BLOOD-GAS TENSION MEASUREMENT IN ANAESTHESIA BY BUBBLE EQUILIBRATION AND MASS SPECTROMETRY

If a small bubble of gas is equilibrated with a volume of bloodthe partial pressures of the components of the bubble afterequilibration approximate to the original tensions in the blood.A method is described in which the bubble is analyscd by a respiratorymass spectrometer connected to a mini-computer. The normal respiratorymonitoring function of the mass spectrometer need be interruptedfor only 20 s for. each sample and the complete equilibrationand analysis pnxedure takes only 3 min. Theoretical studies,experimental tests and records of experimental usage show that,in a subject anaesthetized with halothane in nitrous oxide andoxygen, tensions can be measured with an overall SD of 5% forcarbon dioxode and halothane and, with certain reservations,an SD of about 3% for nitrous oxide.