• P J Mills, J Baptiste, J Preston, and G M Barnas.
• Department of Anesthesiology, University of Maryland, Baltimore. l
• Crit. Care Med. 1991 Nov 1; 19 (11): 1425-31.

Background And MethodsAlthough it is useful in certain clinical situations for manual resuscitator units to be used with spontaneously ventilating patients, there are few data regarding their performance in these settings. We measured the percent-delivered oxygen from 13 adult manual resuscitator units during simulated spontaneous ventilation in the range of respiratory frequency, tidal volume, and oxygen supply in which manual resuscitator units might be used with patients. We also measured the resistive pressure developed during simulated ventilation and at constant inspiratory flow of 50 L/min.ResultsOxygen supply, tidal volume, minute ventilation, and reservoir volume all influenced percent-delivered oxygen, but the most important determinant of percent-delivered oxygen was valve design. Valves incorporating a "disc" element to prevent air entrainment from the expiratory port gave the most efficient oxygen delivery, while "duck-bill" valves did not reliably prevent air entrainment. Only two of the manual resuscitator units tested developed high resistive pressure.ConclusionReliable administration of high percent-delivered oxygen to spontaneously ventilating patients, while retaining the capability to manually ventilate them, is best achieved by a manual resuscitator unit with a valve of low resistance, incorporating a disc to prevent air entrainment. We recommend that manufacturers indicate on the product information sheet the degree (and confidence limits) to which their manual resuscitator unit presents resistance and delivers oxygen to a spontaneously ventilating subject.

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