Sonographic evaluation of vascular pulmonary reactivity following oxygen administration in fetuses with normal lung development

OBJECTIVE: This study aimed to establish nomograms for sonographic assessment of fetal pulmonary vascular reactivity following maternal hyperoxygenation.

STUDY DESIGN: Sixty-two healthy fetuses were assessed at four weekly intervals from 26 weeks onwards. Pulmonary reactivity was evaluated using Doppler ultrasound in the main pulmonary artery and in the first branch of this main pulmonary artery. The difference in pulsatility index (∆PI) during maternal inhalation of a mixture of room air and oxygen (9 L/min) for at least 10 min was expressed as a percentage. Nomograms were constructed, and Kaplan-Meier curves were used to express the occurrence of a reactive test (∆PI ≥ 20%) with advancing gestation.

RESULTS: In the first branch, linear regression analysis revealed a significant correlation of ∆PI (%) with gestational age (r(2) = 0.04, p = 0.0057). Large inter-individual and intra-individual variability was noted. The ∆PI (%) in the main pulmonary artery remained constant throughout gestation (6.62 ± 17.83%).

CONCLUSION: Vascular reactivity in the pulmonary circulation increases in the first branch of the pulmonary artery. Large individual variability is limiting its use as a management tool.