title: Quantifying the correlation between photoplethysmography and laser Doppler flowmetry microvascular low-frequency oscillations.
abstract: Photoplethysmography (PPG) and laser Doppler flowmetry (LDF) are two recognized optical techniques that can track low-frequency perfusion changes in microcirculation. The aim of this study was to determine, in healthy subjects, the correlation between the techniques for specific low-frequency bands previously defined for microcirculation. Twelve healthy male subjects (age range 18 to 50 years) were studied, with PPG and LDF signals recorded for 20 min from their right and left index (PPG) and middle (LDF) fingers. Wavelet analysis comprised dividing the low-frequency integral wavelet spectrum (IWS) into five established physiological bands relating to cardiac, respiratory, myogenic, neurogenic, and endothelial activities. The correlation between PPG and LDF was quantified using wavelet correlation analysis and Spearman correlation analysis of the median IWS amplitude. The median wavelet correlation between signals (right-left side average) was 0.45 (cardiac), 0.49 (respiratory), 0.86 (myogenic), 0.91 (neurogenic), and 0.91 (endothelial). The correlation of IWS amplitude values (right-left side average) was statistically significant for the cardiac (ρ = 0.64, p < 0.05) and endothelial (ρ = 0.62, p < 0.05) bands. This pilot study has shown good correlation between PPG and LDF for specific physiological frequency bands. In particular, the results suggest that PPG has the potential to be a low-cost replacement for LDF for endothelial activity assessments.
authors.affiliation: Institute of Continuous Media Mechanics, ak Koroleva 1, Perm 614013, Russia.
authors.forename: Irina
authors.initials: I
authors.lastname: Mizeva
authors.affiliation: Freeman Hospital, Regional Medical Physics Department, Microvascular Diagnostics Service, Newcastle upon Tyne, NE7 7DN, United KingdomcNewcastle University, Medical School, Institute of Cellular Medicine, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: Costanzo
authors.initials: C
authors.lastname: Di Maria
authors.affiliation: Institute of Continuous Media Mechanics, ak Koroleva 1, Perm 614013, Russia.
authors.forename: Peter
authors.initials: P
authors.lastname: Frick
authors.affiliation: Institute of Continuous Media Mechanics, ak Koroleva 1, Perm 614013, Russia.
authors.forename: Sergey
authors.initials: S
authors.lastname: Podtaev
authors.affiliation: Freeman Hospital, Regional Medical Physics Department, Microvascular Diagnostics Service, Newcastle upon Tyne, NE7 7DN, United KingdomcNewcastle University, Medical School, Institute of Cellular Medicine, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Allen
mesh_terms: D000293:Adolescent; D000328:Adult; D005385:Fingers / Q000098:blood supply; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D008875:Middle Aged; D017156:Photoplethysmography; D010865:Pilot Projects; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply*; D013997:Time Factors; D058067:Wavelet Analysis; D055815:Young Adult