Bootstrap confidence intervals to assess risk factors for early postoperative pulmonary complications after abdominal surgery

Importance. Early postoperative pulmonary complications (EPPCs) after abdominal surgery increase morbidity, mortality, and healthcare costs. Objective. This study aimed to identify risk factors for EPPCs using only easily collected clinical data from a local population. Design, Setting, and Population From December 1, 2020, to December 31, 2021, a singlecenter, prospective cohort study was conducted at Batna University Hospital in Algeria. Adult patients undergoing abdominal surgery under general anesthesia were enrolled, and ten preoperative parameters were analyzed. Exposures. Advanced age over 50, previous laparotomy, a history of chronic obstructive pulmonary disease, uncontrolled diabetes, urgent surgery, chronic corticosteroid use, active smoking, unbalanced diabetes, a preoperative stay of ≥3 days, obesity, and preoperative blood transfusions. Main Outcomes and Measures The crude associations between EPPCs and ten preoperative factors were assessed using univariate analyses. Statistical significance was defined as a two-sided pvalue < 0.05 with 95% confidence intervals excluding 1. After dichotomizing all variables, associations were tested by the chi-square test, and bootstrap methods were applied to estimate 95% confidence intervals for the odds ratios. Results. Of 1,058 eligible patients, 741 were included, with 49 (6.6%) developing EPPCs. Among them, 20.4% had ARDS, 44.9% had pulmonary infections, and 34.7% experienced lung collapse. Half of the EPPCs cases had additional complications, mainly surgical site infections, with one EPPCrelated death. Univariate analysis identified eight significant risk factors: age ≥50 (OR 4.9), anterior laparotomy (OR 3.8), COPD (OR 7.5), preoperative stay ≥3 days (OR 3.6), unbalanced diabetes (OR 4), obesity (OR 2.7), active smoking (OR 3.3), and perioperative transfusion (OR 2.6) (all p < 0.05). The bootstrap confidence intervals showed that only six factors were significantly associated. Conclusions and Relevance. This study applied bootstrap techniques that produced stable estimates with low bias, thus strengthening the validity of the observed associations and the reliability of the inferences. Although some of the identified factors can be modified in elective surgeries, such adjustments are generally not feasible during emergency procedures.