Abstract
BackgroundLung and diaphragm ultrasound methods have recently been introduced to predict the outcome of weaning from mechanical ventilation (MV). The aim of this study is to assess the reliability and accuracy of these techniques for predicting successful weaning in critically ill adults.MethodsWe conducted two studies: a cross-sectional interobserver agreement study between two sonographers and a prospective cohort study to assess the accuracy of lung and diaphragm ultrasound for predicting weaning and extubation outcome. For the interobserver agreement study, we included 50 general critical care patients who were consecutively admitted to the ICU. For the predictive accuracy study, we included consecutively 69 patients on MV who were ready for weaning. We assessed interobserver agreement of ultrasound measurements, using the weighted kappa coefficient for LUSm score (modified lung ultrasound score) and the intraclass correlation coefficient (ICC) and Bland–Altman method for TI (diaphragm thickening index). We assessed the predictive value of LUSm and TI in weaning outcome by plotting the corresponding ROC curves.ResultsWe found adequate interobserver agreement for both LUSm (weighted kappa 0.95) and TI (ICC 0.78, difference according to Bland–Altman analysis ± 12.5%). LUSm showed good-moderate discriminative power for successful weaning and extubation (area under the ROC curve (AUC) for successful weaning 0.80, and sensitivity and specificity at optimal cut-off point 0.76 and 0.73, respectively; AUC for successful extubation 0.78, and optimal sensitivity and specificity 0.76 and 0.47, respectively. TI was more sensitive but less specific for predicting successful weaning (AUC 0.71, optimal sensitivity and specificity 0.93 and 0.48) and successful extubation (AUC 0.76, optimal sensitivity and specificity 0.93 and 0.58). The area under the ROC curve for predicting weaning success was 0.83 for both ultrasound measurements together.ConclusionsInterobserver agreement was excellent for LUSm and moderate-good for TI. A low TI value or high LUSm value indicates high risk of weaning failure.
Highlights
Lung and diaphragm ultrasound methods have recently been introduced to predict the outcome of weaning from mechanical ventilation (MV)
For the thickening fraction (TI) variable, we calculated an intraclass correlation coefficient (ICC) value of 0.78, showing moderate to good interobserver agreement, and a difference in measurements according to the Bland–Altman method of ± 12.5% (Fig. 1)
Regarding the prognostic accuracy of ultrasound for weaning outcome, we found that if TI is below 24% or modified lung ultrasound score (LUSm) is greater than 7 points, the patient has a high risk of weaning failure, with an area under the ROC curve (AUC) of 0.8 for LUSm and 0.71 for TI
Summary
Lung and diaphragm ultrasound methods have recently been introduced to predict the outcome of weaning from mechanical ventilation (MV). Tenza‐Lozano et al Crit Ultrasound J (2018) 10:12 lung aeration patterns in patients with ventilator-associated pneumonia. In later articles, this score was used to predict weaning outcome [8,9,10,11], with promising results. Some studies have shown diaphragm excursion and thickness to be of low predictive value in the assessment of diaphragm function [18, 19, 23], a recent meta-analysis corroborates this and the best use of TI to weaning outcome [24]
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