[Dead space guided positive end-expiratory pressure in patients with acute respiratory distress syndrome]

To evaluate the value of dead space fraction (V(D)/V(T)) guided positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome (ARDS).

Twenty-three intubated and mechanically ventilated patients with early ARDS were enrolled in the study. PEEP was titrated by lowest V(D)/V(T). Parameters of oxygenation and respiratory mechanics were observed.

PEEP titrated by lowest V(D)/V(T) and highest static lung compliance (C(Lst)) (P > 0.05) respectively, were lower than PEEP titrated by optimal oxygenation (P < 0.05), but there was no significant difference between lowest V(D)/V(T) and highest C(Lst) method. The V(D)/V(T) that ventilated on PEEP titrated by the lowest V(D)/V(T) decreased than its basal level. There was no difference significantly between the V(D)/V(T) that ventilated on PEEP elected by the other two methods with basal level (P > 0.05). The the ratio of arterial PO2 to the inspired oxygen fraction (PaO2/FiO2) ratios improved significantly than the baseline values in three ventilation strategies, and that ventilated on PEEP targeting the lowest V(D)/V(T) was lower than PEEP targeting optimal oxygenation. The plateau airway pressure that ventilated on PEEP targeting optimal oxygenation was higher than the other two methods. The functional residual capacity (FRC) of patients ventilated by PEEP targeting optimal oxygenation was increased than the lowest V(D)/V(T) and maximum C(Lst).

V(D)/V(T) could be one of the methods to titrate the optimal PEEP in patients with early ARDS. Optimal PEEP targeting the highest compliance in conjunction with the lowest dead space fraction indicated a maximum amount of effectively expanded alveoli.