Photoplethysmography: a valuable noninvasive tool in the assessment of venous dysfunction?

We have investigated the photoplethysmography findings in 152 patients admitted to the Middlesex Hospital Vascular Laboratory with suspected lower limb venous disease, and we compared the results obtained with patient grouping using clinical criteria and the presence of reflux on color duplex scanning. All photoplethysmography traces were normalized with use of computer software to enable direct comparison between the traces. The parameters investigated were the 95% and 50% refilling times and the initial gradient of the refilling curve. Receiver operating characteristic curves were constructed to determine which parameter was the most useful predictor of disease and to identify which value within each observation gave the greatest sensitivity and specificity. We found a large overlap between interquartile values for all three parameters, with limbs grouped both clinically and by duplex scanning, making differentiation between normal and abnormal limbs difficult on the basis of photoplethysmography traces alone. We found that a 95% refilling time of less than 15 seconds indicated venous dysfunction with the greatest sensitivity and specificity and suggest that this value is most useful. Photoplethysmography readings are reproducible, noninvasive, and correlate well with the presence of clinical disease, and photoplethysmography remains useful in the assessment of venous dysfunction.