Protective ventilation using electrical impedance tomography

Abstract

Dynamic thoracic EIT is capable of detecting changes of the ventilation distribution in the lung. Nevertheless, it has yet to become an established clinical tool. Therefore, it is necessary to consider application scenarios wherein fast and distinct changes of the tissue conductivities are to be found and also have a clear diagnostic significance. One such a scenario is the artificial ventilation of patients suffering from the acute respiratory distress syndrome (ARDS). New protective ventilation strategies involving recruitment manoeuvres are associated with noticeable shifts of body fluids and regional ventilation, which can quite easily be detected by EIT. The bedside assessment of these recruitment manoeuvres will help the attending physician to optimize treatment. Hence, we performed an animal study of lavage-induced lung failure and investigated if EIT is capable of qualitatively as well as quantitatively monitoring lung recruitment during a stepwise PEEP trial. Additionally, we integrated EIT into a fuzzy controller-based ventilation system which allows one to perform automated recruitment manoeuvres (open lung concept) based on online PaO2 measurements. We found that EIT is a useful tool to titrate the proper PEEP level after fully recruiting the lung. Furthermore, EIT seems to be able to determine the status of recruitment when combining it with other physiological parameters. These results suggest that EIT may play an important role in the individualization of protective ventilation strategies.

Tidal recruitment assessed by electrical impedance tomography and computed tomography in a porcine model of lung injury*

“…Changes in distribution and homogeneity of end-expiratory lung volume (43), tidal volume (25,26,31,33,44,45), and collapse (33) were quantified at different PEEP levels.…”

“…Electrical impedance tomography (EIT) of the lungs measures relative impedance changes in lung tissue during tidal breathing and creates images of the local ventilation distribution at bedside (22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). An EIT-based index (regionalventilation-delay [RVD]) describing the scatter of impedance time courses has recently been shown to be able to detect recruitment during a vital capacity inflation maneuver (30).…”

Optimizing Perioperative Ventilation Support with Adequate Settings of Positive End-Expiratory Pressure

“…Besides, the identification of stable, horizontal end-expiratory EIT values may be difficult. Luepschen and colleagues modified the centre of gravity index from Frerichs et al (Frerichs et al, 1998) to evaluate functional lung opening and overdistension of the lung tissue in an animal model of lavageinduced acute lung injury (Luepschen et al, 2007). Dargaville et al have applied EIT during an incremental and decremental PEEP trial to identify the PEEP level at which the most homogeneous distribution of regional C rs and ventilation was observed in healthy, injured and surfactant-treated lungs (Dargaville et al, 2010).…”

Perspectives in respiratory monitoring

“…La fiabilité de la TIE pour mesurer le volume pulmonaire aéré et la ventilation a été évaluée, chez l'animal et l'homme, sans et avec agression pulmonaire, en utilisant de multiples méthodes comparatrices (mesure de la CRF par dilution à l'hélium ou rinçage à l'azote [23,24], tomodensitométrie [19,25,26], tomographie par émission de positon [27], ou Single-photon emission computed tomography (SPECT) [28]). Ces comparaisons ont été compliquées par la nécessité de faire concorder les unités d'expression du volume et de la ventilation, obtenues avec les méthodes de référence, avec les valeurs d'impédance.…”