VALIDITY AND REPRODUCIBILITY OF ELECTRICAL-IMPEDANCE TOMOGRAPHY FOR MEASUREMENT OF CALF BLOOD-FLOW IN HEALTHY-SUBJECTS

The Sheffield electrical impedance tomography; (EIT) system produces i mages of changes in the distribution of resistivity within tissue. The paper reports on the application of electrical impedance tomography i n monitoring volume changes in the limb during venous occlusion. The a im of the study is to assess the feasibility, reproducibility and vali dity of calf blood flow measurements by EIT. In 14 healthy volunteers calf blood flow is compared, as determined in a calf segment by strain -gauge plethysmography (SGP), with the impedance changes measured by E IT during rest and post-ischaemic hyperaemia. The measurements are rep eated to assess reproducibility. The reproducibility for the EIT, asse ssed from the repeated measurements and expressed as a reproducibility coefficient, is 0.88 during rest and 0.89 during hyperaemia. The repr oducibility coefficient for SGP data is 0.83 at rest and 0.67 during h yperaemia. Flow measurements, assessed by means of two methods, correl ate well at rest (r=0.89), but only moderately during hyperaemia (r=0. 51). The correlation coefficient for the pooled flow measurements is 0 .98. It is concluded that EIT is a valid and reliable method for asses sing bloodflow in the limb. Possible applications of EIT in localising fluid changes are discussed.