Fig. 4. Transdiaphragmatic pressure (Pdi) differences evaluated at a frequency of 100 Hz between the adaptive support ventilation (ASV) group (n = 6) and controlled mechanical ventilation (CMV) (n = 6) group during the whole study period. Pdi in the CMV group was lower than that in the ASV group after 48 h of ventilation. Data are mean ± SD. P  values refer to between-group differences. *P < 0.05 vs . baseline values.