Pedal blood flow and transcutaneous PO₂ in normal subjects and in patients suffering from severe arterial occlusive disease

Abstract

Pedal transcutaneous partial pressure of oxygen (tcPO2) has been measured by polarographic method, heating the skin at 44 degrees C. In 50 normal subjects, mean tcPO2 measured 54.5 +/- 7 mmHg. Among 43 patients suffering from chronic ischaemia of lower limbs, mean tcPO2 measured 40.8 +/- 8 mmHg in patients with from claudication and 16.1 +/- 15 mmHg in patients suffering from rest pain and/or gangrene. The variability of repeated tcPO2 measurements, expressed as 1 SD of the mean, was 4.5 mmHg in normal subjects and 2.9 mmHg in patients. The relationships between pedal subcutaneous blood flow measured in xenon-133 clearance method and pedal tcPO2 have been studied in nine normal subjects and in five patients suffering from severe chronic ischaemia of lower limbs (rest pain and/or gangrene). There was a positive correlation between blood flow and tcPO2 in normal subjects (r = 0.77, P less than 0.001). In patients suffering from severe ischaemia, there was no correlation between these two parameters, but measured blood flow was sometimes very high in areas where tcPO2 was low. It is likely that 133Xe clearance method considerably overestimates local blood flow in these patients, because there is considerably less fat in subcutaneous tissue of chronic severely ischaemic areas. Thus, partition coefficient should be determined in each patient. However, tcPO2 may constitute an index of nutritional circulation, while 133Xe clearance actually measures total subcutaneous blood flow.

Microcirculation: its significance in clinical and molecular medicine

“…Transcutaneous measurement of oxygen tension (tcPO # ) has been used extensively in clinical practice to evaluate the skin microcirculation in patients with peripheral arterial obliterative disease (PAOD) [39][40][41][42]. The method is useful in discriminating between all degrees of ischaemia, in both diabetic and nondiabetic patients, but the correlation between ankle\ arm pressure index and tcP # values is rather weak in patients with diabetes [43][44].…”

Clinical Investigation of Skin Microcirculation

“…However, at low flow rate, the importance of Pa0, is negligible, and TCP(), reflects then local blood flow [32], Several other factors may impair the diffusion of O, toward the probe and thus negatively influence the measurement, e.g. local edema, skin thicken ing or local O, tissue consumption [3,5], Nevertheless, TCPq, yields a worthwhile index of the nutritive flow as suggested by a study which compared TCP0, and capillary density in legs of patients with chronic venous insufficiency by means of a transparent TCP(), electrode [6]: a close cor relation was found between TCPo2 values and capillary density. TCP0, and its changes during 0 2 inhalation are of particular interest in patients suffering from severe PAOD, with rest pain and/or gangrene, to quantify ischemia, eval uate skin viability and effects of vasoactive drugs, predict amputation and determine the amputation level [33], By contrast, rest TCP0, is useless in nonsevere PAOD, at the stage of claudication, because TCPo, values are in the nor mal range (>40 mm Hg) [34], However, the pedal TCP()2 falls during or shortly after exercise in claudicants and may help to discriminate between vascular and nonvascular, e.g.…”

“…The isotope is introduced into the skin by means of a thin needle or cpicutancous atraumatic technique, and the skin blood flow is measured from the rate of disappearance of the isotope. This tech nique has often been used as a 'gold standard" but has many serious drawbacks [3], " X e enters all vascular structures of the skin, e.g. arteriovenous anastomoses, and consequent ly the technique cannot be used to evaluate the nutritional circulation.…”

“…Only the initial period of the disappearance curve represents skin flow, and the calculation of the flow depends on a partition coefficient that varies with the fat content of the skin. Consequently, this coefficient should be determined at each measuring location to allow a reli able evaluation [3], Last but not least, this technique can not be used to study fast changes in skin flow, is tedious to use and requires huge equipments. Thus, isotope tech niques cannot be recommended any more.…”

“…Tissue viability is threatened when nutritional circulation is compromised. This situation may be observed in the skin microcirculation despite nor mal or even increased total rest skin blood flow [3,4] and/or hindrance to oxygen diffusion [3,6]. The skin microcircula tion has been mostly studied because of its accessibility and frequent involvement in various pathological conditions, e.g.…”