Comparison of the effects of intercostal tube drainage of pleural fluid (drain group: solid bars) and no intervention (control group: open bars) on oxygenation over 6 days in patients recovering from cardiac surgery as assessed by (A) the ratio of arterial ... Comparison of the effects of intercostal tube drainage of pleural fluid (drain group: solid bars) and no intervention (control group: open bars) on oxygenation over 6 days in patients recovering from cardiac surgery as assessed by (A) the ratio of arterial oxygen tension (PaO2)/fractional inspired oxygen (FiO2) (kPa) and (B) oxygenation index (kPa/cm H2O=PaO2/mean airway pressure×FiO2). Data are displayed as mean±SD. Values determined by analysis of variance with multiple comparisons test, compared to day 0. Fraser J H Brims et al. BMJ Open Resp Res 2015;2:e000080 ©2015 by British Thoracic Society