Department of Intensive Care Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.
MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
J Appl Physiol (1985). 2017 Nov 1;123(5):1063-1070. doi: 10.1152/japplphysiol.00095.2017. Epub 2017 May 18.
Assessment of diaphragmatic effort is challenging, especially in critically ill patients in the phase of weaning. Fractional thickening during inspiration assessed by ultrasound has been used to estimate diaphragm effort. It is unknown whether more sophisticated ultrasound techniques such as speckle tracking are superior in the quantification of inspiratory effort. This study evaluates the validity of speckle tracking ultrasound to quantify diaphragm contractility. Thirteen healthy volunteers underwent a randomized stepwise threshold loading protocol of 0-50% of the maximal inspiratory pressure. Electric activity of the diaphragm and transdiaphragmatic pressures were recorded. Speckle tracking ultrasound was used to assess strain and strain rate as measures of diaphragm tissue deformation and deformation velocity, respectively. Fractional thickening was assessed by measurement of diaphragm thickness at end-inspiration and end-expiration. Strain and strain rate increased with progressive loading of the diaphragm. Both strain and strain rate were highly correlated to transdiaphragmatic pressure (strain = 0.72; strain rate = 0.80) and diaphragm electric activity (strain = 0.60; strain rate = 0.66). We conclude that speckle tracking ultrasound is superior to conventional ultrasound techniques to estimate diaphragm contractility under inspiratory threshold loading. Transdiaphragmatic pressure using esophageal and gastric balloons is the gold standard to assess diaphragm effort. However, this technique is invasive and requires expertise, and the interpretation may be complex. We report that speckle tracking ultrasound can be used to detect stepwise increases in diaphragmatic effort. Strain and strain rate were highly correlated with transdiaphragmatic pressure, and therefore, diaphragm electric activity and speckle tracking might serve as reliable tools to quantify diaphragm effort in the future.
膈肌功能评估具有挑战性，尤其是在脱机阶段的危重症患者中。超声评估吸气时的分数增厚已被用于估计膈肌功能。目前尚不清楚，诸如斑点追踪等更复杂的超声技术是否在吸气努力的量化方面更具优势。本研究评估了斑点追踪超声定量评估膈肌收缩力的有效性。13 名健康志愿者接受了随机逐步阈负荷方案（0-50%最大吸气压力）。记录膈肌电活动和跨膈压。斑点追踪超声用于评估应变和应变速率，分别作为膈肌组织变形和变形速度的指标。通过测量吸气末和呼气末的膈肌厚度来评估分数增厚。随着膈肌负荷的逐步增加，应变和应变速率均增加。应变和应变速率与跨膈压高度相关（应变=0.72；应变速率=0.80），与膈肌电活动也高度相关（应变=0.60；应变速率=0.66）。我们得出结论，与传统超声技术相比，斑点追踪超声在吸气阈负荷下更能估计膈肌收缩力。使用食管和胃气球的跨膈压是评估膈肌功能的金标准。然而，这种技术具有侵入性，需要专业知识，并且解释可能很复杂。我们报告说，斑点追踪超声可用于检测膈肌功能的逐步增加。应变和应变速率与跨膈压高度相关，因此，膈肌电活动和斑点追踪可能成为未来量化膈肌功能的可靠工具。
