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Effect of non-linearity in predicting Doppler waveforms through a novel model.

Gayasen A, Dua SK, Sengupta A, Nagchoudhuri D - Biomed Eng Online (2003)

Bottom Line: Normal pregnancy has been successfully modeled and the doppler output waveforms are simulated for different gestation time using the model.Both these results are established clinical facts.Total harmonic distortion (THD) is found to be informative in determining the Feto-maternal health.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical Engineering, Indian Institute of Technology, New Delhi, India. gayasen@cse.psu.edu

ABSTRACT

Background: In pregnancy, the uteroplacental vascular system develops de novo locally in utero and a systemic haemodynamic & bio-rheological alteration accompany it. Any abnormality in the non-linear vascular system is believed to trigger the onset of serious morbid conditions like pre-eclampsia and/or intrauterine growth restriction (IUGR). Exact Aetiopathogenesis is unknown. Advancement in the field of non-invasive doppler image analysis and simulation incorporating non-linearities may unfold the complexities associated with the inaccessible uteroplacental vessels. Earlier modeling approaches approximate it as a linear system.

Method: We proposed a novel electrical model for the uteroplacental system that uses MOSFETs as non-linear elements in place of traditional linear transmission line (TL) model. The model to simulate doppler FVW's was designed by including the inputs from our non-linear mathematical model. While using the MOSFETs as voltage-controlled switches, a fair degree of controlled-non-linearity has been introduced in the model. Comparative analysis was done between the simulated data and the actual doppler FVW's waveforms.

Results & discussion: Normal pregnancy has been successfully modeled and the doppler output waveforms are simulated for different gestation time using the model. It is observed that the dicrotic notch disappears and the S/D ratio decreases as the pregnancy matures. Both these results are established clinical facts. Effects of blood density, viscosity and the arterial wall elasticity on the blood flow velocity profile were also studied. Spectral analysis on the output of the model (blood flow velocity) indicated that the Total Harmonic Distortion (THD) falls during the mid-gestation.

Conclusion: Total harmonic distortion (THD) is found to be informative in determining the Feto-maternal health. Effects of the blood density, the viscosity and the elasticity changes on the blood FVW are simulated. Future works are expected to concentrate mainly on improving the load with respect to varying non-linear parameters in the model. Heart rate variability, which accounts for the vascular tone, should also be included. We also expect the model to initiate extensive clinical or experimental studies in the near future.

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Elasticity variation
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Figure 9: Elasticity variation

Mentions: Effect of arterial wall elasticity on blood FVW is shown in Fig. 9. The Young's modulus of elasticity is varied from 0.1 to 10 times the normal value for normal 24-week pregnancy. For very low elasticity or a flaccid condition, low systolic and high diastolic peaks are observed. This effect has been observed clinically. Also, increasing elasticity beyond around twice the normal had negligible effect on the waveform. Thus elasticity in these smaller vessels may not be an important factor in determining the flow profile or flow conditions or reason thereof for underlying normal or abnormal pregnancy related flow changes or pathology as suggested by Brosen [1]. Similar conclusion has also been drawn in our previous work on mathematical model [4]. But, there may be other important factors such as rheological parameters, geometry, overall cardiac output (blood volume), heart rate variability, and overall load at the distal end or proximal area, playing a role.


Effect of non-linearity in predicting Doppler waveforms through a novel model.

Gayasen A, Dua SK, Sengupta A, Nagchoudhuri D - Biomed Eng Online (2003)

Elasticity variation
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC222923&req=5

Figure 9: Elasticity variation
Mentions: Effect of arterial wall elasticity on blood FVW is shown in Fig. 9. The Young's modulus of elasticity is varied from 0.1 to 10 times the normal value for normal 24-week pregnancy. For very low elasticity or a flaccid condition, low systolic and high diastolic peaks are observed. This effect has been observed clinically. Also, increasing elasticity beyond around twice the normal had negligible effect on the waveform. Thus elasticity in these smaller vessels may not be an important factor in determining the flow profile or flow conditions or reason thereof for underlying normal or abnormal pregnancy related flow changes or pathology as suggested by Brosen [1]. Similar conclusion has also been drawn in our previous work on mathematical model [4]. But, there may be other important factors such as rheological parameters, geometry, overall cardiac output (blood volume), heart rate variability, and overall load at the distal end or proximal area, playing a role.

Bottom Line: Normal pregnancy has been successfully modeled and the doppler output waveforms are simulated for different gestation time using the model.Both these results are established clinical facts.Total harmonic distortion (THD) is found to be informative in determining the Feto-maternal health.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical Engineering, Indian Institute of Technology, New Delhi, India. gayasen@cse.psu.edu

ABSTRACT

Background: In pregnancy, the uteroplacental vascular system develops de novo locally in utero and a systemic haemodynamic & bio-rheological alteration accompany it. Any abnormality in the non-linear vascular system is believed to trigger the onset of serious morbid conditions like pre-eclampsia and/or intrauterine growth restriction (IUGR). Exact Aetiopathogenesis is unknown. Advancement in the field of non-invasive doppler image analysis and simulation incorporating non-linearities may unfold the complexities associated with the inaccessible uteroplacental vessels. Earlier modeling approaches approximate it as a linear system.

Method: We proposed a novel electrical model for the uteroplacental system that uses MOSFETs as non-linear elements in place of traditional linear transmission line (TL) model. The model to simulate doppler FVW's was designed by including the inputs from our non-linear mathematical model. While using the MOSFETs as voltage-controlled switches, a fair degree of controlled-non-linearity has been introduced in the model. Comparative analysis was done between the simulated data and the actual doppler FVW's waveforms.

Results & discussion: Normal pregnancy has been successfully modeled and the doppler output waveforms are simulated for different gestation time using the model. It is observed that the dicrotic notch disappears and the S/D ratio decreases as the pregnancy matures. Both these results are established clinical facts. Effects of blood density, viscosity and the arterial wall elasticity on the blood flow velocity profile were also studied. Spectral analysis on the output of the model (blood flow velocity) indicated that the Total Harmonic Distortion (THD) falls during the mid-gestation.

Conclusion: Total harmonic distortion (THD) is found to be informative in determining the Feto-maternal health. Effects of the blood density, the viscosity and the elasticity changes on the blood FVW are simulated. Future works are expected to concentrate mainly on improving the load with respect to varying non-linear parameters in the model. Heart rate variability, which accounts for the vascular tone, should also be included. We also expect the model to initiate extensive clinical or experimental studies in the near future.

Show MeSH
Related in: MedlinePlus