Figure 5.

A) Three-dimensional CT reconstructions of the whole lungs obtained in healthy rats while positive end expiratory pressure (PEEP) was raised from 0 to 9 cmH₂O and then lowered back to 0 cmH₂O (in steps of 3 cmH₂O). Images of the lungs during descending PEEP are shown in purple and are superimposed on the images obtained during rising PEEP (in white): the larger lung volumes during descending PEEP document hysteresis. B) Axial maps of apparent diffusion coefficient (ADC) obtained during a PEEP cycle identical to A): ADC values are lower during descending PEEP suggesting a “reverse hysteresis” of the individual airspaces. (Reproduced from Ref 96).