Date of Award
Medical Doctor (MD)
David G. Silverman
Recent research in monitoring aims to the return to the roots of the
photoplethysmography (PPG) and extract volumetric information from its waveform.
Previous studies from our laboratory have shown that a voltage-to-volume conversion
based upon pulsatile volume at rest allows volume monitoring using the PPG. The current
study aims to further extract arterial and venous circulatory volume components from the
PPG via simulated volume loading of 0.75-2L upon release of lower body negative
Data were extracted retrospectively from LBNP studies on five healthy volunteers
with the Institutional Review Board approval. Stroke volumes (SV) were measured by
echocardiography, when available. All PPG waveforms were analyzed in ADInstruments
LabChart. AC and DC were found before LBNP (baseline) by averaging at least 75 beats,
and during LBNP by averaging 10 beats. The release segment (LBNP off) was roughly
divided into 4-8 successive phases. AC and DC of each phase were found by averaging
10-12 beats. ΔAC and ΔDC from baseline were calculated for each phase and converted
to a volume using AC at rest:
ΔAC = (AC recovery phase x - AC at rest) x (SV at rest /AC at rest)
ΔDC = (DC recovery phase x - DC at rest) x (SV at rest /AC at rest).
ΔAC and ΔDC during maximum LBNP and LBNP release were consistent with
literature values. Overshoot of volume return may be attributable to splanchnic
vasculature mobilization. ΔDC/ΔAC ratio tended to be smallest initially and greatest at
the end of volume resuscitation. Distortions in the relationship were accompanied by
abrupt hypotension and bradycardia.
PPG may be used as a non-invasive monitor of arterial and venous volume status,
which can be useful in assessing response to fluid resuscitation. Moreover, the evidence
of Frank-Starling relationship between AC (arterial) and DC (venous) may shed light on
physiologic processes and warrants further study.
Bing, Vicki Zhu Jun, "Photoplethysmographic Delineation Of Arterial And Venous Volume Responses To Release Of Lower Body Negative Pressure" (2015). Yale Medicine Thesis Digital Library. 1951.