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Bubble Continuous Positive Airway Pressure Enhances Lung Volume and Gas Exchange in Preterm Lambs

¹ School of Women's and Infants' Health, The University of Western Australia, Perth, Australia; ² Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center and University of Cincinnati School of Medicine, Cincinnati, Ohio; and ³ Fisher and Paykel Healthcare, Auckland, New Zealand

Correspondence and requests for reprints should be addressed to Jane Pillow, F.R.C.A.P., Ph.D., Neonatal Clinical Care Unit, King Edward Memorial Hospital, 374 Bagot Road, Subiaco 6008, Perth, Australia. E-mail: jane.pillow{at}uwa.edu.au

Rationale: The technique used to provide continuous positive airway pressure (CPAP) to the newborn may influence lung function and breathing efficiency.

Objectives: To compare differences in gas exchange physiology and lung injury resulting from treatment of respiratory distress with either bubble or constant pressure CPAP and to determine if the applied flow influences short-term outcomes.

Methods: Lambs (133 d gestation; term is 150 d) born via cesarean section were weighed, intubated, and treated with CPAP for 3 hours. Two groups were treated with 8 L/minute applied flow using the bubble (n = 12) or the constant pressure (n = 12) technique. A third group (n = 10) received the bubble method with 12 L/minute bias flow. Measurements at study completion included arterial blood gases, oxygraphy, capnography, tidal flow, multiple breath washout, lung mechanics, static pressure–volume curves, and bronchoalveolar lavage fluid protein.

Measurements and Main Results: Birth weight and arterial gas variables at 15 minutes were comparable. Flow (8 or 12 L/min) did not influence the 3-hour outcomes in the bubble group. Bubble technique was associated with a higher pH, Pa_O2, oxygen uptake, and area under the flow–volume curve, and a decreased alveolar protein, respiratory quotient, Pa_CO2, and ventilation inhomogeneity compared with the constant pressure group.

Conclusions: Compared with constant pressure technique, bubble CPAP promotes enhanced airway patency during treatment of acute postnatal respiratory disease in preterm lambs and may offer protection against lung injury.

Key Words: lung compliance • stochastic processes • noninvasive ventilation • respiratory distress syndrome • continuous positive airway pressure

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Bubble continuous positive airway pressure (CPAP) has been used to treat neonatal lung disease for over 30 years, but the mechanistic basis of differences in physiological effects compared with other CPAP systems are not well understood. What This Study Adds to the Field In an ovine model of preterm lung disease, treatment with bubble CPAP immediately after birth enhances gas exchange, lung mechanics, gas mixing efficiency, and lung volume compared with constant pressure CPAP.