The role of unilateral vagotomy on reflex bronchoconstriction

Mechanism of increased tracheo-bronchial response to inhalative acetylcholine aerosol in pulmonary vascular congestion and unilateral pulmonary artery occlusion

The study was carried out in anesthetized, intubated and spontaneously breathing dogs. The aim of this study was to examine the responsiveness of the tracheo-bronchial system to inhalative ACh. It was considered that any change in ACh-sensitivity signifies the involvement of receptors in the lung itself. Increased pressure in the right heart and main pulmonary artery did not affect the ACh-sensitivity. Whereas, the sustained pulmonary vascular congestion produced by blocking the ascending aorta or by glass bead embolism provoked greater ACh-sensitivity. Increased ACh-sensitivity was also observed in unilateral pulmonary artery occlusion. ACh-sensitivity was greater in the later part of occlusion or vascular congestion and persisted even after the occlusion or block was withdrawn. It is concluded that the increased ACh-sensitivities in pulmonary vascular congestion and in unilateral pulmonary artery occlusion are due to the formation of edema and atelectasis respectively. Anyway, the disturbance of the metabolism of the receptor cells around the small vessels of the lung circulation seems to be essential.

[Reaction of the cardio-respiratory-system following acetylcholine inhalation and the dependency from the body position on anaesthetised dogs (author's transl)]

The bronchomotoric reaction following ACH-aerosol in low concentrations is dependend on the position of the body on dogs. Up till one maximal reaction the increase of the airway resistance is always stronger in the lateral position. Nevertheless the breathing minute volume is constant. Concentration reaction curves will be shown. Arterial blood gases, heart rate, and pressure in the arteria femoralis were also measured. The different strongness of the reaction following ACH-inhalation will be caused by the predominantely unilateral ventilation of the animals in the lateral position.