• Anesthesiology · Jun 2004

    Comparative Study

    Continuous, noninvasive, and localized microvascular tissue oximetry using visible light spectroscopy.

    • David A Benaron, Ilian H Parachikov, Shai Friedland, Roy Soetikno, John Brock-Utne, Peter J A van der Starre, Camran Nezhat, Martha K Terris, Peter G Maxim, Jeffrey J L Carson, Mahmood K Razavi, Hayes B Gladstone, Edgar F Fincher, Christopher P Hsu, F Landon Clark, Wai-Fung Cheong, Joshua L Duckworth, and David K Stevenson.
    • Biomedical Optics Laboratory, and Department of Pediatrics, Stanford Hospital and Livermore Veterans Affairs Medical Center, Palo Alto, California 94305, USA. dbenaron@stanford.edu
    • Anesthesiology. 2004 Jun 1;100(6):1469-75.

    BackgroundThe authors evaluated the ability of visible light spectroscopy (VLS) oximetry to detect hypoxemia and ischemia in human and animal subjects. Unlike near-infrared spectroscopy or pulse oximetry (SpO2), VLS tissue oximetry uses shallow-penetrating visible light to measure microvascular hemoglobin oxygen saturation (StO2) in small, thin tissue volumes.MethodsIn pigs, StO2 was measured in muscle and enteric mucosa during normoxia, hypoxemia (SpO2 = 40-96%), and ischemia (occlusion, arrest). In patients, StO2 was measured in skin, muscle, and oral/enteric mucosa during normoxia, hypoxemia (SpO2 = 60-99%), and ischemia (occlusion, compression, ventricular fibrillation).ResultsIn pigs, normoxic StO2 was 71 +/- 4% (mean +/- SD), without differences between sites, and decreased during hypoxemia (muscle, 11 +/- 6%; P < 0.001) and ischemia (colon, 31 +/- 11%; P < 0.001). In patients, mean normoxic StO2 ranged from 68 to 77% at different sites (733 measures, 111 subjects); for each noninvasive site except skin, variance between subjects was low (e.g., colon, 69% +/- 4%, 40 subjects; buccal, 77% +/- 3%, 21 subjects). During hypoxemia, StO2 correlated with SpO2 (animals, r2 = 0.98; humans, r2 = 0.87). During ischemia, StO2 initially decreased at -1.3 +/- 0.2%/s and decreased to zero in 3-9 min (r2 = 0.94). Ischemia was distinguished from normoxia and hypoxemia by a widened pulse/VLS saturation difference (Delta < 30% during normoxia or hypoxemia vs. Delta > 35% during ischemia).ConclusionsVLS oximetry provides a continuous, noninvasive, and localized measurement of the StO2, sensitive to hypoxemia, regional, and global ischemia. The reproducible and narrow StO2 normal range for oral/enteric mucosa supports use of this site as an accessible and reliable reference point for the VLS monitoring of systemic flow.

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