Impact of PEEP on V/Q mismatch according to patient position and recruitability: a clinical prospective study

Figures

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  Fig. 1. (A) V/Q mismatch by PEEP and position in patients with higher and lower R/I ratio; (B) Correlation between R/I ratio and PEEP-induced change in V/Q mismatch in supine and prone positions. (A) Global V/Q mismatch (%) in patients with higher R/I ratio (left) and patients with lower R/I ratio (right) at PEEP 5 cm H2O and 15 cm H2O in supine and prone positions. Data are presented as individual points with median (horizontal line) and interquartile range (box). *P < 0.05 for comparison between PEEP 5 and 15 cm H2O within the same position. (B) Correlation between recruitment-to-inflation (R/I) ratio and change in global V/Q mismatch (%) from PEEP 5 to 15 cm H2O in supine (left) and prone (right) positions. Gray dots and gray triangles represent the change in global V/Q mismatch (calculated as value at 15 cm H2O minus value at 5 cm H2O) caused by PEEP increase in supine position and prone position, respectively. Black dashed lines and black solid lines represent the linear regression in supine position and in prone position, respectively. Pearson correlation coefficients (r) and P values are indicated.

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  Fig. 2. PEEP-induced overdistended (O) and recruited (R) pixels by position in patients with higher and lower R/I ratio. Number of overdistended (O) and recruited (R) pixels, along with O/R pixel ratios, following PEEP adjustment from 5 to 15 cm H2O in supine and prone positions. For better illustration, data are shown as mean (not median) values ± SEM (error bars). Light gray bars represent R pixels (above the zero line); dark gray bars represent O pixels (below the zero line). Solid bars represent supine position, while hatched bars represent prone position. *P < 0.05 for between-group comparisons (patients with higher R/I ratio vs. patients with lower R/I ratio) using Mann-Whitney U test for each variable independently; ns, not significant for within-group comparisons (supine vs. prone) using paired Wilcoxon test for O/R ratio.

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  Fig. 3. Impacts of PEEP and position on gas exchange and respiratory mechanics in (A) patients with higher R/I ratio and (B) patients with lower R/I ratio. PaO2/FiO2 (mmHg), PaCO2 (mmHg), and respiratory system compliance (Crs, mL/cm H2O) at PEEP 5 cm H2O and 15 cm H2O in supine and prone positions for patients with higher R/I ratio (A) and patients with lower R/I ratio (B). Data are presented as individual points with median (horizontal line) and interquartile range (box). *P < 0.05 for comparison between PEEP 5 and 15 cm H2O within the same position.