Time-based pulmonary features from electrical impedance tomography demonstrate ventilation heterogeneity in chronic obstructive pulmonary disease

Milne, S; Huvanandana, J; Nguyen, C; Duncan, JM; Chapman, DG; Tonga, KO; Zimmermann, SC; Slattery, A; King, GG; Thamrin, C

Time-based pulmonary features from electrical impedance tomography demonstrate ventilation heterogeneity in chronic obstructive pulmonary disease

Milne, S Huvanandana, J Nguyen, C Duncan, JM Chapman, DG

Tonga, KO Zimmermann, SC Slattery, A King, GG Thamrin, C

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Publication Type:: Journal Article
Citation:: Journal of Applied Physiology, 2019, 127 (5), pp. 1441 - 1452
Issue Date:: 2019-01-01

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Field	Value	Language
dc.contributor.author	Milne, S	en_US
dc.contributor.author	Huvanandana, J	en_US
dc.contributor.author	Nguyen, C	en_US
dc.contributor.author	Duncan, JM	en_US
dc.contributor.author	Chapman, DG https://orcid.org/0000-0002-8211-1817	en_US
dc.contributor.author	Tonga, KO	en_US
dc.contributor.author	Zimmermann, SC	en_US
dc.contributor.author	Slattery, A	en_US
dc.contributor.author	King, GG	en_US
dc.contributor.author	Thamrin, C	en_US
dc.date.issued	2019-01-01	en_US
dc.identifier.citation	Journal of Applied Physiology, 2019, 127 (5), pp. 1441 - 1452	en_US
dc.identifier.issn	8750-7587	en_US
dc.identifier.uri	http://hdl.handle.net/10453/139213
dc.description.abstract	© 2019 the American Physiological Society. 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 1) to quantify VH using novel time-based EIT metrics and 2) 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 (Z-t) curve for each image pixel: 1) tE, mean expiratory time; 2) PHASE, mean time difference between pixel and global Z-t curves; and 3) AMP, mean amplitude of Z-t curve tidal variation. Distribution was quantified by the coefficient of variation (CV) and the heterogeneity index (HI). Both CV and HI of the tE 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. NEW & NOTEWORTHY Pulmonary electrical impedance tomography (EIT) is a real-time imaging technique capable of monitoring ventilation with exquisite temporal resolution. We report novel, timebased 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.	en_US
dc.relation.ispartof	Journal of Applied Physiology	en_US
dc.relation.isbasedon	10.1152/japplphysiol.00304.2019	en_US
dc.subject.classification	Physiology	en_US
dc.title	Time-based pulmonary features from electrical impedance tomography demonstrate ventilation heterogeneity in chronic obstructive pulmonary disease	en_US
dc.type	Journal Article
utslib.citation.volume	5	en_US
utslib.citation.volume	127	en_US
utslib.for	1102 Cardiorespiratory Medicine and Haematology	en_US
utslib.for	0606 Physiology	en_US
utslib.for	06 Biological Sciences	en_US
utslib.for	11 Medical and Health Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Life Sciences
utslib.copyright.status	closed_access
pubs.issue	5	en_US
pubs.publication-status	Published	en_US
pubs.volume	127	en_US

Abstract:

© 2019 the American Physiological Society. 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 1) to quantify VH using novel time-based EIT metrics and 2) 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 (Z-t) curve for each image pixel: 1) tE, mean expiratory time; 2) PHASE, mean time difference between pixel and global Z-t curves; and 3) AMP, mean amplitude of Z-t curve tidal variation. Distribution was quantified by the coefficient of variation (CV) and the heterogeneity index (HI). Both CV and HI of the tE 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. NEW & NOTEWORTHY Pulmonary electrical impedance tomography (EIT) is a real-time imaging technique capable of monitoring ventilation with exquisite temporal resolution. We report novel, timebased 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.

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http://hdl.handle.net/10453/139213