We developed a method to measure thoracic expansion separately on the left and right sides using a stretchable strain sensor. The purpose of this study was to assess the test-retest reliability of this measurement method in healthy subjects using two stretchable strain sensors.
Thirty healthy males (age, 3 ± 7.4 years; height, 171.3 ± 6.1 cm; and body weight, 64.3 ± 9.6 kg) participated in this study. Two stretchable strain sensors were used to simultaneously measure left and right thoracic expansion.Thoracic expansion was calculated as the difference in thoracic expansion measured at maximal expiration and at maximal inspiration. The unilateral thoracic expansion was calculated by recording the length change of the strain sensor from the maximal expiratory to the maximal inspiratory position three times and averaging these values. Two sets of thoracic expansion were measured to examine the reliability of the test-retest. Absolute test reliability was assessed by the standard error of mean (SEM) and minimum detectable change (MDC) of the thoracic expansion difference, and relative reliability was assessed using the intraclass correlation coefficient (ICC) model. A Bland-Altman analysis was performed to examine the agreement of measurements within and between sets and to quantify any bias. Statistical analysis was performed using R4.4.1 with a significance level of less than 5%.
The reliability of the first set was ICC (1,3) =0.99 (95% CI=0.98-0.99), SEM=1.17mm (95% CI=1.04-1.34), MDC=3.24mm. The reliability of the second set was ICC (1,3) =0.99 (95% CI=0.98-0.99), SEM=1.11mm (95% CI=0.99-1.28), MDC=3.09mm. Test-retest reliability was ICC (1,1) =0.96 (95% CI=0.94-0.98), SEM=1.19mm (95% CI=1.01-1.46), MDC=3.31mm. In 2 of 30 cases, the left-right difference exceeded MDC. The Bland-Altman analysis showed no fixed errors for between-retest measurements (95% CI =－0.64-0.23). Similarly, no proportional error was found (P = 0.31).
These results suggest that separate measurement of left and right thoracic expansion using two stretchable strain sensors is a reliable method.In the future, data from different age groups should be collected to establish an index for determining left-right differences in thoracic expansion.
The method of assessing the mobility of the left and right thorax expansion using stretchable strain sensors was shown to be reliable. We believe that this method can be applied to identify left-right differences in thoracic expansion and to determine the effectiveness of therapeutic interventions.
unilateral thoracic expansion
test -retest reliability
