Background Diaphragm atrophy and dysfunction are consequences of mechanical ventilation and are determinants of clinical outcomes. We hypothesize that partial preservation of diaphragm function, such as during assisted modes of ventilation, will restore diaphragm thickness. We also aim to correlate the changes in diaphragm thickness and function to outcomes and clinical factors. Methods This is a prospective, multicentre, observational study. Patients mechanically ventilated for more than 48 h in controlled mode and eventually switched to assisted ventilation were enrolled. Diaphragm ultrasound and clinical data collection were performed every 48 h until discharge or death. A threshold of 10% was used to define thinning during controlled and recovery of thickness during assisted ventilation. Patients were also classified based on the level of diaphragm activity during assisted ventilation. We evaluated the association between changes in diaphragm thickness and activity and clinical outcomes and data, such as ventilation parameters. Results Sixty-two patients ventilated in controlled mode and then switched to the assisted mode of ventilation were enrolled. Diaphragm thickness significantly decreased during controlled ventilation (1.84 ± 0.44 to 1.49 ± 0.37 mm, p < 0.001) and was partially restored during assisted ventilation (1.49 ± 0.37 to 1.75 ± 0.43 mm, p < 0.001). A diaphragm thinning of more than 10% was associated with longer duration of controlled ventilation (10 [5, 15] versus 5 [4, 8.5] days, p = 0.004) and higher PEEP levels (12.6 ± 4 versus 10.4 ± 4 cmH 2 O, p = 0.034). An increase in diaphragm thickness of more than 10% during assisted ventilation was not associated with any clinical outcome but with lower respiratory rate (16.7 ± 3.2 versus 19.2 ± 4 bpm, p = 0.019) and Rapid Shallow Breathing Index (37 ± 11 versus 44 ± 13, p = 0.029) and with higher Pressure Muscle Index (2 [0.5, 3] versus 0.4 [0, 1.9], p = 0.024). Change in diaphragm thickness was not related to diaphragm function expressed as diaphragm thickening fraction. Conclusion Mode of ventilation affects diaphragm thickness, and preservation of diaphragmatic contraction, as during assisted modes, can partially reverse the muscle atrophy process. Avoiding a strenuous inspiratory work, as measured by Rapid Shallow Breathing Index and Pressure Muscle Index, may help diaphragm thickness restoration.

中文翻译：

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辅助机械通气促进危重患者膈肌厚度恢复：一项前瞻性观察研究

背景 膈肌萎缩和功能障碍是机械通气的后果，是临床结果的决定因素。我们假设部分保留膈肌功能，例如在辅助通气模式期间，将恢复膈肌厚度。我们还旨在将膈肌厚度和功能的变化与结果和临床因素相关联。方法 这是一项前瞻性、多中心、观察性研究。在受控模式下机械通气超过 48 小时并最终切换到辅助通气的患者被纳入研究。每 48 小时进行一次膈肌超声和临床数据收集，直至出院或死亡。10% 的阈值用于定义辅助通气期间控制和恢复期间的减薄。患者还根据辅助通气期间的膈肌活动水平进行分类。我们评估了膈肌厚度和活动变化与临床结果和数据（例如通气参数）之间的关联。结果 62 例以控制模式通气后转为辅助通气模式的患者入选。隔膜厚度在受控通气期间显着降低（1.84 ± 0.44 至 1.49 ± 0.37 毫米，p < 0.001），并在辅助通气期间部分恢复（1.49 ± 0.37 至 1.75 ± 0.43 毫米，p < 0.001）。隔膜变薄超过 10% 与更长的受控通气持续时间（10 [5, 15] 天与 5 [4, 8.5] 天，p = 0.004）和更高的 PEEP 水平（12.6 ± 4 与 10.4 ± 4 cmH 2 O，p = 0.034）。辅助通气期间膈肌厚度增加超过 10% 与任何临床结果无关，但与呼吸频率降低（16.7 ± 3.2 对 19.2 ± 4 bpm，p = 0.019）和快速浅呼吸指数（37 ± 11 对 44 ± 13, p = 0.029) 和更高的压力肌肉指数（2 [0.5, 3] vs 0.4 [0, 1.9], p = 0.024）。隔膜厚度的变化与隔膜功能无关，隔膜功能表示为隔膜增厚分数。结论 通气模式会影响膈肌厚度，而在辅助模式下，保持膈肌收缩可以部分逆转肌肉萎缩过程。通过快速浅呼吸指数和压力肌肉指数测量，避免剧烈的吸气工作可能有助于隔膜厚度的恢复。