CT scan of ARDS patient showing different areas of non-homogeneity, different theoretical TauE compartments, and hence different optimal ventilation frequencies: 1: TauE 0.2 sec (Fopt = 50 bpm); 2: TauE 0.3 sec (Fopt = 33 bpm); 3: Tau 0.5 sec (Fopt = 20 bpm); 4: TauE 0.8 sec (Fopt = 14 bpm); 5: TauE 1.2 sec (Fopt = 8 bpm).