title: Oronasal distribution of respiratory airflow.
abstract: The oronasal distribution of respiratory airflow was determined during incrementally graded submaximal exercise in 30 (14 M, 16 F) healthy adult volunteers. Nasal airflow was measured by a pneumotachograph attached to a nasal mask. Oral airflow was determined as the difference between nasal airflow and total pulmonary airflow, the latter being measured by a head-out exercise body plethysmograph. The two airflow signals were sampled every 20 msec by a microprocessor, which calculated the oral and nasal minute volumes (separating inspiration and expiration) and produced an on-line print-out of the results. Twenty subjects ("normal augmenters") switched from nasal to oronasal breathing at a VE of 35.3 +/- 10.8 1 . min-1, four subjects ("mouth breathers") habitually breathed oronasally, five subjects ("nose breathers") persistently breathed through the nose only, and one subject showed no consistent nose/mouth breathing pattern. After the switch to oronasal breathing, the nasal portion of VE decreased suddenly to 57% of total VE. With a further increase of VE, oral minute volume increased rapidly, equalling nasal minute volume at a VE of 45 1 . min-1, and accounting for 61% of the total ventilation at high respiratory minute volumes (90 1 . min-1). During oronasal breathing, normal augmenters inspired some 2 1 . min-1 more nasally than they expired. Similarly, the nasal inspiration of mouth breathers exceeded expiration by 2 1 . min-1 at rest, but the difference increased to 13.51 . min-1 at a VE of 81.51 . min-1.
mesh_terms: D000293:Adolescent; D000328:Adult; D006801:Humans; D009058:Mouth Breathing / Q000503:physiopathology; D009296:Nasal Cavity / Q000502:physiology; D009960:Oropharynx / Q000502:physiology*; D005082:Physical Exertion; D012119:Respiration