The photoplethysmographic amplitude to pulse pressure ratio can track sudden changes in vascular compliance and resistance during liver graft reperfusion

Abstract

During liver transplantation, the thermodilution cardiac output (CO) technique cannot respond to sudden hemodynamic changes associated with postreperfusion syndrome. Photoplethysmography (PPG) can reflect changes in intravascular volume and thus can be used to assess vasomotor tone and arterial stiffness on the pressure–volume relation. We investigated whether a beat-to-beat analysis of the arterial pressure–PPG relationship can estimate dynamic changes in vascular characteristics immediately after liver graft reperfusion.In 10 recipients, arterial blood pressure and PPG waveforms recorded simultaneously were analyzed from the beginning of fall to nadir in systolic blood pressure immediately after reperfusion. On a beat-to-beat basis, we compared the ratio of the amplitude of PPG to arterial pulse pressure (PPGamp/PP, as relative vascular compliance) to total peripheral resistance (TPR) and Windkessel compliance (Cwk) obtained from the Modelflow CO algorithm.Following graft reperfusion, PPGamp/PP and Cwk increased (median 41.5%; P = .005 and 42.0%; P < .001, respectively), whereas TPR decreased (median −46.4%; P < .001). Beat-to-beat PPGamp/PP was negatively correlated with TPR (median r = –0.80 [95% CI –0.85 to –0.76] on linear regression and r2 = 0.84 [95% CI 0.73–0.92] on curvilinear regression), and was positively correlated with Cwk (median r = 0.86 [95% CI 0.81–0.91] on linear regression and r2 = 0.88 [95% CI 0.75–0.96] on curvilinear regression).Our results suggest that relative compliance, obtained from beat-to-beat analysis of PPG and arterial pressure waveforms, can track abrupt changes in vascular characteristics associated with postreperfusion syndrome. This simple index would contribute to differential diagnoses of sudden hypotension.

Evaluation of Autonomic Nervous System, Saliva Cortisol Levels, and Cognitive Function in Major Depressive Disorder Patients

“…An increase in LF values, a decrease in HF values, and a larger LF/HF ratio have also been observed in a study by Udupa et al [ 18 ]. Furthermore, PPG of MDD group had significant increase in mean pulse pressure (mean PP) and standard deviation of pulse pressure (SDPP) when compared with the control group that reflect pulsatile changes in blood; it can be used to estimate vascular compliance on the pressure–volume loop [ 19 ]. The hyperactivation of SNS might also be responsible for an elevation of mean HR, SDHR, mean PP, and SDPP in MDD patients.…”

An optimal filter for short photoplethysmogram signals

“…The common PPG acquisition methods include transmission and reflection 7 , 8 ; therefore, the PPG represents the aggregated expression of many physiological processes within the cardiovascular system 9 . The PPG is a high-fusion signal that measures activity during the heart’s systolic and diastolic periods, hemodynamics 10 , 11 , hemorheology 12 , and the peripheral microcirculation system 5 , 13 , 14 . PPGs can be easily extracted from human peripheral tissue 15 , such as fingers, toes, earlobes, wrists, and the forehead; therefore, they have great potential for application in wearable health devices.…”

Assessing hemodynamics from the photoplethysmogram to gain insights into vascular age: a review from VascAgeNet

“…The PPG can be used alongside a pressure cuff to assess several parameters. First, the peripheral compliance index, which decreases with chronological age ( 145 ), can be estimated from pulse pressure and PPG pulse wave amplitude ( 119 , 145 , 171 ). Second, the volume-clamp method can be used to measure BP continuously ( 156 , 208 ).…”