[Validation study of a novel diaphragmatic excursion measurement method: evaluation of diaphragmatic excursion by phased-array probe in hepato-renal/spleno-renal section].

Objective: To investigate the accuracy and reproducibility of diaphragmatic excursion (DE) measurements through hepato-renal/spleno-renal section as a novel method for assessing diaphragmatic function.

Methods: Twelve healthy participants were recruited. Each participant underwent DE measurements performed by four operators with varying levels of experience using traditional methods (liver/spleen section) and novel methods (hepato-renal/spleno-renal section), respectively. Among them, two experienced operators were critical care clinicians, and diaphragmatic ultrasound was performed in more than 50 cases. The other two inexperienced operators were respiratory therapists, with less than 10 cases of diaphragmatic ultrasound operations, who received a 2-hour theoretical and operational training before the study. Operators initially used the conventional method with a 1.5-6.0 MHz convex probe in M-mode, placing the sampling line perpendicular to the diaphragm at the point of maximum excursion, and the liver/spleen section DE was determined during normal breathing of participant. Then, they used the novel method with a 1.6-4.5 MHz phased array probe to observe diaphragmatic movement cranio-caudally along the mid-axillary line, employing anatomic M-mode with the sampling line placed perpendicular to the diaphragm at the level of the renal midpoint, and the DE of the hepato-renal/spleno-renal section was measured during normal breathing. The liver and hepato-renal sections were used to assess the right diaphragm, and spleen and spleno-renal sections were used to assess the left diaphragm. Correlation analysis of DE measurements from different sections was conducted using the Deming method, while consistency was assessed using the Bland-Altman method. The consistency of clinical acceptability was defined as the absence of fixed and proportional bias, with a difference of two standard deviations less than 40% of the mean measurement value. Percentage consistency limit = two standard deviations of the differences between measurements/mean measurement value×100%.

Results: Four operators performed image scans of DE in all four sections for each of the twelve subjects, with a high DE acquisition rate of 100% (48/48) for hepato-renal and spleno-renal sections, followed by the liver section [91.7% (44/48)] and the spleen section [66.7% (32/48)], particularly for the left diaphragm assessment, where the DE acquisition rate of spleno-renal section was significantly higher than that of traditional spleen section (P < 0.01). The overall measurement results showed that no significant difference was found in DE determined via the hepato-renal and spleno-renal sections using the novel method (cm: 1.64±0.10 vs. 1.55±0.14, P > 0.05), and they were significantly higher than those determined via the conventional liver and spleen sections (cm: hepato-renal section vs. liver section was 1.64±0.10 vs. 1.44±0.09, spleno-renal section vs. spleen section was 1.55±0.14 vs. 1.09±0.14, both P < 0.01). Correlation analysis revealed good correlations of DE between hepato-renal section and spleno-renal section, between liver section and hepato-renal section, between liver section and spleno-renal section (r values were 0.62, 0.59, and 0.42, all P < 0.01). Consistency analysis showed that the consistency in DE between hepato-renal section and spleno-renal section, as well as between liver section and hepato-renal section was good (both % consistency limits < 40%). However, the DE measured in the spleen section were not correlated with the other three sections, and there was no inconsistency (all % consistency limits > 40%). There was no statistically significant difference in DE measured by the four operators in the liver, spleen, hepato-renal, and spleno-renal sections (cm: 1.49±0.34, 1.44±0.37, 1.43±0.30, and 1.40±0.27 in liver section; 1.10±0.36, 1.05±0.18, 1.09±0.22, and 1.06±0.26 in spleen section; 1.67±0.43, 1.57±0.34, 1.63±0.32, and 1.66±0.36 in hepato-renal section; 1.45±0.33, 1.48±0.34, 1.50±0.24, and 1.65±0.26 in spleno-renal section; all P > 0.05). According to the clinically acceptable range of consistency limits, the DE measured by the four operators in all four sections showed good consistency (all % consistency limits < 40%).

Conclusions: The novel method of measuring DE through hepato-renal/spleno-renal sections is accurate, highly reproducible, and has a high acquisition rate, serving as a viable alternative to the conventional method involving the liver/spleen section.