Evaluation of Pressure of Arterial Oxygen by Age in Supine Position during General Anesthesia

Background: The concentration of supplemental O2 should be measured during general anesthesia to determine whether patients’ pressure of arterial oxygen (PaO2) is correct. Nevertheless, we do not know standard value of PaO2 by age in supine position during general anesthesia. In this study, we evaluated the PaO2 by age at 33% or 40% O2 concentration. Materials and Methods: We retrospectively reviewed the anesthetic charts of 660 patients who were received general anesthesia from January 2001 to December 2013. Patients were divided into two groups by concentration of fraction of inspiratory oxygen: group at 33% or 40%. Second, patients aged 16 - 85 years were classified into 7 groups by age with each group covering one decade. Results: The PaO2 was 185.1 ± 19.2 mmHg (33%) and 209.8 ± 19.8 mmHg (40%) at age 16 - 25 years, 178.7 ± 23.6 mmHg (33%) and 202.7 ± 26.0 mmHg (40%) at age 26 - 35 years, 165.8 ± 30.6 mmHg (33%) and 188.9 ± 22.2 (40%) mmHg at age 36 - 45 years, 154.1 ± 22.8 mmHg (33%) and 181.8 ± 19.2 (40%) mmHg at age 46 - 55 years, 153.7 ± 21.7 mmHg (33%) and 177.5 ± 18.1 mmHg (40%) at age 56 - 65 years, 152.2 ± 24.5 mmHg and 171.0 ± 22.1 mmHg at age 66 - 75 years, and 154.6 ± 24.3 mmHg and 174.1 ± 20.2 mmHg at age 76 - 85 years. Conclusion: The PaO2 tended to decrease with age at both 33% and 40% O2 concentration.