PRESSURE CONTROL IN CENTRAL MEDICAL GAS-S UPPLY SYSTEMS

Objective: To assess whether the pressure gauges at the downstream par t of pressure regulators are accurate enough to ensure that pressure i n O-2 pipeline is always higher than in Air pipeline and that pressure in the latter is higher than pressure in N2O pipeline. A pressure dif ference of at least 0.4 bar between two medical gas supply systems is recommended to avoid the reflow of either N2O or Air into the O-2 pipe line, through a faulty mixer or proportioning device. Study design: Pr ospective technical comparative study. Material and methods: Readings of 32 Bourdon gauges were compared with data obtained with a calibrate d reference transducer. Two sets of measurements were performed at a o ne month interval. Results: Pressure differences between Bourdon gauge s and reference transducer were 8% (0.28 bar) in average for a theoret ical maximal error less than 2.5%. During the first set of measurement s, Air pressure was higher than O-2 pressure in one place and N2O pres sure higher than Air pressure in another. After an increase in the O-2 pipeline pressure and careful setting of pressure regulators, this pr oblem was not observed at the second set of measurements. Discussion: Actual accuracy of Bourdon gauges was not convenient enough to ensure that O-2 pressure was always above Air pressure. Regular controls of t hese pressure gauges are therefore essential. Replacement of the fault y Bourdon gauges by more accurate transducers should be considered. As an alternative, the increase in pressure difference between O-2 and A ir pipelines to at least 0.6 bar is recommended.