthoc analysis of a randomized parallel intervention clinical trial already reported [17]. On the second day after admission (24 to 48 hours after admission), patients with acute physiology and chronic health evaluation (APACHE) II score ≥ 13 were randomly assigned to the intervention group (EMS group) or the control group. Randomized stratification was performed upon age (≤ or >50 years of age, which is the median value of our ICU patients’ age) and gender (male/female). Patients assigned to the EMS group received daily EMS sessions of both lower extremities starting from the second day after admission until ICU discharge and MRC evaluation. Patients in the control group did not receive sham EMS. EMS was applied in addition to the usual ICU care. 2.3. Electrical Muscle Stimulation EMS (45 Hz, 400 μ sec, 12 sec on – 6 sec off, 0.8 sec ramp up/ramp down duration) was implemented simultaneously on vastus lateralis, vastus medialis, and peroneus longus of both lower extremities. After shaving (in the case of hairy skin) and skin cleaning, rectangular electrodes (90 × 50 mm) were placed on the motor points of the aforementioned muscle groups of both legs (Rehab 4 Pro, CEFAR Medical AB, Malmö, Sweden). Amplitude was set at levels able to cause visible contractions. In case of doubt, contraction was confirmed by palpation of the muscles involved. During the session, the angle of the patients’ knee joint was approximately 40° (0° corresponds to full knee extension). EMS sessions lasted for 55 min including 5 minutes for warm up and 5 minutes for recovery. The mean number and proportion of sessions that took place was  8 ± 6  and 82 ± 20%. 2.4. MRC Muscle Strength Scale The Medical Research Council (MRC) score for clinical assessment of muscle strength was used for the evaluation of strength and the diagnosis of ICU-AW. MRC scale application has been previously described in detail [17]. In short, after interruption of sedation, MRC was assessed in three muscle groups in all four limbs on the day the patients had a level of consciousness adequate to cooperate. The movements assessed were shoulder abduction, forearm flexion, wrist flexion, hip flexion, knee extension, and ankle dorsiflexion [18]. For the diagnosis of ICU-AW, the cutoff point of 48 was selected [2]. The MRC score evaluation was performed by two independent investigators, not blinded to patients’ allocation and familiar with this technique, who provided written MRC scoring for each muscle group. The mean value of the MRC score of the two investigators was used in data analysis. Manual muscle strength testing has been observed to have very good interobserver reliability [19]. 2.5. Handgrip Application Handgrip dynamometry (Lafayette 78011, Lafayette Instrument Co. Inc., Lafayette, IN, USA) was applied to a subgroup of consecutive patients to evaluate handgrip strength as an index of upper-limb muscle strength. It was administered immediately after MRC assessment in both hands. Patients were seated nearly upright, positioned at 140° (180° corresponds to the supine position). The patients’ arm was positioned at their side, parallel to the sagittal plane of the body, laid against the bed with the elbow at 90°, and supported by the examiner if necessary. These angles were measured and confirmed with a goniometer. During each trial, patients were continuously encouraged to ‘‘squeeze as forcefully as possible” for 4-5 seconds. Five trials were allowed for each hand alternatively, with a pause of 60 sec between each one. The hand with the higher performance was considered for analysis. Once two efforts differed by less than 5% (with a minimum difference of 1 kg), the larger of the two efforts was considered the maximum value and used for the assessment. Before the measurements, patients were familiarized with the procedure. All measurements were performed by the same experienced examiner, who was not blinded to the patients’ allocation. Handgrip dynamometry absolute values were also transformed to relative values (% predicted), according to the norms provided by Schlüssel et al. [20]. 2.6. Statistical Analysis Power analysis was performed prior to the study initiation, and it was based on a previous epidemiological study from our ICU [4]. Normality of distribution was checked by employing Kolmogorov-Smirnov or Shapiro-Wilk test. Unpaired Student’s t-test or Mann-Whitney U test (in case of not normal distribution) was employed for between-group comparisons. Categorical variables were compared by chi-square test. The Spearman’s r coefficient was used for correlations. Between-group comparisons in relation to handgrip dynamometry were made with analysis of covariance (ANCOVA) to adjust for age and gender. The ‘‘95% limits of agreement” method was used for comparison of dominant and nondominant handgrip dynamometry. One-way repeated measures analysis of variance (ANOVA) was made to compare handgrip performance over the 5 trials. MRC measures are reported as median (25th–75th percentiles). All other variables are presented as mean ± SD. P values ≤0.05 were considered statistically significant. Go to: 3. Results Patient recruitment flow chart, as previously reported [17], is presented in Figure 1. Fifty two patients were finally evaluated, 24 in the EMS group and 28 patients in the control group. Baseline characteristics of all patients in the EMS and control groups have been previously reported [17]. Baseline characteristics of patients finally evaluated in both groups are presented in Table 1.