Robust Repeatable Respiratory Monitoring with EIT

重症监护病房（ICU）的机械通气通常是急性呼吸窘迫综合征（ARDS）和急性肺损伤（ALI）患者的救命干预措施。然而，近年来，机械通气可加重肺损伤，甚至可能是肺损伤的主要因素，如呼吸机诱导肺损伤（VILI）和呼吸机相关性肺炎（VAP）。因此，肺保护性通气（LPV）策略被开发出来，包括呼气末正压通气（PEEP）和高频振荡通气（HFOV）。尽管使用了LPV，与ARDS和ALI相关的死亡率仍然很高，报告的死亡率在33%至55%之间。胸电阻抗断层扫描（EIT）已成为一种很有前途的床边成像工具。这是一种非侵入性技术，它提供基于皮肤电测量的内部电导率分布。现有的研究和商业EIT系统通常将测量电极排列在胸腔周围，并基于过于简化的二维通用形状（如圆形或椭圆截面）产生二维图像切片。不幸的是，这种方法会产生明显的图像伪影，而且可重复性很差。为了消除这个问题，EIT测量和图像重建必须作为一个全三维的问题来处理，同时考虑到电极的位置和患者的身体形状。该项目的目的之一是基于从磁共振成像（MRI）和x射线计算机断层扫描等其他方式获得的三维知情身体形状，提供可靠和健壮的三维EIT图像重建。目前，临床医生在如何优化PEEP呼吸机设置方面没有达成共识。提高通气分布的知识将使临床医生能够设置更合适的通气参数，以减少VILI的潜在发生。特别是，与传统的间接方法（如动脉氧合或总潮汐量）相比，床边EIT监测在确定PEEP效果方面的价值仍然很大程度上未知。此外，尽管肺力学和局部通气之间有明确的联系，但呼吸机的设置通常基于血气和压力-容积曲线，而不是肺力学的测量结果。该项目的一个重要目标是为临床医生提供健壮的基于图像的肺力学模型，这将进一步有助于ICU中EIT的验证。以前的临床EIT研究通常使用的EIT仪器运行在相对较慢的帧速率，不灵活的驱动和测量策略以及有限数量的电极。在这个项目中，我们将开发一个最先进的快速3D EIT系统，使用先进的测量技术，这些技术尚未在临床环境中产生重大影响。事实上，在ICU中从来没有对EIT进行过实质性的研究，该研究将高质量的EIT测量、三维图像重建和肺力学建模的验证结合在一起。我们建议在ICU建立世界领先的EIT测量和成像能力。该项目基于曼彻斯特大学（UoM）在EIT方面的大量专业知识，以及伦敦国王学院和盖伊和圣托马斯NHS信托公司在应用胸部EIT方面的英国领先临床小组。我们还将建立在UoM在建模和动态MRI采集方面的世界领先能力，包括氧增强和动态对比增强MRI。拟议的项目与EPSRC的医疗保健技术研究主题密切相关。

Mechanical ventilation in the intensive care unit (ICU) is often a life-saving intervention for patients suffering from acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). However, in recent years, it has become clear that mechanical ventilation can exacerbate lung damage and may even be the primary factor in lung injury e.g. ventilator-induced lung injury (VILI) and ventilator associated pneumonia (VAP). Consequently, lung protective ventilation (LPV) strategies have been developed, including positive end expiratory pressure (PEEP) and high frequency oscillatory ventilation (HFOV). Despite the use of LPV, the mortality associated with ARDS and ALI is still great, with reported rates between 33 and 55%.Thoracic electrical impedance tomography (EIT) has emerged as a promising new imaging tool for bedside use. It is a non-invasive technique which provides the internal conductivity distribution based on electrical measurements on the skin. Existing research and commercial EIT systems have typically arranged measurement electrodes in rings around the thorax and produced two-dimensional image slices based on over-simplified two-dimensional generic shapes e.g. circular or elliptical cross-sections. Unfortunately, such an approach creates significant image artefacts and poor levels of repeatability. In order to eliminate this problem, EIT measurements and image reconstruction must be treated as a fully three-dimensional problem, taking into account the electrode positions and the body shape of the patient. One of the aims of this project is to provide reliable and robust three-dimensional EIT image reconstruction based on 3D informed body shape acquired from other modalities such as magnetic resonance imaging (MRI) and x-ray computed tomography.Currently, there exists no consensus amongst clinicians on how to optimize PEEP ventilator settings. Improved knowledge about the distribution of ventilation will enable clinicians to set more appropriate ventilation parameters in order to reduce the potential occurrence of VILI. In particular, the value of bedside EIT monitoring for determining the effect of PEEP in comparison with traditional indirect methods, such as arterial oxygenation or global tidal volumes, is still largely unknown. Additionally, despite the clear link between lung mechanics and regional ventilation, ventilator settings are normally based on blood gases and pressure-volume curves rather than measurements of lung mechanics. A significant aim of this project is to provide clinicians with robust image-based lung mechanics models which will further aid the validation of EIT in the ICU.Previous clinical EIT studies have generally utilized EIT instruments operating at relatively slow frame rates, inflexible drive and measurement strategies along with limited number of electrodes. In this project, we will develop a state-of-the-art fast 3D EIT system using advanced measurement techniques which have not yet had a significant impact in the clinical environment. In fact, there has never been a substantial investigation of EIT in the ICU which has drawn together the unique combination of high quality EIT measurements, three-dimensional image reconstruction and the validation of lung mechanics modelling.We propose to establish a world-leading capability in the measurement and imaging by EIT in the ICU. This project builds upon the substantial expertise in EIT at the University of Manchester (UoM) and the UK's leading clinical group in applied thoracic EIT at Kings College London and Guy's and St Thomas' NHS Trust. We will also build upon the world-leading capability at UoM in modelling and dynamic MRI acquisition including oxygen-enhanced and dynamic contrast-enhanced MRI. The proposed project registers strongly on the EPSRC research theme of healthcare technologies.