Effects of pressure-support ventilation with different levels of positive end-expiratory in a mild model of acute respiratory distress syndrome
KeywordsMean Arterial Pressure Acute Respiratory Distress Syndrome Ventilator Strategy Lung Mechanic Baseline Data Collection
Pressure-support ventilation improves lung mechanics, blood gas exchange, hemodynamics, and work of breathing (WOB) in mild acute respiratory distress syndrome (ARDS) [1, 2]. Nevertheless, those beneficial effects could be dependent of positive end-expiratory pressure (PEEP) applied during mechanical ventilation. So far, no study has compared pressure-support ventilation (PSV) with pressure controlled ventilation (PCV) in different PEEP levels.
To compare PSV and PCV target to protective tidal volume (VT=6ml/kg) using two PEEP levels (2 and 5 cmH2O) in a mild ARDS model.
PCV + PEEP = 2 cmH2O (PCV-P2);
PCV + PEEP = 5 cmH2O (PCV-P5);
PSV + PEEP = 2 cmH2O (PSV-P2);
PSV + PEEP = 5 cmH2O (PSV-P5).
Animals were ventilated for 2 hours. Mean arterial pressure (MAP), arterial blood gases, peak airway (Ppeak,RS) and peak transpulmonary (Ppeak,L) pressures, and pressure-time product (PTP), as a surrogate of WOB, were evaluated.
All animals showed better oxygenation along time, regardless of ventilator strategy. Animals submitted to PCV, regardless of PEEP, received more colloids to keep MAP>70 mmHg. Ppeak,RS, and Ppeak,L were higher in animals submitted to PEEP = 5 cmH2O than PEEP = 2 cmH2O, independently of pressure-controlled, and pressure-support ventilator strategies. Nevertheless, at PEEP = 5 cmH2O, but not at PEEP = 2 cmH2O, animals submitted to PSV showed lower Ppeak,RS, and Ppeak,L compared to PCV animals (PSV-P5:11.2 ± 1.9 cmH2O vs PCV-P5:15.3 ± 1.4 cmH2O, p < 0.05). In accordance, PTP was lower in animals submitted to PEEP = 5 cmH2O compared to PEEP = 2 cmH2O during PSV (PSV-P5:0.08 ± 0.03 cmH2O.s vs PSV-P2:0.22 ± 0.09 cmH2O.s, p < 0.05).
In a mild ARDS model, pressure-support ventilation is associated to better hemodynamics, lung mechanics, and it seems to have a dependent effect of the adjusted PEEP level, as depicted by work of breathing.
CNPq, FAPERJ, CAPES, PRONEX, MS-DECIT
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