Rosmina Jaafar
rosmina@vlsi.eng.ukm.my
PhD Candidate Biomedical Instrumentation
M.Sc.: Electronics (Medical Systems)
University of Hertfordshire, UK, 1999-2000
Thesis: Design of Finger Pulse Oximeter for Testing
on a Finger Simulator
B.Sc.: Biomedical Engineering Case Western
Reserve University, USA, 1988-1991
Development of a non-invasive bedside instrument for endothelial
dysfunction assessment using photoplethysmography (PPG)
Supervisor: Assoc. Prof. Dr. Edmond Zahedi
Co-supervisor: Prof. Dr. Mohd Alauddin Mohd Ali
Introduction
The human vascular wall is a complex organ, capable of changing its lumen size
in response to different physiological stimulus; this process is known as
endothelial function. Endothelial dysfunction, on the other hand, has been
recognized as an early marker for cardiovascular disease.
Currently, the golden technique used for endothelial dysfunction assessment is
the evaluation of percentage of flow mediated dilation (FMD) in conduit artery
such as in the brachial or femoral artery by using high-resolution ultrasound
[Corretti et. al., 2002]. In this technique, a pressurized cuff is applied to the arm
stopping the flow of blood for approximately 5 minutes. Then the cuff is suddenly
released and the diameter of the brachial artery is measured in real-time. The
main drawbacks of this technique are that:
-
it requires a very skilled person to operate the ultrasound system and
measure in real-time the diameter;
the procedure is quite uncomfortable to the person undergoing the
assessment due to extended time (5 minutes) of blood flow blockage.
In this study, photoplethysmography (PPG) will be used as an alternative method
to the FMD measurement. PPG signals obtained from the left and right index
fingers will be recorded and evaluated for synthesis of an index for vascular
dysfunction characteristics. Although the study focuses on smaller vessels under
the fingers, it is expected to yield as reliable result as to that of the FMD since
endothelial function impaired in large arteries is similar to its impairment in small
resistance arteries [Iiyama, 1996].
Objectives
The main objective of the study is to design an instrumentation system that will
be used as a tool for assessing the characteristics of the endothelial function
non-invasively. The method of assessment implementing PPG technique, which
has been proven a convenient and non-invasive measurement that can monitor
blood volume flow changes effectively, will be conducted at the comfort of both
the patient and healthcare practitioner. Thus, through the study, an alternative
method of assessment of endothelial dysfunction can be made available to
surrogate for the available technique.
Approach
The research work will involve development of the PPG instrumentation system,
which will include developing the wireless probe system to ease up measurement
and data acquisition. Commercially available PPG sensors will be used to obtain
the PPG signals from the left and right index fingers.
The study will also involve developing test protocols on normal subjects and
pathologic subjects. The experiments will be conducted simultaneous with the
FMD measurement, which will be used as reference for the study. PPG data will
be acquired and recorded for synthesis and signal analysis using MATLAB
programming tools to extract significant features.
The signals will be processed and analyzed offline during the development phase
and later it will be made online as the project progresses. Results from the data
analysis will lead to the formation of an index, which will characterize the good
and poor endothelial function. The results of PPG analysis will then be compared
to that of the ultrasound FMD.
Reference
Corretti MC, Anderson TJ, Benjamin EJ, Celermajer D, Charbonneau F, Creager
MA, Deanfield J, Drexler H, Gerhard-Herman M, Herrington D, et al., Guidelines
for the ultrasound assessment of endothelial-dependent flow-mediated
vasodilation of the brachial artery: A report of the International Brachial Artery
Reactivity Task Force, Journal of the American College of Cardiology, Volume
39, Issue 2, 16 January 2002, Pages 257-265.
Iiyama K, Nagano M, Yo Y,Nagano N, Kamide K, Higaki J. Mikami H, Ogihara T,
Impaired endothelial function with essential hypertension assessed by
ultrasonography, Am Heart J, 1996;132: 779-82.