The Effect of Preemptive Airway Pressure Release Ventilation on Patients With High Risk for Acute Respiratory Distress Syndrome: a Randomized Controlled Trial

This study was planned as a single-centered, prospective, and randomised-controlled study in a general intensive care unit with 18 bed capacity. The majority of the general patient population is made up of trauma and post-operative patients. The local ethics committee reviewed and approved the study protocol (protocol number: 2016/175) prior to the start of the investigation. Enrollment for the study was performed between May 2016-October 2018. Written informed consent was obtained from each patient's relatives.

Study design and sample:

The study included patients who required invasive mechanical ventilation but was not initially diagnosed with ARDS 9, had a LIPS (Lung Injury Prediction Score) of > 7 10, and have been staying in the ICU for more than 24 hours. Patient demographic properties, sedation requirements, inotrope/vasopressor levels, ARDS development status during follow-up, mechanical ventilation times, length of ICU stay, arterial blood gas results, mean airway pressure (Pmean), peak airway pressure (Ppeak) and tidal volume (Vt) in addition to the mode-specific mechanical ventilation parameters were recorded. Exclusion criteria were pregnancy, intracranial hypertension (suspected or confirmed by measurement with external ventricular drainage catheter), severe chronic obstructive pulmonary disease or type II respiratory failure, confirmed bronchopleural fistula, documented barotrauma, history of pneumonectomy, and age below 18 or above 85 years. Consecutive eligible patients were enrolled block randomization with a 1:1 allocation, randomly assigned to APRV or P-SIMV+PS groups using opaque, sealed envelopes.

Ventilator Settings:

All mechanical ventilation settings were made by intensivists, or trained residents on the night shifts. Prior to randomization, all patients were treated with VC-SIMV mode. Patients admitted during the day were ventilated in VC-SIMV mode until the main investigators evaluated the patient (1-2 hours), and patient admitted in the evening-night shift were ventilated in VC-SIMV mode until the main investigators took over the shift in the morning (maximum 16 hours). Assignment to groups was performed after calculation of LIPS score. Microprocessor-controlled mechanical ventilators (Galileo GOLD; Hamilton Medical AG, Bonaduz, Switzerland) and heated humidifiers were used as a standard in all patients. In both groups, mechanical ventilation targets were determined as maintaining plateau airway pressure (Pplateu) < 30 cmH2O and PaO2 between 60-100 mmHg or SO2>88%. In both groups, arterial blood gas measurement was performed at least twice a day. Oxygenation and respiratory mechanics were evaluated by comparing P-SIMV+PS and APRV groups at baseline and on days 1, 2, 3, and 7. Patients were followed until transfer to CPAP/T-tube and extubation, or a maximum of 28 days. During this period, follow-up was terminated once at extubation, exitus, discharge from ICU or ARDS occurred.