Abstract
At birth pulmonary blood flow (PBF) increases ten fold allowing newborn oxygenation replacing feto-placental exchanges. Mechanical and chemical stimuli have been previously investigated in experiment including stress of labor, cold and cord clamping. The aim of our study was to consider sequentially only mechanical and gaseous stimuli applied to the lungs of the fetal lamb and their consequences on PBF. Therefore we studied five steps: control, distension with nitrogen(N2), rhythmic ventilation with N2, with air then with O2. We studied 16 fetal lambs three days after fetal surgery at 134,75±4 days of gestational age, weight: 3.63±0,63 kg. PBF was continually measured by a flowmeter fixed on the left pulmonary artery and validated by microspheres method after flow steady state. Continuous distension pressure was 25±10cm of water. Characteristics of rhythmic ventilation was a frequency of 50±6, I/E:36±13, IP:27±6 mm Hg and a PEEP of 4±5 under N2, followed by air then by O2. For statistical analysis each step was compared to the previous one using the non parametric Wilcoxon test and considered significant for a p<0.01*.
We conclude than distension such as rhythmic ventilation is a preponderant factor to increase PBF more than oxygenation. This is in relationship with lung liquid resorption, increased recruited capillaries, modified alveolocapillary interface and release of hormones such as prostacyclin, bradykinin and EDRF.
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Patrice, M., Christine, R. & Mickael, H. 120 THE CONSEQUENCES OF BIRTH SIMULATION ON PULMONARY BLOOD FLOW IN THE FETAL LAMB. Pediatr Res 28, 297 (1990). https://doi.org/10.1203/00006450-199009000-00144
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DOI: https://doi.org/10.1203/00006450-199009000-00144