Adaptive Support Ventilation in Acute Respiratory Distress Syndrome

This study will compare two different modes of mechanical ventilation: standard lung
protective controlled mandatory ventilation and Adaptive Support Ventilation. The
investigators will enroll adult patients with ARDS who are mechanically ventilated and
admitted to intensive care units, capturing a population with respiratory failure and
significant critical illness. Patient mechanics during each ventilation strategy will be
compared before and after crossover.

After obtaining informed consent, the investigators will place an esophageal balloon which
will be used for simultaneous measurements of airway pressures (Pao) and esophageal pressures
(Pes), to estimate transpulmonary pressures (PL = Pao - Pes), while also measuring Flow and
Volume. Use of esophageal balloon catheters is common practice in the ICUs, and standard of
care at Beth Israel Deaconess Medical Center is to use these balloons in patients with ARDS.
Both the respiratory therapy and physician staff are very comfortable with placement and use.
The esophageal balloon will be left in place until extubation. If the balloon is dislodged or
removed for clinical purposes, it will not be replaced solely for research purposes unless it
occurs on the first day of study measurements.

Patients will then be randomized to be switched to ASV immediately or to be maintained on
their current lung protective ventilation settings.

Inclusion Criteria:

1. Patients ≥ 18 years of age

2. Receiving mechanical ventilation in an intensive care unit

3. ARDS, as defined by the Berlin definition:

1. Hypoxemic respiratory failure with PaO2 / FiO2 ratio < 300 mmHg

2. Bilateral alveolar/interstitial infiltrates on chest x-ray, with opacities not
present for more than 7 days

3. Respiratory failure not fully explained by cardiac failure or fluid overload

4. Intubation on mechanical ventilation and receiving PEEP ≥ 5 cm H2O

4. Receiving mechanical ventilation from a Hamilton ventilator, on a controlled mode of
ventilation.

Exclusion Criteria:

1. Clinical team refusal

2. Esophageal injury or contraindication precluding placement of the esophageal balloon