Abstract
Effects of nasal resistance on distribution of respiratory airflow between nose and mouth were investigated by a minimally invasive computer-assisted method using a modified CPAP nasal mask/pneumotach and a head-out body plethysmograph. In 18 subjects nasal resistance (p = 0.091), breathing frequency (p = 0.084), tidal volume (p = 0.352), and minute (p = 0.433) volumes were undisturbed by the masking procedure. Partial nasal breathing persisted in 16 of 33 healthy adults instructed to breathe through the mouth. Artificial additions to nasal airflow resistance that were made in 10 volunteers from the 16 persistent partial nose breathers whose nasal fraction > 25% increased the oral fraction of respiratory airflow. It is concluded that while the palate provides a switching mechanism for oronasal routing of respiratory airflow, the oral and nasal vestibules provide variable resistors that regulate its distribution.
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