Effects of Different PEEP Levels on Work of Breathing in Morbidly Obese Patients Prior to and After Extubation

Study Overview
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Brief Summary
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The main purpose of this study is to define at the bedside the Titrated-PEEP level for obese patients that increases the likelihood of extubation and ventilator liberation. The investigators hypothesized that a titrated level of PEEP (Titrated-PEEP) during SBT will keep the lung recruited, maintain oxygenation, and decrease the work of breathing resulting in successful ventilator liberation. In addition, post-extubation the investigators hypothesize that these patients will require noninvasive ventilatory support in the form of CPAP at the level of titrated-PEEP used during the SBT.

Detailed Description
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The high WOB of morbidly obese patients is associated with respiratory muscle fatigue and failure in extubation. The investigators hypothesized that the use of a titrated PEEP level prior to and after extubation might improve successful extubation rates and avoid re-intubation. In this study, patients will be awake and ventilated in the pressure support ventilation (PSV) mode. The investigators will apply different PEEP levels to measure WOB, transpulmonary pressure and characterize the response of the respiratory system to increasing or decreasing PEEP. The Titrated-PEEP will be identified as the PEEP level associated with the lowest value of respiratory system elastance and an end expiratory transpulmonary pressure of 2 cmH2O. Then the participants will have two spontaneous breathing trials; one at PEEP 0-5 cmH2O, and the other at the Titrated-PEEP level, with PSV=0 and FiO2 unchanged. After extubation, the participants will first receive CPAP set at Titrated-PEEP, then spontaneous breathing. Electrical impedance tomography (EIT), respiratory system mechanics and gas exchange will be recorded during the study. The investigators believe that the real-time determination of Titrated-PEEP can guide the treatment of mechanical ventilation and give us a better understanding of the physiology and pathophysiology of morbidly obese patients. As a result, this study will improve patient safety; reduce the duration of mechanical ventilation, complications and healthcare costs.

Official Title
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Effects of Different PEEP Levels on Work of Breathing in Morbidly Obese Patients Prior to and After Extubation

Conditions
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Obesity

Intervention / Treatment
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* Procedure: Positive end-expiratory pressure (PEEP)
* Procedure: ZEEP


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Intubated and mechanically ventilated; Weaning from mechanical ventilation; BMI ≥ 35 kg/m2 with waist circumference > 88 cm for women; waist circumference > 102 cm for men. A well functioning arterial line. Exclusion Criteria: Known presence of esophageal varices Recent esophageal trauma or surgery Severe thrombocytopenia (PTL ≤ 5,000/mm3) Severe coagulopathy (INR ≥ 4) Presence of pneumothorax Pregnancy Pacemaker and/or internal cardiac defibrillator

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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Design Details

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


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Patients with BMI > 35<br>ICU patients with a BMI > 35, on pressure support ventilation, scheduled for spontaneous breathing trial for evaluation of extubation After recruitment maneuver and decremental PEEP trial, the Titrated-PEEP is identified. Patients will have two spontaneous breathing trials (SBTs) in randomized order. Either the patient will receive SBT at PEEP = 0-5 cmH2O, with PSV=0 and FiO2 unchanged; or the patient will perform an SBT at Titrated-PEEP, with the PSV=0 and FiO2 unchanged. | Procedure: Positive end-expiratory pressure (PEEP)<br>* Titrated-PEEP. After recruitment maneuver and decremental PEEP trial, the Titrated-PEEP is identified. Patients will have two spontaneous breathing trials (SBTs). In this arm, patients will have SBT at Titrated-PEEP, with the PSV=0 and FiO2 unchanged.<br>Procedure: ZEEP<br>* After recruitment maneuver and decremental PEEP trial, the Titrated-PEEP is identified. Patients will have two spontaneous breathing trials (SBTs). In this arm, patients will have SBT at PEEP = 0-5 cmH2O, with the PSV=0 and FiO2 unchanged.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Differences in WOB at titrated PEEP levels vs. ZEEP level | Work Of Breathing measured as J/L and J/min during a Spontaneous Breathing Trial at titrated PEEP vs. Work Of Breathing measured as J/L and J/min during a Spontaneous Breathing Trial at zero PEEP | 24 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Gas Exchange - Oxygenation | Difference in oxygenation as measured in mmHg of PaO2/FiO2 during a Spontaneous Breathing Trial at titrated PEEP and at zero PEEP. | 24 hours | 
| Gas Exchange - Arterial carbon dioxide | Difference in arterial carbon dioxide as measured in mmHg (PaCO2) during a Spontaneous Breathing Trial at titrated PEEP and at zero PEEP. | 24 hours | 
| Respiratory Mechanics - Compliance | Difference in Compliance, measured as ml/cmH2O, of the respiratory system, lungs and chest wall during a Spontaneous Breathing Trial at titrated PEEP and at zero PEEP. | 24 hours | 
| Gas Volume Distribution | Difference in the images of Electric Impedance Tomography measured as relative variation of regional impedance (deltaZ) (i.e. distribution of ventilation) during a Spontaneous Breathing Trial at titrated PEEP and at zero PEEP. | 24 hours | 
| Hemodynamics - Blood pressure | Changes in arterial blood pressures (BP, mmHg) during a Spontaneous Breathing Trial at titrated PEEP and at zero PEEP. | 24 hours | 
| Hemodynamics - Heart rate | Changes in heart rate (HR, bpm) during a Spontaneous Breathing Trial at titrated PEEP and at zero PEEP. | 24 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Mechanical ventilation, Positive end-expiratory pressure, Work of breathing, Morbidly obese