Assisted ventilation and the Servo ventilator in infants. An assessment of three systems used for CPAP/IMV

A laboratory assessment was made of systems used for Continuous Positive Airway Pressure/Intermittent Mandatory Ventilation (CPAP/IMV) with the Servo 900B and 900C ventilators. Pressure-volume loops recorded during sine wave oscillation using an external CPAP/IMV system were similar to those found during normal respiration. Pressure-volume loops using the systems based on the ventilator's inbuilt trigger mechanism were very different, particularly for the 900B. The results were confirmed by measurements in two infants. The implications of these findings with reference to the weaning of infants from mechanical ventilation are discussed.