Continuous In Vivo Measurement of Gas Tension in Blood and in Tissues

Abstract

Mass spectrometers have been used for many years for continuous analysis of respiratory gases¹²⁾. Hunter, Stacey and Hitchcock¹²⁾ in 1949 made an instrument with three fixed collectors aligned to detect nitrogen, oxygen and carbon dioxide. The way to breath-by-breath analysis of respiratory gases was open. The first attempt to measure blood-gas tensions using a mass spectrometer was that of Strang⁴²⁾) in 1961. He used a bubble equalibration method. The development of mass spectrometers for measurement of gases dissolved in liquid phases started with the design by Hock and Kok¹⁷⁾ of an inlet system incorporating a semipermeable membrane through which gas molecules could diffuse. In 1966 Woldring, Owens and Woolford⁴⁶⁾ designed a catheter system for in vivo use in the blood phase. They were able to measure oxygen and carbon dioxide partial pressures in the aorta of the cat. Two years later, in 1968, Hass, Siew and Yee¹⁶⁾ measured nitrogen and nitrous oxide concentrations both in arterial and mixed venous blood in humans. Mass spectrometry has also been used to measure tissue gas tension. In 1969, Owens, Belmusto and Woldring²⁹⁾ reported their measurements of intracerebral PO₂ and Pco₂ in dogs.