683 Fig. 1 Funnel plot. Selection bias in reporting RR of chronic lung disease (CLD) as suggested by asymmetry of the distribution of studies. x-axis: inverse of the standard error of the RR; y-axis: natu- ral logarithm of the RR. Blue diamonds: studies with either no high lung volume strategy (HLVS) or no lung protective volume strategy (LPVS); pink diamonds: studies with both HLVS and LPVS; dotted line: estimated pooled RR including all studies; dashed colored lines: pooled RR of subgroups of studies. Publication bias was vis- ually appraised by assessing symmetry of distribution of studies around the lines of pooled estimates. CMV conventional mech- anical ventilation Fig. 2 Linear regression analyses. Crude and subgroup linear re- gression analyses of the effect of year of publication, prior time on CMV and gestational age with natural logarithm of RR of CLD as dependent variable. y-axis: natural logarithm of the RR; x-axis: ex- planatory variables. Blue diamonds: studies with either no HLVS or no LPVS; pink diamonds: studies with both HLVS and LPVS. The size of the diamonds reﬂects the weights the individual trials con- tribute to the analyses. Thin blue line: regression line including all studies; thick pink line: regression line including only studies with both HLVS and LPVS. CMV conventional mechanical ventilation Fig. 3 Same as Fig. 2 Fig. 4 Same as Fig. 2 and a higher gestational age and increase of birth weight oscillatory ventilator was used and baseline incidence (data not shown) seemed to be positively associated with in CMV (0.75 vs 0.08) treated patients displayed the a relatively better outcome in HFV (Figs. 3, 4). Table 2 smallest effects on trial outcome (RRR = 0.84 and 0.90 shows the results of linear meta-regression analyses, for CLD and RRR = 0.85 and 0.99 for death or CLD, showing signiﬁcant associations with year of publication respectively). (3.1 times higher RR with change of publication year Figure 5 shows how the incidence of CLD in the CMV from 1992 to 2005) and whether or not a protective treated patients was related to the incidence in HFV treated ventilation strategy was applied (1.9 times higher RR with patients for each of the studies. The diagonal line repre- change of protective ventilation from no to yes; Table 2). sents the line of no effect in this ﬁgure. A trend line was In the linear regression analyses with death or CLD ﬁtted by weighted linear regression, showing a small ef- as composite outcome no signiﬁcant associations were fect of change in incidence in CMV on incidence in HFV- detected. Whether or not a Sensormedics high-frequency treated patients.