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Reassessment of the Assumed A-V Oxygen Content Difference in the Shunt Calculation

HARRISON, RONALD A. M.D.; DAVISON, RICHARD M.D.; SHAPIRO, BARRY A. M.D.; MEYERS, SHERIDAN N. M.D.
Anesthesia & Analgesia: March-April 1975
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A study was undertaken in 15 patients to compare measured and assumed arteriovenous oxygen (A-V O2) content differences and their effects on resultant shunt calculations. All patients were on volume ventilators and demonstrated a stable cardiovascular state. Simultaneous measurements of the O2 content of a pulmonary artery (PA) and of a superior rena cava (SVC) sample were compared. A mean A-V O2 content difference of 3.5 ± 0.8 volumes percent was obtained from the PA and 2.6 ± 1.1 volumes percent from the SVC. The resultant shunt calculations derived from measured A-V O2 content differences were compared with the calculation based on an assumed A-V O2 content difference of 5 volumes percent. A method for extrapolating a “true” A-V O2 content difference from an SVC blood sample was obtained. The extrapolated value resulted in a more representative “true shunt” calculation in 13 of the 15 patients.

This study was supported in part by Grants USPHS No. GM01693 and No. GM015420.

© 1975 International Anesthesia Research Society