Intra-Rater Reliability of Ultrasound Measurements of Diaphragm Thickness and Contractility in Individuals with Nonspecific Chronic Neck Pain

This study aimed to determine within-day intra-rater reliability of ultrasound measurements of the right and left hemidiaphragm thickness and contractility (quantified by percentage thickness change) in supine position during deep breathing in individuals with nonspecific chronic neck pain. Seventeen volunteers (20-55 years of age) participated in this observational study. Bilateral diaphragm muscle thickness and contractility (percentage thickness change) were compared between 2 measurement sessions administered by a radiologist using B-mode real-time ultrasound (30 minutes apart). Intraclass correlation coefficient (ICC [3, 3]) as well as the standard error of measurement (SEM), minimal detectable change (MDC), and the coefficient of variation (CV) were used to determine the intra-rater reliability. The right and left hemidiaphragm thickness showed good to excellent reliability at the end of deep inspiration (ICC, 0.90; 95% confidence interval [CI], 0.72-0.96; and ICC, 0. 93; 95% CI, 0.81-0.97, respectively) as well as at the end of deep expiration (ICC, 0.91; 95% CI, 0.75-0.96; ICC, 0.91; 95% CI, 0.77-0.97; SEM, 0.19; MDC, 0.54; and CV, 7.84%, respectively) and the percentage thickness change (ICC, 0.83; 95% CI, 0.54-0.94; and ICC, 0.93; 95% CI, 0.82-0.97, respectively). This study found that diagnostic ultrasound measurements of the right and left hemidiaphragm thickness and contractility in supine position during deep breathing in individuals with nonspecific chronic neck pain was reliable. The SEM, MDC, and CV reported may allow for accurate interpretation of diaphragm assessment in a clinical research setting.