Imbalances in regional lung ventilation: a validation study on electrical impedance tomography.

Imbalances in regional lung ventilation, with gravity-dependent collapse and overdistention of nondependent zones, are likely associated to ventilator-induced lung injury. Electric impedance tomography is a new imaging technique that is potentially capable of monitoring those imbalances. The aim of this study was to validate electrical impedance tomography measurements of ventilation distribution, by comparison with dynamic computerized tomography in a heterogeneous population of critically ill patients under mechanical ventilation. Multiple scans with both devices were collected during slow-inflation breaths. Six repeated breaths were monitored by impedance tomography, showing acceptable reproducibility. We observed acceptable agreement between both technologies in detecting right-left ventilation imbalances (bias = 0% and limits of agreement = -10 to +10%). Relative distribution of ventilation into regions or layers representing one-fourth of the thoracic section could also be assessed with good precision. Depending on electrode positioning, impedance tomography slightly overestimated ventilation imbalances along gravitational axis. Ventilation was gravitationally dependent in all patients, with some transient blockages in dependent regions synchronously detected by both scanning techniques. Among variables derived from computerized tomography, changes in absolute air content best explained the integral of impedance changes inside regions of interest (r(2) > or = 0.92). Impedance tomography can reliably assess ventilation distribution during mechanical ventilation.

[1]  Yves Goussard,et al.  Regularized reconstruction in electrical impedance tomography using a variance uniformization constraint , 1997, IEEE Transactions on Medical Imaging.

[2]  G Hahn,et al.  Gravity-dependent phenomena in lung ventilation determined by functional EIT. , 1996, Physiological measurement.

[3]  G. Hellige,et al.  End-expiratory lung impedance change enables bedside monitoring of end-expiratory lung volume change , 2002, Intensive Care Medicine.

[4]  G. Hounsfield.  Computerized transverse axial scanning (tomography): Part I. Description of system. 1973. , 1973, The British journal of radiology.

[5]  R. Albert,et al.  The prone position eliminates compression of the lungs by the heart. , 2000, American journal of respiratory and critical care medicine.

[6]  D. Altman,et al.  Statistics notes: Measurement error , 1996 .

[7]  D C Barber,et al.  Quantification in impedance imaging. , 1990, Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics.

[8]  P. Pelosi,et al.  Vertical gradient of regional lung inflation in adult respiratory distress syndrome. , 1994, American journal of respiratory and critical care medicine.

[9]  J. Jansen,et al.  Estimation of regional lung volume changes by electrical impedance pressures tomography during a pressure-volume maneuver , 2003, Intensive Care Medicine.

[10]  D. Altman,et al.  Calculating correlation coefficients with repeated observations: Part 2—correlation between subjects , 1995, BMJ.

[11]  S. Böhm,et al.  Effects of Recruitment Maneuver on Atelectasis in Anesthetized Children , 2003, Anesthesiology.

[12]  Burkhard Lachmann,et al.  Monitoring of recruitment and derecruitment by electrical impedance tomography in a model of acute lung injury , 2000, Critical care medicine.

[13]  Gerhard Hellige,et al.  Distribution of lung ventilation in spontaneously breathing neonates lying in different body positions , 2003, Intensive Care Medicine.

[14]  Joseph Foss,et al.  Comparing Methods of Clinical Measurement: Reporting Standards for Bland and Altman Analysis , 2000, Anesthesia and analgesia.

[15]  A. Jobe,et al.  Surfactant and the adult respiratory distress syndrome. , 1993, The American review of respiratory disease.

[16]  D. Isaacson,et al.  Errors due to measuring voltage on current-carrying electrodes in electric current computed tomography , 1990, IEEE Transactions on Biomedical Engineering.

[17]  L. Puybasset,et al.  Role of the heart in the loss of aeration characterizing lower lobes in acute respiratory distress syndrome. CT Scan ARDS Study Group. , 2000, American journal of respiratory and critical care medicine.

[18]  L Puybasset,et al.  A lung computed tomographic assessment of positive end-expiratory pressure-induced lung overdistension. , 1998, American journal of respiratory and critical care medicine.

[19]  L. Goodman,et al.  What has computed tomography taught us about the acute respiratory distress syndrome? , 2001, American journal of respiratory and critical care medicine.

[20]  J. Arnold,et al.  Identification of optimal lung volume during high-frequency oscillatory ventilation using respiratory inductive plethysmography , 2001, Critical care medicine.

[21]  D C Barber,et al.  A review of image reconstruction techniques for electrical impedance tomography. , 1989, Medical physics.

[22]  B. Jonson,et al.  Surfactant dysfunction makes lungs vulnerable to repetitive collapse and reexpansion. , 1997, American journal of respiratory and critical care medicine.

[23]  Wei Wang,et al.  The number of electrodes and basis functions in EIT image reconstruction , 2002, Physiological measurement.

[24]  Burkhard Lachmann,et al.  Regional pressure volume curves by electrical impedance tomography in a model of acute lung injury , 2000, Critical care medicine.

[25]  G. Hedenstierna,et al.  Correlation of gas exchange impairment to development of atelectasis during anaesthesia and muscle paralysis , 1986 .

[26]  D C Barber,et al.  Applications of applied potential tomography (APT) in respiratory medicine. , 1987, Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics.

[27]  D C Barber,et al.  Applied potential tomography: a new technique for monitoring pulmonary function. , 1988, Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics.

[28]  P. Pelosi,et al.  Effects of positive end-expiratory pressure on regional distribution of tidal volume and recruitment in adult respiratory distress syndrome. , 1995, American journal of respiratory and critical care medicine.

[29]  B H Blott,et al.  Electrical impedance tomography with compensation for electrode positioning variations. , 1998, Physics in medicine and biology.

[30]  José Hinz,et al.  Regional ventilation by electrical impedance tomography: a comparison with ventilation scintigraphy in pigs. , 2003, Chest.

[31]  L Puybasset,et al.  Computed tomography assessment of positive end-expiratory pressure-induced alveolar recruitment in patients with acute respiratory distress syndrome. , 2001, American journal of respiratory and critical care medicine.

[32]  Arthur S Slutsky,et al.  Impairment of lung and chest wall mechanics in patients with acute respiratory distress syndrome: role of abdominal distension. , 1997, American journal of respiratory and critical care medicine.

[33]  L M Heikkinen,et al.  A MATLAB package for the EIDORS project to reconstruct two-dimensional EIT images , 2001, Physiological measurement.

[34]  J. Katz,et al.  Time Course and Mechanisms of Lung‐volume Increase with PEEP in Acute Pulmonary Failure , 1981, Anesthesiology.

[35]  Gerhard Hellige,et al.  Detection of local lung air content by electrical impedance tomography compared with electron beam CT. , 2002, Journal of applied physiology.

[36]  Arthur S Slutsky,et al.  Tidal ventilation at low airway pressures can augment lung injury. , 1994, American journal of respiratory and critical care medicine.

[37]  B. Brown,et al.  Applied potential tomography: possible clinical applications. , 1985, Clinical physics and physiological measurement : an official journal of the Hospital Physicists' Association, Deutsche Gesellschaft fur Medizinische Physik and the European Federation of Organisations for Medical Physics.

[38]  I Basarab-Horwath,et al.  Incorporating a priori anatomical information into image reconstruction in electrical impedance tomography , 1999, Physiological measurement.

[39]  P. Pelosi,et al.  Alterations of lung and chest wall mechanics in patients with acute lung injury: effects of positive end-expiratory pressure. , 1995, American journal of respiratory and critical care medicine.

[40]  Michael Vogelius,et al.  A backprojection algorithm for electrical impedance imaging , 1990 .

[41]  G.J. Saulnier,et al.  An iterative Newton-Raphson method to solve the inverse admittivity problem , 1998, IEEE Transactions on Biomedical Engineering.

[42]  L. Brochard,et al.  Effects of Positive End-expiratory Pressure and Different Tidal Volumes on Alveolar Recruitment and Hyperinflation , 1997, Anesthesiology.

[43]  B H Brown,et al.  Clinical applications of electrical impedance tomography. , 1993, Journal of medical engineering & technology.

[44]  A Adler,et al.  Electrical impedance tomography can monitor dynamic hyperinflation in dogs. , 1998, Journal of applied physiology.

[45]  David Isaacson,et al.  A direct reconstruction algorithm for electrical impedance tomography , 2002, IEEE Transactions on Medical Imaging.

[46]  D C Barber,et al.  Image reconstruction using non-adjacent drive configurations (electric impedance tomography) , 1994 .

[47]  B. H. Brown,et al.  Model for the dielectric properties of human lung tissue against frequency and air content , 1997, Medical and Biological Engineering and Computing.

[48]  G. Hedenstierna,et al.  Pulmonary Densities during Anesthesia with Muscular Relaxation—A Proposal of Atelectasis , 1985, Anesthesiology.

[49]  David S. Holder,et al.  Clinical and physiological applications of electrical impedance tomography , 1993 .

[50]  A. Torresin,et al.  Relationships Between Lung Computed Tomographic Density, Gas Exchange, and PEEP in Acute Respiratory Failure , 1988, Anesthesiology.

[51]  Eric McAdams,et al.  Multi-electrode systems for electrical impedance imaging , 1994 .

[52]  P. Grenier,et al.  Regional distribution of gas and tissue in acute respiratory distress syndrome. I. Consequences for lung morphology , 2000, Intensive Care Medicine.

[53]  G. Hedenstierna,et al.  Effects of inverse ratio ventilation and positive end-expiratory pressure in oleic acid-induced lung injury. , 2000, American journal of respiratory and critical care medicine.

[54]  J C Newell,et al.  Real-time three-dimensional electrical impedance imaging. , 2000, Physiological measurement.

[55]  O. Hoekstra,et al.  Ventilation and perfusion imaging by electrical impedance tomography: a comparison with radionuclide scanning. , 1998, Physiological measurement.

[56]  Béla Suki,et al.  Fluctuations and power laws in pulmonary physiology. , 2002, American journal of respiratory and critical care medicine.

[57]  A. Torresin,et al.  Morphological response to positive end expiratory pressure in acute respiratory failure. Computerized tomography study , 2004, Intensive Care Medicine.

[58]  D. Altman,et al.  Statistics notes: Calculating correlation coefficients with repeated observations: Part 1—correlation within subjects , 1995 .

[59]  G. Hedenstierna,et al.  Effect of different pressure levels on the dynamics of lung collapse and recruitment in oleic-acid-induced lung injury. , 1998, American journal of respiratory and critical care medicine.

[60]  M Molinari,et al.  Adaptive mesh refinement techniques for electrical impedance tomography. , 2001, Physiological measurement.

[61]  P. Pelosi,et al.  Regional effects and mechanism of positive end-expiratory pressure in early adult respiratory distress syndrome. , 1993, JAMA.

[62]  D. Pengelly,et al.  Effect of gravity on the distribution of pulmonary ventilation. , 1966, Journal of applied physiology.

[63]  G.J. Saulnier,et al.  ACT3: a high-speed, high-precision electrical impedance tomograph , 1991, IEEE Transactions on Biomedical Engineering.

[64]  I. Sutherland,et al.  Correction of the non-uniform spatial sensitivity of electrical impedance tomography images. , 1994, Physiological measurement.

[65]  A Adler,et al.  Monitoring changes in lung air and liquid volumes with electrical impedance tomography. , 1997, Journal of applied physiology.