The long term objective of the project is to develop an automated, simple to use system for the measurement of respiratory mechanics in newborns and children with a passive expiratory maneuver. Flow volume measurements following relaxation of the respiratory muscles with the Hering-Breuer reflex allows for calculation of total compliance and resistance using the end inspiratory plateau pressure as mean pleural pressure. Previously described application of this technique used manual controls for shutter closure and data analysis, excluding the method to only research. Special design consideration in Phase II have provisions for managing the low deadspace requirements while interfacing to a ventilator circuit. An automated system would place this technique within the reach of clinicians for the diagnosis and management of newborns and infants with altered lung function.