Pressure variation during ventilator generated nasal intermittent positive pressure ventilation in preterm infants

Background Nasal intermittent positive pressure ventilation (NIPPV) is a mode of non-invasive respiratory support. Its mechanisms of action and optimal delivery techniques are unknown. Aim This observational study aimed to investigate and quantify delivered peak pressures during non-synchronised ventilator-generated NIPPV. Methods Infants born below 30 weeks gestation receiving ventilator-generated NIPPV delivered via Hudson prongs were recruited. Intraprong pressure, change in tidal volume, respiratory rate, oxygen saturations, inspired oxygen and video images were recorded. Results Eleven infants (four infants were female) of median (interquartile range; 108) gestational age 25(+/- 3) (25(+/- 2)26(+/-0)) weeks and birth weight 732 (699-895) g, were studied at 24 (19-41) days of age. Six infants, with set peak pressure (peak inflation pressure; PIP) of 20 cm H(2)O, received a median pressure of 15.9 (IQR 13.6-17.9) cm H(2)O, 37% of inflations were delivered at least 5 cm H(2)O below set PIP. 12.7% of inflations were delivered above set PIP. Five infants with set PIP of 25 cm H(2)O received a median PIP of 17.2 (ICR 15.0-18.3) cm H(2)O. 83% of inflations were delivered at least 5 cm H(2)O below set PIP, with 6.1% delivered higher than set PIP. The difference in delivered PIP between the groups was 1.3 cm H(2)O. PIP was highest and most variable when the infant was moving. Delivered PIP did not vary whether it coincided with spontaneous inspiration or expiration. Conclusion During ventilator-generated non-synchronised NIPPV delivered PIP was variable and frequently lower than set PIP. Delivered PIP was occasionally greater than set PIP.