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.

Objective: To evaluate whether microcirculatory disturbances of the skin in patients with chronic venous insufficiency are a generalized phenomenon or restricted to visible skin changes. Design: Open, prospective study in patients and healthy, age-matched subjects. Setting: Department of Angiology, Hannover Medical School. Patients: Seventy-one patients with chronic venous insufficiency. Measurements: Transcutaneous oxygen pressure (tc Po2) at electrode core temperatures of 37°C and 44°C and laser Doppler flux (LDF) were measured simultaneously in different regions of the legs. Results: On the forefoot, tc Po2 (37°C) at rest and tc Po2 (44°C) during arterial ischaemia were significantly higher in patients ( P<0.05), increasing with the severity of chronic venous insufficiency. Conclusions: Cutaneous capillary flow on the forefoot is increased in patients with chronic venous insufficiency, demonstrating the general effect of venous hypertension.

A cumulative dose response to intravenous PGE1 was established in 12 healthy volunteers. Systolic time intervals, including pre-ejection period (PEP), the ventricular ejection time (VET) and the RR-interval, were continuously determined, and transcutaneous oxygen pressure (tcpO2) was recorded. RR-intervals fell in a dose dependent manner, reaching a significantly lower level at 128 ng.kg-1.min-1 of PGE1 (basal value 842 ms falling to 756 ms). PEP decreased from 89 ms to 74 ms and the ratio PEP/VET decreased from 35% to 30%, indicating increased myocardial contractility. The maximal increase in tcpO2 was 125% on the calf and 60% on the foot. The peak tcpO2 was observed at an infusion rate of 16 ng.kg-1.min-1 PGE1. A decline in tcpO2 was seen at infusion rates greater than 64 ng.kg-1.min-1 PGE1 indicating a decrease in skin perfusion. The results indicate that the effects of intravenous PGE1 on skin perfusion occur at a lower threshold than the increase in myocardial contractility. A maximal increase in skin perfusion can be achieved with doses of PGE1 devoid of systemic haemodynamic effects.

Applying a fast scanning reflection spectrophotometer and multicomponent spectra analysis, oxygen saturation (S_Hb) and relative concentration (C_Hb) of hemoglobin in the skin were determined at eight skin sites in 11 healthy persons. S_Hb was significantly higher at the tip of the index finger and big toe (90 ± 3.9 and 92 ± 4.2%, respectively) compared with the forehead, volar forearm, back of hand, abdomen, calf and forefoot where mean values varied between 52 and 67% (p < 0.001). C_Hb also was higher at acral sites (big toe: 2.04 ± 0.14 arbitrary units (AU); index finger: 2.13 ± 0.19 AU) than at the other locations (p < 0.0001) where it was between 0.56 ± 0.12 AU (abdomen) and 0.95 ± 0.28 AU (forefoot). In the course of time, rhythmical oscillations of both parameters at a frequency of 3-5/min were seen in 68% of the measurements, predominantly at the six proximal sites. Heating the measuring site to 44 °C caused a biphasic increase of C_Hb and S_Hb which was significant at the proximal sites (p < 0.0001). S_Hb values came into the range of arterial blood. Temporal and spatial variation of both parameters decreased. Reflection spectrophotometry gives the possibility to directly assess dermal hemoglobin saturation, its physiological variability and reactions to provocation stimuli. Concentration and saturation of hemoglobin in dermal vessels appear definitely different at acral compared with proximal sites.

Fifteen cases with radial forearm flap harvesting and autologous vein-graft reconstruction of the missing radial artery portion, are reported. Post-repair follow-up examinations, using segment plethysmography, photoplethysmography, and Doppler ultrasound, demonstrated an angiologic donor site morbidity, even when radial artery reconstruction was performed. Typically diminished blood pressure occurred, in comparison with the contralateral healthy extremity. Index shifting of pulse wave peaks, as well as widening of pulse wave bases occurred, especially in the thumb and index finger. These latter findings appear to be discrete indicators of arterial insufficiency.