Comparison of anaesthesia ventilators using a lung model

The ventilatory performance of six anaesthesia ventilators (Alphavent® Dragerwerh; MCM 801 Ventilator® Dameca; Ohmeda 7000 Ventilator® and Ohmeda 7800 Ventilator® Ohmeda; Servo Ventilator 900 D® and Ventilator 710® Siemens-Elema) was tested in a lung model and compared with the ventilatory performance of the old Engstrom 300® (Gambro Engstrom). The lung model consisted of one tracheal tube, two bronchial tubes which could be partially occluded, and two lungs (glass jars filled with water to a suitable compliance). Dialled (set) minute volume was compared to recorded minute volume. Gas distribution between obstructed and non-obstructed lung was calculated. All ventilators had a linear relationship between dialled and measured volume. Only the Servo Ventilator 900 D produced a gas distribution which was as good as, or better than that produced by the Engstrom 300.