Electrical Impedance Tomography for the assessment of spontaneous breathing trials in patients with prolonged weaning

Abstract

<b>Background:</b> Electrical impedance tomography (EIT) provides images of regional ventilation distribution in the lungs by measuring changes in electrical impedance. In patients with prolonged weaning, spontaneous breathing trials (SBT) on a t-piece are difficult due to remaining de-recruitment phenomena. EIT might enable monitoring and analysis of the resulting impairment of regional ventilation distribution. We analyzed the application of EIT on SBT in patients with prolonged weaning. <b>Methods:</b> 31 patients used pressure support ventilation (PSV) during baseline (t0). A t-piece trial (t1) was performed and PSV was re-applied (t2). EIT was measured during all settings. For quantification, the impedance ratio (IR), the global inhomogeneity index (GI) and the regional ventilation delay index (RVD) with use of different thresholds of the percentaged inspiration time (RVD40, RVD 60, RVD 80) were determined. <b>Results:</b> PaO2 significantly decreased at t1 compared to t0 and t2 (p&lt;0.05). The IR tended towards higher values during t1. The GI was significantly increased at t1 (p=0.001) as well all RVDs. A significant correlation between GI and PaO2 was shown. <b>Conclusions:</b> We have shown a safe and reasonable use of EIT in patients with prolonged weaning undergoing SBT. EIT might therefore be a tool to monitor de-recruitment phenomena in this specific patient group, being available online with timely monitoring of (patho-)physiological changes within the lungs and thus, faster than conventional or clinical observations. Quantitative analysis of specific EIT parameters like the GI might have predictive value on success or clinical deterioration of patients on a t-piece trial.