PEEP titration in moderate to severe ARDS: plateau versus transpulmonary pressure.

Background: Although lung protection with low tidal volume and limited plateau pressure (P) improves survival in acute respiratory distress syndrome patients (ARDS), the best way to set positive end-expiratory pressure (PEEP) is still debated.

Methods: This study aimed to compare two strategies using individual PEEP based on a maximum P (28-30 cmHO, the Express group) or on keeping end-expiratory transpulmonary pressure positive (0-5 cmHO, P group). We estimated alveolar recruitment (Vrec), end-expiratory lung volume and alveolar distension based on elastance-related end-inspiratory transpulmonary pressure (P).

Results: Nineteen patients with moderate to severe ARDS (PaO/FiO < 150 mmHg) were included with a baseline PEEP of 7.0 ± 1.8 cmHO and a PaO/FiO of 91.2 ± 31.2 mmHg. PEEP and oxygenation increased significantly from baseline with both protocols; PEEP Express group was 14.2 ± 3.6 cmHO versus 16.7 ± 5.9 cmHO in P group. No patient had the same PEEP with the two protocols. Vrec was higher with the latter protocol (299 [0 to 875] vs. 222 [47 to 483] ml, p = 0.049) and correlated with improved oxygenation (R = 0.45, p = 0.002). Two and seven patients in the Express and P groups, respectively, had P > 25 cmHO.

Conclusions: There is a great heterogeneity of P when P is used to titrate PEEP but with limited risk of over-distension. A PEEP titration for a moderate positive level of P might slightly improve alveolar recruitment and oxygenation but increases the risk of over-distension in one-third of patients.