Continuous mass spectrographic measurement of halothane partial pressure in blood.

Abstract

A method has been devised for the continuous measurement of halothane partial pressure in blood. The technique which was used in 10 dogs employs a silastic covered stainless-steel intra-arterial cannula through which blood gases pass into the analysing portion of a mass spectrometer where they are identified. Halothane produces a spectrographic peak at mass 31 which is proportional to its partial pressure. The peak at 31 results from the splitting of the halothane molecule into an ion composed of an atom of carbon and one of fluorine. The initial response time for the system is 0·4 min. The time from an initial changes to 63% of the final reading (1/e time) is 6·3 min. The calibration of the spectrometer remained stable for up to 7h, the longest test period.