Relationship between the relative nasal diameter and pulmonary function

The present study was made to investigate the effect of the mechanical change in the nasal cavity on the pulmonary function. Compliance and resistance in the respiratory system including the nose and lung during different phases of respiration were obtained and the relative nasal diameter was calculated to represent a mechanical property of the nasal airway. It was found that nasal compliance remained approximately the same as mouth compliance except for those cases with severe nasal obstruction. Inspiratory resistance was greater than expiratory resistance. Measurements of the pressure-flow relationship in the lower airway indicated that the nose accounted for 40% of the total pulmonary resistance during normal nasal breathing. Changes in pulmonary resistance were not linear by related to the degree of nasal obstruction. The non-linearity was considered to be due to reflex control of the respiratory system.