Respiratory Mechanics and Gas Exchange Characteristics in Patient With SARS-CoV-2

Study Overview
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Brief Summary
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The combination of different ventilatory strategies and its effects on respiratory mechanics and gas exchange in patients under mechanical ventilation with acute respiratory distress syndrome secondary to coronavirus-19 has been scarcely described.

Detailed Description
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Investigation in mechanically ventilated patients with with acute respiratory distress syndrome (ARDS) secondary to coronavirus-19 (COVID-19) is emerging due to presumed differences with typical ARDS from other origin. Considering these issues, the effects of ventilatory strategies such as positive end expiratory pressure, end inspiratory pause and fraction of inspired oxygen on respiratory mechanics and gas exchange must be studied in order to characterize the behavior of COVID-19 ARDS during invasive mechanical ventilation and choose the best combination of ventilatory settings. In this study the investigators will evaluate the changes in respiratory mechanics and gas exchange produced by low and high positive end expiratory pressure, low and high inspired oxygen fraction and the application of end inspiratory pause during volume controlled mechanical ventilation.

Official Title
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Respiratory System Mechanics and Gas Exchange Characteristics Applying Different Ventilatory Strategies in Patients With SARS-CoV-2

Conditions
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Covid19, ARDS, Human

Intervention / Treatment
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* Other: High PEEP with end inspiratory pause
* Other: Low PEEP - FiO2 high
* Other: High PEEP without end inspiratory pause
* Other: Low PEEP - FiO2 low


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Older than 18 years old less than 72 hs since ARDS diagnosis Moderate to severe ARDS central venous catheter and arterial line available Need of neuromuscular blocking agents Supine position Informed consent accepted Airway opening pressure lower than 20 cmH2O Exclusion Criteria: RASS target higher than -5 COPD diagnosis Pneumothorax Intracraneal Hypertension Pregnancy Cardiac inssuficiency uncompensated Chest wall deformity Bronchopleural fistula Contraindication to use esophageal manometry

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: High PEEP with end inspiratory pause|Applying a PEEP value 10 cmH2O higher than the lower inflection point of the pressure-volume curve of the respiratory system with end inspiratory pause addition in volumen control ventilation|
|Other: Low PEEP - FiO2 high|Applying a PEEP value equal to the lower inflection point of the pressure-volume curve of the respiratory system with a FiO2 necessary to achieve a SpO2 96-98%|
|Other: High PEEP without end inspiratory pause|Applying a PEEP value 10 cmH2O higher than the lower inflection point of the pressure-volume curve of the respiratory system without end inspiratory pause addition in volumen control ventilation|
|Other: Low PEEP - FiO2 low|Applying a PEEP value equal to the lower inflection point of the pressure-volume curve of the respiratory system with a FiO2 necessary to achieve a SpO2 88-92%|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Driving transpulmonary pressure (cmH2O) | The driving transpulmonary pressure will be evaluated between the high and low PEEP condition using the formula: driving transpulmonary pressure = driving airway pressure - driving esophageal pressure (cmH2O). | 10 minutes | 
| Bohr dead space fraction (%) | The Bohr dead space fraction will be evaluated with high PEEP between the condition with end inspiratory pause and with no end inspiratory pause application using the formula: Bohr dead space fraction = Alveolar pressure of CO2 (PACO2) - Expired pressure of CO2 (PECO2) / PACO2 | 10 minutes | 
| Shunt fraction (%) | The shunt fraction will be evaluated with low PEEP between the condition with high fraction of oxygen to achieve a saturation goal of 96-98% and the condition with low fraction of oxygen to achieve a saturation goal of 88-92%. The shunt fraction will be calculated using the formula: Qs/Qt = (capillary oxygen content - arterial oxygen content)/(capillary oxygen content - venous oxygen content) | 10 minutes |