Diaphragm shear modulus reflects transdiaphragmatic pressure during isovolumetric inspiratory efforts and ventilation against inspiratory loading

Abstract

The reference method for the assessment of diaphragm function relies on the measurement of transdiaphragmatic pressure (Pdi). Local muscle stiffness measured using ultrafast shear wave elastography (SWE) provides reliable estimates of muscle force in locomotor muscles. This study aimed at investigating whether SWE could be used as a surrogate of Pdi to evaluate diaphragm function. Fifteen healthy volunteers underwent a randomized stepwise inspiratory loading protocol of 0–60% of maximal isovolumetric inspiratory pressure during closed-airways maneuvers and 0–50% during ventilation against an external inspiratory threshold load. During all tasks, Pdi was measured and SWE was used to assess shear modulus of the right hemidiaphragm (SMdi) at the zone of apposition. Pearson correlation coefficients ( r) and repeated-measures correlation coefficients ( R) were computed to determine within-individual and overall relationships between Pdi and SMdi, respectively. During closed-airways maneuvers, mean Pdi correlated to mean SMdi in all participants [ r ranged from 0.77 to 0.96, all P < 0.01; R = 0.82, 95% confidence intervals (0.76, 0.86), P < 0.01]. During ventilation against inspiratory threshold loading, Pdi swing correlated to maximal SMdi in all participants [ r ranged from 0.40 to 0.90, all P < 0.01; R = 0.70, 95% confidence intervals (0.66, 0.73), P < 0.001]. Changes in diaphragm stiffness as assessed by SWE reflect changes in transdiaphragmatic pressure. SWE provides a new opportunity for direct and noninvasive assessment of diaphragm function. NEW & NOTEWORTHY Accurate and specific estimation of diaphragm effort is critical for evaluating and monitoring diaphragm dysfunction. The measurement of transdiaphragmatic pressure requires the use of invasive gastric and esophageal probes. In the present work, we demonstrate that changes in diaphragm stiffness assessed with ultrasound shear wave elastography reflect changes in transdiaphragmatic pressure, therefore offering a new noninvasive method for gauging diaphragm effort.

Real-time shear wave ultrasound elastography: a new tool for the evaluation of diaphragm and limb muscle stiffness in critically ill patients

“…We also paid extra attention to measure the shear modulus in muscles with no contractions and at the end of the expiration for the diaphragm. In the healthy controls, we report a diaphragm shear modulus above the range observed by Bachasson et al [23]. Two main differences should be noted between the two studies.…”

“…SWE has been established as an excellent diagnostic method for liver fibrosis, breast cancer and thyroid cancer [21]. In skeletal muscles, it provides a spatial representation and quantifiable measurement of the mechanical properties and an approximate of the muscle fibrosis and the activity of the disease in chronic myopathy [22] as well as a surrogate of diaphragm force production in healthy volunteers during isovolumetric inspiratory efforts [23]. Although SWE muscle analysis may provide new data about muscle quality during critical illness, it has never been evaluated in the very specific critically ill population which is exposed to severe structural muscular alterations.…”

Ultrasound shear wave elastography for assessing diaphragm function in mechanically ventilated patients: a breath-by-breath analysis

“…stiffness) measured using SWE has been shown to provide reliable estimates of passive and active muscle force in locomotor muscles [21,22]. Lately, we demonstrated that changes in diaphragm shear modulus (SMdi) reflect changes in Pdi during isovolumetric inspiratory efforts and ventilation against inspiratory loading in healthy subjects [23]. Recently, Flatres et al performed measurements of shear modulus in the diaphragm (i.e.…”

Respiratory muscle ultrasonography: methodology, basic and advanced principles and clinical applications in ICU and ED patients—a narrative review

“…Moreover, shear wave elastography is considered to be more accurate and reproducible than evaluation of echogenicity, which is highly dependent on ultrasound settings (e.g., gain, contrast, etc.). A recently published proofof-concept work demonstrated that changes in diaphragm stiffness during inspiratory efforts as assessed with ultrasound shear wave elastography reflect changes in transdiaphragmatic pressure [74]. Therefore, it might offer a new non-invasive method for gauging diaphragm effort.…”