SESSION TITLE: Pulmonary Rehabilitation Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Skeletal muscle dysfunction is an important factor in reduced exercise capacity, impaired quality of life and higher health-care utilization in COPD. Reduced quadriceps function is associated with decreased survival, functional status, and quality of life. Relating quadriceps peak torque (Tq) to its peak electromyographic (EMG) signal (Eq) is an index that may predict fatigue during active contraction. It has not been investigated in patients with chronic respiratory disorders. The objective of this study is to assess changes in skeletal muscle function in patients undergoing a standard 8-week outpatient pulmonary rehabilitation (PR) program. We hypothesized that the ratio Eq/Tq in such patients should be increased in comparison to healthy control subjects. METHODS: Peak Tq as measured by dynamometry and its corresponding peak Eq were recorded using surface sensors and electrodes placed over the vastus lateralis in stable patients undergoing PR. Signals were averaged for a train of 5 knee extensions from the knee bent at 90 degrees to the horizontal plane against a graded resistance adjusted on the dynamometer (isokinetic contractions). Maneuvers were performed at beginning, midway through, and at completion of PR. The ratio Eq/Tq was used as an index of muscle fatigue. Results were compared to those of healthy control subjects who had previously tested the equipment for accuracy and reproducibility. RESULTS: Nine patients (F6/M3, mean age 52 y; diagnoses: 5 interstitial lung disease, 2 bronchiectasis, 2 COPD) were tested and their results compared to 8 healthy individuals (F6/M2, mean age 45 y). Their mean Eq/Tq ratio was 3.1 times as high as that of the control subjects (p <0.01). Six patients who underwent testing mid-way through their PR and 3 who were tested at completion of PR have shown variable responses to physical therapy with decrease in Eq/Tq so far. Mean Eq/Tq in patients decreased from baseline by 35% midway through PR, and by 23% at the end of PR. CONCLUSIONS: Baseline skeletal muscle contraction in patients with chronic respiratory disorders shows greater neural stimulation required to generate a force equivalent to that in healthy individuals, as shown by increase in Eq/Tq. The ratio decreases with PR, indicating improvement in skeletal muscle strength. Use of Eq/Tq has the potential to assess skeletal muscle fatigue and its reversal in patients undergoing PR. CLINICAL IMPLICATIONS: Non-invasive measurement of quadriceps muscle fatigue during a pulmonary rehabilitation program can be used as a tool to assess a patient's progress throughout the program. This can be used in conjunction with validated tools to assess a patient's respiratory symptoms to determine how the pulmonary rehabilitation program is helping a patient. DISCLOSURES: No relevant relationships by Ahmet Baydur, source=Admin input No relevant relationships by Spencer Briglio, source=Web Response No relevant relationships by Juan Cortez, source=Web Response No relevant relationships by Gregory Grandio, source=Web Response No relevant relationships by Guadalupe Yetter, source=Web Response