Survivors of acute respiratory distress syndrome (ARDS) and critical illness frequently develop long-lasting muscle weakness. Manual muscle testing (MMT) is a standardized clinical examination commonly used to measure strength of peripheral skeletal muscle groups. This video demonstrates MMT using the 6-point Medical Research Council scale.
Survivors of acute respiratory distress syndrome (ARDS) and other causes of critical illness often have generalized weakness, reduced exercise tolerance, and persistent nerve and muscle impairments after hospital discharge.1-6 Using an explicit protocol with a structured approach to training and quality assurance of research staff, manual muscle testing (MMT) is a highly reliable method for assessing strength, using a standardized clinical examination, for patients following ARDS, and can be completed with mechanically ventilated patients who can tolerate sitting upright in bed and are able to follow two-step commands. 7, 8
This video demonstrates a protocol for MMT, which has been taught to ≥43 research staff who have performed >800 assessments on >280 ARDS survivors. Modifications for the bedridden patient are included. Each muscle is tested with specific techniques for positioning, stabilization, resistance, and palpation for each score of the 6-point ordinal Medical Research Council scale.7,9-11 Three upper and three lower extremity muscles are graded in this protocol: shoulder abduction, elbow flexion, wrist extension, hip flexion, knee extension, and ankle dorsiflexion. These muscles were chosen based on the standard approach for evaluating patients for ICU-acquired weakness used in prior publications. 1,2.
1. Introduction
During manual muscle testing (MMT), each muscle group is tested bilaterally. For demonstration purposes, only one side is tested in this video for each of the 6 muscle groups. One hand of the examiner applies resistance or palpates the muscle or tendon for contraction while the other hand stabilizes the extremity being tested to keep it in the test position. The test is repeated if the patient does not understand the instructions or is not applying maximum effort.
2. Grading follows the Medical Research Council (MRC) system (Table 1).1
Figure 1 illustrates an algorithm for the MRC muscle strength scoring system. If the subject is missing a limb, has a cast, or is unable to be placed in the correct testing position, muscle strength is graded as “unable to assess”. If the patient has a fixed contracture, but can otherwise perform the test, the muscle is graded. Medical devices, such as catheters and drains, and mechanical ventilation usually do not impede muscle testing, unless a joint is immobilized to ensure proper functioning of a device.
Figure 1. Manual Muscle Testing Algorithm
3. Procedure
4. Shoulder Abduction
The remaining assessments will be completed similarly to above using specific test positions for the patient and examiner, and specific instructions for the patient’s movement.
5. Elbow Flexion
6. Wrist Extension
7. Hip Flexion
8. Knee Extension
9. Ankle Dorsiflexion
10. Representative Results:
MMT using this protocol has excellent inter-rater reliability when applied with both ARDS survivors and simulated patents. Quality assurance of 19 trainees examining 12 muscle groups demonstrated an intraclass correlation coefficient (95% confidence interval [CI]) of 0.99 (0.97-1.00).8 Agreement (kappa; 95% CI) for detecting clinically significant weakness (i.e., composite MRC score <80% of maximum) was 1.00 (0.55-1.00). Previous studies have shown high inter-rater reliability with stroke, amyotrophic lateral sclerosis (ALS), Guillain-Barre, and other critically ill patients.12-14
Figure 2. ICU patient with a left shoulder abduction contracture. MMT with a left radial arterial line, cardiac monitoring, and continuous dialysis through a right internal jugular catheter. The patient is positioned for shoulder abduction MMT Grades 3, 4 and 5.
Figure 3. ICU bedridden patient with a right internal jugular catheter for continuous dialysis. The patient is positioned on the right side for knee extension MMT Grade 2.
Figure 4. ICU bedridden patient with a left knee flexion contracture. The patient is positioned supine with a pillow under the knee for knee extension MMT Grades 3, 4 and 5.
Table 1. Manual Muscle Test 3 | |
Grade | Manual Muscle Test |
5 | Movement against gravity plus full resistance |
4 | Movement against gravity plus some resistance |
3 | Completes the available test range of motion against gravity, but tolerates no resistance |
2 | The patient completes full or partial range of motion with gravity eliminated |
1 | Slight contractility without any movement |
0 | No evidence of contractility (complete paralysis) |
Depending on the diagnostic criteria, 9 – 87% of ICU patients develop neuromuscular complications, which are associated with prolonged mechanical ventilation, increased hospital stay and rehabilitation time, and potentially associated with increased mortality.1,2,16-18 Periodic reassessment of muscle strength, using a reliable method which minimizes inter-rater variability is helpful to detect changes over time. An important limitation of MMT using the MRC score system is the 6-point ordinal scale. Muscle strength testing using a hand held dynamometer is less commonly used but has the advantage of using a ratio scale for measurement.19 In addition, some ICU patients may not be awake enough to tolerate a MMT exam.2 However, in our experience, once a patient is awake and cooperative, there are only a small number of patients who do not tolerate the exam. If this intolerance is due to poor endurance, the exam can be completed in smaller portions, rather than all at once. The muscle strength grading described in this video has been administered to ICU survivors and to cooperative, critically ill patients even while undergoing mechanical ventilation with intravascular devices in place that do not interfere with joint motion . Recent developments in ICU clinical practice whereby deep sedation is avoided, enhances the ability of mechanically ventilated patients to participate in MMT examination, rehabilitation therapies, and even ambulate while mechanically ventilated.20 Manual muscle testing of the 6 muscle groups described in this video is a simple, reliable, inexpensive method of obtaining a quantitative muscle strength evaluation for patients during and after critical illness.
The authors have nothing to disclose.
Supported by NIH grant # R01HL088045. Drs. Eddy Fan and Michelle Kho are each supported by a Fellowship Award from the Canadian Institutes of Health Research.