Evaluation of Regional Lung Mechanics in Obese Patients Undergoing Laparoscopic Surgery

Study Overview
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Brief Summary
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This study will evaluate what is the impact of laparoscopy and Trendelenburg position on lung regional ventilation distribution in obese patients, focusing on the differences between the different phases of surgery.

Detailed Description
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Electrical impedance tomography (EIT) is a non invasive monitoring technique that allows to evaluate the regional distribution of ventilation. EIT has been used in different contexts, such as acute respiratory failure or intraoperative ventilation settings. Obesity, by increasing intrabdominal pressure, may reduce functional residual capacity after anesthesia and therefore require a more aggressive intraoperative ventilatory setting. In addition, laparoscopy, by increasing the volume of the abdomen, further pushes the diaphragm and increase the probability of lung collapse. The aim of the current study is to describe the effect of 1) anesthesia and of 2) laparoscopy and trendelenburg position on regional ventilation distribution. Moreover, the investigators will evaluate if the best ventilatory parameters set after anesthesia induction are confirmed also when the condition changes (i.e. during pneumoperitoneum and trendellenburg). Finally, the investigators will explore if the different parameters which can be provided by EIT agree in suggesting the best level of positive-end expiratory pressure in both moments of surgery.

Official Title
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Evaluation of Regional Lung Mechanics in Obese Patients Undergoing Laparoscopic Surgery Using Electrical Impedance Tomography

Conditions
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Obesity, Mechanical Ventilation Pressure High, Intraoperative Respiratory Injury

Intervention / Treatment
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* Procedure: PEEP titration trial


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: age 18-90 years Body mass index > 30 kg/m2 Major surgery Predicted duration of surgery > 2 hours Predicted presence of invasive arterial pressure monitoring Exclusion Criteria: emergency surgery Refuse to participate from patient presence of Implantable cardiac device or pacemaker thoracic wounds thoracic surgery

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Single arm intervention<br>All patients will undergo a PEEP titration trial in each surgery step (before pneumoperitoneum, during pneumoperitoneum, after pneumoperitoneum). The PEEP titration trial will be done in steps of 2 cmH2O, starting from clinical PEEP 16 cmH2O and ending to PEEP 6 cmH2O. Each PEEP level will be kept for 2 minutes. The PEEP titration trial will be stopped in case of haemodynamic instability or severe desaturation (Spo2 < 92%). Each PEEP titration trial will be recorded using Electrical impedance tomography (EIT). | Procedure: PEEP titration trial<br>* PEEP trial, starting from clinical PEEP 16 cmH2O and ending at PEEP 6 cmH2O. The PEEP trial will be stopped for haemodynamic instability (defined as arterial pressure < 80 mmHg and /or heart rate > 150 bpm) or desaturation (defined as SpO2 < 92%).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Best Positive end-expiratory pressure - Laparoscopy variability | The primary outcome will be the best PEEP found using the PEEP titration trial. | Difference between the best PEEP after anesthesia induction and during pneumoperitoneum | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Best Positive end-expiratory pressure - EIT variability | Secondary outcome will be to compare the different values of best PEEP provided by several parameters of EIT to evaluate if the overlap. | After anesthesia induction, during pneumoperitoneum, end of surgery | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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EIT, Obesity, Laparoscopy