title: Fast wavelength scanning reflectance spectrophotometer for noninvasive determination of hemoglobin oxygenation in human skin.
abstract: Oxygen saturation of hemoglobin (HbSO2) in skin vessels may be determined with photometric methods. However, the optical complexity of the skin makes quantitative measurements difficult. A possible approach is the analysis of reflectance spectra using the two-flux theory of Kubelka and Munk. The final equation of this theory which describes the transformation between absorbed and reflected light has been approximated by a hyperbola. Based on this approximation we evaluated skin spectra obtained from the forearm of 23 healthy subjects with a fast scanning reflection photometer (Oxyscan) applying visible light (535-620 nm). The hyperbola was used in a multicomponent analysis in which the measured spectrum is recalculated using reference spectra of oxygenated and deoxygenated hemoglobin (gaussian least-square method). A crucial requirement for the evaluation is the subtraction of the individual skin spectrum, obtained by clearing a spot of skin of hemoglobin exerting external pressure. At rest HbSO2 was in the range between 42 and 89% (mean +/- SD: 72.9 +/- 12.2%). Pharmacological and thermal generation of hyperemia combined with respiration of pure oxygen raised the values to 86-100% (97.9 +/- 4.6%). This was in good agreement with capillary ex vivo analysis yielding 96-100% (98.7 +/- 0.4%). Under arterial occlusion HbSO2 fell below 30% (14.5 +/- 7.8%). Our method allows rapid determinations of absolute HbSO2 values in the skin. The evaluation error is estimated to be between 5% for oxygenated and 10% for deoxygenated values.
authors.affiliation: Max-Planck-Institut für molekulare Physiologie, Dortmund, Deutschland.
authors.forename: U
authors.initials: U
authors.lastname: Merschbrock
authors.forename: J
authors.initials: J
authors.lastname: Hoffmann
authors.forename: L
authors.initials: L
authors.lastname: Caspary
authors.forename: J
authors.initials: J
authors.lastname: Huber
authors.forename: U
authors.initials: U
authors.lastname: Schmickaly
authors.forename: D W
authors.initials: DW
authors.lastname: Lübbers
mesh_terms: D001157:Arterial Occlusive Diseases / Q000175:diagnosis; D016022:Case-Control Studies; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D006940:Hyperemia / Q000175:diagnosis; D010100:Oxygen / Q000097:blood; D010108:Oxyhemoglobins / Q000032:analysis; D012867:Skin / Q000378:metabolism*; D013053:Spectrophotometry / Q000295:instrumentation*
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; D010100:Oxygen