Nasopulmonary reflex: evaluation in the nonparalyzed and paralyzed anesthetized dog

Changes in the pulmonary mechanics of various animal species have been observed after nasal stimulation. In reviewing the methods of these studies, we found that often the respiratory patterns were not controlled well enough to permit conclusions about changes in resistance and compliance. To further investigate the possibility of a nasopulmonary reflex, we first studied the effect of nasal stimulation on pulmonary mechanics in anesthetized, nonparalyzed dogs. In this group of 35 dogs, we found that nasal stimulation typically produced marked changes in breathing patterns, a large transient increase (150%) in pulmonary airflow resistance, but no change in compliance. This response to nasal stimulation could be abolished by interrupting either the trigeminal or the vagus nerves. In an additional group of 12 anesthetized, paralyzed dogs, we found no changes in resistance or compliance after nasal stimulation. From this observation, we concluded that nasal stimulation produced changes in breathing patterns that led to alterations in resistance without an actual change in the intrinsic behavior of the pulmonary airways.