The effect of a decremental PEEP trial on regional ventilation shown in two representative patients. The functional EIT (fEIT) image at the different PEEP levels (15 to 10 to 5 to 0 cm H2O) shows the ventilation distribution in a colour-coded matrix in a patient without lung disorders and a patient with lung disorders. The ΔfEIT images are created by subtracting fEIT before the PEEP step from fEIT after each PEEP step. The increase or decrease in regional ventilation between PEEP (ΔfEIT) steps is displayed in a color-coded matrix. Each EIT image represents a thoracic slice with the ventral lung regions at the top and dorsal lung regions at the bottom.