PEEP and the Bain circuit.

The feasibility of applying positive end expiratory pressure within the Bain circuit using an Emerson PEEP valve was studied. It was determined that varying degrees of PEEP may be applied within the Bain circuit using an Emerson PEEP valve during either mechanically or manually controlled ventilation but not during spontaneous breathing. There was some loss of measured tidal volume with increasing PEEP, due primarily to compression gas losses but also from leakage throughout the system. The maximum gas loss was 100 ml per minute at PEEP 15 cm H2O under test conditions. PEEP may be applied between the Bain tubing and the manifold. However, one should then never allow the patient to breathe spontaneously as the PEEP valve presents an obstruction to inspiratory flow. With the PEEP valve relocated between the Bain manifold and the ventilator hose it was found that application of PEEP was possible without this disadvantage, but only during mechanical ventilation.