Adequate postoperative analgesia is difficult to achieve in patients undergoinglaparoscopic sleeve gastrectomy (LSG). Epidural anesthesia is technically difficult dueto subcutaneous fat, which increases the risk of serious complications. Moreover,patients in this condition often have comorbidities that require anticoagulation therapy.Although ultrasound-guided Transversus Abdominis Plane (TAP) block may be useful, it isstill controversial.Recently, modified thoracoabdominal nerve block via perichondrial approach (M-TAPA) hasbeen reported as a new and promising technique that provides effective analgesia in theanterior and lateral thoracoabdominal wall.The most common reason for hospitalization after laparoscopic surgery is pain afternausea and vomiting. In addition, superficial and tachypneic breathing resulting from thepatient's inability to breathe deeply with pain causes closure of small airways andincrease in intrapulmonary shunts, resulting in hypoxia. Postoperative pain management isimportant not only to prevent pain but also to reduce pulmonary complications that mayoccur due to changes in lung function and to reduce mortality and morbidity bycontrolling the stress response.In this study, The investigators investigated the effect of modified thoracoabdominalnerve block via perichondrial approach (M-TAPA) on pulmonary function in patientsundergoing laparoscopic bariatric surgery under general anesthesia.