The distribution of ventilation-perfusion ratios in the lungs of a dysmature foal.
The distribution of ventilation-perfusion (VA/Q) ratios, before and after 100 per cent oxygen, was studied in an induced-premature foal at 4 h and again at eleven days of age, using the multiple inert gas elimination technique. The major finding was an absence of low VA/Q ratios when breathing air, indicating that low PaO2 in the neonatal period was totally attributable to the right-to-left shunt. At 4 h of age the PaO2 was 5.48 kPa and the right-to-left shunt represented 33.4 per cent of the cardiac output. At eleven days of age the PaO2 was 9.76 kPa and right-to-left shunt was 10.1 per cent of cardiac output. At both ages there was a separate high mode where ventilation was greatly in excess of blood flow but at neither age were units with low VA/Q ratios present. Oxygen breathing for 40 mins did not increase the right-to-left shunt, but at eleven days right-to-left shunt decreased when 100 per cent oxygen was administered.
Stewart
J H
JH
Department of Veterinary Clinical Sciences, Faculty of Veterinary Sciences, University of Sydney, N.S.W., Australia.
Rose
R J
RJ
Young
I H
IH
Costas
L
L
D000136:Acid-Base Equilibrium; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001784:Blood Gas Analysis / Q000662:veterinary; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output; D006736:Horses / Q000502:physiology*; D008168:Lung / Q000502:physiology*; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood; D014692:Ventilation-Perfusion Ratio
D002245:Carbon Dioxide; D010100:Oxygen