Table 2

Linear random intercept model for predictors of expired carbon dioxide (ECO2) in the first 5 min of bag-mask ventilation

CovariatesUnivariate model*Multivariate model
Coefficient (95% CI)P valueR2 (%)Coefficient (95% CI)P valueR2 (%)R2 (%)
ECO2 (unconditional)2.90 (2.75 to 3.05)
Ventilation characteristics Expired tidal volume ( V TE )
Per mL/kg increase
Per standardised unit
0.37 (0.33 to 0.42)
2.37 (2.10 to 2.65)
<0.00119.30.32 (0.27 to 0.37)
2.02 (1.71 to 2.33)
<0.00123.1 30.8
( V TE ) 2
Per 100 (mL/kg)2 increase
Per standardised unit
−0.86 (−1.0 to 0.7)
−1.29 (−1.53 to −1.06)
<0.001−0.78 (−0.9 to −0.6)
−1.17 (−1.40 to −0.94)
<0.001
Mask leak
Per 10% increase
Per standardised unit
−0.30 (−0.33 to −0.27
−0.85 (−0.87 to −0.84)
<0.00116.1−0.056 (−0.098 to −0.014)
−0.16 (−0.29 to 0.42)
0.009
Ventilation frequency
Per 10 bpm increase
Per standardised unit
−0.17 (−0.23 to −0.11)
−0.40 (−0.55 to −0.26)
<0.0017.5−0.16 (−0.19 to −0.12)
−0.37 (−0.45 to −0.28)
<0.00116.1‡
Peak inflation pressure ( PIP )
Per 10 mbar increase
Per standardised unit
0.41 (0.16 to 0.67)
0.46 (0.18 to 075)
0.0011.10.24 (0.064 to 0.29)
0.27 (0.071 to 0.46)
0.008−0.3
( PIP) 2
Per 10 mbar2 increase
Per standardised unit
−0.60 (−0.87 to −0.33)
−0.61 (−0.88 to −0.33)
<0.001−0.47 (−0.64 to −0.29)
−0.47 (−0.65 to −0.29)
<0.001
Clinical factors Birth weight
Per kg increase
Per standardised unit
0.78 (0.51 to 1.04)
0.46 (0.30 to 0.62)
<0.0014.40.81 (0.58 to 1.03)
0.48 (0.34 to 0.61)
<0.0016.810.9
Initial heart rate
Per 10 bpm increase
Per standardised unit
0.081 (0.012 to 0.15)
0.17 (0.024 to 0.31)
0.0220.60.089 (0.034 to 0.14)
0.19 (0.070 to 0.30)
0.0021.3
5  min Apgar score
Per one unit increase
Per standardised unit
0.054 (−0.021 to 0.13)
0.11 (−0.043 to 0.26)
0.160.30.14 (0.068 to 0.22)
0.29 (0.14 to 0.44)
<0.0012.9
Log2 of time in seconds
Per unit increase
Per standardised unit
0.33 (0.28 to 0.38)
0.64 (0.54 to 0.73)
<0.0012.00.15 (0.12 to 0.19)
0.29 (0.23 to 0.36)
<0.0010.90.9
Random-effects parametersVar (_cons) 1.53 (1.31 to 1.77)§
Var (Residual) 1.53 (1.34 to 1.74)
ICC 0.50
  • *Intercorrelation coefficient (ICC) varied between 0.47 and 0.56 for all covariates.

  • †VTE and mask leak were correlated (Spearman’s rho −0.65). Excluding VTE from the model, beta value for mask leak decreased from −0.056 (−0.098 to –0.014) to −0.28 (−0.31 to –0.24). R2 for VTE alone excluding mask leak from the model was 21.9%. R2 for mask leak excluding VTE was 17.1%.

  • ‡Interaction term for VTE and frequency was significant with beta=−0.015 (−0.020 to −0.0091), p<0.001, the model is displayed without this term for interpretability. VTE and frequency were still significant in the model including the interaction term.

  • §R2 for the total model: 36.6%.