Progress in the development of a fluorescent intravascular blood gas system in man

Abstract

In vitro and in vivo animal studies have shown accurate measurements of arterial blood pH (pHa), carbon dioxide tension (PaCO2), and oxygen tension (PaO2) with small intravascular fluorescent probes. Initial human clinical studies showed unexplained intermittent large drops in sensor oxygen tension (PiO2). Normal volunteers were studied to elucidate this problem. In the first part of this study, the probe and cannula were manipulated and the probe configuration and its position within the cannula were varied. The decreases in PiO2 were judged to be primarily due to the sensor touching the arterial wall. Retraction of the sensor tip within the cannula eliminated the problem. In the second part of this study, the accuracy of the retracted probe was evaluated in 4 subjects who breathed varying fractions of inspired oxygen and carbon dioxide. The arterial ranges achieved were 7.20 to 7.59 for pH, 22 to 70 mm Hg for PaCO2, and 46 to 633 mm Hg for PaO2. Linear regression of 48 paired sensor (i) versus arterial values showed pHi = 0.896 pHa + 0.773 (r = 0.98, SEE = 0.017); PiCO2 = 1.05 PaCO2 - 1.33 (r = 0.98, SEE = 2.4 mm Hg); and PiO2 = 1.09 PaO2 - 20.6 (r = 0.99, SEE = 21.2 mm Hg). Bias (defined as the mean differences between sensor and arterial values) and precision (SD of differences) were, respectively, -0.003 and 0.02 for pHi, 0.77 and 2.44 mm Hg for PiCO2, and -2.9 and 25.4 mm Hg for PiO2. The mean in vivo 90% response times for step changes in inspired gas were 2.64, 3.88, and 2.60 minutes, respectively, for pHi, PiCO2, and PiO2.

Application of a Novel Fiber-Optic Biosensor In Situ to Investigate the Metabolic Effect of Lactate Infusion

“…In addition to the advantages of in situ monitoring under near real-time conditions, problems with discrete arterial blood sampling, such as, systematic errors due to air bubbles (Biswas et al 1982;Harsten et al 1988;Thorson et al 1983), dilution from flush solution (Boidin andJorna, 1984;Hamilton et al 1978), storage temperature, or time delay between sampling and measurement (Kelman and Nunn 1966) were avoided using fiber-optic biosensor technology. The biosensor technology described in this report utilized phosphorescence; however, alternative technological approaches using fluorescence or micro electrodes also have been developed for fiber-optic biosensors (Barker and Hyatt 1991;Mahutte et al 1990;Shapiro 1992;Shapiro et al 1989) and could be similarly applied.…”

Continuous intra-arterial blood gas monitoring in rats

“…The differences in pO 2 measurements between continuous and intermittent analyses appeared to be somewhat higher in our study (1.0 kPa) than in previous results (up to 0.78 kPa). One possible explanation may be a phenomenon called the 'wall effect' (Mahutte et al 1990) which occurs when the sensor has direct contact with the vascular wall and cannot oat freely. In this case, the measured value represents the gas tension from the blood as well as in the tissue surrounding the artery.…”

Sensing of Carbon Dioxide by a Decrease in Photoinduced Electron Transfer Quenching

“…These include measurement of dissolved CO 2 in blood (30,31) and measurements of CO 2 as a predictor for shock (32,33). Measurements of CO 2 are also used …”