Ultrasound shear wave elastography for non-invasive assessment of diaphragm activity in mechanically ventilated patients.

Introduction: Mechanical ventilation is a life-saving treatment that is however associated with diaphragm dysfunction. The optimal ventilator settings providing a lung protective ventilation while maintaining a safe diaphragm activity are difficult to determine. A noninvasive and bedside evaluation of the diaphragm activity could be helpful. We investigated whether changes in diaphragm stiffness (ΔSMdi) assessed using ultrasound shear wave elastography (SWE) may be used as a surrogate of changes in transdiaphragmatic pressure (ΔPdi) in mechanically ventilated (MV) patients. Methods: Pdi was continuously monitored using esophageal and gastric balloons and SMdi was measured at the zone of apposition of the right hemi-diaphragm. Measurements were performed twice under initial ventilator settings and every five minutes during a spontaneous breathing trial (SBT). Pearson correlation coefficient (r) were used to determine within-individual and overall relationships between Pdi and SMdi. Results: Among the 25 patients enrolled, 8 displayed a significant ΔSMdi-ΔPdi correlation (r=0.62-0.88, p Conclusion: SMdi obtained by SWE appears as a promising technique to assess diaphragm activity in MV patients. Technological improvements are necessary to increase SWE sampling rate before enabling its generalization in the ICU.