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Effects on Pulmonary Vascular Mechanics of Two Different Lung-Protective Ventilation Strategies in an Experimental Model of Acute Respiratory Distress Syndrome
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Hedenstierna laboratory. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care. CIBER Enfermedades Resp CIBERES, Madrid, Spain.; CNIC, Ctr Nacl Invest Cardiovasc Carlos 3, Madrid, Spain.
Hosp Gen Villalba, Intens Care Unit, Villalba, Spain.
Hosp SAS, Intens Care Unit, Jerez de la Frontera, Spain.
Pontificia Univ Catolica Chile, Dept Med Intens, Santiago, Chile.
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2017 (English)In: Critical Care Medicine, ISSN 0090-3493, E-ISSN 1530-0293, Vol. 45, no 11, p. e1157-e1164Article in journal (Refereed) Published
Abstract [en]

OBJECTIVES: To compare the effects of two lung-protective ventilation strategies on pulmonary vascular mechanics in early acute respiratory distress syndrome.

DESIGN: Experimental study.

SETTING: University animal research laboratory.

SUBJECTS: Twelve pigs (30.8 ± 2.5 kg).

INTERVENTIONS: Acute respiratory distress syndrome was induced by repeated lung lavages and injurious mechanical ventilation. Thereafter, animals were randomized to 4 hours ventilation according to the Acute Respiratory Distress Syndrome Network protocol or to an open lung approach strategy. Pressure and flow sensors placed at the pulmonary artery trunk allowed continuous assessment of pulmonary artery resistance, effective elastance, compliance, and reflected pressure waves. Respiratory mechanics and gas exchange data were collected.

MEASUREMENTS AND MAIN RESULTS: Acute respiratory distress syndrome led to pulmonary vascular mechanics deterioration. Four hours after randomization, pulmonary vascular mechanics was similar in Acute Respiratory Distress Syndrome Network and open lung approach: resistance (578 ± 252 vs 626 ± 153 dyn.s/cm; p = 0.714), effective elastance, (0.63 ± 0.22 vs 0.58 ± 0.17 mm Hg/mL; p = 0.710), compliance (1.19 ± 0.8 vs 1.50 ± 0.27 mL/mm Hg; p = 0.437), and reflection index (0.36 ± 0.04 vs 0.34 ± 0.09; p = 0.680). Open lung approach as compared to Acute Respiratory Distress Syndrome Network was associated with improved dynamic respiratory compliance (17.3 ± 2.6 vs 10.5 ± 1.3 mL/cm H2O; p < 0.001), driving pressure (9.6 ± 1.3 vs 19.3 ± 2.7 cm H2O; p < 0.001), and venous admixture (0.05 ± 0.01 vs 0.22 ± 0.03, p < 0.001) and lower mean pulmonary artery pressure (26 ± 3 vs 34 ± 7 mm Hg; p = 0.045) despite of using a higher positive end-expiratory pressure (17.4 ± 0.7 vs 9.5 ± 2.4 cm H2O; p < 0.001). Cardiac index, however, was lower in open lung approach (1.42 ± 0.16 vs 2.27 ± 0.48 L/min; p = 0.005).

CONCLUSIONS: In this experimental model, Acute Respiratory Distress Syndrome Network and open lung approach affected pulmonary vascular mechanics similarly. The use of higher positive end-expiratory pressures in the open lung approach strategy did not worsen pulmonary vascular mechanics, improved lung mechanics, and gas exchange but at the expense of a lower cardiac index.

Place, publisher, year, edition, pages
2017. Vol. 45, no 11, p. e1157-e1164
National Category
Respiratory Medicine and Allergy
Identifiers
URN: urn:nbn:se:uu:diva-334177DOI: 10.1097/CCM.0000000000002701ISI: 000417107000007PubMedID: 28872540OAI: oai:DiVA.org:uu-334177DiVA, id: diva2:1158884
Funder
Swedish Research Council, K2015-99X-22731-01-4Swedish Heart Lung FoundationEU, FP7, Seventh Framework Programme, 291820Available from: 2017-11-21 Created: 2017-11-21 Last updated: 2018-03-09Bibliographically approved
In thesis
1. Hemodynamic Effects of Lung Function Optimization in Experimental Acute Respiratory Distress Syndrome
Open this publication in new window or tab >>Hemodynamic Effects of Lung Function Optimization in Experimental Acute Respiratory Distress Syndrome
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Acute Respiratory Distress Syndrome (ARDS) is a severe pulmonary inflammation affecting thousands of patients every year in Sweden and has a mortality of 30-50%. Mechanical ventilation (MV) is usually necessary, but could per se augment the inflammation and contribute to mortality. MV strategies protective for the lung parenchyma have been developed but without considering the pulmonary circulation or the right heart ventricle (RV) that also are affected in ARDS. MV should ideally be optimized to protect both the lung parenchyma and the RV/pulmonary vasculature. My hypothesis was that MV that prevents alveolar collapse and overdistension, i.e., the “open lung approach (OLA)” would be optimal. The aims of this project were 1) to carefully describe the pulmonary vascular mechanics (PVM) in ARDS compared with healthy lungs, 2) to assess how different ventilatory methods influence PVM, and 3) to propose a ventilatory method that protects both lung parenchyma and circulation.

In a porcine model, high fidelity pressure and flow sensors were applied directly on the main pulmonary artery to evaluate steady and oscillatory components of PVM.  In this way a complete PVM description was obtained for normal and injured lungs at different MV. In particular, the effects of OLA were compared with standard MV and, in addition, with MV methods where overdistension or collapse were present.

Results: 1) Compared with collapse or overdistension, OLA provided better PVM. 2) The effects on PVM of OLA and the standard protective MV were similar. 3) Early ARDS augmented the effects of pulse wave reflection on PVM leading to a situation in which the RV had to increase its work to maintain adequate blood flow. Thus, a part of this work was wasted by the effect of wave reflections, making the RV/pulmonary vasculature inefficient. 4) Tidal breathing affected PVM cyclically and this effect was enhanced in ARDS compared with healthy lungs.

In conclusion, ARDS and different ventilatory methods, as well as tidal ventilation per se, affected PVM. OLA improved PVM compared with other MV settings where significant collapse and overdistension were allowed. However, OLA was not superior to standard protective MV.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 60
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1419
Keywords
Acute respiratory distress syndrome, Lung protective ventilation, Mechanical ventilation, Open lung approach, Pulmonary heart disease, Pulmonary vascular mechanics, Pulmonary vascular dysfunction, Pulse wave analysis, Right ventricular dysfunction
National Category
Physiology Anesthesiology and Intensive Care
Research subject
Anaesthesiology and Intensive Care; Physiology
Identifiers
urn:nbn:se:uu:diva-338688 (URN)978-91-513-0210-2 (ISBN)
Public defence
2018-03-08, Rosen, Akademiska sjukhuset 75185 Uppsala, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2018-02-13 Created: 2018-01-12 Last updated: 2018-03-07

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Santos, ArnoldoRetamal, JaimeBatista Borges, JoãoHedenstierna, GöranLarsson, AndersSuarez-Sipmann, Fernando

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