Diaphragm assessment by two dimensional speckle tracking imaging in normal subjects

Abstract

BackgroundConventionally, ultrasonographic assessment of diaphragm contractility has involved measuring respiratory changes in diaphragm thickness (thickening fraction) using B-mode or caudal displacement with M-mode. Two-dimensional speckle-tracking has been increasingly used to assess muscle deformation (‘strain’) in echocardiography. We sought to determine in a pilot study if this technology could be utilized to analyze diaphragmatic contraction.MethodsFifty healthy adult volunteers with normal exercise capacity underwent ultrasound imaging. A linear array transducer was used for the assessment of diaphragm thickness, thickening fraction (TF), and strain in the right anterior axillary line at approximately the ninth intercostal space. A phased array transducer was applied subcostally for the assessment of diaphragm displacement on the right mid-clavicular line. Diaphragmatic images were recorded from the end of expiration through the end of inspiration at 60 % maximal inspiratory capacity. Diaphragm strain was analyzed off-line by speckle tracking imaging. Blinded inter- and intra-rater variability was tested in 10 cases.ResultsMean right diaphragm thickness at end-expiration (±SD: standard deviation) was 0.24 cm (±0.1), with TF of 45.1 % (±12) at 60 % peak inspiratory effort. Mean right diaphragm caudal displacement was 4.9 cm (±1). Mean right diaphragm strain was -40.3 % (±9). A moderate correlation was seen between longitudinal strain and TF (R2 0.44, p < 0.0001). A weak correlation was seen between strain and caudal displacement (R2 0.14, p < 0.01), and an even weaker correlation was seen between caudal displacement and TF (R2 0.1, p = 0.04). Age, gender, and body mass index were not significantly associated with right diaphragm strain or TF. Although inter- and intra-rater variability was overall good for TF, caudal displacement, and strain (inter-rater R2; 0.8, 0.9, and 0.7, respectively [p < 0.01], intra-rater R2; 0.9, 0.7, and 0.9, respectively [p < 0.01]), strain values did have a slightly lower inter-rater repeatability.ConclusionsDiaphragmatic strain estimated by speckle tracking imaging was associated with conventional ultrasound measures of diaphragmatic function (TF and caudal displacement). Further clinical studies are warranted to investigate its clinical utility.Electronic supplementary materialThe online version of this article (doi:10.1186/s12871-016-0201-6) contains supplementary material, which is available to authorized users.

Evaluation of Respiratory Muscle Strength and Diaphragm Ultrasound: Normative Values, Theoretical Considerations, and Practical Recommendations

“…Most studies reporting normal values for diaphragm ultrasound measures in healthy subjects focus on either diaphragm thickness [4,5] or excursion amplitude [1]. Only few studies have combined these 2 measures but did not take into account diaphragm excursion velocity and respiratory muscle strength [20,21].…”

High-flow nasal oxygen versus noninvasive ventilation in adult patients with cystic fibrosis: a randomized crossover physiological study

“…We thought it was essential to have all assessments and measurements taken with noninvasive techniques (e.g., external device for volume, ultrasonography for diaphragm activity, transcutaneous gas values) in order to minimize a direct effect of these techniques on the observed values (Heisenberg principle) [ 29 , 30 ]. Importantly, however, these techniques are subject to measurement and performance error and we took great care to standardize the technical conditions for these measurements The lack of effect of diaphragmatic work might probably be explained by the relatively normalized (approximately 30%) TFdi in these patients at baseline [ 31 , 32 ] had been stabilized before protocol implementation. Despite having other clinical and biochemical indicators for ventilatory support, our subjects had improved and been stabilized prior to protocol initiation (all subjects weaned to nasal prong oxygen), making it difficult to demonstrate a difference in diaphragmatic work of breathing.…”

Possibilities of ultrasound research of the diaphragm

“…Проводя аналогию с эхокардиографией, для анализа движения диафрагмы может быть использована оценка скорости движения диафрагмы и методика speckle tracking [9][10][11][12]. Однако в настоящее время имеется недостаточно данных об использовании новых УЗ-технологий для исследования диафрагмы, чтобы обосновать достоверность их применения и определить диапазон нормальных значений.…”