Pressure control in central medical gas supply systems.

Objective: To assess whether the pressure gauges at the downstream part of pressure regulators are accurate enough to ensure that pressure in 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 difference 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 pipeline, through a faulty mixer or proportioning device. Study design: Prospective technical comparative study. Material and methods: Readings of 32 Bourdon gauges were compared with data obtained with a calibrated reference transducer. Two sets of measurements were performed at a one month interval. Results: Pressure differences between Bourdon gauges and reference transducer were 8% (0.28 bar) in average for a theoretical maximal error less than 2.5%. During the first set of measurements, Air pressure was higher than O-2 pressure in one place and N2O pressure higher than Air pressure in another. After an increase in the O-2 pipeline pressure and careful setting of pressure regulators, this problem 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 these pressure gauges are therefore essential. Replacement of the faulty Bourdon gauges by more accurate transducers should be considered. As an alternative, the increase in pressure difference between O-2 and Air pipelines to at least 0.6 bar is recommended.