Clinical Implications of Determining Individualized Positive End-Expiratory Pressure Using Electrical Impedance Tomography in Post-Cardiac Surgery Patients: A Prospective, Non-Randomized Interventional Study

Abstract

Optimal positive end-expiratory pressure (PEEP) can induce sustained lung function improvement. This prospective, non-randomized interventional study aimed to investigate the effect of individualized PEEP determined using electrical impedance tomography (EIT) in post-cardiac surgery patients (n = 35). Decremental PEEP trials were performed from 20 to 4 cmH2O in steps of 2 cmH2O, guided by EIT. PEEP levels preventing ventilation loss in dependent lung regions (PEEPONLINE) were set. Ventilation distributions and oxygenation before the PEEP trial, and 5 min and 1 h after the PEEPONLINE setting were examined. Furthermore, we analyzed the saved impedance data offline to determine the PEEP levels that provided the best compromise between overdistended and collapsed lung (PEEPODCL). Ventilation distributions of dependent regions increased at 5 min after the PEEPONLINE setting compared with those before the PEEP trial (mean ± standard deviation, 41.3 ± 8.5% vs. 49.1 ± 9.3%; p < 0.001), and were maintained at 1 h thereafter (48.7 ± 9.4%, p < 0.001). Oxygenation also showed sustained improvement. Rescue oxygen therapy (high-flow nasal cannula, noninvasive ventilation) after extubation was less frequent in patients with PEEPONLINE ≥ PEEPODCL than in those with PEEPONLINE < PEEPODCL (1/19 vs. 6/16; p = 0.018). EIT-guided individualized PEEP stabilized the improvement in ventilation distribution and oxygenation. Individual PEEP varies with EIT measures, and may differentially affect oxygenation after cardiac surgery.

Setting positive end-expiratory pressure by using electrical impedance tomography

“…The same parameter was applied in obese surgery patients and identified less dependent collapse at 12 than 4 cmH 2 O of PEEP [6]. A well designed prospective clinical study in postcardiac surgery patients determined PEEP by analyzing a decremental PEEP trial with EIT with the aim of avoiding ventilation loss in the dependent regions [7 ▪▪ ]. The EIT-guided PEEP setting prevented alveolar collapse and improved oxygenation and C rs .…”

Distribution of regional lung function in upright healthy subjects determined by electrical impedance tomography in two chest examination planes

“…The generated transverse EIT images allow the assessment of regional lung function in both the gravity-dependent and non-dependent regions that are prone to the development of atelectasis and overdistention. Since EIT can identify these adverse phenomena it helps the physicians to minimize their occurrence by adjustments of the ventilator settings (Gomez-Laberge et al 2012, Bronco et al 2021, Hsu et al 2021, Bito et al 2022, Heines et al 2022.…”