目的·探讨同步间歇指令通气（synchronized intermittent mandatory ventilation，SIMV）模式下机械通气早期小儿膈肌的形态与功能变化状况。方法·纳入2020年10月—2021年12月收治于上海交通大学医学院附属新华医院小儿急危重症医学科（Pediatric Intensive Care Unit，PICU）并接受机械通气治疗满96 h的患儿，通过床旁超声连续测量膈肌的相关数据，分析接受机械通气治疗后3个不同时间点（0、48、96 h）膈肌相关变化。各时间点间皮下脂肪厚度、皮下脂肪萎缩率、膈肌厚度、膈肌移动度比较均采用Kruskal-Wallis H检验，其中膈肌厚度进一步采用Bonferroni法校正显著性水平进行事后两两比较；各时间点膈肌收缩速度、膈肌增厚率、膈肌萎缩率比较均采用单因素方差分析。结果·纳入46例测量数据完整的患儿，平均年龄2.94（1.35，7.00）岁，男女各23例。导致需要机械通气治疗的主要病因为肺炎（52.17%）；观察期间呼吸机的参数选择与机体氧合状态亦无明显差异（均P>0.05）。机械通气早期（96 h内）有50%的患儿出现腹部皮下脂肪的萎缩，36.96%患儿营养供给出现障碍（禁食与肠外营养支持），93.5%患儿接受糖皮质激素治疗，但3个时间点间腹部皮下脂肪的萎缩程度差异无统计学意义（均P>0.05）。床旁超声检测3个时间点的双侧膈肌厚度均发生明显萎缩（均P=0.000）；机械通气48 h后右侧膈肌萎缩率为4.27%±7.36%，左侧膈肌萎缩率为3.88%±6.85%；机械通气96 h后右侧膈肌萎缩率为7.69%±7.74%，左侧膈肌萎缩率为7.55%±7.69%；双侧膈肌的萎缩率在机械通气最初的48 h内比48~96 h内更高（P=0.000）。3个时间点膈肌的功能相关指标（膈肌移动度、膈肌收缩速率、膈肌增厚率）比较，差异均无统计学意义。结论·床旁膈肌超声可以用来监测机械通气儿童的膈肌萎缩程度。SIMV模式的机械通气早期（96 h内）可引起小儿膈肌的结构性萎缩，且以最初48 h更为显著。膈肌早期形态学变化尚未影响患儿膈肌功能。

Objective ·To investigate the morphologic and functional changes of the diaphragm of children during early mechanical ventilation under synchronized intermittent mandatory ventilation (SIMV) mode. Methods ·Children were admitted to the Pediatric Intensive Care Unit (PICU) of Xinhua Hospital, Shanghai Jiao Tong University School of Medicineand received mechanical ventilation for at least 96 h from October 2020 to December 2021. Bedside ultrasonic testing was conducted to inspect the changes in the diaphragm at three different time points (0, 48, and 96 h, respectively). Kruskal-Wallis H test was conducted for examining the abdominal fat thickness, atrophy rate, diaphragm thickness and DE between the groups. The diaphragm thickness was further compared by Bonferroni's test for ex-post hoc comparisons. Univariate ANOVA was performed for analyzing the diaphragm contraction velocity, diaphragm thickening fraction and diaphragmatic atrophy rate between the groups. Results ·Forty-six children in PICU with complete measurement data were included. Their average age was 2.94 (1.35, 7.00) years, including 23 males and 23 females. The main disease leading to perform mechanical ventilation was pneumonia (52.17%). There was no significant difference between the choice of ventilator parameters and oxygenation status during the observation period (P>0.05). In the early stage of mechanical ventilation (within 96 h), 50% of children showed atrophy of abdominal subcutaneous fat, 36.96% showed nutritional disorders (fasting and need parenteral nutrition support), and 93.5% of children received glucocorticoid therapy. However, there was no significant difference in the atrophy degree of abdominal subcutaneous fat between the three time points (all P>0.05). Bedside ultrasonography detected significant atrophy of bilateral diaphragm thickness at three different time points (all P=0.000). After 48 h of mechanical ventilation, the atrophy rate of the right diaphragm was 4.27%±7.36%, and the left diaphragm was 3.88%±6.85%. After 96 h of ventilation, the atrophy rate of the right diaphragm was 7.69%±7.74%, and the atrophy rate of the left diaphragm came to 7.55%±7.69%. The atrophy rate of the bilateral diaphragm was significantly higher in the first 48 h of mechanical ventilation than in the 48 h to 96 h (all P =0.000). However, there were no statistically significant differences in changes of diaphragm function-related indicators (diaphragm excursion, diaphragm contraction velocity, and diaphragm thickening fraction). Conclusion ·The bedside ultrasound is a proven tool to detect diaphragmatic atrophy in mechanically ventilated children. Mechanical ventilation can induce structural atrophy of the diaphragm in children during early mechanical ventilation under SIMV mode, which is more pronounced in the first 48 h. However, the early morphological changes of the diaphragm have not affected its function.