EVALUATION OF THE EFFECT OF RECRUITMENT MANEUVER ON POSTOPERATIVE ATELECTASIS IN LAPAROSCOPIC CHOLECYSTECTOMY SURGERY USING LUS (LUG ULTRASOUND SCALE)
Conditions: Pulmonary Atelectasis
Sponsor: Fatih Sultan Mehmet Training and Research Hospital

STUDY PROTOCOL 
 
Comparison of Protective versus Conventional Ventilation Strategies on Lung Ultrasound Score in Patients 
Undergoing Laparoscopic Cholecystectomy: A Prospective Randomized Controlled Trial 
 
Protocol Version: 1.0 
Date: 28.03.2025 
IRB Approval Number: 2025-KAEK-43 
 
Principal Investigator: MD, Department of AnesthesiologyInstitution: Fatih Sultan Mehmet Training and 
Research Hospital, Istanbul, Turkey 
 
TABLE OF CONTENTS 
 
1. BACKGROUND AND RATIONALE 
2. STUDY OBJECTIVES 
3. STUDY DESIGN 
4. STUDY POPULATION 
5. RANDOMIZATION AND BLINDING 
6. INTERVENTION 
7. OUTCOME MEASURES 
8. DATA COLLECTION AND MANAGEMENT 
9. STATISTICAL ANALYSIS PLAN 
10. ETHICAL CONSIDERATIONS 
11. INFORMED CONSENT FORM 
12. TIMELINE AND MILESTONES 
 
1. BACKGROUND AND RATIONALE 
 
Laparoscopic cholecystectomy is one of the most commonly performed surgical procedures worldwide. While 
laparoscopy offers numerous advantages over open surgery, the pneumoperitoneum and Trendelenburg 
positioning required during the procedure can lead to significant pulmonary complications, particularly 
atelectasis. 
 
Pneumoperitoneum increases intra-abdominal pressure, which can cause cephalad displacement of the 
diaphragm, reduced functional residual capacity, and subsequent ventilation-perfusion mismatch. These 
physiological changes frequently result in intraoperative and postoperative atelectasis, which can manifest as 
hypoxemia, increased risk of pulmonary infections, and prolonged hospital stay. 
 
Protective ventilation strategies, including the use of low tidal volumes, positive end-expiratory pressure (PEEP), 
and alveolar recruitment maneuvers, have been shown to improve pulmonary outcomes in various surgical 
settings. However, the optimal ventilation strategy during laparoscopic cholecystectomy remains a subject of 
ongoing investigation. 
 
Lung ultrasound has emerged as a valuable, non-invasive tool for real-time assessment of lung aeration and 
detection of atelectasis. The lung ultrasound score (LUS) provides a quantitative measure of pulmonary aeration 
status and has been validated for detecting perioperative pulmonary complications. 
 
This study aims to compare the effects of protective versus conventional ventilation strategies on lung aeration, 
as measured by LUS, in patients undergoing laparoscopic cholecystectomy. 
 
2. STUDY OBJECTIVES 
 
2.1 Primary Objective 
To compare the change in lung ultrasound score (LUS) between protective and conventional ventilation 
strategies in patients undergoing laparoscopic cholecystectomy. 
 
2.2 Secondary Objectives 
- To compare the PaO2/FiO2 ratio between groups at different time points 
- To assess the incidence of postoperative respiratory complications 

- To evaluate intraoperative hemodynamic stability 
- To compare recovery profiles between groups 
 
3. STUDY DESIGN 
 
3.1 Study Type 
Prospective, randomized, controlled trial 
 
3.2 Study Setting 
Department of Anesthesiology and Reanimation, Fatih Sultan Mehmet Training and Research Hospital, Istanbul, 
Turkey 
 
3.3 Study Duration 
Approximately 12-18 months from study initiation to completion 
 
4. STUDY POPULATION 
 
4.1 Inclusion Criteria 
- Age 18-65 years 
- ASA physical status I-III 
- Body Mass Index (BMI) < 30 kg/m² 
- Scheduled for elective laparoscopic cholecystectomy under general anesthesia 
 
4.2 Exclusion Criteria 
- Emergency surgery 
- BMI ≥ 30 kg/m² 
- ASA physical status IV or higher 
- Pre-existing pulmonary disease (COPD, asthma, interstitial lung disease) 
- Cardiac failure (NYHA class III-IV) 
- Neuromuscular disorders 
- Contraindications to pneumoperitoneum 
- Conversion to open cholecystectomy 
- Patient refusal 
 
4.3 Sample Size 
Based on power analysis with α=0.05, β=0.20 (power 80%), and expected difference in LUS of 2 points with SD 
of 2.5, the required sample size is 40 patients per group (total N=80). 
 
5. RANDOMIZATION AND BLINDING 
 
5.1 Randomization 
Patients will be randomized to either the protective ventilation group or conventional ventilation group using 
computer-generated random numbers in sealed envelopes. Randomization will occur after induction of 
anesthesia. 
 
5.2 Blinding 
Due to the nature of the intervention, anesthesiologists cannot be blinded to group allocation. However, lung 
ultrasound assessments will be performed by investigators blinded to group assignment. Postoperative outcome 
assessors will also be blinded to group allocation. 
 
6. INTERVENTION 
 
6.1 Standard Anesthesia Protocol (Both Groups) 
All patients will receive standardized anesthetic management: 
 
Preoperative Assessment: 
- Baseline lung ultrasound examination (8 zones) 
- Baseline LUS calculation 
 
Monitoring: 

- Standard ASA monitoring (ECG, non-invasive blood pressure, SpO2, temperature) 
- Bispectral index (BIS) 
- End-tidal CO2 (EtCO2) 
- Airway pressures (peak, plateau) 
- Dynamic compliance 
 
Induction: 
- Preoxygenation with 100% O2 for 2 minutes 
- Propofol 2 mg/kg IV 
- Fentanyl 2 mcg/kg IV 
- Rocuronium 0.6 mg/kg IV 
- Orotracheal intubation after adequate muscle relaxation 
 
Maintenance: 
- Sevoflurane 1.5-2% in 50% O2/air mixture (2 L/min) 
- Remifentanil infusion 0.05-0.5 mcg/kg/min 
- BIS target: 40-60 
- Normothermia maintained with forced-air warming 
 
Analgesia and Antiemetic Prophylaxis (20 minutes before end of surgery): 
- Paracetamol 1 g IV 
- Tramadol 1 mg/kg IV 
- Ondansetron 4 mg IV 
 
Reversal: 
- Sugammadex 2 mg/kg IV at end of surgery 
- Extubation criteria: spontaneous breathing, BIS ≥85, adequate muscle strength 
 
6.2 Group-Specific Ventilation Protocols 
 
Group 1: Protective Ventilation Strategy 
- Tidal volume: 6-8 mL/kg predicted body weight 
- PEEP: 8 cmH2O 
- Recruitment maneuver before extubation: 
  * Driving pressure: 15 cmH2O 
  * Stepwise PEEP increase: 5 → 10 → 15 cmH2O 
  * Each step held for 10-15 seconds 
  * PEEP maintained at 6-8 cmH2O until extubation 
  * Maneuver stopped if PIP >35 cmH2O 
- Respiratory rate adjusted to maintain EtCO2 35-40 mmHg 
- Volume control mode 
 
Group 2: Conventional Ventilation Strategy 
- Tidal volume: 8-10 mL/kg predicted body weight 
- PEEP: 0-5 cmH2O 
- No recruitment maneuver 
- Respiratory rate adjusted to maintain EtCO2 35-40 mmHg 
- Volume control mode 
 
7. OUTCOME MEASURES 
 
7.1 Primary Outcome 
Change in Lung Ultrasound Score (LUS) from baseline to: 
- 30 minutes after pneumoperitoneum (T1) 
- 30 minutes after desufflation (T2) 
 
LUS Assessment Method: 
- 12-zone lung ultrasound examination 
- Scoring: 0 (normal aeration, A-lines) to 3 (consolidation) per zone 
- Total score range: 0-36 (higher scores indicate worse lung aeration) 

 
7.2 Secondary Outcomes 
- PaO2/FiO2 ratio at T0, T1, T2 
- Incidence of desaturation (SpO2 <90%) 
- Postoperative pulmonary complications (atelectasis, pneumonia) 
- Intraoperative hemodynamic parameters (MAP, HR) 
- Dynamic compliance (Cdyn) 
- Peak inspiratory pressure (PIP) 
- Plateau pressure (Pplat) 
- Duration of surgery and anesthesia 
- Time to extubation 
- Length of hospital stay 
 
8. DATA COLLECTION AND MANAGEMENT 
 
8.1 Time Points for Data Collection 
- T0: After induction, before pneumoperitoneum 
- T1: 30 minutes after pneumoperitoneum 
- T2: 30 minutes after desufflation 
- Postoperative: During hospital stay until discharge 
 
8.2 Data Recording 
All data will be recorded on standardized case report forms and entered into a secure electronic database. Patient 
confidentiality will be maintained using study identification numbers. 
 
8.3 Data Quality Assurance 
- Regular monitoring of data completeness 
- Source data verification for key variables 
- Query resolution process for discrepancies 
 
9. STATISTICAL ANALYSIS PLAN 
 
9.1 Statistical Methods 
 
Primary Outcome Analysis: 
- Independent samples t-test will be used to compare the change in LUS between groups at T1 and T2 
- Repeated measures ANOVA for within-group comparisons across time points 
- Significance level: α = 0.05 (two-sided) 
 
Secondary Outcome Analysis: 
- Continuous variables: Independent samples t-test or Mann-Whitney U test (depending on distribution) 
- Categorical variables: Chi-square test or Fisher's exact test 
- Repeated measures: Mixed-effects models 
 
Subgroup Analyses: 
- Analysis by ASA status 
- Analysis by BMI categories 
- Analysis by surgery duration 
 
9.2 Handling of Missing Data 
- Primary analysis: complete case analysis 
- Sensitivity analysis: multiple imputation if missing data >5% 
 
9.3 Interim Analysis 
No interim analysis is planned due to the short study duration and low risk of intervention. 
 
9.4 Statistical Software 
SPSS version 25.0 or later will be used for all statistical analyses. 
 
9.5 Sample Size Justification 

Based on pilot data and previous studies, we anticipate: 
- Mean LUS change in conventional group: 7.0 ± 2.5 
- Mean LUS change in protective group: 4.5 ± 2.5 
- Clinically significant difference: 2.0 points 
 
Power calculation: 
- Alpha: 0.05 (two-sided) 
- Power: 80% (beta = 0.20) 
- Effect size: 2.0 points 
- Pooled SD: 2.5 
- Required sample size: 40 per group 
- Total: 80 patients 
 
10. ETHICAL CONSIDERATIONS 
 
10.1 Ethical Approval 
This study has been approved by the Institutional Review Board/Ethics Committee of  
Istanbul Provıncıal Dırectorate Of Health  Koşuyolu Hıgh Specıalızatıon Educatıon And Research Hospıtal 
IRB Approval Number: 2025-KAEK-43 
Approval Date: 28.03.2025 
 
10.2 Informed Consent 
Written informed consent will be obtained from all participants before enrollment. The informed consent form 
(see Section 11) explains: 
- Study purpose and procedures 
- Potential risks and benefits 
- Right to withdraw at any time without affecting medical care 
- Confidentiality protections 
 
10.3 Patient Safety 
- All interventions are within accepted clinical practice 
- Continuous monitoring during anesthesia 
- Immediate management of any adverse events 
- Stopping criteria clearly defined (e.g., PIP >35 cmH2O during recruitment) 
 
10.4 Data Protection 
- Patient data will be anonymized using study ID numbers 
- Electronic data stored in password-protected databases 
- Access limited to study personnel 
- Data retention as per institutional policy 
 
10.5 Adverse Event Reporting 
All adverse events will be documented and reported to the IRB according to institutional guidelines. 
 
11. INFORMED CONSENT FORM 
 
Study Title: Comparison of Protective versus Conventional Ventilation Strategies on Lung Ultrasound Score in 
Patients Undergoing Laparoscopic Cholecystectomy 
 
Principal Investigator: Cansu Ofluoglu, MD 
Institution: Fatih Sultan Mehmet Training and Research Hospital 
IRB Approval Number: 2025-KAEK-43 
 
INTRODUCTION 
You are being invited to participate in a research study. Before you decide to participate, it is important for you 
to understand why the research is being done and what it will involve. Please take time to read the following 
information carefully. 
 
PURPOSE OF THE STUDY 

This study aims to compare two different breathing strategies during your laparoscopic gallbladder surgery to 
determine which provides better lung function. During laparoscopic surgery, carbon dioxide gas is used to inflate 
your abdomen, which can sometimes affect your lungs. We want to find the best way to support your breathing 
during this procedure. 
 
STUDY PROCEDURES 
If you agree to participate: 
 
1. Before Surgery: 
   - We will perform a lung ultrasound examination (painless, similar to pregnancy ultrasound) 
   - This takes about 5-10 minutes 
 
2. During Surgery: 
   - You will receive standard anesthesia care 
   - You will be randomly assigned (like flipping a coin) to one of two groups: 
     * Group 1: Protective breathing strategy with gentle lung inflation at the end of surgery 
     * Group 2: Standard breathing strategy currently used in our hospital 
   - We will monitor your breathing and vital signs continuously (standard practice) 
 
3. After Surgery: 
   - Another lung ultrasound examination 30 minutes after surgery 
   - Standard recovery room care 
   - We will monitor for any breathing problems during your hospital stay 
 
Total additional time for study procedures: approximately 15-20 minutes 
 
RISKS AND DISCOMFORTS 
The risks of participating in this study are minimal: 
- Lung ultrasound: No known risks (uses sound waves, no radiation) 
- Breathing strategies: Both are commonly used in anesthesia practice 
- Possible temporary discomfort during lung inflation maneuver (you will be asleep) 
- All procedures will be stopped immediately if any problems occur 
 
BENEFITS 
Potential benefits: 
- You may have better lung function after surgery 
- The information gained may help improve care for future patients undergoing similar surgery 
 
There is no guarantee that you will personally benefit from participation. 
 
ALTERNATIVES TO PARTICIPATION 
Your alternative is to receive standard anesthesia care without the research procedures (lung ultrasound and 
specific breathing strategy assignment). This will not affect the quality of your surgical or anesthesia care. 
 
CONFIDENTIALITY 
Your personal information will be kept strictly confidential: 
- You will be assigned a study identification number 
- Your name will not appear in any reports or publications 
- Only the research team will have access to identifiable information 
- Study data will be stored securely for [INSERT PERIOD] years 
 
VOLUNTARY PARTICIPATION 
- Your participation is completely voluntary 
- You may refuse to participate or withdraw at any time 
- Your decision will not affect your medical care in any way 
- You do not need to provide a reason for withdrawal 
 
COMPENSATION 
There is no financial compensation for participation. You will not incur any additional costs. 
 

CONTACT INFORMATION 
If you have questions about the study, please contact: 
Cansu Ofluoğlu, +905358640564 
 
If you have questions about your rights as a research participant, contact: 
Istanbul Provincial Directorate of Health Koşuyolu High Specialization Education and Research 
Hospital Clinical Research Ethics Committee  
Phone: +90 216 459 4440  
Email: kosuyolu.kek@saglik.gov.tr 
 
CONSENT 
I have read and understood the information provided above. I have had the opportunity to ask questions and all 
my questions have been answered satisfactorily. I understand that my participation is voluntary and that I am free 
to withdraw at any time without giving a reason and without affecting my medical care. 
 
12. TIMELINE AND MILESTONES 
 
Month 1-2: 
- IRB approval finalization 
- Staff training on lung ultrasound technique 
- Case report form development 
 
Month 3-14: 
- Patient recruitment and enrollment 
- Data collection 
 
Month 15-16: 
- Data cleaning and analysis 
- Manuscript preparation 
 
Month 17-18: 
- Results dissemination 
- Study completion report 
 
REFERENCES 
 
1. Futier E, Constantin JM, Paugam-Burtz C, et al. A trial of intraoperative low-tidal-volume ventilation in 
abdominal surgery. N Engl J Med. 2013;369(5):428-437. 
 
2. Bluth T, Serpa Neto A, Schultz MJ, et al. Effect of Intraoperative High Positive End-Expiratory Pressure 
(PEEP) With Recruitment Maneuvers vs Low PEEP on Postoperative Pulmonary Complications in Obese 
Patients: A Randomized Clinical Trial. JAMA. 2019;321(23):2292-2305. 
 
3. Acosta CM, Maidana GA, Jacovitti D, et al. Accuracy of transthoracic lung ultrasound for diagnosing 
anesthesia-induced atelectasis in children. Anesthesiology. 2014;120(6):1370-1379. 
 
4. Bouhemad B, Brisson H, Le-Guen M, Arbelot C, Lu Q, Rouby JJ. Bedside ultrasound assessment of positive 
end-expiratory pressure-induced lung recruitment. Am J Respir Crit Care Med. 2011;183(3):341-347. 
 
5. Güldner A, Kiss T, Serpa Neto A, et al. Intraoperative protective mechanical ventilation for prevention of 
postoperative pulmonary complications: a comprehensive review of the role of tidal volume, positive end-
expiratory pressure, and lung recruitment maneuvers. Anesthesiology. 2015;123(3):692-713. 
 
6. Tusman G, Böhm SH, Warner DO, Sprung J. Atelectasis and perioperative pulmonary complications in high-
risk patients. Curr Opin Anaesthesiol. 2012;25(1):1-10. 
 
7. Ball L, Costantino F, Orefice R, et al. Intraoperative mechanical ventilation: state of the art. Minerva 
Anestesiol. 2017;83(10):1075-1088. 
 

8. Monastesse A, Girard F, Massicotte N, Chartrand-Lefebvre C, Girard M. Lung ultrasonography for the 
assessment of perioperative atelectasis: A pilot feasibility study. Anesth Analg. 2017;124(2):494-504. 
 
9. Severgnini P, Selmo G, Lanza C, et al. Protective mechanical ventilation in the operating room: effect on 
postoperative pulmonary complications: a randomized controlled trial. Anesthesiology. 2013;118(6):1307-1321. 
 
10.Erlandsson K, Odenstedt H, Lundin S, Stenqvist O. Positive end-expiratory pressure optimization using 
electric impedance tomography in morbidly obese patients during laparoscopic gastric bypass surgery. Acta 
Anaesthesiol Scand. 2006;50(7):833-839. 
 
APPENDICES 
 
Appendix A: Lung Ultrasound Scoring Protocol 
Appendix B: Case Report Forms 
Appendix C: Data Collection Sheets 
Appendix D: IRB Approval Letter