OBJECTIVE: Sustained pharyngeal inflation (SPI) with pharyngeal oxygen and nose-close (PhO2-NC) can create positive peak inflation pressure (PIP) inside the pharyngolaryngeal space (PLS). This study measured and compared effects of four different SPI durations in the PLS. METHOD: In this prospective observational study, 20 consecutive infants aged less than 3 years, scheduled for elective flexible-bronchoscopy were enrolled. SPI was performed twice in four different durations (0, 1, 3 and 5 seconds) sequentially in each infant. PIP was measured for each SPI in the pharynx, and simultaneously took images at two locations of oropharynx and supra-larynx. Infants’ demographic details and PIP levels, lumen expansion scores and images of PLS were measured and analyzed. RESULTS: Twenty infants with 40 measurements were collected. The mean (SD) age and weight were 11.6 (9.1) months and 6.8 (2.4) kg, respectively. The measured mean (SD) pharyngeal PIPs were 4.1 (3.3), 21.9 (7.0), 42.2 (12.3) and 65.5 (18.5) cm H2O at SPI duration of 0, 1, 3 and 5 seconds, respectively; which showed significant positive association (p<0.001). At assigned locations, the corresponding PLS images also show significant increase in lumen expansion scores and number of detected lesions with increase in SPI duration (p<0.001). The mean (SD) study time was 5.7 (1.2) minutes. No study related complication was noted. CONCLUSIONS: SPI with PhO2-NC up to 5 seconds is a simple, safe and feasible clinical ventilation modality. It may provide enough PIP to expand the PLS and facilitate flexible-bronchoscopy performance in infants.