Bariatric Electrical Impedance Tomography

Study Overview
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Brief Summary
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This study investigates under controlled conditions the variation of poorly ventilated lung units (silent spaces) in obese patients scheduled for laparoscopic bariatric surgery in the perioperative phase.

Detailed Description
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Eligible patients with written informed consent, scheduled for laparoscopic bariatric surgery. As for standard of care no premedication will be given for bariatric patients. Patients will be monitored according the local standard. Thoracic electrical impedance tomography measurements (each measurement will last 1 min) will be performed at the following time points: before induction of the anaesthesia; before the surgical procedure when the induction is terminated and recruitment manoeuvers have been performed; after the termination of the surgical procedure; before transport to the Post anaesthesia Care Unit (PACU); before the discharge from the PACU after 2 hours of monitoring. An additional thoracic electrical impedance tomography measurement (duration 1 min) will be performed before discharge at home. For this, resulting potential differences are measured, and impedance distribution sampled at 30 Hz will be calculated by an automated linearized Newton-Raphson reconstruction algorithm. Relative change in poorly ventilated lung regions (silent spaces) and end-expiratory lung impedance (EELI) and measures of ventilation inhomogeneity such as the global inhomogeneity index will be calculated.

Official Title
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Evaluation of Atelectasis Formation and Regression With Electrical Impedance Tomography in the Perioperative Phase of Obese Patients Scheduled for Laparoscopic Bariatric Surgery

Conditions
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Anesthesia

Intervention / Treatment
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* Other: Electrical impedance tomography during anesthesia


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: BMI >40 ASA physical status 1 to 4 Over 18 years of age providing written informed consent Exclusion Criteria: BMI <40 Known severe pulmonary hypertension, Need of home oxygen therapy Known heart failure Suspected, or known recent pulmonal infections

Ages Eligible for Study
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Minimum Age: 18 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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Arms and Interventions

| Intervention/Treatment |
| --- |
|Other: Electrical impedance tomography during anesthesia|Thoracic electrical impedance tomography measurements ( min each) will be performed at the following time points: before induction of the anaesthesia; before the surgical procedure when the induction is terminated and recruitment manoeuvers have been performed; after the termination of the surgical procedure; before transport to the Post anaesthesia Care Unit (PACU); before the discharge from the PACU after 2 hours of monitoring. An additional thoracic EIT-measurement will be performed before discharge at home. For this, resulting potential differences are measured, and impedance distribution sampled at 30 Hz will be calculated. Relative change in poorly ventilated lung regions (silent spaces) and end-expiratory lung impedance (EELI) and measures of ventilation inhomogeneity will be calculated using customised code (Matlab R2021a, The MathWorks, Nattick, Massachusetts, USA).|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Proportion of poorly ventilated lung areas (silent spaces) | Proportion of poorly ventilated lung areas (silent spaces) by using electrical impedance tomography (EIT) before the discharge from PACU (two hours after admission to PACU). | 2 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| EIT-Measurement after the end of induction before the surgical procedure | Detection of changes in silent spaces, ventilation inhomogeneity and end-expiratory lung impedance (EELI) by using electrical impedance tomography (EIT) | 2 minutes after the end of anesthesia induction | 
| EIT-Measurement at the end of the surgical procedure | Detection of changes in silent spaces, ventilation inhomogeneity and end-expiratory lung impedance (EELI) by using electrical impedance tomography (EIT) | 5 minutes after Capnoperitoneum | 
| EIT-Measurement 2 minutes after the end of anaesthesia, before the transport in PACU | Detection of changes in silent spaces, ventilation inhomogeneity and end-expiratory lung impedance (EELI) by using electrical impedance tomography (EIT) | 2 minutes after the end of anaesthesia, before the transport to PACU. | 
| EIT-Measurement before discharge from the PACU | Detection of changes in silent spaces, ventilation inhomogeneity and end-expiratory lung impedance (EELI) by using electrical impedance tomography (EIT) | Two hours after admission of the patient at PACU, before first mobilisation and before discharge from PACU | 
| EIT-Measurement before discharging the patient at home | Detection of changes in silent spaces, ventilation inhomogeneity and end-expiratory lung impedance (EELI) by using electrical impedance tomography (EIT) | At hospital discharge, up to 3 days | 
| Duration of surgical procedure. | Duration of surgical procedure. | Up to 90 to 150 minutes | 
| Duration of anaesthesia | Duration of anaesthesia | Up to 90 to 180 minutes | 
| Desaturation below 90%. | Difference of formation and course of silent lung areas in patients with and without pre-existing CPAP-therapy | During anaesthesia monitoring, from 1 to 10 minutes | 
| Follow up at 14 days | Follow-up by phone, regarding respiratory complications or need for rehospitalization. | 14 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Bariatric, Obese, Laparoscopic, Electrical impedance tomography