CD8A and susceptibility to pneumonia measurement: The levels of CD3+, CD4+/CD8+, IgA, and IgM in the EN group were higher than those of the PN group at pre-operation and post-operation; the EN group had a significantly lower incidence of poor wound healing, peritoneal cavity infection, pneumonia, and a shorter first bowel sound time, first flatus time, and post-operation hospital stay than the PN group.