title: Fingertip photoplethysmographic waveform variability and systemic vascular resistance in intensive care unit patients.
abstract: Low frequency variability in the fingertip photoplethysmogram (PPG) waveform has been utilized for inferring sympathetic vascular control, but its relationship with a quantitative measure of vascular tone has not been established. In this study, we examined the association between fingertip PPG waveform variability (PPGV) and systemic vascular resistance (SVR) obtained from thermodilution cardiac output (CO) and intra-arterial pressure measurements in 48 post cardiac surgery intensive care unit patients. Among the hemodynamic measurements, both CO (P < 0.05) and SVR (P < 0.0001) had statistically significant relationships with the normalized low frequency power (LF(nu)) of PPGV. The LF(nu) of baseline PPGV had moderate but significant positive correlation with SVR (r = 0.54, P < 0.0001), and a value below 52.5 nu was able to identify SVR < 900 dyn s cm⁻⁵ with sensitivity of 59% and specificity of 95%. The results have provided quantitative evidence to confirm the link between fingertip PPGV and sympathetic vascular control. Suppression of LF vasomotor waves leading to dominance of respiration-related HF fluctuations in the fingertip circulation was a specific (though not sensitive) marker of systemic vasodilatation, which could be potentially utilized for the assessment of critical care patients.
authors.affiliation: Ambulance Research Institute, Ambulance Service of New South Wales, Sydney, NSW 2039, Australia. pmmiddleton@ambulance.nsw.gov.au
authors.forename: Paul M
authors.initials: PM
authors.lastname: Middleton
authors.forename: Gregory S H
authors.initials: GS
authors.lastname: Chan
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Steel
authors.forename: Philip
authors.initials: P
authors.lastname: Malouf
authors.forename: Christopher
authors.initials: C
authors.lastname: Critoph
authors.forename: Gordon
authors.initials: G
authors.lastname: Flynn
authors.forename: Emma
authors.initials: E
authors.lastname: O'Lone
authors.forename: Branko G
authors.initials: BG
authors.lastname: Celler
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Lovell
mesh_terms: D000368:Aged; D006348:Cardiac Surgical Procedures; D005260:Female; D005385:Fingers / Q000098:blood supply*; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D017156:Photoplethysmography / Q000379:methods*; D011182:Postoperative Care / Q000379:methods; D011446:Prospective Studies; D012815:Signal Processing, Computer-Assisted; D014655:Vascular Resistance / Q000502:physiology