Abstract
BACKGROUND: A global diaphragm thickness measurement technique was developed for the zone of apposition (ZOA) using an image edge identification approach. The method was assessed in terms of its repeatability and reliability when applied in patients with critical illness. METHODS: Diaphragm thickness measurements were conducted by experienced ultrasound examiners in 60 critically ill adult patients. The performance of continuous global diaphragm thickness measurements was compared to traditional localized diaphragm thickness measurements with regard to intra-observer and inter-observer consistency. RESULTS: End-expiratory diaphragm thickness was measured to assess consistency. For the traditional local diaphragm thickness measurements, the intraclass correlation coefficients (ICC) were 0.882 for intra-observer and 0.848 for inter-observer assessments (p < 0.001). The global diaphragm thickness measurements yielded ICC values of 0.968 and 0.955 for intra-observer and inter-observer assessments, respectively (p < 0.001). These findings indicated good reliability for the conventional method and excellent reliability for the global measurement method. The maximum observed variability was 16.5% with the traditional method and 3.9% with the continuous measurement approach. When using a 10% decrease in diaphragm thickness as the threshold for clinically relevant diaphragmatic atrophy, 16.7% of measurements obtained through the traditional method exceeded this error margin, whereas all measurements acquired through the continuous method remained within the acceptable range. CONCLUSIONS: Compared to traditional localized diaphragm thickness ultrasonography, the continuous approach demonstrated superior repeatability and reliability. This newly developed methodology may enhance the precision of diaphragm thickness evaluations within the ZOA in patients with critical illness.