Oronasal distribution of ventilation during exercise in normal subjects and patients with asthma and rhinitis.

This study was undertaken to determine whether the resistance to nasal airflow and differences in oronasal distribution of ventilation at rest and during exercise alter the pattern of breathing. We observed six normal subjects, six patients with symptomatic allergic rhinitis, and six patients with asymptomatic bronchial asthma (three men and three women in each group), all of whom had normal pulmonary function. At rest, five of the six normal subjects breathed nasally but 11 of the 12 patients breathed with an oronasal distribution. Five normal subjects who breathed nasally at rest breathed with an oronasal distribution of ventilation during exercise, and one normal subject who breathed oronasally at rest had slightly less oral ventilation during exercise. In the patients, the change in oral distribution of ventilation during exercise was variable. Among the three groups, there were no significant differences from the resting oronasal distribution for ventilation during exercise, and all subjects breathed oronasally during exercise. The oronasal distribution of ventilation did not correlate with the level of nasal airflow resistance. Analysis of the timing, volume, and flow components of breathing showed no statistically significant differences among the three groups at rest and exercise. Thus, neither the level of resistance to nasal airflow, even up to moderately high values, nor the nasal distribution of ventilation at rest and with moderate exercise appears to have a major role in the pattern of breathing.