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Evaluation of Respiratory Muscle Activation Using Respiratory Motor Control Assessment (RMCA) in Individuals with Chronic Spinal Cord Injury

Published: July 19th, 2013



1Department of Neurological Surgery, University of Louisville, 2Spinal Cord Injury Laboratory, Shepherd Center, 3Department of Medicine: Division of Pulmonary, Critical Care and Sleep Disorders, University of Louisville

The purpose of this publication is to present our original work on a multi-muscle surface electromyographic approach to quantitatively characterize respiratory muscle activation patterns in individuals with chronic spinal cord injury using vector-based analysis.

During breathing, activation of respiratory muscles is coordinated by integrated input from the brain, brainstem, and spinal cord. When this coordination is disrupted by spinal cord injury (SCI), control of respiratory muscles innervated below the injury level is compromised1,2 leading to respiratory muscle dysfunction and pulmonary complications. These conditions are among the leading causes of death in patients with SCI3. Standard pulmonary function tests that assess respiratory motor function include spirometrical and maximum airway pressure outcomes: Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), Maximal Inspiratory Pressure (PImax) and Maximal Expiratory Pressure (PEmax)4,5. These values provide indirect measurements of respiratory muscle performance6. 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. However, variability in the sEMG amplitude inhibits efforts to develop objective and direct measures of respiratory motor function6. Based on a multi-muscle sEMG approach to characterize motor control of limb muscles7, known as the voluntary response index (VRI)8, we developed an analytical tool to characterize respiratory motor control directly from sEMG data recorded from multiple respiratory muscles during the voluntary respiratory tasks. We have termed this the Respiratory Motor Control Assessment (RMCA)9. This vector analysis method quantifies the amount and distribution of activity across muscles and presents it in the form of an index that relates the degree to which sEMG output within a test-subject resembles that from a group of healthy (non-injured) controls. The resulting index value has been shown to have high face validity, sensitivity and specificity9-11. We showed previously9 that the RMCA outcomes significantly correlate with levels of SCI and pulmonary function measures. We are presenting here the method to quantitatively compare post-spinal cord injury respiratory multi-muscle activation patterns to those of healthy individuals.

1. Settings

  1. Surface electrode heads were placed over the muscle bellies of left (L) and right (R) respiratory muscles: sternocleidomastoid (SC), scalene (S), upper trapezius on midclavicular line (UT), clavicular portion of pectoralis on midclavicular line (P), diaphragm on parasternal line (D), intercostal at 6th intercostal space on anterior axillary line (IC), rectus abdominus at umbilical level (RA), obliquus abdominis on midaxillary line (O), lower trapezius paraspinally at midscapular level (.......

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Figure 3 represents the electromyogram and airway pressure (on top) simultaneously recorded during MEPT from a non-injured (left) and SCI (right) individuals. Note decreased airway pressure and absence of sEMG activity in expiratory muscles in an SCI subject when compared to a non-injured individual (marked with gray ellipses). Note also that start of the task, as marked on the bottom, is associated with increased sEMG activity and raising airway pressure.

Figure 4

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Standard clinical tests to evaluate respiratory motor function after SCI and other disorders include the pulmonary function tests and the American Spinal Injury Association Impairment Scale (AIS) evaluation14,15. However, these tools are not designed for quantitative evaluation of the trunk and respiratory motor control. In our previously published work9, we have shown that the RMCA is a valid method to quantitatively evaluate the respiratory motor function affected by SCI. We have demonstrated that.......

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This work was supported by Christopher and Dana Reeve Foundation (Grant CDRF OA2-0802-2), Kentucky Spinal Cord and Head Injury Research Trust (Grant 9-10A - KSCHIRT), Craig H. Neilsen Foundation (Grant 1000056824 - HN000PCG) and National Institutes of Health: National Heart Lung and Blood Institute (Grant 1R01HL103750-01A1).


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Name Company Catalog Number Comments
Name of the Device Vendor Product # Comments
PowerLab System 16/35 ADInstruments PL3516 Number of units depends on number of channels recorded
EMG System MA 300 Motion Lab Systems MA300-XVI Number of units depends on number of channels recorded
Low Pressure Transducer MP45 Validyne MP45-40-871
Basic Carrier Demodulator CD15 Validyne CD15-A-2-A-1
Air Pressure Manometer Boehringer 4103 Needed for MP45 calibration
Event Marker Hand held switch that when pressed gives a DC voltage and sound output (including 5-sec long mark)
Alcohol Wipes Henry Schein 1173771 Needed for electrodes placement
Electrode Gel Lectron II 36-3000-25 Needed for electrodes placement
Tagaderm Henry Schein 7779152 Needed for electrodes placement
Noseclip Henry Schein 1089460
T-piece Ventilator Monitoring Circuit with One-way Valves Alleglance (Airlife) 1504
Air Tube UnoMedical 400E
Table 1. List of specific equipment and supplies used for the Respiratory Motor Control Assessment.

  1. Schilero, G. J., Spungen, A. M., Bauman, W. A., Radulovic, M., Lesser, M. Pulmonary function and spinal cord injury. Respir. Physiol. Neurobiol. 166, 129-141 (2009).
  2. Winslow, C., Rozovsky, J. Effect of spinal cord injury on the respiratory system. Am. J. Phys. Med. Rehabil. 82, 803-814 (2003).
  3. Garshick, E., et al. A prospective assessment of mortality in chronic spinal cord injury. Spinal Cord. 43, 408-416 (2005).
  4. Jain, N. B., Brown, R., Tun, C. G., Gagnon, D., Garshick, E. Determinants of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC in chronic spinal cord injury. Arch. Phys. Med. Rehabil. 87, 1327-1333 (2006).
  5. Stolzmann, K. L., Gagnon, D. R., Brown, R., Tun, C. G., Garshick, E. Longitudinal change in FEV1 and FVC in chronic spinal cord injury. Am. J. Respir. Crit. Care Med. 177, 781-786 (2008).
  6. . American Thoracic Society/European Respiratory Society. ATS/ERS Statement on respiratory muscle testing. Am. J. Respir. Crit. Care Med. 166, 518-624 (2002).
  7. Sherwood, A. M., McKay, W. B., Dimitrijevic, M. R. Motor control after spinal cord injury: assessment using surface EMG. Muscle Nerve. 19, 966-979 (1996).
  8. Lee, D. C., et al. Toward an objective interpretation of surface EMG patterns: a voluntary response index (VRI). J. Electromyogr. Kinesiol. 14, 379-388 (2004).
  9. Ovechkin, A., Vitaz, T., de Paleville, D. T., Aslan, S., McKay, W. Evaluation of respiratory muscle activation in individuals with chronic spinal cord injury. Respir. Physiol. Neurobiol. 173, 171-178 (2010).
  10. Lim, H. K., Sherwood, A. M. Reliability of surface electromyographic measurements from subjects with spinal cord injury during voluntary motor tasks. J. Rehabil. Res. Dev. 42, 413-422 (2005).
  11. Lim, H. K., et al. Neurophysiological assessment of lower-limb voluntary control in incomplete spinal cord injury. Spinal Cord. 43, 283-290 (2005).
  12. Sherwood, A. M., Graves, D. E., Priebe, M. M. Altered motor control and spasticity after spinal cord injury: subjective and objective. 37, 41-52 (2000).
  13. McKay, W. B., Lim, H. K., Priebe, M. M., Stokic, D. S., Sherwood, A. M. Clinical neurophysiological assessment of residual motor control in post-spinal cord injury paralysis. Neurorehabil. Neural Repair. 18, 144-153 (2004).
  14. Marino, R. J., et al. International standards for neurological classification of spinal cord injury. J. Spinal. Cord. Med. 26, S50-S56 (2003).
  15. American Spinal Injury Association and International Spinal Cord Society. . International Standards for Neurological Classification of Spinal Cord Injury. , (2006).

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