Individualized risk estimation for postoperative pulmonary complications after hepatectomy based on perioperative variables

Table 4 New scoring system

Variable	Conditions	Scores
χ1: Age	< 65 years old	0
	≥ 65 years old	2
χ2: Medical diseases requiring drug treatment	No	0
	Yes	4
χ3: Number of segments resected	≤ 2	0
	≥ 3	2
χ4: Operation duration	< 180 min	0
	≥ 180 min	2
χ5: Blood transfusion	No	0
	Yes	2

Note: The total score was calculated as the sum of the five variables.