Continuous recording of arterial pO₂, pCO₂, pH, and O₂ saturation in vivo

¹ Department of Neurology, Wayne State University College of Medicine, and Receiving Hospital, Detroit, Michigan

Methods are described for concurrent, continuous, and automatic recording of paO₂, paCO₂, apH, and SaO₂ of the arterial or venous blood. Measurements were obtained by catheterization of vessels as small as 1 mm in diameter. Graphs of these parameters may be compared with similar measurements in tissue, such as the brain, and correlated with records of function (EKG, EEG, pneumograph). Continuously flowing blood was brought into contact with electrodes and a cuvette for measuring pCO₂, pO₂, pH, and arterial oxygen saturation by means of catheters and an electrode housing and was then returned to the circulation. For arterial measurements, an arteriovenous shunt was used, for venous blood a mechanical pump is necessary. pCO₂ was determined by a membrane-covered pH electrode, pO₂ by a membrane-covered polarograph electrode, pH by a small glass electrode, SaO₂ by a flow-through oximeter cuvette. Alterations in arterial pH influence SaO₂ and paO₂ in opposite directions (Bohr effect). Brain tissue parameters reflect changes in arterial pO₂, pCO₂, and pH but often move independently due to localized changes in tissue circulation and metabolism.