title: Quantifying tissue mechanical properties using photoplethysmography.
abstract: Photoplethysmography (PPG) is a non-invasive optical method that can be used to detect blood volume changes in the microvascular bed of tissue. The PPG signal comprises two components; a pulsatile waveform (AC) attributed to changes in the interrogated blood volume with each heartbeat, and a slowly varying baseline (DC) combining low frequency fluctuations mainly due to respiration and sympathetic nervous system activity. In this report, we investigate the AC pulsatile waveform of the PPG pulse for ultimate use in extracting information regarding the biomechanical properties of tissue and vasculature. By analyzing the rise time of the pulse in the diastole period, we show that PPG is capable of measuring changes in the Young's Modulus of tissue mimicking phantoms with a resolution of 4 KPa in the range of 12 to 61 KPa. In addition, the shape of the pulse can potentially be used to diagnose vascular complications by differentiating upstream from downstream complications. A Windkessel model was used to model changes in the biomechanical properties of the circulation and to test the proposed concept. The modeling data confirmed the response seen in vitro and showed the same trends in the PPG rise and fall times with changes in compliance and vascular resistance.
authors: Department of Biomedical Engineering, Texas A&M University, 5045 Emerging Technologies Building, 3120 TAMU, College Station, TX 77843-3120, USA.
authors: Tony J
authors: TJ
authors: Akl
authors: Department of Surgery, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213 USA ; VA Pittsburgh Healthcare System, University Dr. C-1w142, Pittsburgh, PA 15240 USA.
authors: Mark A
authors: MA
authors: Wilson
authors: Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6006 USA.
authors: M Nance
authors: MN
authors: Ericson
authors: Department of Biomedical Engineering, Texas A&M University, 5045 Emerging Technologies Building, 3120 TAMU, College Station, TX 77843-3120, USA.
authors: Gerard L
authors: GL
authors: Coté
keywords: (170.3660) Light propagation in tissues; (280.1415) Biological sensing and sensors