ELECTROMYOGRAM AND THE RESPIRATORY PATTERN

SUMMARY Different respiratory patterns were provoked experimentally in rabbit and were analyzed with simultaneous recording of pneumogram and of electromyograms from the inspiratory muscle (diaphragm), expiratory muscle (m. transversus thoracis or m. intercostalis internus) and deep expiratory muscle (m. obliquus abdominis externus). 1. Normal respiration with normal rhythm (eupnea) is maintained by alternate contractions of inspiratory and expiratory muscles. A decresse in the depth of respiration is caused by decreased activity of expiratory muscles and an increase, on the contrary, by increased discharge of inspiratory muscles. 2. In the case of increased respiration rate with increased depth of respiration (hyperpnea), three types can be differentiated: an alternating increase in contraction of both the inspiratory and expiratory muscles, the increase of inspiratory muscles alone, and that of expiratory muscle alone. 3. In the case of increased rate with decreased depth of respiration (panting), there are also three types distinguishable: a type with decreased discharge of inspiratory muscles, another type with continuous discharge of inspiratory muscles and still another type with both high amplitude discharge of inspiratory and continuous discharge of abdominal muscles. 4. Gasping is characterized by big discharge of inspiratory muscles with either synchronized discharges of expiratory muscles or without such of expiratory ones. 5. Synchronized continuous discharging of both inspiratory and expiratory muscles are observed in the cases of inspiratory apnea or of spitting. 6. Continuous discharging of expiratory muscles occurs in the case of expiratory apnea and is accompanied in some cases by weak intercurrent discharges of inspiratory muscles. 7. It is evidenced by the present study that the behavior of respiratory centers could not be fully understood relying on changes in pneumogram alone.