Predicting Tracheostomy Capping Tolerance in Neurocritical Patients Using Respiratory Muscle Ultrasonography and Clinical Indicators: A Prospective Nomogram Study

Background Tracheostomy capping failure is highly prevalent in the neurointensive care unit (NICU). This failure is frequently attributed to impaired airway protection and ineffective cough rather than isolated ventilatory pump failure. Although diaphragmatic ultrasonography is widely utilized to predict weaning outcomes, the prognostic value of combining inspiratory and expiratory muscle assessments in this specialized population remains underexplored. This study aimed to evaluate the predictive value of combined diaphragmatic and abdominal muscle ultrasonography for capping tolerance and to develop a visualized clinical predictive nomogram. Methods This single-center, prospective observational study (N = 58) enrolled neurocritical patients who underwent bedside ultrasonographic evaluation prior to a 48-hour continuous capping trial. We measured the diaphragmatic thickening fraction (DTF) and the transversus abdominis thickening fraction (TrA-TF) during a standardized endotracheal suctioning-induced reflex cough. Multivariable logistic regression analysis was employed to identify independent predictors and construct the nomogram. Model performance was comprehensively assessed using the area under the receiver operating characteristic curve (AUC), calibration curves, and decision curve analysis (DCA). Results A total of 35 patients (60.3%) successfully tolerated capping. Multivariable analysis demonstrated that, following rigorous adjustment for the Coma Recovery Scale-Revised (CRS-R) score, both DTF (odds ratio [OR] = 1.24, 95% confidence interval [CI]: 1.05–1.45, P = 0.009) and TrA-TF (OR = 1.17, 95% CI: 1.05–1.32, P = 0.006) emerged as independent predictors of capping success. The combined nomogram model, integrating DTF, TrA-TF, and CRS-R, exhibited excellent discrimination (AUC = 0.878, 95% CI: 0.791–0.965), significantly outperforming the isolated diaphragm model (AUC = 0.761) and the isolated abdominal muscle model (AUC = 0.800). Calibration curves indicated a high concordance between predicted probabilities and observed frequencies. Furthermore, DCA confirmed that utilizing this model for decision-making provided a substantial net clinical benefit across a broad probability threshold range of 10% to 90%. Conclusions In neurocritical patients, isolated evaluation of inspiratory muscle function is inadequate. A multidimensional assessment strategy incorporating inspiratory reserve (DTF), expiratory expulsive power (TrA-TF), and central arousal state (CRS-R) significantly enhances the predictive accuracy for capping tolerance. The nomogram proposed herein offers an objective, non-invasive, and volition-independent bedside tool to assist clinicians in optimizing decannulation decision-making and mitigating airway-related risks.