Diaphragm Dysfunction

Rationale: Patients with invasive mechanical ventilation (IMV) frequently develop diaphragm dysfunction and experience difficult weaning. Recent ex vivo work suggests that a subset of mechanically ventilated ICU patients may exhibit diaphragm hibernation, an energy conserving myosin state that reduces force generation and may lead to a reversible increase in diaphragm strength over time. However, it is unknown whether diaphragm hibernation can be demonstrated in vivo during IMV and which clinical and biological factors are associated with this phenotype. Objective: Primary objective is to determine the driving factors (biomarkers) of diaphragm hibernation during IMV. Secondary objectives are to determine the proportion of ventilated critically ill patients who exhibit diaphragm hibernation during IMV, to investigate inflammatory and metabolic factors and other clinical exposures associated with diaphragm hibernation, and to explore associations between diaphragm hibernation and weaning related and survival outcomes. Study design: Prospective, observational, longitudinal cohort study. Study population: Adult ICU patients receiving IMV, expected to remain mechanically ventilated for at least 72 hours. Intervention (if applicable): Not applicable. This is an observational study. Study specific procedures consist of repeated phrenic nerve magnetic stimulation and additional blood sampling. Main study parameters/endpoints: The primary study parameter is the proportion of participants exhibiting diaphragm hibernation during IMV. Diaphragm hibernation is defined as an increase in stimulated twitch tracheal pressure (Ptr,stim), a measure of diaphragm strength, of at least 10% relative to baseline (Day 0-1) at any follow up assessment (Day 2, 3, 5, or 7) obtained before extubation or death. Ptr,stim will be assessed repeatedly on Day 0-1, Day 2, Day 3, Day 5, and Day 7, or until extubation or death, whichever occurs first. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Participant burden is limited and mainly consists of repeated phrenic nerve magnetic stimulation during a ventilator delivered end expiratory occlusion and additional blood sampling of 9.5 mL per time point, up to a total of 47.5 mL across the study period. Magnetic stimulation is non-invasive and expected discomfort is transient. Rare transient physiological changes may occur and measurements are performed under continuous ICU monitoring and will be postponed or omitted if considered unsafe or interfering with clinical care. Direct benefit for participants is limited, but the study may provide clinically relevant knowledge on diaphragm hibernation and its driving factors. The research questions are specific to diaphragm physiology during IMV in critically ill patients, therefore the study is group related and cannot be performed in a different population.

Pulmonary atelectasis and loss of lung aeration are common complications following cardiac surgery with cardiopulmonary bypass (CPB) and are associated with impaired oxygenation and prolonged mechanical ventilation. Diaphragm dysfunction occurring in the perioperative period may further delay extubation and prolong intensive care unit (ICU) stay. Flow-Controlled Ventilation (FCV) is a novel ventilation modality that provides continuous, flow-based delivery of tidal breaths with a triangular flow profile, potentially offering superior dynamic compliance optimisation compared to conventional Pressure-Controlled Ventilation (PCV).

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.

This study investigates the effect of threshold inspiratory muscle training on diaphragm thickness and diaphragm excursion, measured using ultrasonography, in patients with stable chronic obstructive pulmonary disease (COPD).

Changes in intrapleural pressure after lung volume reduction in Chronic Obstructive Pulmonary disease (COPD) patients can lead to complications, including an increased risk of pneumothorax. This procedure, intended to improve lung function, may disturb the pressure balance within the pleural space, potentially precipitating pneumothorax. Careful monitoring of intrapleural pressure could help predict patients at risk. However, intrapleural pressure can currently only be measured invasively. Diaphragm shear-wave elastography (SWE) has been shown to reflect transdiaphragmatic pressure during isovolumetric inspiratory efforts and ventilation against inspiratory loading, and therefore may serve as a non-invasive surrogate for intrapleural pressure. This project outlines a stepwise study plan to evaluate SWE as a tool for intrapleural pressure monitoring (Figure 1). The project only moves to the next phase is the study previous phase was achieved successfully. The current protocol involves the first phase: to validate diaphragm SWE against transdiaphragmatic pressure and assess measurement reliability for local ultrasound systems in healthy adults.This prospective, single-centre, observational validation study will include twelve healthy adult volunteers. During a single study session, participants will perform standardized inspiratory efforts while simultaneous measurements of diaphragm SWE, transdiaphragmatic pressure (via esophageal and gastric balloon catheters), and mouth pressures are obtained. These methods are routinely applied in physiological research and carry minimal risk. Apart from brief nasal or throat discomfort during catheter placement, no significant adverse effects are expected. By establishing the relationship between diaphragm SWE, transdiaphragmatic pressure, and mouth pressures, this study aims to provide the essential validation step for future clinical research in COPD patients following lung volume reduction.

ICU survivors are at an increased risk of hospital and ICU readmission. Among the complications of ICU stay, diaphragmatic dysfunction is common, with a prevalence of 60 to 80%, and is associated with increased mortality and prolonged hospital stays. Furthermore, several studies have reported that the observation of impaired respiratory muscle function upon ICU discharge is associated with a poor long-term prognosis. However, the incidence and prognostic impact of persistent diaphragmatic dysfunction at ICU discharge have never been evaluated. The measurement of dyspnea, a composite evaluation of respiratory muscle function, has not been assessed for predicting prognosis upon ICU discharge. The hypothesis of the project is that the presence of ICU-acquired diaphragmatic dysfunction at ICU discharge is associated with a poorer prognosis within 90 days.