Behavior of pulmonary venous flow during fetal respiratory movements.
OBJECTIVE
To test the hypothesis that fetal pulmonary venous flow pulsatility index is lower during fetal respiratory movements than in apnea.


METHODS
Case control. SETTINGS/PATIENTS: Twenty-two normal fetuses of mothers without systemic disease were examined in apnea (controls) and in the presence of fetal respiratory movements (cases). Fetuses were examined by prenatal Doppler echocardiography with color flow mapping. The pulsatility index of the pulmonary vein was obtained by placing the pulsed Doppler sample volume over the right upper or left lower pulmonary vein, and calculating the ratio (maximum velocity [systolic or diastolic]-presystolic velocity/mean velocity).


RESULTS
Mean gestational age was 28.9 +/- 2.9 weeks. During fetal apnea, mean systolic, diastolic, and presystolic velocities were, respectively, 0.35 +/- 0.08 m/s, 0.26 +/- 0.07 m/s, and 0.09 +/- 0.03 m/s. In the presence of fetal respiratory movements, mean systolic, diastolic, and presystolic velocities were, respectively, 0.33 +/- 0.1 m/s, 0.28 +/- 0.08 m/s, and 0.11 +/- 0.04 m/s. Pulsatility index pulmonary vein in apnea was 1.25 +/- 0.23 (1.69 to 0.82), and during fetal respiratory movements it was 0.97 +/- 0.2 (1.53 to 0.61).


CONCLUSIONS
We showed a significant reduction in impedance of pulmonary venous flow, represented by pulmonary vein pulsatility index, during fetal respiratory movements, reflecting modifications of the left atrial dynamics and enhancement of left ventricular compliance.
Chemello
Keli
K
Institute of Cardiology of Rio Grande do Sul, Porto Alegre, RS, Brazil.
Zielinsky
Paulo
P
Nicoloso
Luiz Henrique
LH
de Morais
Marina Resener
MR
D016279:Atrial Function, Left / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D016022:Case-Control Studies; D003971:Diastole / Q000502:physiology; D015150:Echocardiography, Doppler; D005260:Female; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011652:Pulmonary Circulation / Q000502:physiology*; D011667:Pulmonary Veins / Q000000981:diagnostic imaging / Q000196:embryology* / Q000502:physiology*; D011673:Pulsatile Flow / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D013599:Systole / Q000502:physiology; D016216:Ultrasonography, Prenatal; D014655:Vascular Resistance / Q000502:physiology