Effects of Individualized PEEP Guided by Driving Pressure on Postoperative Atelectasis in Patients With Morbid Obesity

Study Overview
=================
Brief Summary
-----------------
Atelectasis is a common complication in patients undergoing surgery under general anesthesia, particularly in obese patients. Postoperative atelectasis could last for more than 24h and contribute to a variety of other complications, including hypoxemia and pneumonia. We plan to conduct a single-center, randomized controlled trial in patients undergoing bariatric surgery to test the hypothesis that driving pressure guided PEEP could reduce the postoperative atelectasis.

Detailed Description
-----------------
Positive end-expiratory pressure (PEEP) is a strategy that helps to keep alveoli open during surgery and to prevent postoperative atelectasis. A fixed PEEP without considering the respiratory mechanics in individual patients, however, is not optimal. Individualized PEEP therefore has been increasingly studied, and has been shown to improve oxygenation in both nonobese and obese patients. Studies have shown that the occurrence and prognosis of PPCs are significantly associated with high driving pressure (DP), but not with VT and PEEP. Driving pressure-guided individualized PEEP is expected to be a novel perioperative lung protection strategy. Consequently, the main aim of this study is to investigate the effect of a driving pressure-guided individualized PEEP ventilation strategy on postoperative pulmonary atelectasis in morbidly obese patients undergoing bariatric surgery.

Official Title
-----------------
Effects of Individualized Positive End-expiratory Pressure Guided by Driving Pressure on Postoperative Atelectasis After Bariatric Surgery in Patients With Morbid Obesity: A Single-center, Prospective, Randomized Controlled Study

Conditions
-----------------
Pulmonary Atelectasis, Obesity, Morbid

Intervention / Treatment
-----------------
* Procedure: Individualized PEEP group
* Procedure: Fixed PEEP group


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: 1.Age 18 to 60 years old; 2.Body mass index (BMI) ≥ 40 kg/m2; 3.ASA classification I to III; 4.signing the informed consent form for this clinical study; Exclusion Criteria: 1.Respiratory infection within 4 weeks; severe respiratory system diseases; history of pulmonary and/or thoracic surgery; neuromuscular dysfunction; 2.Serious cardiac, renal or haematopoietic diseases; 3.Contraindications to PEEP；

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Individualized PEEP group<br>After recruitment maneuver, PEEP is titrated decreasingly using driving pressure guided individualised PEEP ventilation strategy, and the PEEP corresponding to the lowest driving pressure is the individualised PEEP. | Procedure: Individualized PEEP group<br>* Individualized PEEP group: Recruitment Maneuver (RM) is performed first. In pressure control mode, PEEP and airway plateau pressure are increased to 20 cmH2O and 35 cmH2O at a rate of 5 cmH2O every 30s, and driving pressure is maintained at 15 cmH2O throughout. Subsequently, in volume-controlled ventilation mode, PEEP decreases from 20 cmH2O to 4 cmH2O at gradient of 2 cmH2O, and each PEEP level is maintained for 30s. The PEEP corresponding to the lowest driving pressure is the individualized PEEP we need. If multiple PEEP levels showed the same lowest driving pressure, the lowest PEEP value as the individualized PEEP. The above procedures are performed three times during the surgery (5 minutes after intubation,5 minutes after the beginning of pneumoperitoneum, and 5 minutes after the end of pneumoperitoneum).<br>|
| Other: Fixed PEEP group<br>After recruitment maneuver, PEEP is fixed at 8cmH2O. | Procedure: Fixed PEEP group<br>* After the same RM, PEEP is fixed at 8 cmH2O.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence of postoperative pulmonary atelectasis | The primary outcome of this study is postoperative atelectasis measured by lung ultrasound. Each hemithorax is divided into 6 regions using 3 longitudinal lines (parasternal, anterior and posterior axillary)and 2 axial lines (one above the diaphragm and the other 1 cm above the nipples). The 12 lung regions were scanned sequentially from right to left, cranial to caudal and anterior to posterior. Each region is assessed using a 2-dimen-sional view with the probe placed parallel to the ribs. It distinguishes four progressive steps of loss of aeration according to the artifacts visualized in a scan: score 0, normal aeration (A-lines or no more than two B-lines); score 1, moderate loss of aeration (three or more well-spaced B-lines); score 2, severe loss of aeration(coalescent B-lines); and score 3, complete loss of aeration(tissue-like pattern). We define atelectasis to be significant if any region had a lung consolidation score of ≥2. | After 30 minutes of extubation | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postoperative pulmonary ultrasound score | Each hemithorax is divided into 6 regions using 3 longitudinal lines (parasternal, anterior and posterior axillary)and 2 axial lines (one above the diaphragm and the other 1 cm above the nipples). The 12 lung regions were scanned sequentially from right to left, cranial to caudal and anterior to posterior. Each region is assessed using a 2-dimen-sional view with the probe placed parallel to the ribs. It distinguishes four progressive steps of loss of aeration according to the artifacts visualized in a scan: score 0, normal aeration (A-lines or no more than two B-lines); score 1, moderate loss of aeration (three or more well-spaced B-lines); score 2, severe loss of aeration(coalescent B-lines); and score 3, complete loss of aeration(tissue-like pattern). We define atelectasis to be significant if any region had a lung consolidation score of ≥2. Based upon the LUS scoring system, each area is scored from 0-3, so a minimum zero or maximum 36 score is possible. | After 30 minutes of extubation | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Individual Positive End-expiratory Pressure, Driving Pressure, Ventilator-induced Lung Injury