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BMC Pulmonary Medicine

, 14:73

COPD and occupational lung disease


BackgroundA recent method determines regional gas flow of the lung by electrical impedance tomography EIT. The aim of this study is to show the applicability of this method in a porcine model of mechanical ventilation in healthy and diseased lungs. Our primary hypothesis is that global gas flow measured by EIT can be correlated with spirometry. Our secondary hypothesis is that regional analysis of respiratory gas flow delivers physiologically meaningful results.

MethodsIn two sets of experiments n = 7 healthy pigs and n = 6 pigs before and after induction of lavage lung injury were investigated. EIT of the lung and spirometry were registered synchronously during ongoing mechanical ventilation. In-vivo aeration of the lung was analysed in four regions-of-interest ROI by EIT: 1 global, 2 ventral non-dependent, 3 middle and 4 dorsal dependent ROI. Respiratory gas flow was calculated by the first derivative of the regional aeration curve. Four phases of the respiratory cycle were discriminated. They delivered peak and late inspiratory and expiratory gas flow PIF, LIF, PEF, LEF characterizing early or late inspiration or expiration.

ResultsLinear regression analysis of EIT and spirometry in healthy pigs revealed a very good correlation measuring peak flow and a good correlation detecting late flow. PIFEIT = 0.702 · PIFspiro + 117.4, r = 0.809; PEFEIT = 0.690 · PEFspiro-124.2, r = 0.760; LIFEIT = 0.909 · LIFspiro + 27.32, r = 0.572 and LEFEIT = 0.858 · LEFspiro-10.94, r = 0.647. EIT derived absolute gas flow was generally smaller than data from spirometry. Regional gas flow was distributed heterogeneously during different phases of the respiratory cycle. But, the regional distribution of gas flow stayed stable during different ventilator settings. Moderate lung injury changed the regional pattern of gas flow.

ConclusionsWe conclude that the presented method is able to determine global respiratory gas flow of the lung in different phases of the respiratory cycle. Additionally, it delivers meaningful insight into regional pulmonary characteristics, i.e. the regional ability of the lung to take up and to release air.

KeywordsRegional respiratory gas flow Electrical impedance tomography Mechanical ventilation Acute respiratory distress syndrome Acute lung injury Acute respiratory failure Intensive care medicine Spirometry AbbreviationsARDSAcute respiratory distress syndrome

CTComputed tomography

EITElectrical impedance tomography

FiO2Inspiratory fraction of oxygen

IE ratio: Inspiratory to expiratory ratio

LEFLate expiratory flow

LIFLate inspiratory flow

PEEPPositive end-expiratory pressure

PEFPeak expiratory flow

PIFPeak inspiratory flow

ROIRegion of interest

RRRespiratory rate

VTTidal volume

VROItRegional gas content

VROI’tRegional gas flow first derivative of VROIt.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2466-14-73 contains supplementary material, which is available to authorized users.

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Autor: Marc Bodenstein - Stefan Boehme - Stephan Bierschock - Andreas Vogt - Matthias David - Klaus Markstaller


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