Continuous measurement of blood gases in vivo by mass spectrography

Abstract

The application of the mass spectrometer to the continuous monitoring of blood gases in humans is described. At the heart of the system is an intravascular catheter consisting of a cannula impermeable to gas tipped with a membrane whose special gas permeability characteristics permits accurate calibration. Expressions are presented which describe gas flow through the membrane in response to a step increase in gas concentration; characterize thermal effects on gas diffusion and illustrate the effect of the cannula and carrier tubing on steady state gas flow. The system has been successfully employed in the study of arterial nitrogen washout and the determination of human cerebral blood flow by the nitrous oxide technique. © 1970 International Federation for Medical and Biological Engineering.