In the bi-variable logistic regression analysis, variables like age, ASA, preoperative anemia, category of surgery, preoperative Spo2, duration of surgery, NG tube in situ, intraoperative blood loss, post-operative albumin, and post-operative fasting blood glucose had a p-value of <0.2 and were considered as potential factors associated with post-operative pulmonary complications (Table 3). This evidence concerns the gene ALB and anemia (phenotype).