Airway Pressure Release Ventilation (APRV) Versus AC/VC Conventional Ventilation

Airway Pressure Release Ventilation (APRV) vs. Conventional Volume Control Mechanical Ventilation for Patients With Respiratory Failure Requiring Invasive Mechanical Ventilator Support

APRV mode of ventilation will result in an improved partial pressure of arterial oxygenation/ fraction of inspired oxygen (P/F ratio) on day 3 of mechanical ventilation. Sub hypotheses: APRV will be associated with a reduced amount of sedation used during the ICU stay in patients with respiratory failure. APRV will be associated with a reduction in the amount of vasoactive medication used for blood pressure support in patients with respiratory failure.

This prospective un-blinded randomized trial will follow patients with respiratory failure and ALI/ARDS who require invasive mechanical ventilation in select ICUs. Patients will be allocated to respiratory support with either APRV mode or volume control (AC) mode of mechanical ventilation. Qualifying patients will be randomized by permuted block randomization within 24 hours of admission to the ICU. Identical ventilation and oxygenation thresholds will be utilized to guide titration of each ventilator protocol. Patients will remain on the assigned mode of ventilation until they are extubated and discharged from the ICU. Procedures for treatment evaluation include daily monitoring of the Ventilator protocol in each arm. Clinical coordinator and study respiratory therapist will perform 2 daily checks of the study patients to determine compliance with the protocol and if patient meets weaning criteria. The previously published ARDS Network continuous positive airway pressure (CPAP) weaning protocol will be used for all patients enrolled.

Patients who experience problems breathing and require assistance in breathing are placed on a machine that delivers air to the lungs through a tube through the vocal cords. This study is testing 3 protocols for that machine.

Our first objective is to measure and compare the partial pressure of oxygen in the artery to the inspired oxygen ratio (P/F ratio) on day 3 of mechanical ventilation. We will also collect and compare common variables used to evaluate lung injury and severity of respiratory failure in both groups. These variables and markers include: the Oxygenation index (OI) and standard blood gas parameters (PH, PaCO2 and PaO2).

Our second objective is to compare the amount and duration of sedative medication and vasoactive medication per patient per/day required in each group. Duration of vasoactive medications and sedation (# of days) and quantitative amounts per kilogram will be compared. Measurements will include Mean Arterial Blood Pressure (MAP), Central venous pressure (CVP), and daily fluid balance between patients on AC and APRV.

Our third objective is to evaluate the feasibility of 2 previously developed APRV paper protocols (APRVa and APRVb) and document the clinician compliance with each paper APRV protocol. We will also track common events associated with mechanical ventilation. The incidence of pneumothorax defined as any ventilator-barotrauma resulting in chest tube placement, will be carefully followed.

Inclusion Criteria: Hypoxemic respiratory failure requiring mechanical ventilation for >24 hours. Exclusion Criteria: Age under 18 Severe chronic obstructive lung disease Patients in whom the only indication for mechanical ventilation is airway protection from poor neurological status.