because oscillatory resistance of the respiratory system is often measured during tidal breathing , we studied the interaction between simultaneous oscillatory and unidirectional flows in three straight tubes ( radius ranging from 0.3025 to 0.679 cm and length either 30.7 or 173 cm ) and a central airway cast ( tracheal radius 0.685 cm ) .
C0035237
respiratory system
C0040578
tracheal