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.