Learned activation of thoracic inspiratory muscles in tetraplegics.

The aim of this study was to determine whether tetraplegics can learn to activate accessory inspiratory muscles of the upper rib cage, and how this learning affects respiratory motion. Ten tetraplegics with lesional levels ranging from C5 to C7 were trained to increase the upper rib cage expansion during nine 20-min sessions. They were shown an electromyogram (EMG) feedback of the inspiratory muscles of the upper thorax and a signal indicating their current breathing phase (inspiration or expiration). The subjects were instructed to increase EMG during inspiration and to decrease it during expiration. Analysis of variance with session and respiratory phase as factors showed that the subjects progressively learned to increase inspiratory EMG. Thoracic motion, tidal volume and minute ventilation were correlated with inspiratory EMG and tended to increase as a function of practice. These preliminary results lend some support to the clinical use of EMG feedback in breathing therapy aimed at increasing thoracic motion and preventing or reducing paradoxical breathing in tetraplegics.