Electrical impedance tomography: A compass for the safe route to optimal PEEP. (October 2021)

• Record Type: Journal Article
• Authors: Sella, Nicolò; Pettenuzzo, Tommaso; Zarantonello, Francesco; Andreatta, Giulio; De Cassai, Alessandro; Schiavolin, Chiara; Simoni, Caterina; Pasin, Laura; Boscolo, Annalisa; Navalesi, Paolo
• Is Part Of: Respiratory medicine. Volume 187(2021)
• Publication Date: 2021-10
• Subjects: Positive end-expiratory pressure -- PEEP -- Electrical impedance tomography -- EIT -- Mechanical ventilation -- Acute respiratory failure -- Acute respiratory distress syndrome -- ARDS; Chest -- Diseases -- Periodicals; Chest -- Diseases -- Great Britain -- Periodicals; Respiratory organs -- Diseases -- Periodicals; Respiratory Tract Diseases -- Periodicals; Appareil respiratoire -- Maladies -- Périodiques; Thorax -- Maladies -- Périodiques; Appareil respiratoire -- Maladies -- Traitement -- Périodiques; Electronic journals; 616.2
• DOI: 10.1016/j.rmed.2021.106555
• Languages: English
• ISSNs: 0954-6111

Abstract

Abstract: Setting the proper level of positive end-expiratory pressure (PEEP) is a cornerstone of lung protective ventilation. PEEP keeps the alveoli open at the end of expiration, thus reducing atelectrauma and shunt. However, excessive PEEP may contribute to alveolar overdistension. Electrical impedance tomography (EIT) is a non-invasive bedside tool that monitors in real-time ventilation distribution. Aim of this narrative review is summarizing the techniques for EIT-guided PEEP titration, while providing useful insights to enhance comprehension on advantages and limits of EIT for current and future users. EIT detects thoracic impedance to alternating electrical currents between pairs of electrodes and, through the analysis of its temporal and spatial variation, reconstructs a two-dimensional slice image of the lung depicting regional variation of ventilation and perfusion. Several EIT-based methods have been proposed for PEEP titration. The first described technique estimates the variations of regional lung compliance during a decremental PEEP trial, after lung recruitment. The optimal PEEP value is represented by the best compromise between lung collapse and overdistension. Later on, a second technique assessing alveolar recruitment by variation of the end-expiratory lung impedance was validated. Finally, the global inhomogeneity index and the regional ventilation delay, two EIT-derived parameters, showed promising results selecting the optimal PEEP value as the one that presents the lowest global inhomogeneity index or the lowest regional ventilation delay. In conclusion EIT represents a promising technique to individualize PEEP in mechanically ventilated patients. Whether EIT is the best technique for this purpose and the overall influence of personalizing PEEP on clinical outcome remains to be determined. Highlights: EIT allows non-invasive bedside assessment of distribution of lung aeration. Varying PEEP affects end-expiratory lung volume (recruitment and overdistension). Both collapse and overdistension cause loss of lung compliance. EIT detects changes in lung volume and calculates loss of lung compliance. Based on these changes, EIT allows setting individualized PEEP.