Diaphragm assessment by two dimensional speckle tracking imaging in normal subjects

Area of Science:

• Medical imaging
• Physiology
• Ultrasound technology

Background:

• Conventional ultrasonography assesses diaphragm contractility via thickness changes (thickening fraction) or caudal displacement.
• Two-dimensional speckle-tracking, used in echocardiography for muscle deformation (strain), is explored for diaphragmatic contraction analysis.

Purpose of the Study:

• To pilot the use of two-dimensional speckle-tracking technology for analyzing diaphragmatic contraction.

Main Methods:

• Fifty healthy volunteers underwent ultrasound imaging to assess diaphragm thickness, thickening fraction (TF), and strain.
• Measurements were taken at 60% maximal inspiratory capacity using linear and phased array transducers.
• Diaphragm strain was analyzed offline using speckle tracking; inter- and intra-rater variability was assessed.

Main Results:

• Mean diaphragm strain was -40.3% (±9), with a moderate correlation to TF (R²=0.44) and weak correlation to caudal displacement (R²=0.14).
• No significant association was found between strain/TF and age, gender, or BMI.
• Good inter- and intra-rater variability was observed for TF, caudal displacement, and strain, though strain had slightly lower inter-rater repeatability.

Conclusions:

• Diaphragmatic strain assessed by speckle tracking correlates with conventional ultrasound measures of diaphragmatic function.
• Further clinical studies are recommended to establish the clinical utility of this technique.