Postoperative pulmonary complications (PPCs) are adverse outcomes following major elective upper abdominal surgeries, with atelectasis being one of the most common [l .PPC are major source of morbidity and mortality for patients undergoing abdominal surgeries [5]. Atelectasis, characterized by the partial or complete collapse of lung tissue,[4] can contribute to hypoxemia, prolonged hospital stays, and increased morbidity. Atelectasis is defined as lung opacification with a shift of the mediastinum, hilum, or hemidiaphragm towards affected area and compensatory overinflation in the adjacent non atelectactic lung on chest X-rays[2] .Atelectasis has been reported to contribute to postoperative pulmonary complications through ventilation perfusion mismatch, reduced alveolar clearance, or structural dysfunction [3]. Traditional methods for diagnosing atelectasis, such as chest X-rays and computed tomography scans, may have limitations in sensitivity, accessibility, and radiation exposure and atelectasis is not evident on conventional chest X-rays until it’s significant [1,4] . Lung ultrasonography (LUS) has emerged as a reliable, non-invasive, bedside tool for detecting atelectasis, offering real-time imaging with high diagnostic accuracy, successfully predicting the severity of pulmonary complications compared to computed tomography [5]. This study aims to estimate the incidence of postoperative atelectasis in patients undergoing major elective upper abdominal surgeries using lung ultrasonography. By identiWing the frequency and severity of atelectasis, this research may help improve early detection, guide preventive strategies, and optimize perioperative respiratory care, ultimately enhancing patient outcomes.

After obtaining IEC approval, patients who meet the inclusion criteria and consenting for the study will be enrolled. Preoperative assessment of patients like demographics-name,age,sex, ASA score,height, weight,BMI will be noted. Any comorbidities like diabetes, hypertension ,asthma, history of smoking and other habits will be noted . Surgical diagnosis and procedure planned will be noted. Preoperatively, before induction of anesthesia ultrasound of lungs will be done and ultrasound scores of upper anterior, lower anterior, and PLAPs points will be noted with the patient in supine position. Ultrasound of lungs will be done with new ultrasound machine Versana active and curvilinear probe will be used. PLAPS point is Posterolateral Alveolar And/or Pleural Syndrome Point located in posterolateral chest wall between the posterior axillary line and the paravertebral region often at the level of diaphragm. To find the upper and lower points, place 4 fingers (except the thumb) of the left hand below the clavicle , on the right side of the patient with the fingertips on the sternum. The upper point is at the base of the second and third fingers. The lower point is in the centre of the palm when the right hand is placed below the left with the forefingers touching. Then we will switch sides and repeat the same. To scan base of the lungs at the thoracoabdominal border, move from lower blue point around the chest wall to the posterior axillary line. B lines will be observed. B lines, also called comet tails are vertical artefacts that appear as echogenic lines and extend from the pleural line into the lung parenchyma. They are created by discreet short path reverberation artifacts due to interstitial edema,increased fluid, or fibrosis in the interlobular septae seen in conditions like pulmonary edema, interstitial lung diseases and pneumonia. Score 0 is given for normal aeration with LUS showing 0-2 B lines. Score I is given for small loss of aeration, with LUS showing greater than or equal to 3 B lines. Score 2 is given for moderate loss of aeration with multiple coalescent B lines on LUS. Score 4 is given for severe loss of aeration with tissue sign positive ( atelectasis) on LUS. The maximum score is 3 for each lung area and total scoring is out of 18. Inside the operation theatre, standard monitors will be attached. General anaesthesia, induction and maintenance of anaesthesia will be done as per standard protocols. Ventilatory parameters are standardized according to : Mode : Volume Controlled Tidal Volume: 6-8 ml/kg Respiratory Rate: 12-14 Inspiratory : Expiratory ratio : 1:2 Positive End Expiratory Pressure (PEEP) : 5-6 cm H20 Choice of analgesia will be chosen as per discretion of concerned anesthesiologists. After extubation patient will be shifted to postoperative recovery area and then Lung ultrasound will be repeated in recovery room after 30 minutes after extubation as per protocols. LUS scores will be evaluated. Subsequently patient will be followed up for 5 days. Vitals, patient level of consciousness, body temperatures will be noted along with need for any ventilatory support/reintubation, oxygen support, ICU admission, mode of analgesia ,method of physiotherapy and need of any bronchodilators. Chest Xray will be noted on postoperative days land 3. Postoperative pulmonary complications will be assessed like pneumonia, pneumothorax etc.Pneumonia is defined as two or more serial chest Xrays showing new infiltrates and atleast two of the following clinical findings: l.Fever, 2. New onset worsening cough or dyspnea, 3.new onset purulent sputum or increased secretions or 4. Bronchial breathing or rales,5. Decrease in Sp02, 6. Leucopenia/ leucocytosis. Total length of hospital stay of the patient will be noted. Incidence of Atelectasis will be calculated based on lung USG. Preoperative and intraoperative factors will be correlated with incidence of atelectasis. Atelectasis will be correlated with incidence of pneumonia , ICU stay and length of hospital stay.