Airway Physiology and Imaging Group and Woolcock Emphysema Centre, Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia.
Faculty of Medicine and Health, Central Clinical School, University of Sydney, Sydney, New South Wales, Australia.
J Appl Physiol (1985). 2019 Nov 1;127(5):1441-1452. doi: 10.1152/japplphysiol.00304.2019. Epub 2019 Sep 26.
Pulmonary electrical impedance tomography (EIT) is a functional imaging technique that allows real-time monitoring of ventilation distribution. Ventilation heterogeneity (VH) is a characteristic feature of chronic obstructive pulmonary disease (COPD) and has previously been quantified using features derived from tidal variations in the amplitude of the EIT signal. However, VH may be better described by time-based metrics, the measurement of which is made possible by the high temporal resolution of EIT. We aimed ) to quantify VH using novel time-based EIT metrics and ) to determine the physiological relevance of these metrics by exploring their relationships with complex lung mechanics measured by the forced oscillation technique (FOT). We performed FOT, spirometry, and tidal-breathing EIT measurements in 11 healthy controls and 9 volunteers with COPD. Through offline signal processing, we derived 3 features from the impedance-time (-) curve for each image pixel: ) , mean expiratory time; ) PHASE, mean time difference between pixel and global - curves; and ) AMP, mean amplitude of - curve tidal variation. Distribution was quantified by the coefficient of variation (CV) and the heterogeneity index (HI). Both CV and HI of the and PHASE features were significantly increased in COPD compared with controls, and both related to spirometry and FOT resistance and reactance measurements. In contrast, distribution of the AMP feature showed no relationships with lung mechanics. These novel time-based EIT metrics of VH reflect complex lung mechanics in COPD and have the potential to allow real-time visualization of pulmonary physiology in spontaneously breathing subjects. Pulmonary electrical impedance tomography (EIT) is a real-time imaging technique capable of monitoring ventilation with exquisite temporal resolution. We report novel, time-based EIT measurements that not only demonstrate ventilation heterogeneity in chronic obstructive pulmonary disease (COPD), but also reflect oscillatory lung mechanics. These EIT measurements are noninvasive, radiation-free, easy to obtain, and provide real-time visualization of the complex pathophysiology of COPD.
肺部电阻抗断层成像（EIT）是一种功能成像技术，可实时监测通气分布。通气异质性（VH）是慢性阻塞性肺疾病（COPD）的特征，以前曾使用源自 EIT 信号幅度的潮气量变化的特征来量化。然而，VH 可能通过基于时间的指标更好地描述，EIT 的高时间分辨率使其能够测量这些指标。我们旨在）使用新的基于时间的 EIT 指标来量化 VH，）通过探索它们与通过强迫振荡技术（FOT）测量的复杂肺力学的关系来确定这些指标的生理相关性。我们在 11 名健康对照者和 9 名 COPD 志愿者中进行了 FOT、肺活量测定和潮气呼吸 EIT 测量。通过离线信号处理，我们从每个图像像素的阻抗-时间（-）曲线中得出 3 个特征：），平均呼气时间；）PHASE，像素和全局-曲线之间的平均时间差；和）AMP，-曲线潮气量变化的平均幅度。分布通过变异系数（CV）和异质性指数（HI）进行量化。与对照组相比，COPD 患者的和 PHASE 特征的 CV 和 HI 均显著增加，并且与肺活量测定和 FOT 阻力和电抗测量均相关。相比之下，AMP 特征的分布与肺力学无关。这些 VH 的新型基于时间的 EIT 指标反映了 COPD 中的复杂肺力学，并且有可能允许在自主呼吸的受试者中实时可视化肺生理学。肺部电阻抗断层成像（EIT）是一种实时成像技术，能够以极好的时间分辨率监测通气。我们报告了新的基于时间的 EIT 测量，这些测量不仅在慢性阻塞性肺疾病（COPD）中显示出通气异质性，而且还反映了振荡性肺力学。这些 EIT 测量是非侵入性的、无辐射的、易于获得的，并且提供了 COPD 复杂病理生理学的实时可视化。
