Figure 6

Changes in the volume of overdistended areas (upper panel) and inthe volume of nonaerated areas (lower panel) induced by two PEEP levels inpatients with (n =8, clear circle) and without (n =6, filled circle) alowerinflection point. PEEP₁, lower inflection point+2 cmH₂O or +10 cmH₂O in the absence of lower inflectionpoint; PEEP₂, lowerinflection point +7 cmH₂O or+15 cmH₂O in the absence of a lowerinflection point. The lung volumeswere measured by an analysis of the volume distribution of CT attenuations witha spiral thoracic CT scan. Alveolar recruitment is defined as the reduction ofthe nonaerated lung zones with a CT attenuation ranging between -100 and+100 HU. Pulmonary over-distension is defined as the appearance of lung regionswith CT attenuation less than -900 HU. In patients without a lower inflectionpoint, increasing levels of PEEP are associated with PEEP-induced lungover-distension. From Vieira et al [31].