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J Appl Physiol (1985). 2014 Sep 1;117(5):535-43. doi: 10.1152/japplphysiol.01358.2013. Epub 2014 Jul 3.

Ventilation/perfusion mismatch during lung aeration at birth.

Author information

1
The Ritchie Centre, MIMR-PHI Institute of Medical Research, Melbourne, Australia; Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia;
2
Monash Biomedical Imaging, Melbourne, Australia; Australian Synchrotron, Melbourne, Australia;
3
Department of Pediatrics, Leiden University Medical Centre, Leiden, Netherlands;
4
School of Physics, Monash University, Melbourne, Australia;
5
Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Australia;
6
Medical Imaging and Radiation Sciences, Monash University, Melbourne, Australia; Department of Medical Imaging, University of Saskatchewan, Saskatoon, Canada;
7
The Ritchie Centre, MIMR-PHI Institute of Medical Research, Melbourne, Australia; Royal Hobart Hospital, Hobart, Australia; and.
8
Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan.
9
The Ritchie Centre, MIMR-PHI Institute of Medical Research, Melbourne, Australia; Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia; Stuart.Hooper@monash.edu.

Abstract

At birth, the transition to newborn life is triggered by lung aeration, which stimulates a large increase in pulmonary blood flow (PBF). Current theories predict that the increase in PBF is spatially related to ventilated lung regions as they aerate after birth. Using simultaneous phase-contrast X-ray imaging and angiography we investigated the spatial relationships between lung aeration and the increase in PBF after birth. Six near-term (30-day gestation) rabbits were delivered by caesarean section, intubated and an intravenous catheter inserted, before they were positioned for X-ray imaging. During imaging, iodine was injected before ventilation onset, after ventilation of the right lung only, and after ventilation of both lungs. Unilateral ventilation increased iodine levels entering both left and right pulmonary arteries (PAs) and significantly increased heart rate, iodine ejection per beat, diameters of both left and right PAs, and number of visible vessels in both lungs. Within the 6th intercostal space, the mean gray level (relative measure of iodine level) increased from 68.3 ± 11.6 and 70.3 ± 7.5%·s to 136.3 ± 22.6 and 136.3 ± 23.7%·s in the left and right PAs, respectively. No differences were observed between vessels in the left and right lungs, despite the left lung not initially being ventilated. The increase in PBF at birth is not spatially related to lung aeration allowing a large ventilation/perfusion mismatch, or pulmonary shunting, to occur in the partially aerated lung at birth.

KEYWORDS:

angiography; newborn; perfusion; pulmonary blood flow; ventilation

PMID:
24994883
DOI:
10.1152/japplphysiol.01358.2013
[Indexed for MEDLINE]
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