A device for the controlled ventilation of infants and children.

There is a limited choice of paediatric ventilators and most of these are specially designed for neonates and infants and are inadequate for ventilating older children. Most adult ventilators are unsuitable for infants and small children mainly because they are unable to provide the smaller tidal volumes and inspiratory flow rates which are required. Modifications of adult ventilators to make them suitable for paediatric use have drawbacks. The ventilator itself may be converted but this usually means that it is then unsuitable for adult use. A lower inspiratory flow may be obtained by either placing a restriction in series with the ventilator or by disposal of the excess flow through a leak in the circuit or by a dummy lung (artificial compliance and resistance) in parallel with the child's lung. A restriction may only be used with pressure generators and the value of the resistance may be critical. If a dummy lung is used it should have a timeconstant equal to the product of the child's lung compliance and airway resistance so that inflation of the child's lungs and the dummy lung occurs simultaneously (Mushin, Mapleson and Lunn, 1962). Changes in the patient's lung compliance and/or airway resistance may require repeated adjustment of these artificial devices in order to maintain steady ventilation. The central problem in artificial ventilation of infants is related to the administered volume (Okmian, 1966). The minute volume provided should be predictable since its measurement in