Table 4. VAP incidence rate of different risk grade groups in the verification group.

Risk grade	Patient number	VAP number	VAP incidence rate (%)	χ2	P
Low	113	2	1.77	3.896a	0.048
Medium	221	15	6.79	26.442b	<0.001
High	271	65	23.99	27.324c	<0.001

^a, compared between low- and medium-risk grade; ^b, compared between medium- and high-risk grade; ^c, compared between high- and low-risk grade. VAP, ventilator-associated pneumonia.