Increase in pulmonary blood flow at birth: role of oxygen and lung aeration.
Lung aeration stimulates the increase in pulmonary blood flow (PBF) at birth, but the spatial relationships between PBF and lung aeration and the role of increased oxygenation remain unclear. Using simultaneous phase-contrast X-ray imaging and angiography, we have investigated the separate roles of lung aeration and increased oxygenation in PBF changes at birth using near-term (30 days of gestation) rabbit kits (n = 18). Rabbits were imaged before ventilation, then the right lung was ventilated with 100% nitrogen (N2), air or 100% O2 (oxygen), before all kits were switched to ventilation in air, followed by ventilation of both lungs using air. Unilateral ventilation of the right lung with 100% N2 significantly increased heart rate (from 69.4 ± 4.9 to 93.0 ± 15.0 bpm), the diameters of both left and right pulmonary axial arteries, number of visible vessels in both left and right lungs, relative PBF index in both pulmonary arteries, and reduced bolus transit time for both left and right axial arteries (from 1.34 ± 0.39 and 1.81 ± 0.43 s to 0.52 ± 0.17 and 0.89 ± 0.21 s in the left and right axial arteries, respectively). Similar changes were observed with 100% oxygen, but increases in visible vessel number and vessel diameter of the axial arteries were greater in the ventilated right lung during unilateral ventilation. These findings confirm that PBF increase at birth is not spatially related to lung aeration and that the increase in PBF to unventilated regions is unrelated to oxygenation, although oxygen can potentiate this increase.
The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
Justin A R
JA
Lang
Monash Biomedical Imaging Facility and Department of Physiology, Monash University, Melbourne, Australia.|Australian Synchrotron, Melbourne, Australia.
James T
JT
Pearson
The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.|Medical University of Graz, Austria.
Corinna
C
Binder-Heschl
The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
Megan J
MJ
Wallace
The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
Melissa L
ML
Siew
School of Physics and Astronomy, Monash University, Melbourne, Australia.
Marcus J
MJ
Kitchen
Department of Pediatrics, Leiden University Medical Centre, Leiden, Netherlands.
Arjan B
AB
te Pas
Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Australia.
Andreas
A
Fouras
Medical Imaging and Radiation Sciences, Monash University, Melbourne, Australia.|Department of Medical Imaging, University of Saskatchewan, Saskatoon, Canada.
Robert A
RA
Lewis
The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
Graeme R
GR
Polglase
Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan.
Mikiyasu
M
Shirai
The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, Australia.|Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
Stuart B
SB
Hooper
D000818:Animals; D000831:Animals, Newborn; D005260:Female; D006339:Heart Rate; D008168:Lung / Q000098:blood supply / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D011247:Pregnancy; D011651:Pulmonary Artery / Q000502:physiology; D011652:Pulmonary Circulation; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D011817:Rabbits
D010100:Oxygen