Fig. 3

The impacts of body position and PEEP on gas exchange, respiratory mechanics and silents spaces in EIT in A high recruiter and B low recruiter. Black bars represent median and interquartile range. A-high recruiter Oxygenation was lowest in low PEEP + supine and highest in high PEEP + prone (a). Respiratory system compliance was worst in high PEEP + supine (b). This is because high PEEP in supine position caused the largest amount of non-dependent silent spaces in EIT (presumably lung overinflation) (c). The amount of dependent silent spaces in EIT (presumably lung collapse) was largest in low PEEP + supine and least in high PEEP conditions (d). *p < 0.01 compared with other conditions, +p < 0.05 compared with other conditions. B-low recruiter High PEEP (vs. low PEEP) did not improve oxygenation both in supine position and prone position. Prone position per se achieved the highest oxygenation, independent of PEEP levels (a). High PEEP (vs. low PEEP) worsened respiratory system compliance in supine position and prone position (b), because high PEEP increased the amount of non-dependent silent spaces in EIT (presumably lung overinflation) in supine position and prone position (c). The amount of dependent silent spaces in EIT (presumably lung collapse) was highest in low PEEP + supine and it was similar among rest of conditions (d). *p < 0.01 compared with other conditions, + p < 0.01 compared with supine conditions, ‡p < 0.01 compared with high PEEP + prone. EIT, electrical impedance tomography; PEEP, positive end expiratory pressure