Lung Recruitment and Breathing Pattern During Variable Versus Continuous Flow Nasal Continuous Positive Airway Pressure in Premature Infants: An Evaluation of Three Devices

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Abstract
Objective. To determine whether lung volume changes and breathing pattern parameters differ among 3 devices for delivery of nasal continuous positive airway pressure (CPAP) in premature infants. Methods. Thirty-two premature infants receiving nasal CPAP for apnea or mild respiratory distress were enrolled. Birth weight was (mean ± standard deviation) 1081 ± 316 g, gestational age 29 ± 2 weeks, age at study 13 ± 12 days, and fraction of inspired oxygen (Fio2) at study .29 ± .1. Three devices, applied in random order, were studied in each infant: continuous flow nasal CPAP via CPAP prongs, continuous flow nasal CPAP via modified nasal cannula, and variable flow nasal CPAP. After lung recruitment to standardize volume history, changes in lung volume (ΔVL) were assessed at nasal CPAP of 8, 6, 4, and 0 cm H2O using calibrated direct current-coupled respiratory inductance plethysmography. Results. ΔVL was significantly greater overall with the variable flow device compared with both the nasal cannula and CPAP prongs. However, ΔVL was not different between the cannula and the prongs. Respiratory rate, tidal volume, thoraco-abdominal asynchrony, and Fio2 were greater with the modified cannula than for either of the other 2 devices. Conclusion. Compared with 2 continuous flow devices, the variable flow nasal CPAP device leads to greater lung recruitment. Although a nasal cannula is able to recruit lung volume, it does so at the cost of increased respiratory effort and Fio2.