Electromyographic feedback for learning to activate thoracic inspiratory muscles.

The utility of EMG feedback for modifying the muscular pattern of breathing was investigated in twenty-four subjects divided into two groups (feedback, no feedback. Each took part in three 20-min training sessions, 24 h apart. All the subjects were instructed to increase the thoracic contribution of inspired gas. The feedback subjects were shown an EMG signal of the inspiratory muscles of the upper thorax and a signal indicating their current breathing phase (inspiration or expiration). The no feedback subjects only saw the breathing phase signal. The subjects' ability to control muscular activity was assessed as the relative increase in EMG from expiration to the subsequent inspiration. Analysis of variance with group and session as factors showed that feedback subjects performed significantly better, although the improvement in performance over the sessions by the two groups was not significantly different. These results lend some support to the clinical use of EMG feedback in breathing therapy aimed at changing the thoracoabdominal distribution of ventilation. However, further research for improving learning is necessary.

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.