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      Detection of inspiratory recruitment of atelectasis by automated lung sound analysis as compared to four-dimensional computed tomography in a porcine lung injury model

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          Abstract

          Background

          Cyclic recruitment and de-recruitment of atelectasis (c-R/D) is a contributor to ventilator-induced lung injury (VILI). Bedside detection of this dynamic process could improve ventilator management. This study investigated the potential of automated lung sound analysis to detect c-R/D as compared to four-dimensional computed tomography (4DCT).

          Methods

          In ten piglets (25 ± 2 kg), acoustic measurements from 34 thoracic piezoelectric sensors (Meditron ASA, Norway) were performed, time synchronized to 4DCT scans, at positive end-expiratory pressures of 0, 5, 10, and 15 cmH 2O during mechanical ventilation, before and after induction of c-R/D by surfactant washout. 4DCT was post-processed for within-breath variation in atelectatic volume (Δ atelectasis) as a measure of c-R/D. Sound waveforms were evaluated for: 1) dynamic crackle energy (dCE): filtered crackle sounds (600–700 Hz); 2) fast Fourier transform area (FFT area): spectral content above 500 Hz in frequency and above −70 dB in amplitude in proportion to the total amount of sound above −70 dB amplitude; and 3) dynamic spectral coherence (dSC): variation in acoustical homogeneity over time. Parameters were analyzed for global, nondependent, central, and dependent lung areas.

          Results

          In healthy lungs, negligible values of Δ atelectasis, dCE, and FFT area occurred. In lavage lung injury, the novel dCE parameter showed the best correlation to Δ atelectasis in dependent lung areas (R 2 = 0.88) where c-R/D took place. dCE was superior to FFT area analysis for each lung region examined. The analysis of dSC could predict the lung regions where c-R/D originated.

          Conclusions

          c-R/D is associated with the occurrence of fine crackle sounds as demonstrated by dCE analysis. Standardized computer-assisted analysis of dCE and dSC seems to be a promising method for depicting c-R/D.

          Electronic supplementary material

          The online version of this article (10.1186/s13054-018-1964-6) contains supplementary material, which is available to authorized users.

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          Lung opening and closing during ventilation of acute respiratory distress syndrome.

          Michael Quintel, Pietro Caironi, Riccarda Russo … (2010)
          The effects of high positive end-expiratory pressure (PEEP) strictly depend on lung recruitability, which varies widely during acute respiratory distress syndrome (ARDS). Unfortunately, increasing PEEP may lead to opposing effects on two main factors potentially worsening the lung injury, that is, alveolar strain and intratidal opening and closing, being detrimental (increasing the former) or beneficial (decreasing the latter). To investigate how lung recruitability influences alveolar strain and intratidal opening and closing after the application of high PEEP. We analyzed data from a database of 68 patients with acute lung injury or ARDS who underwent whole-lung computed tomography at 5, 15, and 45 cm H(2)O airway pressure. End-inspiratory nonaerated lung tissue was estimated from computed tomography pressure-volume curves. Alveolar strain and opening and closing lung tissue were computed at 5 and 15 cm H(2)O PEEP. In patients with a higher percentage of potentially recruitable lung, the increase in PEEP markedly reduced opening and closing lung tissue (P < 0.001), whereas no differences were observed in patients with a lower percentage of potentially recruitable lung. In contrast, alveolar strain similarly increased in the two groups (P = 0.89). Opening and closing lung tissue was distributed mainly in the dependent and hilar lung regions, and it appeared to be an independent risk factor for death (odds ratio, 1.10 for each 10-g increase). In ARDS, especially in patients with higher lung recruitability, the beneficial impact of reducing intratidal alveolar opening and closing by increasing PEEP prevails over the effects of increasing alveolar strain.
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            The role of time and pressure on alveolar recruitment.

            Robert Allen, Jason Bates, John Adams Fischer … (2009)
            Inappropriate mechanical ventilation in patients with acute respiratory distress syndrome can lead to ventilator-induced lung injury (VILI) and increase the morbidity and mortality. Reopening collapsed lung units may significantly reduce VILI, but the mechanisms governing lung recruitment are unclear. We thus investigated the dynamics of lung recruitment at the alveolar level. Rats (n = 6) were anesthetized and mechanically ventilated. The lungs were then lavaged with saline to simulate acute respiratory distress syndrome (ARDS). A left thoracotomy was performed, and an in vivo microscope was placed on the lung surface. The lung was recruited to three recruitment pressures (RP) of 20, 30, or 40 cmH(2)O for 40 s while subpleural alveoli were continuously filmed. Following measurement of microscopic alveolar recruitment, the lungs were excised, and macroscopic gross lung recruitment was digitally filmed. Recruitment was quantified by computer image analysis, and data were interpreted using a mathematical model. The majority of alveolar recruitment (78.3 +/- 7.4 and 84.6 +/- 5.1%) occurred in the first 2 s (T2) following application of RP 30 and 40, respectively. Only 51.9 +/- 5.4% of the microscopic field was recruited by T2 with RP 20. There was limited recruitment from T2 to T40 at all RPs. The majority of gross lung recruitment also occurred by T2 with gradual recruitment to T40. The data were accurately predicted by a mathematical model incorporating the effects of both pressure and time. Alveolar recruitment is determined by the magnitude of recruiting pressure and length of time pressure is applied, a concept supported by our mathematical model. Such a temporal dependence of alveolar recruitment needs to be considered when recruitment maneuvers for clinical application are designed.
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              Neglected evidence in idiopathic pulmonary fibrosis and the importance of early diagnosis and treatment

              Vincent Cottin, Luca Richeldi (2014)
              In idiopathic pulmonary fibrosis (IPF), some facts or concepts based on substantial evidence, whilst implicit for learned subspecialists, have previously been neglected and/or not explicitly formulated or made accessible to a wider audience. IPF is strongly associated with cigarette smoking and is predominantly a disease of ageing. However, its cause(s) remain elusive and, thus, it is one of the most challenging diseases for the development of novel effective and safe therapies. With the approval of pirfenidone for patients with mild-to-moderate IPF, an earlier diagnosis of IPF is a prerequisite for earlier treatment and, potentially, improvement of the long-term clinical outcome of this progressive and ultimately fatal disease. An earlier diagnosis may be achieved in IPF by promoting thin-slice chest high-resolution computed tomography screening of interstitial lung disease as a “by-product” of large-scale lung cancer screening strategies in smokers, but other techniques, which have been neglected in the past, are now available. Lung auscultation and early identification of “velcro” crackles has been proposed as a key component of early diagnosis of IPF. An ongoing study is exploring correlations between lung sounds on auscultation obtained using electronic stethoscopes and high-resolution computed tomography patterns.
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                Author and article information

                Contributors
                Stefan Boehme:
                ORCID: http://orcid.org/0000-0003-3132-2486
                +43 1 40400 41020 , stefan.boehme@meduniwien.ac.at
                Frédéric P. R. Toemboel: frederic.toemboel@meduniwien.ac.at
                Erik K. Hartmann: hartmane@uni-mainz.de
                Alexander H. Bentley: A.Bentley@gmx.de
                Oliver Weinheimer: mail@oliwe.com
                Yang Yang: yang.yang@unimedizin-mainz.de
                Tobias Achenbach: tobias.achenbach@live.de
                Michael Hagmann: michael.hagmann@medma.uni-heidelberg.de
                Eugenijus Kaniusas: eugenijus.kaniusas@tuwien.ac.at
                James E. Baumgardner: jbaumgardner@oscillogy.com
                Klaus Markstaller: klaus.markstaller@meduniwien.ac.at
                Journal
                Journal ID (nlm-ta): Crit Care
                Title: Critical Care
                Publisher: BioMed Central (London )
                ISSN (Print): 1364-8535
                ISSN (Electronic): 1466-609X
                Publication date (Electronic): 24 February 2018
                Publication date PMC-release: 24 February 2018
                Publication date Collection: 2018
                Volume: 22
                Electronic Location Identifier: 50
                Affiliations
                [1 ]ISNI 0000 0000 9259 8492, GRID grid.22937.3d, Department of Anesthesia, General Intensive Care Medicine and Pain Management, , Medical University Vienna, ; Waehringer Guertel, 18-20 Vienna, Austria
                [2 ]ISNI 0000 0001 1941 7111, GRID grid.5802.f, Department of Anesthesiology, , Medical Center of the Johannes-Gutenberg University Mainz, ; Mainz, Germany
                [3 ]ISNI 0000 0001 1941 7111, GRID grid.5802.f, Department of Diagnostic and Interventional Radiology, , Medical Center of the Johannes-Gutenberg University Mainz, ; Mainz, Germany
                [4 ]ISNI 0000 0000 9259 8492, GRID grid.22937.3d, Center for Medical Statistics, Informatics, and Intelligent Systems, , Medical University Vienna, ; Vienna, Austria
                [5 ]ISNI 0000 0001 2348 4034, GRID grid.5329.d, Institute of Electrodynamics, Microwave and Circuit Engineering, , Vienna University of Technology, ; Vienna, Austria
                [6 ]ISNI 0000 0001 0650 7433, GRID grid.412689.0, Department of Anesthesiology, , University of Pittsburgh Medical Center, ; Pittsburgh, PA 15261 USA
                [7 ]ISNI 0000 0001 0328 4908, GRID grid.5253.1, Department of Diagnostic and Interventional Radiology, , University Hospital of Heidelberg, ; Heidelberg, Germany
                [8 ]ISNI 0000 0001 0328 4908, GRID grid.5253.1, Translational Lung Research Center Heidelberg (TLRC), Member of the German Center for Lung Research (DZL), ; Heidelberg, Germany
                [9 ]Institute of Diagnostic and Interventional Radiology, St. Vinzenz Hospital, Cologne, Germany
                Author information
                http://orcid.org/0000-0003-3132-2486
                Article
                Publisher ID: 1964
                DOI: 10.1186/s13054-018-1964-6
                PMC ID: 6389194
                PubMed ID: 29475456
                SO-VID: 6ab6d16e-f060-4e50-bcdc-f2dae24b2da9
                Copyright © © The Author(s). 2018
                License:

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                Date received : 14 July 2017
                Date accepted : 24 January 2018
                Funding
                Funded by: German Research Council
                Award ID: DFG Pak 415: Ma 2398/6
                Award Recipient :
                Categories
                Subject: Research
                Custom metadata
                issue-copyright-statement © The Author(s) 2018

                ScienceOpen disciplines: Emergency medicine & Trauma
                Keywords: cyclic recruitment,lung sounds,dynamic computed tomography,atelectasis,positive end-expiratory pressure
                Data availability:
                ScienceOpen disciplines: Emergency medicine & Trauma
                Keywords: cyclic recruitment, lung sounds, dynamic computed tomography, atelectasis, positive end-expiratory pressure

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