The study evaluates the influence of carotid baroreceptors activation and the combined activation of baroreceptors and mechanoreceptors located in the larynx and upper part of the trachea, on airway resistance in humans. The selective activation of baroreceptors was induced by generating a negative pressure (-40 mmHg) for 5 s in two capsules placed bilaterally on the neck over the bifurcation of the carotid arteries. The single chamber encompassing both frontal and lateral parts of the neck was used for simultaneous activation of the baroreceptors and upper airway mechanoreceptors. The above methods were validated by measurement of intra-oesophageal pressure. 50% of the negative pressure in the single chamber was transmitted to the oesophagus, whereas the pressure changes in the single capsules were not reflected at oesophagal level. Selective stimulation of carotid baroreceptors decreased airway resistance, whereas the opposite was true when both carotid baroreceptors, and upper airway mechanoreceptors were stimulated concomitantly. As atropine abolished the above changes in the airway resistance, it is suggested that the cholinergic efferent pathway is responsible for their occurrence. We conclude that in humans reflexes originating from carotid baroreceptors and mechanoreceptors in the larynx and trachea influence the airway resistance. In case of simultaneous activation of baroreceptors and mechanoreceptors of the upper airways the later one prevails the former.

Keywords: Airway Resistance, laryngeal mechanoreceptors, tracheal mechanoreceptors, carotid baroreceptors