Is volume and leak monitoring feasible during nasopharyngeal continuous positive airway pressure in neonates?

Objective: To investigate tidal volume (VT) and leak measurements during continuous positive airway pressure (CPAP) in neonates using a commercial ventilatory device equipped with a flow sensor at the Y-piece.

Design: Randomized cross-over trial.

Setting: Neonatal intensive care unit level III.

Patients: Thirty-two infants, median (range) birth weight 1,435 (710-2,730) g, gestational age 30 (24-38) weeks.

Interventions: During nasopharyngeal CPAP, leak and VT were measured with and without occlusion of the contralateral nostril using the Leoni ventilator (Heinen & Löwenstein, Germany) and a recently developed algorithm to correct measured VT in the presence of leaks. The measuring range of the Leoni is limited to leaks <90%.

Main Results: Analyzable measurements with leaks <90% could be obtained in 12.5% of the patients with open nostril, and in 65.6% with occluded nostril. Calculated leak flow after nostril occlusion was 23 (3-77) ml min(-1) with closed mouth. Leak flow increased significantly if mouth was opened (548 (0-1,394) ml min(-1), p<0.001), but was probably even higher where leaks exceeded 90%. Mean expiratory volume +/- SD was 5.8 +/- 1.3 ml kg(-1) (corrected VT 5.9 +/-1.2 ml kg(-1)) for leaks <20%, and 3.7 +/-1.4 ml kg(-1) (corrected VT 5.8 +/- 2.2 ml kg(-1)) for leaks between 20 and 69%.

Conclusions: Leak and corrected VT could be determined in the presence of leaks of up to 69%, but leaks during CPAP often exceeded the measuring range. Reliable volume and leak monitoring was not possible with the tested equipment during nasopharyngeal CPAP. Advanced equipment is necessary to further investigate the effects of leaks on neonatal CPAP therapy.