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

BACKGROUND: Although lung protection with low tidal volume and limited plateau pressure (P(plat)) 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(plat) (28–30 cmH(2)O, the Express group) or on keeping end-expiratory transpulmonary pressure positive (0–5 cmH(2)O, P(Lexpi) group). We estimated alveolar recruitment (Vrec), end-expiratory lung volume and alveolar distension based on elastance-related end-inspiratory transpulmonary pressure (P(L,EL)). RESULTS: Nineteen patients with moderate to severe ARDS (PaO(2)/FiO(2) < 150 mmHg) were included with a baseline PEEP of 7.0 ± 1.8 cmH(2)O and a PaO(2)/FiO(2) of 91.2 ± 31.2 mmHg. PEEP and oxygenation increased significantly from baseline with both protocols; PEEP Express group was 14.2 ± 3.6 cmH(2)O versus 16.7 ± 5.9 cmH(2)O in P(Lexpi) 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(2) = 0.45, p = 0.002). Two and seven patients in the Express and P(L,expi) groups, respectively, had P(L,EL) > 25 cmH(2)O. CONCLUSIONS: There is a great heterogeneity of P(Lexpi) when P(plat) is used to titrate PEEP but with limited risk of over-distension. A PEEP titration for a moderate positive level of P(Lexpi) might slightly improve alveolar recruitment and oxygenation but increases the risk of over-distension in one-third of patients.