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Arterial and Venous Oxygen based on PPG





Contact Person

Idoia Badiola Aguirregomezcorta

Project Description

Deficient oxygenation in tissues causes hypoxic cell damage, which is critical in vital organs such as the heart and brain. Under normal physiological conditions, oxygen delivery and consumption relate to each other and are crucial for sustaining the fluctuating demands of cellular metabolism. Some microcirculatory dysfunctions such as diabetes mellitus and sepsis can alter the cohesion between oxygen supply and consumption. Thus, determining these factors is crucial for the early diagnosis of tissue abnormality.
To monitor regional oxygen distribution, the pulse oximeter can non-invasively be used, which uses photoplethysmography (PPG). Its working principle is to illuminate the skin with two specific wavelengths to distinguish absorbing property between oxygenated and deoxygenated hemoglobin, yielding peripheral oxygen saturation in arteries.
In this project, we are developing a non-invasive monitoring system for arterial oxygen saturation in parallel with the venous one so that oxygen consumption in the organs can be estimated as the difference between both. For that, we are developing a hardware platform to generate and acquire both arterial and venous blood flows and implementing the signal processing and algorithms to treat the signals and estimate the saturation. The novelty relies on the use of the Venous Muscle Pump, which considers dorsal ankle extensions at a fixed frequency for generating easily identifiable venous blood volume variations, as shown in Figure 1. A PPG sensor placed on the foot detects these variations.
In this context, we focus on implementing different algorithms, including mathematical models of light-tissue interaction in tissue to estimate the saturation, and filtering techniques and Machine Learning approaches to separate the arterial and venous sources and remove motion artifacts. Besides, Monte Carlo simulations of the light interaction based on dynamic mathematical models of the skin further help validate our results, improve our design and gain a deeper understanding of the physiological processes.

Project Goals

  • Construction of a non-invasive optical device to generate and acquire venous blood pulses
  • Development of algorithms to estimate venous oxygen saturation based on PPG
  • Simulation of light-tissue interaction on simultaneous arterial and venous blood pulses in skin

Project Partner

ELCAT (Munich)