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 Pa0(2) <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.