RÔLE OF THE HERRING-BREUR REFLEX UNDER DEEP PENTOTHAL ANESTHESIA

Abstract

Periods of respiratory arrest were produced in dogs by intraven. pentothal. Continuous oxygen flow was maintained through an endotracheal tube. Brief appln. of light pressure to the thoracic wall during periods of inhibition elicited a single respiratory response even though other forms of stimulation were ineffective. The minimal strength of stimulus was evaluated roughly by using a 1000-g., 500-g. or 300-g. wt. The response disappeared following bilateral cervical vagotomy. Unilateral cervical vagotomy or unilateral pneumonectomy caused the response to disappear when the animal was lying on the operated side. An appropriate depth of anesthesia produced a condition in which the animal breathed spontaneously when lying with the operated side up, but remained in inhibition when the operated side was down. A change in respiratory rate with change in position persisted indefinitely in the unanesthetized animal. The effects of position in the unilateral vagotomized animal may be explained by assuming deformation of lung tissue due to shift of mediastinal structures such as the heart. With the animal lying on his vagotomized side, the excitation from compressing the "bottom" lung has been removed but the inhibitory effect from stretching the "upper" lung is unimpaired. On reversing the position, the excitatory effects are unimpaired but the inhibitory influences have been removed. A similar explanation may be applied to the unilateral pneumonectomized animal.