Clinical and Physiological Assessment of a Nearly Ultra-protective Lung Ventilation Strategy: A Quasi-experimental Preliminary Study in ARDS Patients

Study Overview
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Brief Summary
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This study aims to determine whether a protective mechanical ventilator strategy generates a reduction in the Bohr´s dead space in patients with moderate or severe acute respiratory distress syndrome (ARDS). Commonly used ventilatory strategies in the clinical practice were applied sequentially to assess their impact. Data obtained from volumetric capnography will be recorded after each ventilatory strategy is applied

Detailed Description
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Protective mechanical ventilation strategies are currently the cornerstone of treatment for patients undergoing mechanical ventilatory support. Among them, we can mention the reduction in tidal volume, the reduction in driving pressure, the PEEP setting, and the respiratory rate reduction. All of these strategies are aimed at preventing ventilator-induced lung injury. Few clinical studies have evaluated the effects of protective mechanical ventilation strategies on dead-space. This study was designed to evaluate dead space and alveolar ventilation with a sequence of protective ventilatory strategies, keeping PEEP levels constant. The ventilatory strategy was developed to reduce tidal volume, set an end-inspiratory pause, and reduce the frequencies of lung tissue impact. Baseline: All the patients kept the variables under study constant for 60 minutes. Each of the participants was studied for a period of 150 minutes. PEEP programming was set with transpulmonary end-expiratory pressures to maintain between 0 and 5 cmH2O and was remained constant throughout the study. Protocol design: Baseline: Vt 7 ml/kg/PBW Phase I: Vt 6 ml/kg/PBW. Phase II: Vt 5 ml/kg/PBW. Phase III: end-inspiratory pause prolongation until achieving I:E ratio equal to 1, maintaining a constant Vt level (5 ml/kg/PBW) Phase IV: Respiratory rate reduction by 20% of basal conditions, maintaining constant VT level (5 ml/kg/PBW). After 30 minutes of continuous monitoring, minute ventilation, mechanical power, variables obtained by volumetric capnography, and arterial blood gases were recorded in each study phase. This study will be performed in the Intensive Care Unit of a University Hospital.

Official Title
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Clinical and Physiological Assessment of a Nearly Ultra-protective Lung Ventilation Strategy: A Quasi-experimental Preliminary Study in ARDS Patients

Conditions
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ARDS, Volumetric Capnography

Intervention / Treatment
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* Other: protective mechanical ventilation strategies


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age older than 18 years The requirement of invasive mechanical ventilation for more than 4 hours and less than 72 hours Severe hypoxemia (PAFI < 200) secondary to ARDS Exclusion Criteria: Heart failure stage IV Chronic obstructive pulmonary disease (COPD) on home oxygen Bronchopulmonary fistula Hypovolemic Shock with active hemorrhage Gastrointestinal bleeding Oesophageal Varices Nasopharynx surgery, recent oesophageal or gastric surgery Massive Pulmonary Thromboembolism Catastrophic respiratory failure requiring urgent extracorporeal life support Respiratory acidosis. Hydrogen potential (pH) is less than 7.20 and PaCO2 higher than 60 mmHg at baseline.

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: Other
Intervention Model: Single Group Assignment
Interventional Model Description: A quasi-experimental, non-randomized study
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: protective mechanical ventilation<br>Ten patients with moderate to severe ARDS were subjected to a nearly ultra-protective ventilation strategy generating a reduction in minute ventilation (Tidal volume of 5 ml/kg of predicted body weight together with a 20% reduction in respiratory rate). In addition to end-inspiratory pause, prolongation was set to avoid hypercapnia. Protocol phases: Baseline conditions: Tidal volume of 7 ml/kg. I: Tidal volume of 6 ml/kg. II: Tidal volume of 5 ml/kg. III: Increase end-inspiratory pause until achieving an I:E ratio equal to 1. IV: Respiratory rate reduction until 20% of the basal condition keeping constant I:E ratio equal to 1 | Other: protective mechanical ventilation strategies<br>* 1. Reduce tidal volume from 7 ml/kg to 5 ml/kg. 2 Set end-inspiratory pausa. 3 respiratory rate reduction until 20% of the basal condition<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| To analyse the effects of different protective mechanical ventilator strategies on Bohr's dead space (VDBohr/VT) in patients with acute respiratory distress syndrome | After the systematic reduction of the tidal volume, end-inspiratory pause prolongation, and the reduction of the respiratory rate, the optimisation of the dead space and the alveolar ventilation could be generated. | 150 minutes | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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dead space, end-inspiratory pause, respiratory rate, ARDS