Table 3 Multivariable linear regression analysis CLD (Constant) SensorM TimeCMV Age HLVS LPVS Death or CLD (Constant) SensorM TimeCMV Age HLVS LPVS CLD (Constant) SensorM HLVS LPVS Death or CLD (Constant) SensorM HLVS LPVS Adjusted B Model A -0.66 -0.04 -0.02 0.03 -0.88 0.70 -1.86 -0.17 0.01 0.08 -0.88 0.68 0.07 -0.06 -0.81 0.72 -0.11 -0.79 0.46 Model B Sig. 0.900 0.884 0.903 0.850 0.306 0.506 0.412 0.309 0.722 0.299 0.407 0.127 0.904 0.698 0.203 0.011 0.318 0.363 0.089 -13.03 -0.75 -0.38 -0.36 -2.80 -1.73 -7.22 -0.55 -0.05 -0.09 -3.38 -0.28 -1.21 -0.38 -2.14 0.21 -0.33 -2.66 -0.09 11.70 0.66 0.34 0.42 1.04 3.14 3.49 0.21 0.06 0.25 1.62 1.65 1.35 0.26 0.52 1.23 0.12 1.08 1.01 RRR 0.96 0.85 1.17 0.42 2.02 0.85 1.07 1.47 0.42 1.98 0.94 0.44 2.06 0.90 0.45 1.59 0.47 0.04 0.16 0.06 0.18 0.58 0.68 0.62 0.03 0.76 0.69 0.12 1.23 0.72 0.07 0.92 95% conﬁdence interval Lower Upper boundary boundary 95% conﬁdence interval Lower Upper boundary boundary Multiple linear regression analyses were calculated for chronic lung disease (CLD), deﬁned as on oxygen at 30-36 weeks postgesta- tional age, and death or CLD. The following co-variates were evaluated: SensorM whether or not a Sensormedics type of HFV was used; TimeCMV mean time on CMV before start of the study (in hours). HLVS high lung volume strategy in the HFV group, LPVS lung protective ventilation strategy in the CMV group. B was the adjusted estimated coefﬁcient. RRR relative risk ratio=RRcovariate=1 /RRcovariate=0 , for binary variables (SensorM, HLVS and LPVS), for continues variables the extreme values reported in the studies were used, 8.7 for Time on CMV (RRRage = RRage=31 weeks /RRyear=26 weeks ) Fig. 5 Linear regression analysis of incidence of CLD in CMV on incidence of CLD in HFV. y-axis: incidence of CLD in HFV; x-axis: incidence of CLD in CMV. Thin pink line: regression line including all studies was ﬁtted in the model. One study contributed to the fact that surfactant was not used; therefore, surfactant was not used in the multiple linear regression analyses. Two models were ﬁtted. Model A used Sensormedics, time on CMV, gestational age, HLVS, and LPVS as covariates. The largest estimated effects were caused by ventilation strategies, HLVS, and LPVS, adjusted for use of Sensormedics ventilator, prior time on CMV, and gestational age. These estimations were consistent for the outcomes CLD (RRR = 0.42 and RRR = 2.02 for HLVS and LPVS, respectively) and death or CLD (RRR = 0.42 and RRR = 1.98 fro HLVS and LPVS, respectively). Use of a Sensormedics ventilator seemed to have a much smaller effect on RR for outcome. The RRR of gestational age, comparing 26 weeks with 31 weeks, for CLD and death or CLD were larger (RRR = 1.17 and RRR = 1.47). The effect of a difference in prior time on CMV of 8.7 h on CLD vs death or CLD was not consistent (RRR = 0.85 and RRR = 1.07, respectively). A sensitivity analysis was conducted by ﬁtting a se- cond model (model B) with the most important variables, 1.94 19.22 8.32 2.84 23.12 1.24 1.69 3.47 5.06 5.19 1.30 1.68 3.43 1.13 2.93 2.74 685