Open AccessEffect of tidal volume and positive end‐expiratory pressure on expiratory time constants in experimental lung injury
Author(s) -
Henderson William R.,
Dominelli Paolo B.,
MolgatSeon Yannick,
Lipson Rachel,
Griesdale Donald E. G.,
Sekhon Mypinder,
Ayas Najib,
Sheel A. William
Publication year - 2016
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.12737
Subject(s) - expiration , medicine , tidal volume , positive end expiratory pressure , anesthesia , lung volumes , lung , respiratory system , respiratory physiology , cardiology
We utilized a multicompartment model to describe the effects of changes in tidal volume ( V T ) and positive end‐expiratory pressure ( PEEP ) on lung emptying during passive deflation before and after experimental lung injury. Expiratory time constants ( τ E ) were determined by partitioning the expiratory flow–volume ( V ˙E V ) curve into multiple discrete segments and individually calculating τ E for each segment. Under all conditions of PEEP and V T , τ E increased throughout expiration both before and after injury. Segmented τ E values increased throughout expiration with a slope that was different than zero ( P < 0. 01). On average, τ E increased by 45.08 msec per segment. When an interaction between injury status and τ E segment was included in the model, it was significant ( P < 0.05), indicating that later segments had higher τ E values post injury than early τ E segments. Higher PEEP and V T values were associated with higher τ E values. No evidence was found for an interaction between injury status and V T , or PEEP . The current experiment confirms previous observations that τ E values are smaller in subjects with injured lungs when compared to controls. We are the first to demonstrate changes in the pattern of τ E before and after injury when examined with a multiple compartment model. Finally, increases in PEEP or V T increased τ E throughout expiration, but did not appear to have effects that differed between the uninjured and injured state.