Detecting Lung's Closing Pressure by Capnography

Study Overview
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Brief Summary
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General anesthesia is associated with loss of pulmonary functional residual capacity and the consequent development of atelectasis and closure of the small airway. Mechanical ventilation in a lung with reduced functional residual capacity and atelectasis increased the dynamic alveolar stress-strain, inducing a local inflammatory response in atelectatic lung areas known as ventilatory-induced lung injury. This phenomenon may appear even in healthy patients undergoing general anesthesia and predisposes them to hypoxemic episodes that can persist in the early postoperative period. Lung recruitment maneuvers restore the functional residual capacity and, therefore, protect the lungs from lung injury. A key issue in this kind of treatment is detecting the lung's closing pressure in order to maintain the end-expiratory pressure above such a limit.

Detailed Description
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This is a prospective and observational study designed to measure the lung's closing pressure. The investigators will study 20 mechanically ventilated patients scheduled for mediastinoscopy surgery under general anesthesia. Lung mechanics and capnography will be assessed during surgery. A slow pressure-volume curve will be automatically performed by the ventilator, and the small airway closing pressure will be determined as the inflection point in the alveolar slope of the pressure-CO2 and volume-CO2 curves. Then, a lung recruitment maneuver will be applied following a descending positive end-expiratory pressure trial to determine the lung's closing pressure. The investigator will see if the lung's closing pressure found with these two techniques is similar.

Official Title
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Analysis of CO2/Volume and CO2-pressure Curves to Detect the Lung's Closing Pressure in Ventilated Patients

Conditions
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Atelectasis

Intervention / Treatment
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* Diagnostic Test: Slow pressure-volume curve


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age > 17 years ole Programmed surgery Exclusion Criteria: Pregnancy No programmed surgery Hemodynamic instability Severe COPD Acute respiratory infection

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 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

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Adults anesthetized patients undergoing mediastinoscopy<br>Determination of the lung's closing pressure by pressure-CO2 and volume-CO2 curves using a slow pressure-volume curve after anesthesia induction. Later on, a standard lung recruitment maneuver followed by a positive end-expiratory pressure trial was done to detect the lung's closing pressure. | Diagnostic Test: Slow pressure-volume curve<br>* Patients will be sequentially subjected to a slow pressure-volume curve and a lung recruitment maneuver<br>* Other names: Lung recruitment maneuver;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Airway pressure | Airway pressure will be measured at the airways opening and expressed in cmH2O. | 30 minutes | 
| Carbon dioxide | Expired carbon dioxide will be measured at the airways opening by a main-stream capnograph, expressed in mmHg. | 30 minutes | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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carbon dioxide, mechanical ventilation