Fig. 3: Diaphragm monitoring during respiration and validity study.

A Example B-mode ultrasound and SMGs from two participants using Aixplorer’s during respiration. Since the images were not collected simultaneously, the SMGs from the two views are synchronized according to the respiration belt. B Example B-mode ultrasound and SMGs from two participants using wearable probe during respiration. The images were captured synchronously by multi-view system. In A, B, the respiration cycle is defined by the valley of the respiration belt signal, from the beginning of the inhalation to the end of the exhalation. The line and shaded area represent mean ± standard deviation of SMG (n = 3 cycles). The gray and red markers indicate the beginning and end of inspiration. The quintic Savitzky-Golay filter with a window length of eleven was used to smooth the signals for better illustration. The white markers inside the ultrasound images indicate the distance representation of the target layers or the expected direction of displacement. C–E Three SMG features measured by wearable probes vs. Aixplorer’s with Bland-Altman plots across all participants (n = 60). In scatter plots, the distribution graphs in the top and right margins correspond to the parameters on the horizontal and vertical axes, respectively. The two-sided Pearson correlation analysis was used to assess if there is a significant correlation (Thickness: p < 0.001; Thickening fraction: p < 0.001; Excursion: p < 0.001). F Outcome SMG features from different genders across all participants (n = 60).