The usefulness of capillary microscopy, transcutaneous oximetry and laser Doppler fluxmetry in the assessment of the severity of lower limb ischaemia

TMo date, capillary microscopy, transcutaneous oximetry (tcpO2) and laser Doppler fluxmetry are frequently used in the investigation of skin microcirculation in patients with lower limb ischaemia. The concomitant microcirculatory disturbances may be useful in addition to macrocirculatory parameters to discriminate the different degrees of ischaemic severity. The best ways of application of these methods and the choice of the best parameters to assess ischaemia have been insufficiently investigated. Therefore, skin microcirculation was investigated with the use of these techniques in 130 patients with different stages of lower limb ischaemia, divided according to their ankle-to-brachial pressure index (ABI). Patients were investigated in the sitting and the supine position. Measurements were performed at rest and during reactive hyperaemia following arterial occlusion, and before and after local skin heating. The reactive hyperaemic response using laser Doppler fluxmetry differed in every patient group investigated. Capillary red blood cell velocity was markedly impaired in critically ischaemic patients (ABI <25%). Transcutaneous oxygen pressure measurements at rest rendered the highest positive predictive value (PV; 87%) to classify patients as having clinically severe ischaemia (Fontaine 3 or 4). Ankle and toe pressure measurements provided a PV value of 78%. Microcirculatory parameters and techniques appear to be useful as an addition to standard macrocirculatory techniques to assess the severity of lower limb ischaemia. This is particularly of importance in patients in whom macrocirculatory parameters are unattainable