Variables predicting weaning outcome in prolonged mechanically ventilated tracheotomized patients: a retrospective study

Background: Several studies have assessed predictors of weaning and extubation outcome in short-term mechanically ventilated patients, but there are only few studies on predictors of weaning from prolonged mechanical ventilation. Methods: Retrospective, single-center, observational study at a specialized national weaning center in Germany. Patients' medical records were reviewed to obtain data on demographics, comorbidities, respiratory indices, and the result of a prospectively documented, standardized spontaneous breathing trial (SBT) upon admission to the weaning center. Respiratory indices assessed were the ventilatory ratio (VR) and parameters derived from calculated mechanical power (MP). Predictors associated with failure of prolonged weaning and failure of the SBT were assessed using a binary logistic regression model. Results: A total of 263 prolonged mechanically ventilated, tracheotomized patients, treated over a 5-year period were analyzed. After 3 weeks of mechanical ventilation, patients with unsuccessful weaning failed a SBT more frequently and showed significantly increased values for inspiratory positive airway pressure, driving pressure, VR, absolute MP, and MP normalized to predicted body weight and dynamic lung-thorax compliance (LTC-MP). In the logistic regression analyses, variables independently correlated with weaning failure were female gender (adjusted odds ratio 0.532 95% CI 0.291-0.973; p = 0.040), obesity (body mass index ≥ 30 kg/m2) (2.595 1.210-5.562; p = 0.014), COPD (3.209 1.563-6.589; p = 0.002), LTC-MP (3.470 1.067-11.284; p = 0.039), PaCO2 on mechanical ventilation (1.101 95% CI 1.034-1.173; p = 0.003), and failure of the SBT (4.702 2.250-9.825; p < 0.001). In addition, female gender (0.401 0.216-0.745; p = 0.004), LTC-MP (3.017 1.027-8.862; p = 0.046), and PaCO2 on mechanical ventilation (1.157 1.083-1.235; p < 0.001) were independent risk factors for an unsuccessful SBT. Conclusions In the present study, the derived predictors of weaning point to a crucial role of the workload imposed on respiratory muscles during spontaneous breathing. Mechanical power normalized to lung-thorax compliance was independently correlated with weaning outcome and may identify patients at high risk for weaning failure

Mechanical power normalized to lung-thorax compliance predicts prolonged ventilation weaning failure: a prospective study

Abstract Background Mechanical power (MP) of artificial ventilation, the energy transferred to the respiratory system, is a chief determinant of adequate oxygenation and decarboxylation. Calculated MP, the product of applied airway pressure and minute ventilation, may serve as an estimate of respiratory muscle workload when switching to spontaneous breathing. The aim of the study was to assess MP’s discriminatory performance in predicting successful weaning from prolonged tracheostomy ventilation. Methods Prospective, observational study in 130 prolonged mechanically ventilated, tracheotomized patients in a specialized weaning center. Predictive weaning outcome ability of arterial blood gas analyses and indices derived from calculated MP at beginning and end of weaning was determined in terms of area under receiver operating characteristic curve (AUROC) and measures derived from k-fold cross-validation (likelihood ratios, diagnostic odds ratio, F1 score, and Matthews correlation coefficient [MCC]). Results Forty-four (33.8%) patients experienced weaning failure. Absolute MP showed poor discrimination in predicting outcome; whereas specific MP (MP normalized to dynamic lung-thorax compliance, LTCdyn-MP) had moderate diagnostic accuracy (MCC 0.38; AUROC 0.79, 95%CI [0.71‒0.86], p < 0.001), further improved by correction for corresponding mechanical ventilation PaCO2 (termed the power index of the respiratory system [PIrs]: MCC 0.52; AUROC 0.86 [0.79‒0.92], p < 0.001). Diagnostic performance of MP indices increased over the course of weaning, with maximum accuracy immediately before completion (LTCdyn-MP: MCC 0.49; AUROC 0.86 [0.78‒0.91], p < 0.001; PIrs: MCC 0.68; AUROC 0.92 [0.86‒0.96], p < 0.001). Conclusions MP normalized to dynamic lung-thorax compliance, a surrogate for applied power per unit of ventilated lung volume, accurately discriminated between low and high risk for weaning failure following prolonged mechanical ventilation

Ventilatory ratio and mechanical power in prolonged mechanically ventilated COVID-19 patients respiratory failures of other etiologies

Background: Evidence suggests differences in ventilation efficiency and respiratory mechanics between early COVID-19 pneumonia and classical acute respiratory distress syndrome (ARDS), as measured by established ventilatory indexes, such as the ventilatory ratio (VR; a surrogate of the pulmonary dead-space fraction) or mechanical power (MP; affected, e.g., by changes in lung-thorax compliance). Objectives: The aim of this study was to evaluate VR and MP in the late stages of the disease when patients are ready to be liberated from the ventilator after recovering from COVID-19 pneumonia compared to respiratory failures of other etiologies. Design: A retrospective observational cohort study of 249 prolonged mechanically ventilated, tracheotomized patients with and without COVID-19-related respiratory failure. Methods: We analyzed each group’s VR and MP distributions and trajectories [repeated-measures analysis of variance (ANOVA)] during weaning. Secondary outcomes included weaning failure rates between groups and the ability of VR and MP to predict weaning outcomes (using logistic regression models). Results: The analysis compared 53 COVID-19 cases with a heterogeneous group of 196 non-COVID-19 subjects. VR and MP decreased across both groups during weaning. COVID-19 patients demonstrated higher values for both indexes throughout weaning: median VR 1.54 versus 1.27 ( p  < 0.01) and MP 26.0 versus 21.3 Joule/min ( p  < 0.01) at the start of weaning, and median VR 1.38 versus 1.24 ( p  < 0.01) and MP 24.2 versus 20.1 Joule/min ( p  < 0.01) at weaning completion. According to the multivariable analysis, VR was not independently associated with weaning outcomes, and the ability of MP to predict weaning failure or success varied with lung-thorax compliance, with COVID-19 patients demonstrating consistently higher dynamic compliance along with significantly fewer weaning failures (9% versus 30%, p  < 0.01). Conclusion: COVID-19 patients differed considerably in ventilation efficiency and respiratory mechanics among prolonged ventilated individuals, demonstrating significantly higher VRs and MP. The differences in MP were linked with higher lung-thorax compliance in COVID-19 patients, possibly contributing to the lower rate of weaning failures observed