Self-inflating bag-mask device with duckbill nonrebreather valve

(A) The components of the self-inflating bag with a unidirectional, duckbill, nonrebreather outlet valve.

(B) The duckbill valve is a thin, flexible diaphragm with two protruding leaflets. During bag compression (inhalation), the leaflets open, allowing gas to flow from the device to the patient. During patient exhalation, the leaflets return to the original closed position and the valve relaxes off the expiratory port allowing expired gas to exit. This mechanism permits delivery of 95 to 100% oxygen when oxygen flow to the device is 10 to 15 L/minute.

During spontaneous patient inhalation, the leaflets are opened by sufficient negative inspiratory pressure generated by the patient and assisted by forward flow of fresh gas. The amount of air entrainment from the expiratory port is determined by the opening pressure of the valve and the relative resistance to airflow through the valve and expiratory port. If no expiratory valve cap is present as is the case in this figure, then delivery of oxygen during spontaneous breathing can be significantly less than 100%.