Mass spectrometer system for continuous skin-surface and intravascular blood gas measurement of maternal-fetal respiration in labour.

This paper describes the performance characteristics of a dual-inlet mass spectrometer suitable for continuous monitoring of maternal and fetal blood gases using intra-arterial mass spectrometer catheters in the pregnant ewe and skin-surface mass spectrometer probes during human labour. Skin-surface measurements in newborn and adult sheep bore a close and easily interpretable relationship to intra-arterial measurements. The performance of the skin-surface mass spectrometer probe on the human forearm compared favourably with a commercially available transcutaneous electrochemical system for the measurement of oxygen and carbon dioxide but the mass spectrometer was capable of measuring additional gases such as nitrogen and argon.