ObjectiveAerosol delivery holds potential to release surfactant or perfluorocarbon (PFC) to the lungs of neonates with respiratory distress syndrome with minimal airway manipulation. Nevertheless, lung deposition in neonates tends to be very low due to extremely low lung volumes, narrow airways and high respiratory rates. In the present study, the feasibility of enhancing lung deposition by intracorporeal delivery of aerosols was investigated using a physical model of neonatal conducting airways.MethodsThe main characteristics of the surfactant and PFC aerosols produced by a nebulization system, including the distal air pressure and air flow rate, liquid flow rate and mass median aerodynamic diameter (MMAD), were measured at different driving pressures (4–7 bar). Then, a three-dimensional model of the upper conducting airways of a neonate was manufactured by rapid prototyping and a deposition study was conducted.ResultsThe nebulization system produced relatively large amounts of aerosol ranging between 0.3±0.0 ml/min for surfactant at a driving pressure of 4 bar, and 2.0±0.1 ml/min for distilled water (H2Od) at 6 bar, with MMADs between 2.61±0.1 µm for PFD at 7 bar and 10.18±0.4 µm for FC-75 at 6 bar. The deposition study showed that for surfactant and H2Od aerosols, the highest percentage of the aerosolized mass (∼65%) was collected beyond the third generation of branching in the airway model. The use of this delivery system in combination with continuous positive airway pressure set at 5 cmH2O only increased total airway pressure by 1.59 cmH2O at the highest driving pressure (7 bar).ConclusionThis aerosol generating system has the potential to deliver relatively large amounts of surfactant and PFC beyond the third generation of branching in a neonatal airway model with minimal alteration of pre-set respiratory support.

Surfactant aerosol delivery in conjunction with a noninvasive respiratory support holds the potential to treat neonatal respiratory distress syndrome in a safe manner. The objective of the present study was to gain knowledge in order to optimize the geometry of an intracorporeal inhalation catheter and improve surfactant aerosol delivery effectiveness in neonates. Initially, a mathematical model capable of predicting the aerosol flow generated by this inhalation catheter within a physical model of the neonatal trachea was implemented and validated. Subsequently, a numerical study was performed to analyze the effect of the aerosol liquid droplet size and mass flow rate on surfactant delivery and on the required aerosolization time period. Experimental validation of the mathematical model showed a close prediction of the air axial velocity at the distal end of the physical model, with an absolute error between 0.01 and 0.15 m/s. Furthermore, an admissible absolute error between 0.2 and 2 mm was attained in the prediction of the aerosol mean aerodynamic diameter and mass median aerodynamic diameter in this region. The numerical study highlighted the beneficial effects of generating an intracorporeal aerosol with a mass median aerodynamic diameter higher than 4 mm and a surfactant mass flow rate above 8.93 mg/s in order to obtain effective surfactant delivery in neonates with minimal airway manipulation.

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AbstractsMethods 18 preterm lambs were randomly assigned to receive aerosolized PFC (10 ml/kg/h for 2h) delivered via an inhalation catheter, (PFC-aero group), instilled intratracheal PFC (20 ml/kg; PLV group), or just mechanical ventilation (CONTROL group). Gas exchange, pulmonary mechanics, and histological scores were assessed. Mean ± SD, ANOVA, p<0.05. Results Both PFC administration techniques significantly improved gas exchange and pulmonary mechanics compared to CONTROL group (two-way ANOVA). 15 minutes after PLV, OI and VEI were significantly better in the PLV group compared to other groups. However, in terms of OI, aerosolized PFC remained significantly better than CONTROL group for the entire observational period (360 min), whereas at 240 min and on, the differences between PLV and CONTROL groups were not significant. PLV and aerosolized PFC significantly decreased the degree of atelectasis but did not significantly improve the general histological score.

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