Bubble and ventilator-derived nasal continuous positive airway pressure in premature infants: work of breathing and gas exchange

Abstract

During bubble nasal continuous positive airway pressure (B-NCPAP), gas flows through the expiratory limb of CPAP tubing submerged underwater to a depth in centimeters considered equal to the desired end expiratory pressure. Ventilator-derived NCPAP (V-NCPAP) controls the delivered pressure at the expiratory orifice. Limited data exist comparing the two forms of NCPAP on work of breathing (WOB) and other short-term respiratory outcomes. We compared WOB and gas exchange between B-NCPAP and V-NCPAP at equivalent delivered nasal prong pressures among a cohort of preterm infants on NCPAP. We performed a randomized crossover study in 18 premature infants <1500 g (BW 1101±254 g, GA 28±2 weeks, study age 13±8 days (means±s.d.)), who were already on NCPAP for mild respiratory distress, comparing B-NCPAP to V-NCPAP. Each infant was studied at a constant flow rate and varying pressures of 3, 5, 7, 4 and 2 cm H(2)O in that order. Tidal volumes were obtained by calibrated respiratory inductance plethysmography. Intrapleural pressure was estimated by an esophageal catheter. WOB (inspiratory, elastic and resistive) was calculated from pressure volume data. Breathing asynchrony was assessed with phase angle. Comparisons of respiratory rate, heart rate, tidal volume, minute ventilation, breathing asynchrony, lung compliance, oxygen saturation and transcutaneous (Tc) O(2) and CO(2) were also made. WOB and most respiratory parameters were not different between B-NCPAP and V-NCPAP. TcO(2) was higher with B-NCPAP compared to V-NCPAP (P=0.01). TcCO(2) was not different. None of the other measured parameters was significantly different between the two devices. WOB and ventilation with B-NCPAP and V-NCPAP are similar when equivalent delivered prong pressures are assured. Improved oxygenation with B-NCPAP is intriguing and requires further investigation.