An electromyographic study of the abdominal muscles of tetraplegic patients

Bipolar fine wire electrodes were used to make electromyographic (EMG) recordings of the abdominal muscles of 8 stable complete tetraplegic patients. Synchronous recordings were made of ventilation, and in 5 subjects an oesophageal electrode was used to record diaphragm EMG. In all 8 subjects we demonstrated phasic inspiratory EMG activity which we have shown to be localised to the abdominal muscles. We believe that this activity was triggered by stretching of the abdominal wall on inspiration. Its effect will be to decrease abdominal wall compliance allowing the diaphragm to generate greater intra-abdominal pressure as it descends, thus promoting inflation of the lower rib cage.