Fig. 5
Effects of FiO2s ≤ 0.60 and > O.21 (FiO2 ≤ 0.60/ > O.21) (Panel A) or FiO2s > 0.60 (Panel B) vs. FiO2s = 0.21 (controls) on standardized mean differences (± SD) (SMD) in two measures of lung injury, lung weight and lung lavage protein concentration, in studies [author (y)] that did not include an infectious or noninfectious inflammatory challenge. Animal type and increased FiO2 level and duration employed in studies and groups are shown. Also shown for each study or group are the standardized means (± SD) and numbers of animals (n) used to calculate individual SMDs. Data from studies used to calculate SMDs for these parameters and parameter units are shown in Additional file 1: Table S7. Analysis for two studies (Nylen and Lagishetty) that included more than one regimen of FiO2 ≤ 0.60/ > O.21 or FiO2 > 0.60 showed that the level of significance for heterogeneity across these regimens prevented pooling groups (I2 ≥ 79%, p < 0.01; I2 ≥ 81%, p < 0.01) and these are shown as solid circles and used in analysis individually here. While it was possible to calculate an overall SMD for lavage protein concentration in studies with FiO2 ≤ 0.60/ > 0.21 (I2 = 0%, p = 0.40), heterogeneity prevented an overall calculation for lung weights for FiO2 ≤ 0.60/ > 0.21 (I2 = 73%, p < 0.01) or for lung weights and lavage protein concentration for FiO2 > 0.60 (I2 = 89%, p < 0.01 and I2 = 76%, p = 0.02, respectively)