Diaphragm Ultrasound and Neuromuscular Monitoring for Predicting Early Respiratory Events After Extubation

The goal of this prospective observational study is to learn whether diaphragm ultrasound and quantitative neuromuscular monitoring can predict early respiratory events after extubation in adults having elective surgery under general anesthesia. The main questions it aims to answer are: * Are lower diaphragm thickening fraction and diaphragm excursion before extubation associated with early respiratory events after extubation? * How well do diaphragm ultrasound parameters and the train-of-four (TOF) ratio predict these events? Participants will receive their usual anesthesia care. Diaphragm ultrasound will be performed at four time points: before induction of anesthesia, 5 minutes after induction, before extubation, and 30 minutes after extubation in the post-anesthesia care unit (PACU). The TOF ratio will be recorded with routine quantitative neuromuscular monitoring. Respiratory events will be recorded from extubation until discharge from the PACU.

Inclusion Criteria: * Age 18-75 years * ASA physical status I-III * Elective surgery under general anesthesia * Supine position during surgery * Use of a neuromuscular blocking agent during surgery * Quantitative TOF monitoring available before extubation * Adequate ultrasound window for diaphragm assessment * Written informed consent Exclusion Criteria: * Refusal to participate * Emergency surgery * ASA physical status IV or higher * Pregnancy * Known diaphragm paralysis or phrenic nerve injury * Previous diaphragm or thoracic surgery * Moderate-to-severe COPD, advanced restrictive lung disease or severe respiratory failure * Neuromuscular disease (e.g., myasthenia gravis, myopathy) * Preoperative need for invasive or non-invasive mechanical ventilation * Hemodynamic instability or vasopressor requirement * Inability to obtain diaphragm ultrasound images * Extubation not planned at the end of surgery * Planned postoperative intensive care unit admission