A comparative study of diaphragm ultrasound using multimodal parameters in healthy adults

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To compare multimodal ultrasonographic parameters for diaphragmatic assessment across different intercostal spaces (ISs) in healthy adults, and to evaluate the feasibility and inter-method consistency of various measurement approaches. This cross-sectional study enrolled 337 healthy volunteers at Zhejiang Provincial People’s Hospital(November 2024–June 2025). Diaphragmatic thickness (DT), thickening fraction (TF), and shear-wave elastography (SWE) were evaluated at the 7th–9th ISs by 2D and M-mode ultrasonography. Statistical analyses included Paired t-tests and Paired Wilcoxon signed-rank tests. No significant differences in echogenicity classification were observed between the 8th and 9th ISs ( p = 0.09). However, end-inspiratory thickness (Tei) and TF differed significantly between ISs ( p < 0.05) and between 2D and M-mode measurements ( p < 0.001). SWE image quality was superior at the 9th IS (76.55 ± 7.17% vs. 74.97 ± 9.15%, p = 0.012), though elastic modulus values did not differ ( p = 0.105). A standardized protocol for diaphragmatic ultrasonography was developed and meticulously outlined. Both the 8th and 9th ISs demonstrate adequate feasibility for routine diaphragmatic assessment, though thickness measurements require level-specific reference ranges due to significant inter-level variability. The 9th IS is recommended for SWE given its superior image quality. Notably, 2D imaging may be preferred in routine practice due to its lower dependence on high image quality.