Diaphragmatic Ultrasonography in Difficult Weaning

Weaning from mechanical ventilation (MV) is a gradual process that includes several steps until the complete withdrawal of ventilatory support. Difficult weaning is defined as weaning completed only after the first attempt to withdraw the patient from ventilatory support, that is, a patient who failed the first spontaneous breathing trial (SBT). The use of ultrasound (US) to assess diaphragmatic and extradiaphragmatic muscles, such as the parasternal muscles, has been employed to determine diaphragmatic dysfunction and ventilatory effort, contributing to the decision-making process regarding weaning. Among the tools used for bedside monitoring and evaluation of patients are ventilatory variables that indicate an adequate level of ventilatory assistance in spontaneous modes through ventilatory drive, such as P0.1 (occlusion pressure in the first 100 ms) and assessment of ventilatory effort-inspiratory muscle pressure (Pmus)-which have also contributed to the downscaling of ventilatory support. However, there is still no consensus in the literature regarding predicted values or the effective role of these tools as predictors of weaning during the spontaneous breathing trial (SBT). The available studies investigating the relationship between diaphragmatic US, through measurements of diaphragmatic excursion and thickening fraction, and weaning failure from mechanical ventilation are mostly observational, which limits the strength of the current evidence. Therefore, it is essential to conduct randomized clinical trials, which are still unprecedented on this topic, to more robustly assess the efficacy of this technique as a decision-support tool during the weaning process, thereby contributing to more precise clinical practice. OBJECTIVES: The primary objective of this study is to evaluate the effect of diaphragmatic US use on ventilator-free days in patients with difficult weaning. The secondary objective is to analyze the relationship between the ventilatory variables P0.1 and Pmus, diaphragmatic US, and parasternal muscle recruitment during the SBT. METHODS: This is a randomized clinical trial, following CONSORT recommendations, which will be prospectively registered on the ClinicalTrials platform. Patients will be included after failing the first SBT. Subsequently, they will be randomized into two groups: In the shared US group, the results of diaphragmatic assessment via US will be shared with the attending team for decision-making regarding extubation. In the second group, the non-shared US group, the attending team will not have access to the diaphragmatic assessment for decision-making. EXPECTED RESULTS: It is expected that the shared US group of patients will have a shorter duration of MV and a lower number of extubation failures.