1 / 41

Electrical Impedance Tomography

Electrical Impedance Tomography. A path-breaking monitoring technique?. My affiliations. Chair for Medical Information Technologies Helmholtz Institute for Biomedical Engineering. Department of Anaesthesiology University Hospital Aachen. Outline.

venice
Download Presentation

Electrical Impedance Tomography

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Electrical Impedance Tomography A path-breaking monitoring technique?

  2. My affiliations Chair for Medical Information Technologies Helmholtz Institute for Biomedical Engineering Department ofAnaesthesiology University Hospital Aachen

  3. Outline • Do we need another monitoring technique? • How does Electrical Impedance Tomography work? • Is there any evidence that EIT generates more than colourful images? • Is EIT clinically established yet? • What will be in future?

  4. Do we need another monitoring technique?

  5. Manoeuvring in respiratory treatment

  6. Mechanical ventilation in 2012

  7. Acute respiratory distress syndrome (ARDS) • Acute onset • Bilateral infiltrates • Horowitz ratio (paO2/FiO2)<300 / <200 / <100 mmHg • Exclusion of a cardiac origin

  8. “Therapy” of ARDS

  9. Birth of protective ventilation Mortality 12ml 6ml Tidal volume ARDSnetwork. (2000) New Engl J Med 342:1301-8

  10. Current ICU “concept”

  11. Individual variation • Protective ventilation needs an individual tuning of ventilation pressures, especially of PEEP Non-responder responder

  12. Role of CT imaging • Pro • precise anatomical information • Radiological density measure • 1000 to -900 HU overdistended • -900 to -500 HU normal • -400 to -200 HU reduced ventilation • -100 to +100 HU atelectatic • Con • High level of radiation • No functional image • Not at the bedside Over- distended areas Collapsed areas

  13. How does Electrical Impedance Tomography work?

  14. Bioimpedance vs. biopotentials • Internal electrical power sources • Monitoring of internal ion currents flowing through bio membranes • Examples: ECG, EMG, EEG, … • External electrical power sources • Inject a small electrical AC current • Evaluation of passive electrical properties of all body tissues • Examples: BIS, EIT

  15. Electrical impedance of biological tissue

  16. Principle of impedance tomography Circular attachment of N electrodes (e.g. N=16) Pairwise current injection (e.g. 5 mA at 50-200 kHz) Voltage measurement between all remaining pairs Recording of N x (N-3) voltages per frame (e.g. 208)

  17. Presentation of impedance measures 1 1 Static or absolute EIT frames Relative or dynamic sequences of EIT frames 2 3 Functional EIT images (fEIT) 4 Time course of impedances

  18. Is there any evidence that EIT generates more than colourful images?

  19. Assessment of tidal volume

  20. Analysis of regional ventilation Correlation of air content changes determined by CT and impedance changes in 10 adult patients during slow inflation. Victorino et al. Am J RespirCrit Care Med 2004; 169: 791-800

  21. Analysis of regional ventilation II • Animal model, 12 pigs • ARDS induction with oleic acid • EIT compared to scintigraphy • Correlation coefficient (20 segments): 0,92 [0,86-0,97] Hinz J et al. Chest 2003; 123: 314-22.

  22. Estimation of regional compliance • 9 patients suffering from ARDS • Aim: Evaluation of regional ventilation regarding compliance • Successful recognition of breathes (96,0%; 97,6%) • Calculation of compliance: correlation coefficient of 0.8 • Examination of regional ventilation under stepwise pressure increase Gómez-LabergeC et al. IEEE Trans Med Imaging. 2012; 31: 834-42

  23. Monitoring of recruitment effects

  24. Clinical application: endotracheal suction • Porcine animal model, ARDS induced by surfactant depletion • Comparison of two suction techniques • Effect depends on catheter diameter >> technique TingayDG et al. Intensive Care Med. 2010; 36: 888-96.

  25. Clinical application: one-lung ventilation • Clinical trial, 40 patients • Thorax surgery requiring one-lung ventilation • Correct placement of double-lumen tube was clearly visible Steinmann D et al. BJA 2008 Sep; 101: 411-8.

  26. Clinical application: one-lung ventilation • Clinical trial, 10 patients • Thorax surgery requiring one-lung ventilation • Reliable detection necessitates ROI definition Pulletz S et al. ActaAnaesthesiol Scand. 2008; 52:1131-9.

  27. Clinical application: emergency medicine • Conclusion: EIT is an imaging modality for monitoring mechanical ventilation during the relocation of patients. The application is non-invasive and without any exposure to radiation Karmrodt J et al. Notfall & Rettungsmedizin2004; 7:572–576

  28. Is EIT clinically established yet? Is there any evidence that EIT improves clinical outcome?

  29. Clinical trial examining outcome • Title: Strategies to Optimize Positive End-expiratory Pressure (PEEP) in Patients With Acute Lung Injury (EIT-PEEP) (University Hospital Bonn) • Primary Outcome Measures:homogeneity of regional ventilation delay • Estimated enrollment: 40 patients • Estimated study completion: June 2013

  30. What will be in future?

  31. Clinical application: Monitoring of cerebral oedema • Clinical trial, 200 healthy patients vs. 107 patients with cerebral infarction • 0,1mA @ 50kHz • Usage of contralateral side as reference • Aim: Monitoring of volume of cerebral oedemawith EIT compared to MRT or CT  Accordance of about 75-85% (dependent on absolute volume) He LY et al. Application of non-invasive cerebral electrical impedance measurement on brain edema in patients with cerebral infarction. Neurol Res. 2010;32:770-4

  32. Clinical application: Cerebral haemorrhage • Porcine animal model • Blood injection to the cerebral frontal lobe • Usage of contralateral side as reference • 16 electrodes attached to the head • Calculation of mean impedance and relative changes in defined ROI  High correlation with injected blood volume was achieved Xu CH et al. Real-time imaging and detection of intracranial haemorrhage by electrical impedance tomography in a piglet model. J. Int. Med. Res 2010; 38: 1596-1604.

  33. Cardiac related impedance changes • Clinical trial, 10 patients • Measurement of ventilation, perfusion and ventilations-perfusions-ratio • Signal processing by band-pass filtering Grant CA et al. Crit Care. 2011;15:R37.

  34. Separation of ventilation and perfusion I

  35. Separation of ventilation and perfusion II Overlap of frequency bands Pikkemaat, Leonhardt et al. Unpublished data

  36. Separation of ventilation and perfusion III Approach: using constrasting agents (10% NaCl) Reference: SPECT / CT (99mTC labelled albumine) Collaboration with Uppsala University (G. Hedenstierna) • 4 healthy pigs (28-33 kg) • Volume-controlled ventilation • EIT device EEK2

  37. Separation of ventilation and perfusion IV • NaCl-Bolus: 10 ml of 10 % • First, NaCl-Bolus reaches the right heart • Then, high NaCl-concentration is flowing to the lungs • Finally, bolus reaches the left heart • The impedance curves show curves similiar to thermodilution • Regional separation of the signal according to the physiology seems possible Quelle: Henning Lüpschen, "Automatisierte protektive Beatmung durch Bestimmung von Ventilation und Perfusion der Lunge mittels Elektrischer Impedanztomographie“, Shaker Verlag, 2012, to appear. Pikkemaat, Leonhardt et al. Unpublished data

  38. Application of internal electrodes Image reconstruction conv tracheal oesoph Perfusion/ventilation voltage ratio conv tracheal oesoph Czaplik, Hoog-Antik et al. Unpublished data

  39. The future

  40. Thanksforyourattention! The future II

More Related