POLLUTION AND RETROPOLLUTION OF A MEDICAL GAS-PIPELINE

The anaesthetic machine, the recovery room or the ICU ventilator as we ll as any other simple oxygenation device can be accidentally supplied with a ''wrong'' gas, or a mixture of ''wrong'' and ''true'' gases, o r a gas containing chemical impurities, as a result of one of the foll owing causes: a) the source of the medical gas pipeline supply contain s a ''wrong'' gas or impurities; b) the gas pipeline is polluted by a ''wrong'' gas or solvents, introduced during the installation or maint enance of the pipeline; c) the pipeline is polluted by a wrong gas at a point of inter-connection or cross-connection of two pipelines; d) s upply of a ''wrong'' gas through wrong quick couplers connected to the pipeline; e) back flow of a gas in another pipeline supply through a defective gas mixer, which is today the most common cause of pipeline contamination or retropollution. It occurs with some types of mixers i n case of absence or malfunction of non-return valves, associated with a pressure difference between the two gas lines. The means of prevent ion, recognition and emergency treatment of these events include: a) s ystematic removal of mixers and flowmeter-mixers from supplies when no t in use; b) periodical checking of these devices for an accidental co mmunication between the gases to be mixed; c) systematic use of an oxy gen analyser for a continuous measurement of FIO2, especially when the machine is connected to the N2O pipeline supply; d) the presence of a reserve cylinder of oxygen connected to every anaesthetic machine.