“…In this study, we included age, biological sex, marital status, race and ethnicity, admission source (i.e., home, skilled nursing facility, or other facilities), and insurance payor (i.e., Medicare or other) as the controlled patient demographic characteristics. Discharge disposition (i.e., home or non-home) was included as a candidate covariate for hospital length of stay; patients who are discharged to non-home locations tend to have longer hospital length of stay (Dang et al, 2022). To control for perioperative health status, we included body mass index (BMI), Charlson Comorbidity Index (CCI), preoperative serum hemoglobin level, preoperative serum albumin measurement, SpO 2 , preoperative respiratory condition (i.e., Category 1 = no supplemental oxygen; Category 2 use of supplemental oxygen with FiO 2 < 60% longer than 24 hours postoperatively; Category 3 = use of supplemental oxygen with FiO 2 ≥ 60%, or high flow oxygen via nasal cannula, or both; Category 4 = use of noninvasive ventilatory support or invasive ventilatory support), American Society of Anesthesiologist (ASA) physical status, and admission to ICU during hospitalization.…”