Abstract
Right to left shunt determinations in newborn infants have suggested that alveoli are unstable with inspired oxygen concentrations of 100%. Theoretically alveoli with very low VA/Q ratios should collapse with inspired 100% oxygen, resulting in a decrease in alveolar-arterial nitrogen difference (A-ADN2) and an increase or no change in alveolar-arterial oxygen difference (AaDO2), and an increase or no change in shunt.
Four newborn lambs were ventilated at constant tidal volume initially with 40% oxygen for 1½ hours, then with 100% oxygen for 3 hours and then returned to 40% oxygen for 1½ hours. Arterial and mixed venous blood was sampled at the end of each period and analyzed for PO2, PN2, PCO2. Alveolar PO2 and PN2 were calculated.
Three lambs (Table) had a large number of alveoli with very low VA/Q. Decrease in a a-ADN2, with an increase in A-aDO2 and shunt, indicates conversion of alveoli with very low VA/Q to alveoli with collapse.
One lamb had a small number of alveoli with low VA/Q. In this animal no changes were anticipated nor found with 100% O2 inhalation.
It is concluded that in the newborn period, alveoli with very low VA/Q may collapse with inspired 100% O2.
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Parks, C., Alden, E., Woodrum, D. et al. Alveolar instability with inspired 100% O2 in the newborn lung. Pediatr Res 5, 429 (1971). https://doi.org/10.1203/00006450-197108000-00242
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DOI: https://doi.org/10.1203/00006450-197108000-00242