The efferent phrenic nerve activity measured 1 day or 10 days after the upper abdominal incision (Protocol B). (A-F) A significant decrease in spike frequency area-under-the-curve (AUC)/respiratory cycle (A), spike frequency AUC/minute (B), integrated phrenic neurogram (∫Phr) AUC/respiratory cycle (C), ∫Phr AUC/minute (D), central respiratory rate (E), and inspiratory-to-expiratory duration ratio (T_I:T_E; F) was observed 1 day after the abdominal incision (Postoperative Day 1 group, n = 9), compared with the Sham group (n = 7). The median values of the Postoperative Day 10 group (n = 7) were not different than the Sham group. The colored dots represent the individual data points, horizontal lines represent median, and error bars represent interquartile range. *P < 0.05; **P < 0.01 versus Sham, and †P < 0.05; ††P < 0.01 versus Postoperative Day 10 by Kruskal-Wallis test followed by post hoc Dunn’s multiple comparison tests. POD, postoperative day.