Table 4:

Univariable linear analysis with proportion of blood pixels and bleeding volume and multivariable linear regression model with proportion of blood pixels and $10000\times \mathrm{ }{\left(\mathrm{bleeding}\mathrm{ }\mathrm{volume}\right)}^{-1/5}$ (model r² = 0.273)

Characteristics	Univariable analysis			Multivariable linear regression analysis
	Regression coefficient(β)	95% CI	P value	Regression coefficient(β)	95% CI	P value
Age at surgery	10.952	2.345-19.560	0.013
Male	360.72	188.224-533.213	<0.001
Immediate postoperative air leakage	237.23	61.350-413.109	0.008
Surgery duration	0.140	0.110-0.170	<0.001	0.097	0.053-0.141	<0.001
SumPBP	0.364	0.280-0.448	<0.001	0.171	0.053-0.289	0.005
SumPBP-Flushing	1.029	0.404-1.653	0.001

CI: confidence interval; PBP: proportion of blood pixels; SumPBP: sum of PBP; SumPBP-Flushing: sum of PBP from flushing to the end of the operation.