CARDIOVASCULAR JOURNAL OF AFRICA • Volume 33, No 3, May/June 2022 AFRICA 133 patient population ever reported in the current literature, also provides new reference values. A plethysmograph is a device for measuring volume changes within an organ or body part by detecting fluctuations in the blood volume. The word is derived from pletyhsmos, which in Greek means enlarging, increasing and becoming full. SGP has been used for the detection and evaluation of venous incompetence of the lower extremities.11 It provides information about the degree of venous filling (venous capacitance) and the rate of venous emptying (venous outflow).12 The principles of venous occlusion SGP were first introduced in 1953 by Whitney, who used a mercury-in-rubber strain gauge.14 Clinical use of a computerised version of SGP was then introduced in the 1990s.11 At the same time, there was an increasing interest in non-invasive functional tests, which could quantitatively describe the exact haemodynamic pathology, and providing additional information over imaging techniques.15 By using novel indium gallium strain gauges, SGP became easier to handle and a user-friendly instrument with better reproducibility than its predecessors.16 Our results demonstrate that SGP is a practical and sensitive method to define venous outflow capacity and to evaluate venous reflux and muscle pump function. The demographics 0,0 0,2 0,4 0,6 0,8 1,0 1 – Specificity Diagonal segments are produced by ties. Sensitivity 1,0 0,8 0,6 0,4 0,2 0,0 Fig. 5. ROC curve of expelled volume ratio in four seconds (EV4/V) measurements of right-sided pathology. 0,0 0,2 0,4 0,6 0,8 1,0 1 – Specificity Diagonal segments are produced by ties. Sensitivity 1,0 0,8 0,6 0,4 0,2 0,0 Fig. 4. ROC curve of venous volume (V) measurements of left-sided pathology. 0,0 0,2 0,4 0,6 0,8 1,0 1 – Specificity Diagonal segments are produced by ties. Sensitivity 1,0 0,8 0,6 0,4 0,2 0,0 Fig. 6. ROC curve of expelled volume ratio in four seconds (EV4/V) measurements of left-sided pathology. 0,0 0,2 0,4 0,6 0,8 1,0 1 – Specificity Diagonal segments are produced by ties. Sensitivity 1,0 0,8 0,6 0,4 0,2 0,0 Fig. 7. ROC curve of refilling volume (RV) measurements of right-sided pathology.
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