Research
Obstetrics
Modelflow: a new method for noninvasive assessment of cardiac output in pregnant women

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Objective

Estimation of cardiac output by continuous finger arterial pressure waveform analysis with Modelflow is a noninvasive technique for beat-to-beat hemodynamic assessment. The purpose of this study was to compare this method in pregnant women with the more commonly used Doppler echocardiography.

Study design

In 16 primigravid women, stroke volume was measured serially in first, second, and third trimester and after pregnancy by the Modelflow method and by Doppler echocardiography. Aortic diameter and compliance were assessed serially by echocardiography and pulse wave velocity measurements.

Results

Aortic compliance was increased significantly in pregnancy compared with nonpregnant values, but aortic diameter did not change. After adjustment for pregnancy-related changes in pulse wave velocity, blood pressure, and heart rate, Modelflow stroke volume measurements gave comparable results to Doppler echocardiography during and after pregnancy. The observed variation was similar to reported comparisons of Doppler echocardiography with thermodilution.

Conclusion

After adjustment for pregnancy the Modelflow method is a useful research tool for assessment of stroke volume in pregnant women and offers the advantage of continuous measurement and convenience of application.

Section snippets

Subjects

Twenty-one healthy, normotensive primigravid women with a singleton pregnancy and a gestational age of <12 weeks were selected at the outpatient clinic of our hospital. Gestational age was confirmed by crown-rump measurement during the first trimester. They had no medical history of cardiovascular disease, and no subject had vasoactive medication. All of the women had a normal blood pressure (systolic, ≤120 mm Hg; diastolic, ≤80 mm Hg) that was measured by sphygmomanometer.

The Medical Ethical

Results

Twenty-one women were included, but 5 women did not complete all measurements. Four women resigned from participation after the first measurement, and 1 woman was hospitalized for preterm uterus contractions.

Results of 16 women who completed all measurements were used for the analysis. Characteristics are presented in Table 1. The pregnancies were uneventful, and all women were delivered at term of healthy babies with a birth weight of >10th percentile.28 Data on aorta characteristics (PWV and

Comment

Our results indicate that, as expected, Modelflow underestimates SV in pregnant women. We observed that PWV was lower; therefore, aorta compliance was higher during pregnancy than in the nonpregnant state after delivery. However, values at the 3 measurement periods during pregnancy were similar. Our observations on the change in aortic compliance are in accordance with the observations of Poppas et al14 and Slangen et al.15 Assuming that postpartum values were comparable with values before

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    Cite this article as: Rang S, de Pablo Lapiedra B, van Montfrans GA, et al. Modelflow, a new method for noninvasive assessment of cardiac output in pregnant women. Am J Obstet Gynecol 2007;196:235.e1-235.e8.

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