This is a multicenter randomized controlled clinical trial with an adaptive design assessing the efficacy of setting the ventilator based on measurements of respiratory mechanics (recruitability and effort) to reduce Day 60 mortality in patients with acute respiratory distress syndrome (ARDS).

The CAVIARDS study is also a basket trial; a basket trial design examines a single intervention in multiple disease populations. CAVIARDS consists of an identical 2-arm mechanical ventilation protocol implemented in two different study populations (COVID-19 and non-COVID-19 patients). As per a typical basket trial design, the operational structure of both the COVID-19 substudy (CAVIARDS-19) and non-COVID-19 substudy (CAVIARDS-all) is shared (recruitment, procedures, data collection, analysis, management, etc.).

Acute respiratory distress syndrome (ARDS) is a major public health problem affecting approximately 10% of patients in the intensive care unit (ICU) and 23% of all patients on a breathing machine (mechanical ventilator). The short-term mortality of patients with ARDS is approximately 40% and better ventilation of these patients has the greatest potential to improve outcomes.

The lungs in patients with ARDS are severely inflamed which reduces lung volume and their ability to stretch, making ventilation difficult and dangerous. However, mechanical ventilation is the mainstay of supportive therapy. Although it is life-saving, it can also can generate secondary injury and inflammation, called ventilator-induced lung injury (VILI). The investigators know that inadequate mechanical ventilation worsens outcomes but are uncertain of the optimal way to manage ventilators at the bedside.

Furthermore, ARDS is challenging because there is no treatment for the alveolar-capillary leak characterizing this syndrome; aside from treating the underlying cause, the only supportive therapy is mechanical ventilation. This is specially the case for COVID-19 induced ARDS. Despite best practices, over-distension of the lung or inappropriate positive end expiratory pressure (PEEP) is common. Finally, once spontaneous breathing has resumed and is assisted by the ventilator, an additional phenomenon occurs, called patient self-inflicted lung injury. The drive for breathing in many patients is stimulated by lung inflammation, and strong breathing efforts can generate high distending pressures, causing lung (and systemic) inflammation and organ damage. Whether the management of COVID-19 induced ARDS should differ from all other ARDS has been debated at length but has no clear response

Recent advances in our understanding of bedside physiology (airway closure, recruitability, lung distension, respiratory drive) can now be applied for an individual titration of mechanical ventilation.

Inclusion Criteria:

1. Age ≥ 18 y
2. Moderate or severe ARDS (PaO2/FiO2 ≤ 200 mmHg) within 48 h of meeting Berlin ARDS criteria (Patients who were eligible at the time of screening and whose PaO2/FiO2 became > 200 mm Hg under prone positioning when starting the protocol remained eligible)

Exclusion Criteria:

1. Received continuous mechanical ventilation > 7 days
2. Known or clinically suspected elevated intracranial pressure (>18mmHg) necessitating strict control of PaCO2
3. Known pregnancy
4. Broncho-pleural fistula
5. Severe liver disease (Child-Pugh Score ≥ 10)
6. BMI >40kg/m2
7. Anticipating withdrawal of life support and/or shift to palliation as the goal of care
8. Patient is receiving ECMO at time of randomization

The final anonymized trial dataset will be available on reasonable written request to the principal investigator one year after publication of the main manuscript.