·To analyze the postoperative pulmonary function of children with congenital diaphragmatic hernia (CDH) and explore the related factors affecting the recovery of pulmonary function.

·The medical data of children with CDH who were treated in the Department of Pediatric Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, and underwent infant pulmonary function test (IPFT) from November 2016 to November 2020 were retrospectively reviewed. According to the type of ventilatory dysfunction in the examination, the children were divided into restrictive group, obstructive group, mixed group and healthy group. The differences in prenatal diagnosis, diagnostic gestational week, observed/expected lung-to-head ratio (O/E LHR), birth weight, 1 min Apgar score, hernia side, liver-up, use of patch during operation, duration of mechanical ventilation, length of hospital stay, month age at the time of IPFT and postoperative follow-up time in each group were analyzed. The pulmonary function results of the first-time test were analyzed in the diagnosis of whether the gestational age was less than 25 weeks, whether there was a liver-up and whether the patch was used during the operation. The difference between the results of the first and last test was analyzed.

·Fourty-two children were included in the analysis. A total of 96 tests were conducted in patients. Sixteen cases underwent IPFT once, and 26 cases had 2 or more tests. There were significant differences in month age at the time of IPFT and postoperative follow-up time among the restrictive (n=6), obstructive (n=68), mixed (n=9) and healthy (n=13) groups (P=0.004, P=0.002). Overall, the tidal volume per kg of body weight (TV/kg), and tidal expiratory flow 50% remaining tidal volume (TEF50%) in children with diagnosis of gestational age less than 25 weeks were lower (P=0.022, P=0.043), TEF75% and TEF50% in children with liver-up were lower (both P=0.040), and TEF50% and TEF25% in children with use of patch during operation were lower (P=0.034, P=0.020). The higher the O/E LHR, the higher the ratio of time to peak tidal expiratory flow to total expiratory time (TPEF/TE) and the ratio of volume at peak tidal expiratory flow to expiratory tidal volume (VPEF/VE) (r=0.393, P=0.005; r=0.324, P=0.023). The less the duration of mechanical ventilation, the higher the TPEF/TE and VPEF/VE (r=-0.377, P=0.000; r=-0.314, P=0.002). Within 1 month after operation, obstructive ventilatory dysfunction occurred 6 times (46.2%), and obstructive ventilatory dysfunction was found 49 times (77.8%) 3 months after operation. In patients who received IPFT twice or more, with the increase of follow-up time, TV/kg, TEF75%, TEF50% and TEF25% in the last IPFT were higher than those in the first test (P=0.001, P=0.003, P=0.001, P=0.000), and the respiratory rate decreased (P=0.010).

·The tidal respiratory function of CDH children diagnosed before the first 25 weeks of pregnancy, with liver-up and intraoperative patch use is even worse. The main manifestation of early and late postoperative ventilatory dysfunction is obstruction. With the passage of time of postoperative follow-up, the pulmonary function of children with CDH is improved.