PERFORMANCE AND APPLICATION OF THE QUANTIFLEX AIR/OXYGEN MIXER

The Quantiflex air/oxygen mixer is designed to dispense mixtures of air and oxygen with separate controls for total gas flow rate and oxygen concentration of the mixture within the range 21–100%. A monitoring flowmeter is provided for the mixture and also, as a safety measure, for the oxygen component. This serves as an indicator that oxygen is flowing and also permits independent calculation of the oxygen concentration of the mixture. Delivered oxygen concentrations were found to be within ±2% of the indicated value at flow rates between 4 and 12 litre/min with the input pressures of either or both gases at 208–415 kPa (30–60 lbf/in2.) gauge, and with or without an output pressure of 20 kPa. At total flow rates of 1.5–2 litre/min there was a maximum discrepancy of 4% below and 8% above the indicated concentration in some delivered concentrations. Acceptability, ease, accuracy and quickness of use by nurses were compared with current methods using separate flowmeters for air and oxygen and calculating the required flow rates by means of arithmetic, graph and special-purpose slide-rule (Blease). The Quantiflex prototype was the most acceptable, the easiest, the most accurate and the fastest of the techniques investigated.