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Angus SA, Henderson WR, Banoei MM, Molgat‐Seon Y, Peters CM, Parmar HR, Griesdale DEG, Sekhon M, Sheel AW, Winston BW, Dominelli PB. Therapeutic hypothermia attenuates physiologic, histologic, and metabolomic markers of injury in a porcine model of acute respiratory distress syndrome. Physiol Rep 2022; 10:e15286. [PMID: 35510328 PMCID: PMC9069168 DOI: 10.14814/phy2.15286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 03/29/2022] [Accepted: 04/02/2022] [Indexed: 06/14/2023] Open
Abstract
Acute respiratory distress syndrome (ARDS) is a lung injury characterized by noncardiogenic pulmonary edema and hypoxic respiratory failure. The purpose of this study was to investigate the effects of therapeutic hypothermia on short-term experimental ARDS. Twenty adult female Yorkshire pigs were divided into four groups (n = 5 each): normothermic control (C), normothermic injured (I), hypothermic control (HC), and hypothermic injured (HI). Acute respiratory distress syndrome was induced experimentally via intrapulmonary injection of oleic acid. Target core temperature was achieved in the HI group within 1 h of injury induction. Cardiorespiratory, histologic, cytokine, and metabolomic data were collected on all animals prior to and following injury/sham. All data were collected for approximately 12 h from the beginning of the study until euthanasia. Therapeutic hypothermia reduced injury in the HI compared to the I group (histological injury score = 0.51 ± 0.18 vs. 0.76 ± 0.06; p = 0.02) with no change in gas exchange. All groups expressed distinct phenotypes, with a reduction in pro-inflammatory metabolites, an increase in anti-inflammatory metabolites, and a reduction in inflammatory cytokines observed in the HI group compared to the I group. Changes to respiratory system mechanics in the injured groups were due to increases in lung elastance (E) and resistance (R) (ΔE from pre-injury = 46 ± 14 cmH2 O L-1 , p < 0.0001; ΔR from pre-injury: 3 ± 2 cmH2 O L-1 s- , p = 0.30) rather than changes to the chest wall (ΔE from pre-injury: 0.7 ± 1.6 cmH2 O L-1 , p = 0.99; ΔR from pre-injury: 0.6 ± 0.1 cmH2 O L-1 s- , p = 0.01). Both control groups had no change in respiratory mechanics. In conclusion, therapeutic hypothermia can reduce markers of injury and inflammation associated with experimentally induced short-term ARDS.
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Affiliation(s)
- Sarah A. Angus
- Department of KinesiologyUniversity of WaterlooWaterlooOntarioCanada
| | - William R. Henderson
- Division of Critical Care MedicineDepartment of MedicineFaculty of MedicineUniversity of British ColumbiaVancouverBritish ColumbiaCanada
| | - Mohammad M. Banoei
- Department of Critical Care MedicineUniversity of CalgaryCalgaryAlbertaCanada
| | - Yannick Molgat‐Seon
- Department Kinesiology and Applied HealthUniversity of WinnipegWinnipegManitobaCanada
| | - Carli M. Peters
- School of KinesiologyUniversity of British ColumbiaVancouverBritish ColumbiaCanada
| | - Hanna R. Parmar
- School of KinesiologyUniversity of British ColumbiaVancouverBritish ColumbiaCanada
| | - Donald E. G. Griesdale
- Division of Critical Care MedicineDepartment of MedicineFaculty of MedicineUniversity of British ColumbiaVancouverBritish ColumbiaCanada
- Department of AnesthesiologyPharmacology & TherapeuticsUniversity of British ColumbiaVancouverBritish ColumbiaCanada
| | - Mypinder Sekhon
- Division of Critical Care MedicineDepartment of MedicineFaculty of MedicineUniversity of British ColumbiaVancouverBritish ColumbiaCanada
| | - Andrew William Sheel
- School of KinesiologyUniversity of British ColumbiaVancouverBritish ColumbiaCanada
| | - Brent W. Winston
- Department of Critical Care MedicineUniversity of CalgaryCalgaryAlbertaCanada
- Departments of Medicine and Biochemistry & Molecular BiologyUniversity of CalgaryCalgaryAlbertaCanada
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Henderson WR, Dominelli PB, Molgat-Seon Y, Lipson R, Griesdale DEG, Sekhon M, Ayas N, Sheel AW. Effect of tidal volume and positive end-expiratory pressure on expiratory time constants in experimental lung injury. Physiol Rep 2016; 4:4/5/e12737. [PMID: 26997633 PMCID: PMC4823592 DOI: 10.14814/phy2.12737] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
We utilized a multicompartment model to describe the effects of changes in tidal volume (VT) and positive end‐expiratory pressure (PEEP) on lung emptying during passive deflation before and after experimental lung injury. Expiratory time constants (τE) were determined by partitioning the expiratory flow–volume (V˙EV) curve into multiple discrete segments and individually calculating τE for each segment. Under all conditions of PEEP and VT, τE increased throughout expiration both before and after injury. Segmented τE values increased throughout expiration with a slope that was different than zero (P < 0. 01). On average, τE increased by 45.08 msec per segment. When an interaction between injury status and τE segment was included in the model, it was significant (P < 0.05), indicating that later segments had higher τE values post injury than early τE segments. Higher PEEP and VT values were associated with higher τE values. No evidence was found for an interaction between injury status and VT, or PEEP. The current experiment confirms previous observations that τE values are smaller in subjects with injured lungs when compared to controls. We are the first to demonstrate changes in the pattern of τE before and after injury when examined with a multiple compartment model. Finally, increases in PEEP or VT increased τE throughout expiration, but did not appear to have effects that differed between the uninjured and injured state.
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Affiliation(s)
- William R Henderson
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Paolo B Dominelli
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Yannick Molgat-Seon
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Donald E G Griesdale
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada Department of Anesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mypinder Sekhon
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Najib Ayas
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
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Henderson WR, Molgat-Seon Y, Dominelli PB, Brasher PMA, Griesdale DEG, Foster GE, Yacyshyn A, Ayas NT, Sheel AW. Gas density alters expiratory time constants before and after experimental lung injury. Exp Physiol 2016; 100:1217-28. [PMID: 26289254 DOI: 10.1113/ep085205] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 08/17/2015] [Indexed: 01/10/2023]
Abstract
NEW FINDINGS What is the central question of this study? Does the induction of a model of lung injury affect the expiratory time constant (τE) in terms of either total duration or morphology? Does ventilation with gases of different densities alter the duration or morphology of τE either before or after injury? What is the main finding and its importance? The use of sulfur hexafluoride in ventilating gas mixtures lengthens total expiratory time constants before and after lung injury compared with both nitrogen and helium mixtures. Sulfur hexafluoride mixtures also decrease the difference and variability of τE between fast- and slow-emptying compartments before and after injury when compared with nitrogen and helium mixtures. Acute lung injury is characterized by regional heterogeneity of lung resistance and elastance that may lead to regional heterogeneity of expiratory time constants (τE). We hypothesized that increasing airflow resistance by using inhaled sulfur hexafluoride (SF6) would lengthen time constants and decrease their heterogeneity in an experimental model of lung injury when compared with nitrogen or helium mixtures. To overcome the limitations of a single-compartment model, we employed a multisegment model of expiratory gas flow. An experimental model of lung injury was created using intratracheal injection of sodium polyacrylate in anaesthetized and mechanically ventilated female Yorkshire-cross pigs (n = 7). The animals were ventilated with 50% O2 and the remaining 50% as nitrogen (N2), helium (He) or sulfur hexafluoride (SF6). Values for τE decreased with injury and were more variable after injury than before (P < 0.001). Values for τE increased throughout expiration both before and after injury, and the rate of increase in τE was lessened by SF6 (P < 0.001 when compared with N2 both before and after injury). Altering the inhaled gas density did not affect indices of oxygenation, dead space or shunt. The use of SF6 in ventilating gas mixtures lengthens total expiratory time constants before and after lung injury compared with both N2 and He mixtures. Importantly, SF6 mixtures also decrease the difference and variability of τE between fast- and slow-emptying compartments before and after injury when compared with N2 and He mixtures.
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Affiliation(s)
- William R Henderson
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Yannick Molgat-Seon
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Paolo B Dominelli
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Penelope M A Brasher
- Centre for Clinical Epidemiology & Evaluation, Vancouver Coastal Health Research Institute, Vancouver, British Columbia, Canada
| | - Donald E G Griesdale
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Glen E Foster
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Alexandra Yacyshyn
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Najib T Ayas
- Division of Critical Care Medicine, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
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