Large airway constriction in allergic rhinitis: response to inhalation of helium-oxygen.

Pulmonary function results were compared in 15 allergic rhinitis and 30 normal subjects. Airways resistance (RAW) was higher (p less than 0.01) and specific conductance (SGAW) and lower (p less than 0.01) in the rhinitis group. Maximal expiratory flow (VeMax), lung volumes, and results of tests measuring airways closure, distribution of ventilation, diffusing capacity, volume of isoflow, and density-dependence of VeMax at 50% of vital capacity (deltaVeMax50) did not differ significantly between the two groups. Following inhalation of isoproterenol, RAW decreased and SGAW and VeMax increased significantly in both groups. On the other hand, delta-VeMax50 decreased significantly in the rhinitis group (p less than 0.01) and increased significantly in the control group (p less than 0.05). In addition to comparing pulmonary function in rhinitis patients and control subjects, physiologic measurements were also made on two separate occasions in the rhinitis subjects (minimal or no symptoms; very symptomatic). Although rhinitis symptomatology varied considerably (p less than 0.001), pulmonary function results were not significantly different. Hence we conclude that: (1) Rhinitis subjects have large airway constriction which does not vary with season or symptoms. (2) As in normal control subjects, airflow limitation occurs in the large airways of rhinitis subjects. (3) The predominant site of isoproterenol-associated bronchodilatation differs between allergic rhinitis and normal subjects.