Set and measured ventilatory parameters, SpO2 and ETPCO2 will be stored in the S1 ventilator. SpO2 will be measured via pulse oximetry placed on infant's extremities (in addition to usual monitoring) during the 5 hours of the study. End Tidal PCO2 measurements will also be made via probe placed on the Y piece of the respirator circuit (usual practice) during the 5 hours of the study.