An evaluation of the resistance to flow through the patient valves of twelve adult manual resuscitators.
What is the inspiratory and expiratory resistance to flow through the patient valves of adult manual resuscitators?


METHODS
We evaluated the resistance to flow through the patient valves of 12 adult resuscitators (Ambu, Code Blue, DMR, Hope 4, Hospitak, Hudson, Intertech, Laerdal, Mercury, Respironics, SPUR, Vitalograph). Expiratory resistance was evaluated by directing a flow of oxygen through the valve in the direction that the patient expires. Inspiratory resistance was evaluated by directing oxygen through the valve in the direction of flow when the bag is squeezed. Flow was controlled by a Timeter 0-75 flowmeter, and measured using a calibrated Timeter RT-200. Flows of 10, 20, 30, 40, 50, 60, 70, 80, and 90 L/min were used. Resistive back pressure of the resuscitator valves was measured using a calibrated Timeter RT-200. Resistance was calculated by dividing back pressure by flow. Five measurements were made at each flow setting for each resuscitator.


RESULTS
Significant differences in back pressures and resistances existed between the resuscitators for both expiratory and inspiratory flows (p less than 0.001 in each case). Significant interaction effects also existed between resuscitator brands and flows (p less than 0.001 in each case). At an expiratory flow of 50 L/min, all resuscitators except the Hospitak and Vitalograph produced a back pressure less than 5 cm H2O (the International Standards Organization standard). At an inspiratory flow of 50 L/min, all resuscitators but the Hospitak, Mercury, and Vitalograph produced a back pressure less than 5 cm H2O.


CONCLUSIONS
Significant differences existed in the back pressures produced due to the flow resistance through the patient valves of these resuscitators, and these might be considered excessive in some cases. Because this was a bench study, further work is needed to determine the clinical importance of these findings.
Hess
D
D
York Hospital, PA 17405.
Simmons
M
M
D000403:Airway Resistance; D003625:Data Collection; D005069:Evaluation Studies as Topic; D005221:Fatigue; D005540:Forced Expiratory Flow Rates; D006801:Humans; D012151:Resuscitation / Q000295:instrumentation* / Q000706:statistics & numerical data; D014481:United States; D012122:Ventilators, Mechanical / Q000592:standards* / Q000706:statistics & numerical data