Graphic representation of in-vivo data from preterm lambs supported by high-frequency nasal ventilation via VDR4 high-frequency ventilator (Percussionaire, Sand Point, ID, USA). (A) High-frequency pressure pulsations are seen throughout both the inspiratory (solid white arrow) and expiratory (dashed white arrow) phases of background convective breaths. (B) Change in peak delivered pressure and convective tidal volume following increased high-frequency pressure amplitude. (C) Measured tidal volume by respiratory inductive plethysmography (Respitrace, CareFusion, San Diego, CA, USA) during convective breaths with simultaneous pressure recordings via Samba 3200 fiberoptic micropressure transducer (Harvard Apparatus Canada, Saint-Laurent, QC, Canada) integrated with a BIOPAC MP150 system (BIOPAC Systems, Goleta, CA, USA) and inserted into posterior nasopharyngeal space.