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noninvasive technique for early detection of atherosclerosis using the impedance plethysmograph: Longitudinal study on cynomolgus monkeys

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Date Issued:
1991
Summary:
This study evaluates the use of an electrical impedance plethysmograph as a noninvasive technique for early detection of atherosclerosis. The instrument is inexpensive, easily portable and causes no health risks. Thus, the system is ideally suited for mass screemng and epidemiological studies, if proven to be effective. We have conducted experiments usmg a three-channel impedance plethysmograph once every 8 - 10 weeks on a colony of 20 male cynomolgus monkeys (macaca fascicularis). Five monkeys were on a control diet (monkey chow) and fifteen on a high cholesterol diet (1 mg cholesterol/Kcal with 40% of the calories derived from fat). The diet period for the monkeys ranged from 16-28 months (25 months typically). We wrapped a pressure cuff with one pair of electrodes around the upper left leg of the monkey. Two other sets of electrodes were wrapped, one distal to the pressure cuff on the lower left leg and the other as reference on the upper arm. We measured impedance pulses at these three different sites simultaneously using a three channel impedance plethysmograph. The signals were recorded when the pressure in the pressure cuff was changed from 200 mm Hg to 20 mm Hg in steps of 10 mm Hg. Arterial volume change was evaluated from this. Experiments were repeated with the cuffed segment on the right leg, and then on the left arm. The arterial volume change vs cuff pressure (V- Pc) characteristics were used to follow the progression of the disease. The V- Pc characteristic, initially with a well defined peak, changed to a flatter characteristic with increased period on the cholesterol diet. Monkeys on the control diet showed no flattening of the curve with time. In order to understand theoretically the effect of disease on the compliance - transmural pressure (C-Pt) characteristic (and hence V - Pc characteristic), we developed an arterial model to study the pressure - radius relationship of an artery under different disease states. We have also developed an expression for the equivalent incremental modulus of elasticity based on the incremental modulus of elasticity of the individual arterial wall layers. The resulting expressions were used to study the effect of increase in stenosis and calcification on the V - Pc and C-Pt characteristics. The simulation results obtained using the arterial model match our experimentally observed data of decrease m peak compliance with disease. The peak compliance was seen to decrease m amplitude and shift left (towards decreasing transmural pressure) as the artery got thicker with atherosclerotic disease. The V - Pc characteristic, initially with a well defined peak, got flatter with disease. Our simulation results lead us to believe that the noninvasive technique 1s sensitive enough to follow progressiOn of the atherosclerotic disease. Morphometric and histochemical data were collected subsequent to the sacrifice of the monkeys. Evaluation of these data and correlations with our compliance data will lead us to a more definitive statement on the method's sensitivity. This however, is beyond the scope of this dissertation.
Title: A noninvasive technique for early detection of atherosclerosis using the impedance plethysmograph: Longitudinal study on cynomolgus monkeys.
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Name(s): Kolluri, Sai M. S.
Florida Atlantic University, Degree grantor
Shankar, Ravi, Thesis advisor
College of Engineering and Computer Science
Department of Computer and Electrical Engineering and Computer Science
Type of Resource: text
Genre: Electronic Thesis Or Dissertation
Issuance: monographic
Date Issued: 1991
Publisher: Florida Atlantic University
Place of Publication: Boca Raton, Fla.
Physical Form: application/pdf
Extent: 195 p.
Language(s): English
Summary: This study evaluates the use of an electrical impedance plethysmograph as a noninvasive technique for early detection of atherosclerosis. The instrument is inexpensive, easily portable and causes no health risks. Thus, the system is ideally suited for mass screemng and epidemiological studies, if proven to be effective. We have conducted experiments usmg a three-channel impedance plethysmograph once every 8 - 10 weeks on a colony of 20 male cynomolgus monkeys (macaca fascicularis). Five monkeys were on a control diet (monkey chow) and fifteen on a high cholesterol diet (1 mg cholesterol/Kcal with 40% of the calories derived from fat). The diet period for the monkeys ranged from 16-28 months (25 months typically). We wrapped a pressure cuff with one pair of electrodes around the upper left leg of the monkey. Two other sets of electrodes were wrapped, one distal to the pressure cuff on the lower left leg and the other as reference on the upper arm. We measured impedance pulses at these three different sites simultaneously using a three channel impedance plethysmograph. The signals were recorded when the pressure in the pressure cuff was changed from 200 mm Hg to 20 mm Hg in steps of 10 mm Hg. Arterial volume change was evaluated from this. Experiments were repeated with the cuffed segment on the right leg, and then on the left arm. The arterial volume change vs cuff pressure (V- Pc) characteristics were used to follow the progression of the disease. The V- Pc characteristic, initially with a well defined peak, changed to a flatter characteristic with increased period on the cholesterol diet. Monkeys on the control diet showed no flattening of the curve with time. In order to understand theoretically the effect of disease on the compliance - transmural pressure (C-Pt) characteristic (and hence V - Pc characteristic), we developed an arterial model to study the pressure - radius relationship of an artery under different disease states. We have also developed an expression for the equivalent incremental modulus of elasticity based on the incremental modulus of elasticity of the individual arterial wall layers. The resulting expressions were used to study the effect of increase in stenosis and calcification on the V - Pc and C-Pt characteristics. The simulation results obtained using the arterial model match our experimentally observed data of decrease m peak compliance with disease. The peak compliance was seen to decrease m amplitude and shift left (towards decreasing transmural pressure) as the artery got thicker with atherosclerotic disease. The V - Pc characteristic, initially with a well defined peak, got flatter with disease. Our simulation results lead us to believe that the noninvasive technique 1s sensitive enough to follow progressiOn of the atherosclerotic disease. Morphometric and histochemical data were collected subsequent to the sacrifice of the monkeys. Evaluation of these data and correlations with our compliance data will lead us to a more definitive statement on the method's sensitivity. This however, is beyond the scope of this dissertation.
Identifier: 12281 (digitool), FADT12281 (IID), fau:9184 (fedora)
Collection: FAU Electronic Theses and Dissertations Collection
Note(s): College of Engineering and Computer Science
Thesis (Ph.D.)--Florida Atlantic University, 1991.
Subject(s): Impedance plethysmography
Atherosclerosis--Diagnosis
Atherosclerosis--Animal models
Impedance, Bioelectric
Diagnosis, Noninvasive
Held by: Florida Atlantic University Libraries
Persistent Link to This Record: http://purl.flvc.org/fcla/dt/12281
Sublocation: Digital Library
Use and Reproduction: Copyright © is held by the author, with permission granted to Florida Atlantic University to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Use and Reproduction: http://rightsstatements.org/vocab/InC/1.0/
Host Institution: FAU
Is Part of Series: Florida Atlantic University Digital Library Collections.