Patient-ventilator Asynchrony in Conventional Ventilation Modes During Short-term Mechanical Ventilation After Cardiac Surgery

Study Overview
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Brief Summary
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This study evaluates the effects of VCV, PCV and PSV ventilatory modes during the immediate postoperative period on the variables resulting from regional and global pulmonary electrical impedance and diaphragmatic mobility, as well as perform ventilator synchrony analysis in PSV mode by mechanical ventilator. Half of the participants will receive VCV followed by PSV for weaning, while the other half will receive PCV followed by PSV for weaning.

Detailed Description
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In the immediate postoperative period of cardiac surgery, patients are found under mechanical ventilatory support. Commonly, they are ventilated in controlled and assisted-controlled volume (VCV) or pressure (PCV) modes, with weaning at pressure support (PSV). Systematic reviews indicate that there is no difference between the VCV and PCV ventilatory modes for some clinical outcomes or that the existing evidence is insufficient. The distribution of regional ventilation and diaphragmatic mobility can be measured from the use of electrical impedance tomography (EIT) and diaphragmatic ultrasonography (US) to clarify the physiological changes and / or mechanisms of adaptation of the organism submitted to controlled modes cycled at volume or at pressure and spontaneously flow cycled mode. Besides EIT and US measures, gasometric, hemodynamic and respiratory data will also be recorded. The statistical analysis will be considered α≤0.05 for a statistically significant difference.

Official Title
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Effects of Mechanical Ventilation on Controlled Volume, Controlled Pressure and Pressure Support in the Immediate Postoperative Period of Cardiac Surgery on Pulmonary Electrical Impedance and Patient-ventilator Asynchrony: a Parallel Clinical Trial

Conditions
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Thoracic Surgery

Intervention / Treatment
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* Device: VCV+PSV
* Device: PCV+PSV


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: IMC 18.5-29.9 kg/m² Two thoracic tubes (one mediastinal and one left-sided pleural) under mechanical ventilation after surgery submitted to intraoperative extracorporeal circulation Exclusion Criteria: Over 2h of cardiopulmonary bypass Over 12h of post-operative mechanical ventilation Post-operative bleeding above 500 ml in the first hour or above 300 ml in the first two hours History of special conditions (neuromuscular and chronic pulmonary disease, thoracic deformity, abdominal distension).

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 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
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: A parallel group study is a simple and commonly used clinical design which compares two treatments. Usually a test therapy is compared with a standard therapy. The allocation of subjects to groups is usually achieved by randomisation. The groups are typically named the treatment group and the control group. Parallel group designs do not require the same number of subjects in each group, although often similar numbers are observed. The design is commonly used in randomised controlled trials. Statistical analysis often boils down to a simple t-test of the between group difference in the outcome, which is usually a mean or a proportion.
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: VCV+PSV<br>volume controlled cycled, assisted-controlled cycled ventilation mode + pressure support ventilation mode. Progression of invasive ventilatory assistance as the patient recovers during post-surgery. | Device: VCV+PSV<br>* invasive mechanical mechanical modes by volume cycling and by pressure support which the patients will be submitted to before weaning. Post-operative mechanical ventilation average time: 6 hours after ICU admission.<br>* Other names: pressure support ventilation mode;|
| Experimental: PCV+PSV<br>pressure controlled cycled, assisted-controlled cycled ventilation mode + pressure support ventilation mode. Progression of invasive ventilatory assistance as the patient recovers during post-surgery. | Device: PCV+PSV<br>* invasive mechanical mechanical modes by pressure cycling and by pressure support which the patients will be submitted to before weaning. Post-operative mechanical ventilation average time: 6 hours after ICU admission.<br>* Other names: pressure support mode;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| electrical impedance measures | impedance variation data recorded by a tomograph. | 5 minutes of recording at each step of mechanical ventilation progression before extubation. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| arterial gas blood analysis data | measures of pH, PaCO2 (mmHg), PaO2 (mmHg), PaO2/FiO2 | up to 12h, following routine care while patients are mechanically ventilated | 
| patient-ventilator synchrony | events of discomfort between patient and ventilator: ineffective efforts and auto-triggering. Expressed in present or ausent. | 5 minutes of recording at each step of mechanical ventilation progression before extubation |