Change in PaO2 during artificial ventilation with added dead space

The Bain anaesthetic system. An assessment during controlled ventilation

The Bain anaesthetic breathing system-a modified Mapleson 'D' circuit10-had been evaluated during anaesthesia using controlled ventilation. Results obtained from over 140 patients show that a highly predictable PaCO2 may be obtained by adjusting the fresh gas inflow according to body weight in patients weighing over 40 kg (mean PaCO2 at a fresh gas inflow of 70 ml/kg/minute=40.8 mmHg; mean PaCO2 at a fresh gas inflow of 100 ml/kg/minute=34.3 mmHg). The circuit is long enough to provide flexibility but may even be doubled in length without affecting performance. Simple lung ventilators delivering air or oxygen may be used satisfactorily as anaesthetic ventilators for patients of all ages. In addition, the circuit is lightweight, disposable but re-usable, facilitates pollution control and is easily used as an independent resuscitator. It is suggested that it may qualify as a universal breathing system.