Oronasal distribution of respiratory airflow.
Level 4 - case-series / case-control
Cross-sectional physiological study without comparative intervention groups.
PubMed 7244427 · doi:10.1016/0034-5687(81)90089-x
What was done
Researchers measured the partitioning of nasal and oral airflow during incrementally graded submaximal exercise in 30 healthy adult volunteers (14 men, 16 women). Nasal airflow was measured via a pneumotachograph attached to a nasal mask, and total pulmonary airflow was measured with a head-out exercise body plethysmograph. Oral airflow was derived as the difference between total pulmonary airflow and nasal airflow. Airflow signals were sampled every 20 msec by a microprocessor to compute inspiratory and expiratory oral and nasal minute volumes.
What was found
Participants demonstrated four distinct breathing patterns: 20 ("normal augmenters") transitioned from nasal to oronasal breathing at a minute ventilation (VE) of 35.3 ± 10.8 L/min; 4 ("mouth breathers") habitually breathed oronasally at rest; 5 ("nose breathers") breathed exclusively through the nose throughout exercise; and 1 had an inconsistent pattern. After normal augmenters switched to oronasal breathing, the nasal fraction dropped suddenly to 57% of total VE. Oral minute volume matched nasal minute volume at a VE of 45 L/min and reached 61% of total ventilation at 90 L/min. Normal augmenters inspired ~2 L/min more nasally than they expired; mouth breathers showed an excess of nasal inspiration over expiration of 2 L/min at rest that increased to 13.51 L/min at a VE of 81.51 L/min.
Why it matters
This paper quantifies the physiological switching threshold from nasal to oronasal breathing during exercise and demonstrates that human breathing route preferences vary substantially between individuals.
Limits
The study sample was small (n = 30) and limited to healthy adult volunteers. Oral airflow was estimated by subtraction rather than measured directly, potentially propagating measurement error. The use of facial masks and a plethysmograph may have influenced spontaneous breathing behavior.
Cited by
- supports During vigorous or intensive exercise, the majority of ventilation transitions to oral (mouth) breathing.