Platform of Randomized Adaptive Clinical Trials in Critical Illness

PRACTICAL is a randomized multifactorial adaptive platform trial for acute hypoxemic respiratory failure (AHRF). This platform trial will evaluate novel interventions for patients with AHRF across a range of severity states (i.e., not intubated, intubated with lower or higher respiratory system elastance, requiring extracorporeal life support) and across a range of investigational phases (i.e., preliminary mechanistic trials, full-scale clinical trials). AHRF is a common and life-threatening clinical syndrome affecting millions globally every year. Patients with AHRF are at high risk of death and long-term morbidity. Patients who require invasive mechanical ventilation are at risk of ventilator-induced lung injury and ventilator-induced diaphragm dysfunction. New treatments and treatment strategies are needed to improve outcomes for these very ill patients. Utilizing advances in Bayesian adaptive trial design, the platform will facilitate efficient yet rigorous testing of new treatments for AHRF, with a particular focus on mechanical ventilation strategies and extracorporeal life support techniques as well as pharmacological agents and new medical devices. The platform is designed to enable evaluation of novel interventions at a variety of stages of investigation, including pilot and feasibility trials, trials focused on mechanistic surrogate endpoints for preliminary clinical evaluation, and full-scale clinical trials assessing the impact of interventions on patient-centered outcomes. Interventions will be evaluated within therapeutic domains. A domain is defined as a set of interventions that are intended to act on specific mechanisms of injury using different variations of a common therapeutic strategy. Domains are intended to function independently of each other, allowing independent evaluation of multiple therapies within the same patient. Once feasibility is established, Bayesian adaptive statistical modelling will be used to evaluate treatment efficacy at regular interim adaptive analyses of the pre-specified outcomes for each intervention in each domain. These adaptive analyses will compute the posterior probabilities of superiority, futility, inferiority, or equivalence for pre-specified comparisons within domains. Each of these potential conclusions will be pre-defined prior to commencing the intervention trial. Decisions about trial results (e.g., concluding superiority or equivalence) will be based on pre-specified threshold values for posterior probability. The primary outcome of interest, the definitions for superiority, futility, etc. (i.e., the magnitude of treatment effect) and the threshold values of posterior probability required to reach conclusions for superiority, futility etc., will vary from intervention to intervention depending on the phase of investigation and the nature of the intervention being evaluated. All of these parameters will be pre-specified as part of the statistical design for each intervention trial. In general, domains will be designed to evaluate treatment effect within four discrete clinical states: non-intubated patients, intubated patients with low respiratory system elastance (\<2.5 cm H2O/(mL/kg)), intubated patients with high respiratory system elastance (≥2.5 cm H2O/(mL/kg)), and patients requiring extracorporeal life support. Where appropriate, the model will specify dynamic borrowing between states to maximize statistical information available for trial conclusions. In this perpetual trial design, different interventions may be added or dropped over time. Where possible, the platform will be embedded within existing data collection repositories to enable greater efficiency in outcome ascertainment. Standardized systems for acquiring both physiological and biological measurements are embedded in the platform, to be acquired at sites with appropriate training, expertise, and facilities to collect those measurements.

EXPAND-ECLS domain: The EXPAND-ECLS pilot trial is a multi-center, randomized, open-label, feasibility trial, embedded as a domain within the PRACTICAL platform trial. The ULTIMATE arm of this domain will evaluate the effect of ultra-low intensity ventilation facilitated by CO2 removal through VV-ECMO versus best current conventional ventilation on all-cause hospital mortality among patients with early moderate-severe AHRF with high respiratory system elastance receiving potentially injurious mechanical ventilation. The PROACTIVE arm of this domain will evaluate the effect of ECMO-facilitated strategy of earlier awakening, extubation, and rehabilitation versus best current conventional ventilation on all-cause hospital mortality among patients with early moderate-severe AHRF with high respiratory system elastance receiving potentially injurious mechanical ventilation. Invasive Mechanical Ventilation (IMV) Strategies domain: The IMV Strategies domain will evaluate multiple novel invasive ventilation strategies in comparison to conventional lung-protective ventilation in patients with acute hypoxemic respiratory failure (AHRF). Multiple approaches to mechanical ventilation are used, and the optimal approach is unknown. An efficient strategy to identify the best strategy is to compare multiple potential approaches simultaneously to determine more rapidly (a) which interventions are least effective (and should be dropped), and (b) which interventions result in the best outcomes for patients. In the current domain design, we will compare the current recommended ventilation strategy to two new approaches: a strategy that targets lung-inflating (driving) pressure instead of lung-inflating (tidal) volume, and a strategy that aims to maintain an optimal level of breathing effort to prevent diaphragm atrophy and injury while maintaining safe lung-inflating pressures. CORT-E2 domain: The Corticosteroid Early and Extended (CORT-E2) Trial is a phase III, multicentre Bayesian randomized controlled trial (RCT), which includes two cohorts within the domain; one examining the role of early corticosteroids as compared to not extending in persisting AHRF due to COVID or non-COVID (Extended Cohort). ESCAPE domain: Evaluating Subphenotypes in Immunocompromized Patients with ARF (ESCAPE) Domain is a prospective, multicentre observational cohort study, to identify subphenotypes across immunocompromised patients with acute hypoxemic respiratory failure (AHRF) using clinical characteristics and biomarkers. This study will prospectively collect biomarkers at the onset of AHRF which will allow us to characterize the underlying pathophysiology of AHRF with better precision. FLUDRO domain: The Fludrocortisone in Acute Hypoxemic Respiratory Failure with Airspace Disease (FLUDRO-1) domain is a phase II I trial. The trial aims to provide direct clinical evidence to resolve a critical long-standing question regarding the use of steroids in the treatment of AHRF with airspace disease. FAST-3 domain: The Nebulized Furosemide for the Treatment of Pulmonary Inflammation in Patients with Respiratory Failure Secondary to Pulmonary Infection domain is a phase III trial. It aims to use nebulized furosemide as supportive therapy to improve Advanced Respiratory Support (ARS) free days up to day 28 in critically ill patients with AHRF. IMV-ECLS domain: The Invasive Mechanical Ventilation Strategies in Venovenous-Extracorporeal Life Support (PRESSURE; Positive Pressure to Maintain Lung Recruitment during Extracorporeal Life Support for Acute Hypoxemic Respiratory failure) is a pilot and feasibility trial. It aims to identify which positive end-expiratory pressure (PEEP) strategies improve lung function in patients with AHRF supported by ECLS. IMPROV domain: The Inspiratory Muscle Training in Patients Receiving Ongoing Mechanical Ventilation is a pilot and feasibility RCT. It is designed to establish the feasibility of a definitive RCT of inspiratory muscle training to accelerate recovery from AHRF.