The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts

EVALUATION OF EXPIRATORY MUSCLE ACTIVATION PATTERNS IN INDIVIDUALS WITH SPINAL CORD INJURY

Alexander V. Ovechkin1,2, Susan J. Harkema1,2, Daniela G. Terson De Paleville3,2, William B. McKay1,2



Background: Individuals with spinal cord injury (SCI) suffer from paresis and paralysis of their trunk muscles. After SCI, disorganized trunk neuromuscular activation leads to respiratory insufficiency. The objective of this study was to develop an algorithm to evaluate expiratory muscle activity in individuals with intact phrenic nerves following SCI. We hypothesized that post-SCI respiratory multi-muscle activation patterns can be quantitatively compared to those of non-injured subjects.

We performed spirometry including maximum expiratory pressure (PEmax) in the sitting position. We also recorded surface electromyographic (sEMG) patterns from upper trapezius, pectoralis, intercostals, rectus abdominus, and oblique abdominus muscles during motor tasks and loaded respiratory maneuvers in neurologically intact (NI) subjects (n=8) and individuals with SCI (n=8) in the supine position. sEMG amplitude for each muscle was measured using a root-mean-square algorithm and averaged for the three repetitions for each task. Expiratory pressure was recorded simultaneously during respiratory tasks. Multi-muscle activity parameters were calculated using averaged sEMG amplitudes from each SCI subject for comparison to group values from NI subjects (Lee et al, 2004)*. The resulting magnitude parameter is the amount of combined sEMG activity (μV/sec) during a specific task. The similarity index provides a value between 0 and 1.0 that expresses how similar the multi-muscle distribution of activation in SCI subject is to that of NI subjects.

The major finding was that this sEMG-based analytic algorithm was sensitive to severity and level of SCI. Magnitude and similarity index values correlated with spirometrical parameters and levels of SCI (Fig.1). Compared to NI subjects, muscle activation patterns were altered, showing both increased and decreased activity in trunk muscles in SCI subjects. With the use of this analytic tool to quantify the muscle activation pattern impairments, we will be able to objectively evaluate the effects of existing and new intervention strategies in SCI and other neurological disorders.

*Lee DC and others. Toward an objective interpretation of surface EMG patterns: a voluntary response index (VRI). JEK, 2004 14:379-388.