Vector analysis of Respiratory Muscle Activation in Individuals with Amyotrophic lateral sclerosis


Clinical Trials

Poster Number: 68


Priscila Sales de Campos, PhD, University of Florida, Wendy L. Olsen, PhD, University of Florida, Barbara Smith, PhD, PT, University of Florida

Standard pulmonary function tests can be used as a clinical marker of neuromuscular disease prognosis and progression in Amyotrophic lateral sclerosis (ALS), but they cannot identify subtle differences in respiratory motor recruitment at rest. In clinical practice and research, a surface electromyography (sEMG) recorded from respiratory muscles can be used to assess respiratory motor function and help to diagnose neuromuscular pathology. We hypothesized that vector analysis, an analytical tool to characterize respiratory motor control directly from sEMG data recorded from multiple respiratory muscles, could detect differences of muscle recruitment in ALS. Surface EMG was recorded in four respiratory muscles bilaterally from patients with mild-moderate respiratory involvement (vital capacity >60% predicted, n=14) and unaffected adults (n=12) during quieting breathing and MIP efforts. EMG signal intensity was analyzed by computing the root mean square and identifying the peak amplitude of each muscle. Then, amplitude and frequency of the composite EMG activity were calculated and compared between groups using Matlab software and unpaired t-tests for statistical analyses. During quiet breathing, neither baseline tidal volume, respiratory rate, nor minute ventilation differed between ALS and control groups. However, collective muscle activity was more than double in ALS versus control subjects during quiet breathing, indicating differences in the pattern of respiratory muscle activity. Additionally, EMG peak amplitudes of several muscle groups were significantly lower in ALS patients during MIP. Differences were observed in both intensity (RMS) and the pattern of recruitment of muscle activity during MIP. Respiratory muscle utilization pattern differs in patients with ALS during quiet breathing and MIP, when compared to healthy controls. These findings indicate that respiratory muscle activation patterns differ between ALS and healthy subjects, even in early disease when minute ventilation remains normal. Vector analysis of respiratory muscles may be a useful research tool and warrants further study.