Novel Test Bench for Inhaler Characterization Including Real-Time Determination of Output, Output Rate, and Liquid Water Content of Delivered Aerosols
Background: Developing new (triggered) or improving existing inhaler systems for (preterm) neonates and adults requires test benches for the determination of aerosol output and aerosol output rate. Furthermore, real-time measurement of aerosol output and output rate is advantageous with respect to both development costs and development time, especially when using liquid or humidified dry aerosols. The current standard test procedures following ISO 27427, however, are time-consuming. Moreover, these procedures are not applicable to inhalers for preterm neonates, due to their high breathing frequency, low tidal volume, and the dead space in commercially available test benches. We are describing a novel test bench approach combining gravimetric and optical detection to facilitate real-time measurement of aerosol output, aerosol output rate, and aerosol liquid water content in inhalation systems for (preterm) neonates and adults. Methods: We integrated a laser-based optical measurement unit into test benches for inhalers for adults and preterm neonates, based on ISO 27427. Breathing was simulated by a sine pump for adults and by a test lung for preterm neonates on continuous positive airway pressure respiratory support. Dry or humidified aerosol was released by a continuous powder aerosolizer system. Simultaneous particle measurement by gravimetry (filter) and light extinction (laser system) was performed using the novel test benches. Results: We developed test benches for inhalers for (preterm) neonates and adults in accordance with ISO 27427, combining optical and gravimetric particle detection. Optical and gravimetric measurements conducted with these test benches were highly correlated, thus enabling real-time measurement of aerosol output and output rate. In addition, our test benches are suitable to determine the aerosol water content in situ directly at the patient interface. Conclusion: This novel test bench allows characterization of inhalation devices in real time and therefore will accelerate optimization and development cycles. Conformity with ISO 27427 allows its use in various applications.