Characteristics of pulse-waveform and laser-Doppler indices in frozen-shoulder patients

This study tested the hypothesis that measuring and analyzing the arterial pulse waveform and the skin-surface blood flow makes it possible to noninvasively discriminate the different microcirculatory states of patients with frozen shoulder (FS). Radial blood pressure waveform (BPW), finger photoplethysmography (PPG), and skin-surface laser Doppler flowmetry (LDF) signals were measured noninvasively on the back of the hand in 25 FS and 18 control subjects. Beat-to-beat, spectral, and variability analyses were applied to the 3-minute-long recorded signals. Significant intergroup differences were found in the BPW, PPG, and LDF indices. For example, the amplitude indices of the predominant (lower-frequency) BPW components were significantly larger in FS subjects than controls. Some of the PPG phase-angle variability indices were significantly larger on the diseased side than on the contralateral side. The present results illustrate that LDF indices can be used to evaluate the blood-flow-perfusion responses and their regulation, and that pulse-waveform indices can help to evaluate changes in the arterial pulse-wave transmission condition and its regulation in FS. Moreover, the trends in the changes in certain spectral pulse-waveform indices were similar for the wrist BPW and finger PPG signals. These findings could facilitate the development of a rapid, inexpensive, and objective technique for evaluating the blood-flow responses induced by FS.