Objective:

Pneumoperitoneum resulted into alteration in gas exchange is due to intraoperative atelectasis resulting in collapse of alveoli and increase in resistance of airways which leads to intrapulmonary shunting, ventilation perfusion mismatch and ultimately arterial hypoxemia. In a recent pilot study on the model of laparoscopic surgery-induced atelectasis demonstrated the feasibility of lung ultrasonography during the perioperative period. Lung ultrasonography also allowed the tracking of perioperative atelectasis and facilitates the diagnosis of respiratory complications. Studies demonstrated that in patients undergoing laparoscopic cholecystectomy, the open lung approach was suitable for bedside PEEP setting, improved lung mechanics and gas exchange without significant adverse hemodynamic effects.

We therefore planned a study to evaluate effect of different lung maneuver on modified lung ultrasound score with the use of point of care lung ultrasound during laparoscopic cholecystectomy.

Methods

This prospective randomized double blind controlled study will be conducted in patients of age of 18 to 60 years , of either sex , belonging to ASA physical status of I and II undergoing laparoscopic cholecystectomy surgery under GA. Patient with morbid obesity, history of smoking or chronic respiratory disease, bronchial asthma, cardiac, pulmonary, renal or neuromuscular disorders, contraindication of laparoscopic surgery and patient with history of previous abdominal surgery will be excluded from this study

All patients will be given anesthesia as per departmental protocol. Tidal volume will be set at 8ml/kg of predicted body weight, FiO2 0.40, respiratory rate of 12 / minute adjusted to obtain an end tidal carbon dioxide 35+ 2, inspiratory to expiratory ratio of 1:2, and no positive end-expiratory pressure (PEEP). Pneumoperitoneum during laparoscopic cholecysytecomy will be maintained with co₂ insufflated in abdomen to pressure of 15 mm of Hg.

Depending upon the computer generated random number patient has been assigned the any of the three groups. In control group (group I): No application of PEEP or alveolar recruitment before extubation. In Alveolar recruitment group 5 (group II): PEEP of 5 cm of H₂O will be applied 10 min before extubation and will be maintained till extubation. Alveolar recruitment group 10 (group III): PEEP of 10 cm of H₂O will be applied 10 min before extubation and will be maintained till extubation. For safety reason, working pressure of ventilator will be limited to 30cm of H₂O. PEEP will be increased to desired level after obtaining the information of hemodynamic state of the individual patient. Lung ultrasonography will be performed by 2 trained echographists (DG and RV respectively, with 10 years and 3 years of experience in lung ultrasonography) using a convex array 2- to 5-MHz transducer. Aeration loss will be assessed by calculating the modified LUS score in each of the 12 quadrants. Images will be obtained at 5 predefined time points: before GA induction (time point A), 5 minutes after GA induction (time point B), after pneumoperitoneum and before recruitment maneuver (time point C), 10 minutes after the arrival of patients in the recovery room (time point D), and 60 minutes after the arrival of patients in the recovery room or immediately before the discharge from the recovery room  (time point E). Care will be taken to set the focal zone on the pleural line. No second harmonic imaging will be used. Thorax will be divided into 12 quadrants (Figure 1): anterior, lateral, and posterior zones (separated by the anterior and posterior axillary lines) each divided in upper and lower portions for the right and left lung. Intercostal spaces of each of these areas will be scanned and a cine-loop of the most pathologic area of each quadrant will be saved to digital format for offline analysis.

Primary outcome will be the effect of different lung recruitment maneuvers on modified lung ultrasound score. Secondary outcome will be postoperative complications and pain score. To test the effect of different lung recruitment maneuvers on modified LUS, sample size will be taken 30 patients in each of the three study groups with total of 90 patients.