Background Venturi masks are commonly used in the hospital setting to deliver controlled percentages of oxygen. This is important for those at risk of hypercapnic respiratory failure and to accurately assess ventilation and gas exchange. Hospital oxygen supplies deliver high velocity and pressure, which are required for Venturi masks to operate as designed. Home oxygen is commonly delivered via concentrators, which work at lower pressures and this may affect the performance of Venturi masks if they are requested for home use.
Aim We aimed to review the oxygen delivered by the concentrator and the performance of Venturi barrels (24%, 28% 31% and 35%) with the Intensity concentrator at the usual flow rates used.
Methods Venturi barrels from the three manufacturers were tested using a TSI® Certifier® FA Test system, pressure gauge, flow metre and oxygen sensor. The Intensity concentrator was set at the specified flow rate and allowed to stabilise, oxygen concentration and outlet pressure were noted. We attached the Venturi barrels and recorded the flow rate, back pressure and delivered oxygen concentration. If the Venturi under performed we adjusted the concentrator to deliver the stated FiO2 and noted the flow rate required.
Results The concentrator delivered between 95.8 % and 84.7% oxygen, with concentration reducing at higher flows (see Abstract P139 table 1). Most Venturi barrels delivered a lower FiO2 than intended. Those closest to the desired FiO2 were designed to work at higher flow rates. The 24% Venturi barrels caused significant back pressure which reduced delivered FiO2 and caused the concentrator to alarm.
Conclusions Venturi barrels used with oxygen concentrators in the home are likely to deliver a lower oxygen concentration than expected and are unlikely to lead to hypercapnic respiratory failure. For a controlled FiO2 to be delivered, the chosen concentrator and Venturi need to be tested so flow rate can be set accordingly but concentrators alarm systems may prevent practical use.
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