Table of Contents

HK J Paediatr (New Series)
Vol 2. No. 1, 1997

HK J Paediatr (New Series) 1997;2:89

Proceedings of Scientific Meeting

Functional FiO2 Predicts Alveolar pO2 during Perfluorocarbon-associated Gas Exchange

LJ Hernan, S Penfil, BP Fuhrman, MS Dowhy, MC Papo, CL Leach

HK J Paediatr (new series) 1997;2:81-97

Chinese Paediatric Forum
Department of Paediatrics, The University of Hong Kong
November 15-17, 1996

Perfluorocarbon-associated gas exchange or partial liquid ventilation (gas ventilation of the liquid-filled lung) supports gas exchange in patients with lung disease. Perflubron, a perfluorocarbon suitable for the gas exchange process, can carry 50 ml O2 per 100 ml while an equal volume of gas has twice that capacity. Owing to this limited solubility, uptake of O2 by blood reduces alveolar pO2 more during gas exchange than during gas ventilation. The alveolar gas equation overestimates alveolar pO2 and calculations using this variable during perfluorocarbon-associated gas exchange. Functional FiO2 is the theoretical FiO2 predicted by the alveolar gas equation to yield the pO2 measured in tracheal perflubron during this gas exchange. We hypothesize there exists a consistent relationship between the FiO2 during gas exchange and the functional FiO2. Ten piglets had perflubron (30 ml/kg) instilled into the trachea. FiO2 was randomly varied between 0.45 and 1.0. At each FiO2, alveolar pO2 was estimated using the alveolar gas equation and by directly measuring the pO2 of perflubron. An equation was derived to describe the relationship between FiO2 during gas exchange and functional FiO2. Functional FiO2= 0.72* (FiO2 during perfluorocarbon-associated gas exchange) + 0.059. At a full liquid functional residual capacity, functional FiO2 predicts the pO2 of perflubron and will be a more accurate measurement of alveolar PO2.


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