ARDSnet Protocol vs. Open Lung Approach in ARDS

Many patients with Acute Respiratory Distress Syndrome or ARDS need breathing support that is provided by a machine called a ventilator or respirator. The purpose of this study is to find out if a new method of setting the ventilator for patients with severe ARDS is better than the standard, commonly used way of setting the ventilator.

The ARDSnet protocol is the current, standard of care for ARDS. Mechanical ventilation is managed using low tidal volumes, relatively high respiratory rates, with oxygenation managed according to PEEP and FIO2 relationships as defined in a table. This study compares the ARDSnet protocol with an open lung approach to mechanical ventilation. The open lung approach uses a technique to recruit collapsed lung areas and then uses the lowest PEEP level that prevents recollapse of recruited lung units. The best PEEP level is determined by a decremental PEEP trial involving a series of pressure measurements taken after the recruitment maneuver. Both the ARDSnet protocol and the open lung approach require low tidal volumes and plateau pressures.

Evidence suggests that using a mechanical ventilation strategy of recruitment maneuvers (to open the collapsed lung) followed by high PEEP (to prevent collapse of the opened lung) with control of transpulmonary pressure through lower plateau pressures would maximize homogeneity within the lung and as such, minimize shearing forces in the lung parenchyma, thus improving ventilation and outcome in mechanically ventilated ARDS patients.

Eligibility Criteria:
Inclusion Criteria:

* Intubated and mechanically ventilated
* Diagnosis of ARDS using American-European consensus criteria
* Enrollment in study \< 48 hours since diagnosis of ARDS
* For 12-36 hrs. (ideally 12-24 hrs) after diagnosis of ARDS, patient must be ventilated as follows: Volume A/C, Tidal volume of 4-8 ml/kg PBW, Plateau pressure ≤ 30 cmH2O, PEEP/FIO2 adjustments using ARDSnet table, Ventilator rate to keep PaCO2 = 35-60 mmHg
* During the 12-36 hour(ideally 12-24 hr) period, PaO2/FIO2 must remain \< 200 mm Hg for an ABG obtained 30 minutes after placement on the following specific ventilator settings: Volume A/C, Tidal volume = 6 ml/kg PBW, Plateau pressure ≤ 30 cmH2O, Inspiratory time ≤ 1 second, PEEP ≥ 10 cmH2O, FIO2 ≥ 0.5, Ventilator rate to keep PaCO2 = 35-60 mmHg
* No lung recruitment maneuvers or adjunct therapy.
* Total time on mechanical ventilation \< 96 hrs. at time of randomization.

Exclusion Criteria:

* Age \< 18 years or \> 80 years
* Weight \< 35 kg PBW
* Body mass index \> 60
* Intubated 2° to acute exacerbation of a chronic pulmonary disease
* Acute brain injury (ICP \> 18 mmHg)
* Immunosuppression 2° to chemo- or radiation therapy
* Severe cardiac disease(one of the following): New York Heart Association Class 3 or 4, acute coronary syndrome or persistent ventricular tachyarrhythmias
* Positive laboratory pregnancy test
* Sickle cell disease
* Neuromuscular disease
* High risk of mortality within 3 months from cause other than ARDS, e.g. cancer
* More than 2 organ failures (not including pulmonary system)
* Documented lung barotrauma, i.e. chest tube placement other than for fluid drainage
* Persistent hemodynamic instability or intractable shock
* Penetrating chest trauma
* Enrollment in another interventional study