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Zero expiratory pressure and low oxygen concentration promote heterogeneity of regional ventilation and lung densities
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Hedenstierna laboratory. Univ Sao Paulo, Fac Med, Hosp Clin, Pulm Div,Heart Inst Incor, BR-05508 Sao Paulo, Brazil..
Univ Helsinki, Dept Phys, Helsinki, Finland.;Univ Helsinki, Cent Hosp, Helsinki, Finland..
Univ Bari, Dept Emergency & Organ Transplant, I-70121 Bari, Italy..
Univ Bari, Dept Emergency & Organ Transplant, I-70121 Bari, Italy..
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2016 (English)In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 60, no 7, 958-968 p.Article in journal (Refereed) PublishedText
Abstract [en]

BackgroundIt is not well known what is the main mechanism causing lung heterogeneity in healthy lungs under mechanical ventilation. We aimed to investigate the mechanisms causing heterogeneity of regional ventilation and parenchymal densities in healthy lungs under anesthesia and mechanical ventilation. MethodsIn a small animal model, synchrotron imaging was used to measure lung aeration and regional-specific ventilation (sV.). Heterogeneity of ventilation was calculated as the coefficient of variation in sV. (CVsV.). The coefficient of variation in lung densities (CVD) was calculated for all lung tissue, and within hyperinflated, normally and poorly aerated areas. Three conditions were studied: zero end-expiratory pressure (ZEEP) and FIO2 0.21; ZEEP and FIO2 1.0; PEEP 12 cmH(2)O and F(I)O(2)1.0 (Open Lung-PEEP = OLP). ResultsThe mean tissue density at OLP was lower than ZEEP-1.0 and ZEEP-0.21. There were larger subregions with low sV. and poor aeration at ZEEP-0.21 than at OLP: 12.9 9.0 vs. 0.6 +/- 0.4% in the non-dependent level, and 17.5 +/- 8.2 vs. 0.4 +/- 0.1% in the dependent one (P = 0.041). The CVsV. of the total imaged lung at PEEP 12 cmH(2)O was significantly lower than on ZEEP, regardless of FIO2, indicating more heterogeneity of ventilation during ZEEP (0.23 +/- 0.03 vs. 0.54 +/- 0.37, P = 0.049). CVD changed over the different mechanical ventilation settings (P = 0.011); predominantly, CVD increased during ZEEP. The spatial distribution of the CVD calculated for the poorly aerated density category changed with the mechanical ventilation settings, increasing in the dependent level during ZEEP. ConclusionZEEP together with low FIO2 promoted heterogeneity of ventilation and lung tissue densities, fostering a greater amount of airway closure and ventilation inhomogeneities in poorly aerated regions.

Place, publisher, year, edition, pages
2016. Vol. 60, no 7, 958-968 p.
National Category
Medical and Health Sciences
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URN: urn:nbn:se:uu:diva-301009DOI: 10.1111/aas.12719ISI: 000379931500015PubMedID: 27000315OAI: oai:DiVA.org:uu-301009DiVA: diva2:953273
Funder
Swedish Research Council, K2015-99X-22731-01-4Swedish Heart Lung Foundation
Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2016-08-17Bibliographically approved

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Borges, João BatistaLarsson, AndersPerchiazzi, GaetanoHedenstierna, G.
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