Peak Expiratory Flow Variability after Abdominal Surgery: A Prospective Observational Study in Peru.

Introduction: Peak Expiratory Flow (PEF) is a practical marker of airway patency and cough effectiveness, yet perioperative evidence from Latin American surgical populations is limited. This study aimed to quantify postoperative PEF variability after abdominal surgery and identify associated factors. Methods: We conducted a prospective observational study at a Peruvian hospital in 2024. Adults undergoing elective abdominal surgery performed PEF testing with a Mini-Wright meter preoperatively and on postoperative day 7 using a standard three-maneuver protocol. The highest valid value was retained. The primary outcome was PEF variability, defined as the difference between preoperative and postoperative PEF (L/min). Group comparisons used non-parametric tests, and multivariable linear regression identified independent predictors. Results: Eighty-two patients were included; 58.5% were women, and the median age was 48 years. Mean preoperative and postoperative PEF values were 367.9 ± 71.9 and 346.0 ± 74.8 L/min, respectively. Median PEF variability was 20 L/min (IQR 10-30). Variability did not differ by sex or BMI. Age was the only independent predictor of greater decline. Discussion: Abdominal surgery was associated with an early postoperative reduction in expiratory flow, particularly in older adults. Conclusion: Routine perioperative PEF assessment may help identify patients who require closer respiratory monitoring and early supportive therapy in resource-constrained surgical settings.