No abstract

Abstract. Appiah R, Hiller S,

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.

Summary:Infl ammatory aortic diseases may occur with and without dilatation and are complicated by obstruction, rupture and dissection. Infections originate from periaortic foci or septicaemia and tend to result in the rapid development of aneurysms. Large vessel vasculitis due to Takayasu arteritis in younger and giant cell arteritis (GCA) in older patients is located in all layers of the aortic wall and prevails in the thoracic section. GCA patients are prone to developing aortic complications in the late course of disease. In Behçet's disease, aneurysms may have an unusual morphology and localisation. The diagnosis of aortitis is usually obtained by vascular imaging, but partly made only by biopsy on occasion of an operation, especially in case of isolated aortitis of the ascending aorta which mostly remains inapparent until dissection or large aneurysms have developed. Periaortitis typically occurs in the abdominal aorta and may lead to infl ammatory aortic aneurysm (IAA). It is looked upon as a special form of vasculitis, with an overlap to primary retroperitoneal fi brosis (RF). An identical pathology is discussed for the three diseases. On the other hand, about 50 % of isolated aortitides and periaortitides as well as retroperitoneal fi broses can be classed among IgG4-related diseases. Periaortitis also is observed after treatment of aortic aneurysms by stent-graft implantation. Special attention should be paid to ureteral obstruction along with RF or IAA. Once infection is ruled out, immunosuppression is applied to all forms of infl ammatory aortic diseases, primarily with glucocorticoids. However, after successful surgery for isolated thoracic aortitis or infl ammatory aortic aneurysm immunosuppression may be dispensable and it is not required if periaortic tissue enlargement persists in chronic inactive disease. For some patients with periaortitis and RF, tamoxifen may be a valuable alternative.