Determination of respiratory gas flow by electrical impedance tomography in an animal model of mechanical ventilation
Marc Bodenstein, Stefan Boehme, Stephan Bierschock, Andreas Vogt, Matthias David, Klaus Markstaller, Marc Bodenstein, Stefan Boehme, Stephan Bierschock, Andreas Vogt, Matthias David, Klaus Markstaller
Abstract
Background: A 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.
Methods: In 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.
Results: Linear 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(2) = 0.809; PEFEIT = 0.690 · PEFspiro-124.2, r(2) = 0.760; LIFEIT = 0.909 · LIFspiro + 27.32, r(2) = 0.572 and LEFEIT = 0.858 · LEFspiro-10.94, r(2) = 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.
Conclusions: We 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.
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References
- Bodenstein M, David M, Markstaller K. Principles of electrical impedance tomography and its clinical application. Crit Care Med. 2009;37:713–724. doi: 10.1097/CCM.0b013e3181958d2f.
- Richard JC, Pouzot C, Gros A, Tourevieille C, Lebars D, Lavenne F, Frerichs I, Guerin C. Electrical impedance tomography compared to positron emission tomography for the measurement of regional lung ventilation: an experimental study. Crit Care. 2009;13:R82. doi: 10.1186/cc7900.
- Hinz J, Neumann P, Dudykevych T, Andersson LG, Wrigge H, Burchardi H, Hedenstierna G. Regional ventilation by electrical impedance tomography: a comparison with ventilation scintigraphy in pigs. Chest. 2003;124:314–322. doi: 10.1378/chest.124.1.314.
- Kunst PW, Vonk Noordegraaf A, Hoekstra OS, Postmus PE, de Vries PM. Ventilation and perfusion imaging by electrical impedance tomography: a comparison with radionuclide scanning. Physiol Meas. 1998;19:481–490. doi: 10.1088/0967-3334/19/4/003.
- Victorino JA, Borges JB, Okamoto VN, Matos GF, Tucci MR, Caramez MP, Tanaka H, Sipmann FS, Santos DC, Barbas CS, Carvalho CR, Amato MB. Imbalances in regional lung ventilation: a validation study on electrical impedance tomography. Am J Respir Crit Care Med. 2004;169:791–800. doi: 10.1164/rccm.200301-133OC.
- Frerichs I, Hinz J, Herrmann P, Weisser G, Hahn G, Quintel M, Hellige G. Regional lung perfusion as determined by electrical impedance tomography in comparison with electron beam CT imaging. IEEE Trans Med Imag. 2002;21:646–652. doi: 10.1109/TMI.2002.800585.
- Hahn G, Sipinkova I, Baisch F, Hellige G. Changes in the thoracic impedance distribution under different ventilatory conditions. Physiol Meas. 1995;16:A161–A173. doi: 10.1088/0967-3334/16/3A/016.
- Wrigge H, Zinserling J, Muders T, Varelmann D, Gunther U, von der Groeben C, Magnusson A, Hedenstierna G, Putensen C. Electrical impedance tomography compared with thoracic computed tomography during a slow inflation maneuver in experimental models of lung injury. Crit Care Med. 2008;36:903–909. doi: 10.1097/CCM.0B013E3181652EDD.
- Frerichs I, Hahn G, Golisch W, Kurpitz M, Burchardi H, Hellige G. Monitoring perioperative changes in distribution of pulmonary ventilation by functional electrical impedance tomography. Acta Anaesthesiol Scand. 1998;42:721–726. doi: 10.1111/j.1399-6576.1998.tb05308.x.
- Zhao Z, Steinmann D, Frerichs I, Guttmann J, Moller K. PEEP titration guided by ventilation homogeneity: a feasibility study using electrical impedance tomography. Crit Care. 2010;14:R8. doi: 10.1186/cc8860.
- Dargaville PA, Rimensberger PC, Frerichs I. Regional tidal ventilation and compliance during a stepwise vital capacity manoeuvre. Intensive Care Med. 2010;36(11):1953–1961. doi: 10.1007/s00134-010-1995-1.
- Bodenstein M, Wang H, Boehme S, Vogt A, Kwiecien R, David M, Markstaller K. Influence of crystalloid and colloid fluid infusion and blood withdrawal on pulmonary bioimpedance in an animal model of mechanical ventilation. Physiol Meas. 2012;33:1225–1236. doi: 10.1088/0967-3334/33/7/1225.
- Polak AG, Mroczka J. Nonlinear model for mechanical ventilation of human lungs. Comput Biol Med. 2006;36:41–58. doi: 10.1016/j.compbiomed.2004.08.001.
- David M, Karmrodt J, Bletz C, David S, Herweling A, Kauczor HU, Markstaller K. Analysis of atelectasis, ventilated, and hyperinflated lung during mechanical ventilation by dynamic CT. Chest. 2005;128:3757–3770. doi: 10.1378/chest.128.5.3757.
- Markstaller K, Kauczor HU, Weiler N, Karmrodt J, Doebrich M, Ferrante M, Thelen M, Eberle B. Lung density distribution in dynamic CT correlates with oxygenation in ventilated pigs with lavage ARDS. Br J Anaesth. 2003;91:699–708. doi: 10.1093/bja/aeg246.
- Ferrario D, Grychtol B, Adler A, Sola J, Bohm SH, Bodenstein M. Toward Morphological Thoracic EIT: Major Signal Sources Correspond to Respective Organ Locations in CT. IEEE Trans Bio-Med Eng. 2012;59:3000–3008.
- Grychtol B, Lionheart WR, Bodenstein M, Wolf GK, Adler A. Impact of model shape mismatch on reconstruction quality in electrical impedance tomography. IEEE Trans Med Imag. 2012;31:1754–1760.
- Frerichs I, Bodenstein M, Dudykevych T, Hinz J, Hahn G, Hellige G. Effect of lower body negative pressure and gravity on regional lung ventilation determined by EIT. Physiol Meas. 2005;26:S27–S37. doi: 10.1088/0967-3334/26/2/003.
- Frerichs I, Dudykevych T, Hinz J, Bodenstein M, Hahn G, Hellige G. Gravity effects on regional lung ventilation determined by functional EIT during parabolic flights. J Appl Physiol. 2001;91:39–50.
Source: PubMed