Blood gas monitoring using micro-flow colorimetry

Christopher Cooney, Bruce C. Towe

Research output: Chapter in Book/Report/Conference proceedingChapter


Optical monitoring of blood gas concentrations is achieved using sub microliter quantities of a colorimetric indicator continuously perfused through microdialysis hollow fiber membranes in blood contact. The hollow fiber membranes, selected based on their permeabilities in blood, are silicone for both oxygen and carbon dioxide sensing, and cuproammonium rayon for pH sensing. A sweep fluid passed through the lumen of these fibers undergoes a diffusive equilibrium with the blood and then is continuously mixed with an indicator. A 450 nm gallium nitride LED is used to excite an oxygen-sensitive fluorophore, ruthenium tris-(2,2′-bipyridyl) II dichloride, which has a 620 nm emission peak that is analyzed with an orange coated photodetector. Gallium phosphide 555 nm LEDs are used to excite the 550 nm absorbance peak of phenol red for pH measurement and phenol red in a 35 mm bicarbonate buffer for CO 2 measurement. Accurate measurement of small absorbance and fluorescence changes using small bore capillary tubes allows good resolution of biochemical concentrations. Continuous replenishment of the indicator by flow lends itself to a stable method of biochemical analysis that has potential for long term performance. In vitro buffer studies demonstrate a resolution of +/-0.5 mmHg for pCO 2, a +/-1.5 mmHg for pO 2, and a +/-0.003 pH.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
PublisherSociety of Photo-Optical Instrumentation Engineers
Number of pages7
StatePublished - 1999
EventProceedings of the 1999 Optical Diagnostics of Biological Fluids IV - San Jose, CA, USA
Duration: Jan 26 1999Jan 27 1999


OtherProceedings of the 1999 Optical Diagnostics of Biological Fluids IV
CitySan Jose, CA, USA

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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