Objective: The objective of the study was to examine the superiority of postoperative noninvasive pressure techniques over each other in terms of pulmonary function tests (PFTs), arterial blood gas tests, and lung complication development in pa-tients undergoing major abdominal surgery.Material and Methods: In total, 45 patients aged between 20 and 80 years, with ASA (American Society of Anesthesiologists) I-III, and undergoing major abdominal surgery were equally and prospectively randomized into three groups in terms of the use of post-operative control (Group A), continuous positive airway pressure (Group B), and noninvasive pressure support ventilation (Group C). Preoperatively and at postoperative hour 0, hour 6, and hour 24, hemodynamic and arterial blood gas test data were recorded. Additionally, PFTs and chest radiography were performed using pre- and postoperative techniques.Results: A statistically significant difference was found between the systolic and diastolic blood pressures at postoperative hour 6 among the groups in our study. However, when arterial CO2 pressures at postoperative hour 6 in the groups were compared, they were determined to be higher in Group A than in Groups B and C. In groups of patients with and without the development of atelectasis, significant differences were found in terms of age, operation time, and duration of intensive care stay and hospital stay.Conclusion: Postoperative noninvasive pressure techniques yielded better results in preventing the development of atelec-tasis than control techniques. However, we believe that assessment with arterial blood gas tests and PFTs is also important for preventing and predicting the development of atelectasis as well as considering a patient’s age, smoking history, operation time, and duration of intensive care stay.