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APNEUSTIC breathing, characterized by deep, sustained inspiratory activity, has figured prominently in theories on the neural control of respiratory rhythmicity<sup>1</sup>. This intriguing respiratory phenomenon has been described in the vagotomized, midpontile decerebrate animal<sup>2â 4</sup>. In this preparation, the Heringâ Breuer afferent system in the vagi and the pneumotaxic area in the rostral pons have been eliminated. Both the Heringâ Breuer and the pneumotaxic influences appear to be predominantly inhibitory to the inspiratory mechanisms of the lower brain stem<sup>4</sup>. However, the apneustic area in the lower pons is not destroyed by midpontile decerebration and continues to provide a powerful facilitatory influence on the inspiratory neurones of the medulla<sup>2â 4</sup>. In the presence of apneustic facilitation and the absence of Heringâ Breuer and pneumotaxic inhibition, the medullary inspiratory neurones are excessively stimulated. The resultant excessive activity of the inspiratory neurones produces apneustic breathing<sup>1â 4</sup>. |
