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Title: Factors affecting the use of Neurally Adjusted Ventilatory Assist in the management of critically ill adult patients
Author: Hadfield, Daniel James
ISNI:       0000 0004 8500 6961
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2019
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Invasive ventilation can be a lifesaving treatment, but prolonged application is common and associated with increased morbidity and mortality, as well as long term physical and cognitive problems. The economic cost is also significant as ventilated patients consume a disproportionate amount of resource. Research aiming to reduce the duration of ventilation has recently focused on sedation limitation and protocolised weaning care, but newly developed ventilation modes, such as Neurally Adjusted Ventilatory Assist (NAVA) may be of potential benefit in reducing time on ventilation. The studies in this thesis investigate the use of NAVA technology in the adult Intensive Care Unit (ICU) through a randomised, controlled, feasibility trial (the RESTUS trial) and an associated user survey. These studies investigate the feasibility both of using this technology with critically ill adult patients who have risk factors for prolonged mechanical ventilation (PMV), and of conducting a subsequent, larger randomised controlled trial (RCT) comparing NAVA technology to Pressure Support Ventilation (PSV) in this patient population. The RESTUS study is the first to report NAVA mode adherence beyond 48 hours and demonstrates the feasibility of the trial protocol by meeting the pre-defined protocol compliance target. Good median adherence to the assigned ventilation mode was observed and adequate protocol acceptability demonstrated through acceptable physician recruitment refusal and the high participant consent rate. Importantly, the study also reports mechanisms of cross-over, highlighting a mix of human and technological factors, enabling targeted protocol modifications prior to a subsequent trial. While acknowledging the lack of power in the secondary clinical outcomes in the current trial, the study provides preliminary evidence of efficacy of NAVA ventilation with increased ventilator free days (VFDs) to day-28 and day-90, increased probability of breathing without assistance and alive ICU discharge, and reduced hospital mortality. These results are consistent with those reported previously in the majority of physiological studies and trends toward superior clinical outcomes reported in RCTs. While intention to treat analysis of sedation load and sedation scores showed broadly similar results between the groups, per-protocol analysis suggested a potential association between NAVA and improved adherence to target sedation levels and improved sedation management, which may be an important mechanistic factor underlying any potential benefit from NAVA. A multidisciplinary survey of 301 critical care clinicians was also conducted to investigate the experience, attitudes, beliefs and perceived barriers in relation to the use of NAVA ventilation and the conduct of a clinical trial. The survey demonstrated that most staff believed the NAVA mode and diaphragmatic monitoring to be clinically effective, and most staff supported the aims of the RESTUS feasibility research trial. The survey also highlighted key barriers to the acceptance and implementation of NAVA, including technological difficulties and perceptions of inexperience, and difficulty in application. These results reflected and supported the findings of the RCT and provided additional context and feasibility information that is of great value to the design of a future trial. In summary, with appropriate protocol modifications, these data suggest that it is both justified and feasible to conduct a randomised controlled trial to establish the effectiveness of NAVA in patients experiencing difficult or prolonged mechanical ventilation.
Supervisor: Rafferty, Gerrard Francis Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available