K. L. Haines1, H. S. Jung1, S. K. Agarwal1 1University Of Wisconsin,Surgery,Madison, WI, USA
Introduction: Acute respiratory distress syndrome (ARDS) is currently associated with 30-40% mortality and responsible for approximately 75,000 deaths in the United States yearly. Low tidal volume ventilation [the Acute Respiratory Distress Syndrome Network (ARDSNet) strategy] and Airway Pressure Release Ventilation (APRV) are routinely used for these patients. Past studies comparing known injurious ventilator strategies have shown increases in cytokines after 1 hour of exposure with a return to baseline between 1-6 hours after re-institution of a protective strategy. This study was undertaken to determine if these modes could be compared at this rate in the same critically ill patients.
Methods: This was a prospective blinded randomized comparison trial of ARDSNet and APRV in clinically stable consented subjects with ARDS for less than 7 days prior to enrollment. Patients were randomized to APRV followed by ARDSNet or ARDSNet followed by APRV. Arterial blood gasses and physiologic parameters were collected for analysis prior to intervention, 6 hours, and 12 hours. Patients with respiratory failure for greater than 14 days, a diagnosis of ARDS for greater than 7 days, or history of lung disease prior to evaluation were excluded.
Results:15 patients were screened for the study, 6 qualified, 4 were able to complete the study and be randomized. No patients in this trail had symptoms of Left sided heart failure and none were on vasopressors at any point in the trial. Patients were on the ventilator for 3±1 day prior to study initiation. Pre-intervention measures were RR 16±3, PEEP 8±2, PIP 24±4, Plateau Pressure 20±5, MAP 89±13, Temp 38±0.1, and Riker 4±1. There was no difference in Fi02 48±10 for any patient throughout the intervention and oxygen saturation improved or was unchanged in all patients throughout the trial period. Respiratory rate was unchanged throughout the trial in all patients. No adverse events occurred in this study. Data are mean ± STDEV unless otherwise stated.
Conclusion: Data from the trial shows that ARDSNet and APRV can both be utilized quickly and safely back to back in surgical critical care patients with ARDS despite being known injurious ventilator strategies. Not one patient was harmed by this intervention, and all except one patients oxygenation parameters improved. This will allow further studies to evaluate biomarkers of lung injury in the same surgical critical care patients back to back to see how these ventilator strategies correlate with the degree of lung injury on the molecular level.