Reflex relationships between the cervical esophagus and the respiratory system in cats

The present study focused on reflex relationships between the esophagus and the respiratory system in cats, namely the changes in airway tone and pulmonary circulation elicited by mechanical or acid (pH 2) stimulation of esophageal afferents. One-minute of sustained distension of the cervical esophagus increased tracheal pressure (PTr), decreased pulmonary artery pressure (PPA) and to a higher extent pulmonary blood flow (QPA) and lowered arterial blood pressure (Pa). This was associated with significant variations in arterial blood gases (increased PaO2 and decreased PaCO2). Acid stimulation of the cervical esophagus caused a marked increase in PTr and a modest fall in QPA. In both circumstances, cervical bivagotomy abolished PTr changes, whereas the changes in pulmonary hemodynamics but not in Pa were then accentuated. Further cervical sympathectomy suppressed the vascular response. These observations show the existence of reflex influences of esophageal afferents on the control of airway tone and pulmonary vascular resistance. The vagus nerve is the efferent arm of the bronchomotor reflex whereas modulation of the sympathetic control of pulmonary circulation seems to be responsible for the changes in pulmonary hemodynamics.