Intra- and Inter-examiner Reliability of Diaphragmatic Ultrasound Parameters in People with Stable Chronic...

This study aimed to evaluate the intra- and inter-examiner reliability of ultrasound-derived diaphragm thickness (Tdi) and diaphragmatic excursion (DE) in individuals with chronic obstructive pulmonary disease (COPD).

This prospective cross-sectional study included outpatients with stable COPD. Six participants were analyzed for intra-examiner reliability and 16 for inter-examiner reliability. Two trained examiners performed diaphragmatic ultrasound using a same-day standardized protocol. In the intra-examiner phase, 1 examiner performed 2 repeated measurements in 6 participants on the same day. In the inter-examiner phase, 2 examiners performed 2 measurements in 16 participants under the same-day standardized protocol. Tdi was measured at functional residual capacity (FRC), residual volume (RV), and total lung capacity (TLC), and DE was measured from resting expiration to maximal inspiration. Intra-examiner reliability was assessed using intraclass correlation coefficients (ICCs; ICC [1,1]), and inter-examiner reliability was evaluated using ICC (2,1); standard error of measurement and minimal detectable change were also calculated.

Intra-examiner ICCs ranged from 0.70 to 0.98. Tdi at TLC (Tdi_TLC) and DE demonstrated high intra-examiner reliability (ICCs ≥0.83 for both examiners). Inter-examiner analysis showed high agreement for Tdi_TLC and DE (ICCs = 0.83 and 0.88, respectively), whereas Tdi at FRC and RV showed moderate agreement (ICCs = 0.57 and 0.59, respectively).

Ultrasound-derived diaphragm parameters-particularly Tdi_TLC and DE-demonstrated high intra- and inter-examiner reliability in individuals with stable COPD under a same-day standardized protocol. This suggests the potential clinical utility of diaphragmatic ultrasound for the reliable evaluation and short-term monitoring of diaphragmatic function in clinical and research settings.