An observational study in Atelectasis, Perioperative Oxygenation and Laparoscopic Inguinal Hernia Repair, sponsored by Fatih Sultan Mehmet Training and Research Hospital. Not yet recruiting at 1 site in Turkey (Türkiye). Open to participants aged 18 Years to 75 Years. Per ClinicalTrials.gov, last updated 2026-08-20.
Sponsored by Fatih Sultan Mehmet Training and Research Hospital · Observational
During laparoscopic surgery under general anesthesia, lung function can be affected by increased abdominal pressure and patient positioning. Positive end-expiratory pressure (PEEP) is a ventilator setting that helps keep the lungs open during surgery. In standard practice, a fixed PEEP level is applied to all patients. An individualized PEEP approach tailors this setting to each patient based on lung recruitment maneuvers.
This study investigates whether individualized PEEP improves oxygenation compared to standard PEEP in patients undergoing laparoscopic inguinal hernia surgery. Oxygenation will be continuously monitored using the Oxygen Reserve Index (ORI), a non-invasive sensor. Lung aeration will also be assessed before and after surgery using bedside lung ultrasound.
General anesthesia combined with pneumoperitoneum and Trendelenburg positioning significantly alters respiratory mechanics. These changes can reduce functional residual capacity (FRC), promote atelectasis, and impair gas exchange - particularly in laparoscopic surgery.
Individualized PEEP, determined through a recruitment maneuver followed by PEEP titration, has been shown to reduce driving pressure and improve dynamic lung compliance compared to fixed PEEP strategies.
The Oxygen Reserve Index (ORI) is a novel non-invasive monitoring parameter that continuously tracks partial oxygen pressure changes in the 100-200 mmHg range, providing early warning of desaturation before SpO2 drops.
In this prospective observational study, 60 adult patients (ASA I-III, aged 18-75) scheduled for elective laparoscopic unilateral inguinal hernia repair under general anesthesia will be enrolled. Patients will receive either standard PEEP (5 cmH₂O) or individualized PEEP based on the attending anesthesiologist's routine clinical preference.
Hemodynamic and respiratory parameters including ORI, SpO2, airway pressures, tidal volume, dynamic compliance, and BIS will be recorded at six time points: before anesthesia (T0), 5 minutes post-intubation (T1), 10 minutes post-Trendelenburg (T2), 20 minutes post-Trendelenburg (T3), after desufflation (T4), and at postoperative 20 minutes (T5).
Lung ultrasound scoring (0-3 per zone, 12-zone protocol) will be performed preoperatively and postoperatively to assess atelectasis. Arterial blood gas analysis will provide additional oxygenation data.
The primary outcome is the effect of individualized versus standard PEEP on perioperative oxygenation as measured by ORI. The secondary outcome is the comparison of atelectasis prevention efficacy between the two PEEP strategies assessed by lung ultrasound score.
377 studies on the registry are indexed under Pulmonary Atelectasis; 93 are open to participants now.
This study's planned enrollment of 60 is below the median of 76 across 100 observational studies indexed under Pulmonary Atelectasis.
Browse Pulmonary Atelectasis studies →Fatih Sultan Mehmet Training and Research Hospital is the lead sponsor of 120 studies on the registry; 34 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Adult patients scheduled for elective laparoscopic unilateral inguinal hernia repair under general anesthesia at Fatih Sultan Mehmet Training and Research Hospital, Istanbul, Turkey.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
ASA physical status
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
NYHA class (heart failure)
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Patients receiving standard mechanical ventilation with a fixed PEEP of 5 cmH₂O throughout the surgical procedure. Ventilation is maintained in volume-controlled mode with tidal volume 6-8 ml/kg ideal body weight, I/E ratio 1:2, and FiO₂ 0.40. Respiratory rate is adjusted to maintain EtCO₂ between 35-40 mmHg. Anesthesia is maintained with 1.5-2% sevoflurane and remifentanil infusion 0.05-0.5 mcg/kg/min, titrated to BIS 40-60.
Procedure: Standard PEEP Ventilation
Patients receiving individualized PEEP determined by a recruitment maneuver followed by PEEP titration, applied at 10 minutes after Trendelenburg positioning. The individualized PEEP level is maintained throughout the surgery. All other ventilation parameters are identical to the standard PEEP group: volume-controlled mode, tidal volume 6-8 ml/kg, I/E ratio 1:2, FiO₂ 0.40, EtCO₂ 35-40 mmHg. Anesthesia maintained with 1.5-2% sevoflurane and remifentanil 0.05-0.5 mcg/kg/min, BIS 40-60.
Procedure: Individualized PEEP Ventilation
Mechanical ventilation with a fixed positive end-expiratory pressure (PEEP) of 5 cmH₂O applied throughout the surgical procedure. Volume-controlled ventilation mode with tidal volume 6-8 ml/kg ideal body weight, inspiratory-to-expiratory ratio 1:2, and fraction of inspired oxygen (FiO₂) 0.40. Respiratory rate adjusted to maintain end-tidal CO₂ (EtCO₂) between 35-40 mmHg. No recruitment maneuver is performed.
Individualized PEEP determined by a stepwise recruitment maneuver followed by PEEP titration, applied at 10 minutes after Trendelenburg positioning. The optimal PEEP level is identified based on best dynamic lung compliance and maintained for the remainder of surgery. All other ventilation parameters are identical: volume-controlled mode, tidal volume 6-8 ml/kg, I/E ratio 1:2, FiO₂ 0.40, EtCO₂ 35-40 mmHg.
Perioperative Oxygenation Assessed by Oxygen Reserve Index (ORI)
Continuous non-invasive monitoring of the Oxygen Reserve Index (ORI) to assess perioperative oxygenation. ORI values range from 0 to 1 and reflect partial oxygen pressure changes in the 100-200 mmHg range. ORI is recorded at six time points: before anesthesia induction (T0), 5 minutes after intubation (T1), 10 minutes after Trendelenburg positioning (T2), 20 minutes after Trendelenburg positioning (T3), after desufflation (T4), and at postoperative 20 minutes (T5). ORI values will be compared between the standard PEEP and individualized PEEP groups.
Time frame: From anesthesia induction to postoperative 20 minutes (approximately 3 hours)
Perioperative Atelectasis Assessed by Lung Ultrasound Score
Lung aeration assessed using a 12-zone lung ultrasound protocol in supine position. Each zone is scored 0-3: 0 = normal aeration (A-lines, fewer than 3 B-lines), 1 = mild interstitial syndrome (3 or more well-defined B-lines), 2 = moderate interstitial syndrome (confluent B-lines), 3 = severe interstitial syndrome or lung consolidation. Total score ranges from 0 to 36. Scores will be compared between standard PEEP and individualized PEEP groups.
Time frame: Preoperatively and at postoperative 20 minutes
Dynamic Lung Compliance (Cdyn)
Dynamic lung compliance (Cdyn), expressed in mL/cmH₂O, recorded from the anesthesia ventilator at six predefined perioperative time points. All six observations represent repeated measurements of the same outcome using the same unit of measure
Time frame: From anesthesia induction to 20 minutes after admission to the post-anesthesia care unit
Arterial Partial Pressure of Oxygen (PaO₂)
Arterial partial pressure of oxygen (PaO₂), measured in mmHg in blood samples obtained through the radial arterial cannula at the predefined time points.
Time frame: From anesthesia induction to 20 minutes after admission to the post-anesthesia care unit
Postoperative Pulmonary Complications
Incidence of postoperative pulmonary complications including desaturation, dyspnea, pneumonia, or respiratory-related hospital readmission assessed at postoperative day 7 via telephone follow-up.
Time frame: Up to 7 days after surgery
Arterial Partial Pressure of Carbon Dioxide (PaCO₂)
Arterial partial pressure of carbon dioxide (PaCO₂), measured in mmHg in blood samples obtained through the radial arterial cannula at the predefined time points.
Time frame: From anesthesia induction to 20 minutes after admission to the post-anesthesia care unit
Arterial Blood pH
Arterial blood pH, reported as a unitless numerical value in blood samples obtained through the radial arterial cannula at the predefined time points.
Time frame: From anesthesia induction to 20 minutes after admission to the post-anesthesia care unit
This study is not yet recruiting, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Fatih Sultan Mehmet Training and Research Hospital →