Background: The blood pressure (BP) waveform is suggested to reflect the whole-body blood supply distribution, but its non-invasive assessment is not sufficiently user friendly for practical applications. The present authors studied the correlation between BP and photoplethysmography (PPG) waveforms, with the aim of determining the optimal range for contact pressure stimulation (PS) to produce a reliable transfer function in their harmonic parameters.
Methods: Finger PPG and radial-artery BP signals were measured simultaneously and noninvasively on healthy volunteers (n = 45). PS of 0-200 mmHg was applied to the finger, and 1 min data sequences were recorded. In frequency-domain analysis, linear regression was applied to the calculated amplitude ratios or the first five harmonics between BP and PPG waveforms.
Results: In the 60 mmHg-PS group, the BP-PPG regression of amplitude ratios was highest, and the agreements between them were also the best verified by Bland-Altman analysis.
Conclusion: In the present study, frequency-domain analysis was performed to study the correlation between BP and PPG waveforms. Differences in pressure-induced-vasodilation responses underlie the different BP-PPG waveform correlations obtained by applying different PSs. The non-invasively derived PPG parameters might help to provide an easier method to acquire the radial-artery BP waveform, and hence broaden the application of BP waveform analysis.