Oxygen and Reduced Umbilical Blood Flow Trigger the First Breath of Human Neonates


Dr Hajime Togari, Department of Pediatrics, Nagoya City University, Kawa-sumi 1, Mizuho-ku, Nagoya 467, Japan.


The mechanism triggering the first breath of human neonates is still unclear. In order to investigate the role of oxygen and umbilical blood flow in the onset of the first breath, a total of 20 rat and rabbit fetuses were studied. AH five rat fetuses delivered in a nitrogen chamber did not commence breathing of their own accord, whereas all five rabbit fetuses delivered in oxygenated fluorocarbon fluid commenced their own breathing, suggesting that contact with oxygen rather than release from submergence is more crucial in the initiation of the first breath.