Comparing results of digital photoplethysmography in two groups of chronic obstructive pulmonary disease patients with and without high pulmonary artery pressure

Abstract

Background Digital photoplethysmography (D-PPG) is a newly introduced method of optical screening of deep vein thrombosis (DVT) by recording changes in the size of limb due to tissue fluid. Objectives The objective of this study is to assess the effect of high pulmonary artery pressure (PAP) and consequently increased venous system pressure on D-PPG test results. Methods Forty-five patients with and 45 patients without PAP pressure were enrolled in the study and divided into two groups. All the patients had a history of chronic obstructive pulmonary disease (COPD). D-PPG test was performed for both legs of all the patients and the results of the two groups were compared. Also, all patients underwent duplex sonography for ruling out DVT. Results Using venous refilling time (RT) of <22 s as the optimal cut-off point, it was found that 32 (35%) legs of patients with and 39 (43%) legs of patients without high PAP had positive D-PPG test. Although the rate of positive D-PPG test was higher in patients with high PAP, this was not statistically significant ( P = 0.28). Moreover, overall correlation between RT and venous pump detected by D-PPG and PAP was r = −0.11 ( P = 0.2) and r = −0.01 ( P = 0.6), respectively. Conclusion Our results showed that the rate of positive D-PPG test results is slightly higher in patients with pulmonary hypertension, but this difference is not statistically significant. Therefore, increased PAP could be excluded as a confounding factor of D-PPG test.