title: Functional respiratory imaging, regional strain, and expiratory time constants at three levels of positive end expiratory pressure in an ex vivo pig model.
abstract: Heterogeneity in regional end expiratory lung volume (EELV) may lead to variations in regional strain (ε). High ε levels have been associated with ventilator-associated lung injury (VALI). While both whole lung and regional EELV may be affected by changes in positive end-expiratory pressure (PEEP), regional variations are not revealed by conventional respiratory system measurements. Differential rates of deflation of adjacent lung units due to regional variation in expiratory time constants (τE) may create localized regions of ε that are significantly greater than implied by whole lung measures. We used functional respiratory imaging (FRI) in an ex vivo porcine lung model to: (i) demonstrate that computed tomography (CT)-based imaging studies can be used to assess global and regional values of ε and τEand, (ii) demonstrate that the manipulation of PEEP will cause measurable changes in total and regional ε and τEvalues. Our study provides three insights into lung mechanics. First, image-based measurements reveal egional variation that cannot be detected by traditional methods such as spirometry. Second, the manipulation of PEEP causes global and regional changes in R, E, ε and τEvalues. Finally, regional ε and τEwere correlated in several lobes, suggesting the possibility that regional τEcould be used as a surrogate marker for regional ε.
authors.affiliation: Division of Critical Care Medicine, Vancouver General Hospital, Vancouver, British Columbia, Canada william.henderson@vch.ca.
authors.forename: William R
authors.initials: WR
authors.lastname: Henderson
authors.affiliation: School of Kinesiology, Vancouver, Canada.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Molgat-Seon
authors.affiliation: FluidDA, Leuven, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Vos
authors.affiliation: Emmes Canada, Vancouver, Canada.
authors.forename: Rachel
authors.initials: R
authors.lastname: Lipson
authors.affiliation: FluidDA, Leuven, Belgium.
authors.forename: Francisca
authors.initials: F
authors.lastname: Ferreira
authors.affiliation: Radiology, The University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Miranda
authors.initials: M
authors.lastname: Kirby
authors.affiliation: FluidDA, Leuven, Belgium.
authors.forename: Cedric Van
authors.initials: CV
authors.lastname: Holsbeke
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Paolo B
authors.initials: PB
authors.lastname: Dominelli
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Donald E G
authors.initials: DE
authors.lastname: Griesdale
authors.affiliation: Division of Critical Care Medicine Vancouver General Hospital, Vancouver, British Columbia, Canada.
authors.forename: Mypinder
authors.initials: M
authors.lastname: Sekhon
authors.affiliation: Centre for Heart Lung Innovation St Paul's Hospital University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Harvey O
authors.initials: HO
authors.lastname: Coxson
authors.affiliation: Department of Radiology Vancouver General Hospital University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Mayo
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: A William
authors.initials: AW
authors.lastname: Sheel
mesh_terms: D000818:Animals; D005260:Female; D021621:Imaging, Three-Dimensional / Q000379:methods / Q000592:standards; D008168:Lung / Q000000981:diagnostic imaging* / Q000502:physiology; D012129:Respiratory Function Tests / Q000379:methods* / Q000592:standards; D015656:Respiratory Mechanics; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000592:standards
keywords: Positive end‐expiratory pressure; strain; time constant