Electromyography of respiratory muscles in cough, glottal reflexes and vomiting

Abstract

The respiratory track reflexes and the vomit are studied by electromyogram registers (EMG) of the inspiratory and expiratory muscles. The experimental animal, was the midcollicular decerebrated dog, carried out 24 hours previous to the experiment. 

The following data were simultaneously collected: the integrated EMG of the diaphragm and the oblique abdominal external muscle, the resistance of the separated glottis by the authors original method (10), pleural pressure, pneumotachogram, spirogram, and intraabdominal and intragastric pressures. The vomit was provoked by apomorphine. The following results were obtained.

Effects of iracheal excitation. The EMG of the diaphragm of the excited animal shows a greater potential than in the control animal. It is observed that the final portion of the diaphragm EMG is overlapped by the beginning of the abdominal muscle EMG.

The expiratory contraction of the ab­dominal muscle must be isometric during the first portion of its contraction because it reaches the maximum state of contraction before the current of ex­piratory air begins. As the inspiratory muscles relax the convulsive expiratory contraction dominates, producing the initial rapid acceleration of the air cur­rent typical of the cough.

Effects of larynx excitation. A meclianical stimulation at vocal cord level always diminishes the general muscular activity of the respiratory muscles. This inhibition of the muscular contraction is called by the authors expiratory apnea.

The vomit. The characteristic effect is a violent synergie contraction of both the inspiratory and expiratory muscles, wich obviously are anthagonist on respiratory movements. The EMG of the diaphragin has more potential than in the cough. The oblique external muscle registers an EMG already in the inspiratory phase and is more contracted than in the cough. The correlation of the two EMG, that of the diaphragm and that of the oblique external muscle, is essential for an interpretation of the vomit mechanism. This mechanism, on the basis of the EMG data, can be described as a simultaneous contraction of the dia­phragm and the abdominal expiratory muscles, strongly increasing the gastric pressure enough to empty the stomach.