Regional pressure volume curves by electrical impedance tomography in a model of acute lung injury

Objective: A new noninvasive method, electrical impedance tomography (EIT), was used to make pressure‐impedance (PI) curves in a lung lavage model of acute lung injury in pigs. The lower inflection point (LIP) and the upper deflection point (UDP) were determined from these curves and from the traditional pressure‐volume (PV) curves to determine whether the PI curves resemble the traditional PV curves. Furthermore, regional differences in the mentioned determinants were investigated. Design: Prospective, experimental study. Setting: Animal research laboratory. Interventions: In nine anesthetized pigs, repeated lung lavage was performed until a PaO2 <80 torr was reached. Thereafter, an inspiratory PV curve was made using a constant flow of oxygen. During the intervention, EIT measurements were performed. Measurements and Main Results: In this study, the LIPEIT was within 2 cm H2O of the LIPPV. Furthermore, it was possible to visualize regional PI curves by EIT. No significant difference was found between the LIPPV (21.3 ± 3.0 cm H2O) and the LIPEIT of the total lung (21.5 ± 3.0 cm H2O) or the anterior parts of the lung (21.5 ± 2.9 cm H2O). A significantly higher LIP (29.5 ± 4.9 cm H2O) was found in the posterior parts of the lung. A UDPPV could be found in three animals only, whereas in all animals a UDPEIT could be determined from the anterior part of the lung. Conclusions: Using EIT, determination of LIP and UDP from the regional PI curves is possible. The obtained information from the regional PI curves may help in understanding alveolar recruitment. The use of this new bedside technique for clinical decision making remains to be examined.

[1]  B Lachmann,et al.  In Vivo Lung Lavage as an Experimental Model of the Respiratory Distress Syndrome , 1980, Acta anaesthesiologica Scandinavica.

[2]  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.

[3]  V. Ranieri,et al.  Effects of positive end-expiratory pressure on alveolar recruitment and gas exchange in patients with the adult respiratory distress syndrome. , 1991, The American review of respiratory disease.

[4]  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.

[5]  A. Armaganidis,et al.  Should mechanical ventilation be optimized to blood gases, lung mechanics, or thoracic CT scan? , 1995, American journal of respiratory and critical care medicine.

[6]  M. Amato,et al.  Beneficial effects of the "open lung approach" with low distending pressures in acute respiratory distress syndrome. A prospective randomized study on mechanical ventilation. , 1995, American journal of respiratory and critical care medicine.

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

[8]  L. Brochard,et al.  Pressure-volume curves in acute respiratory failure: automated low flow inflation versus occlusion. , 1997, American journal of respiratory and critical care medicine.

[9]  H. Magnussen,et al.  Assessment of mycobacterial DNA in cells and tissues of mycobacterial and sarcoid lesions. , 1996, American journal of respiratory and critical care medicine.

[10]  D. Matamis,et al.  Total respiratory pressure-volume curves in the adult respiratory distress syndrome. , 1984, Chest.

[11]  A. Pesenti,et al.  Pressure-volume curve of total respiratory system in acute respiratory failure. Computed tomographic scan study. , 1987, The American review of respiratory disease.

[12]  G. Hahn,et al.  Changes in the thoracic impedance distribution under different ventilatory conditions. , 1995, Physiological measurement.

[13]  D C Barber,et al.  Possibilities and problems of real-time imaging of tissue resistivity. , 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.

[14]  B.H. Brown,et al.  A real-time electrical impedance tomography system for clinical use-design and preliminary results , 1995, IEEE Transactions on Biomedical Engineering.