Individualization of PEEP and tidal volume in ARDS patients with electrical impedance tomography: a pilot feasibility study

Abstract Background In mechanically ventilated patients with acute respiratory distress syndrome (ARDS), electrical impedance tomography (EIT) provides information on alveolar cycling and overdistension as well as assessment of recruitability at the bedside. We developed a protocol for individualization of positive end-expiratory pressure (PEEP) and tidal volume (VT) utilizing EIT-derived information on recruitability, overdistension and alveolar cycling. The aim of this study was to assess whether the EIT-based protocol allows individualization of ventilator settings without causing lung overdistension, and to evaluate its effects on respiratory system compliance, oxygenation and alveolar cycling. Methods 20 patients with ARDS were included. Initially, patients were ventilated according to the recommendations of the ARDS Network with a VT of 6 ml per kg predicted body weight and PEEP adjusted according to the lower PEEP/FiO2 table. Subsequently, ventilator settings were adjusted according to the EIT-based protocol once every 30 min for a duration of 4 h. To assess global overdistension, we determined whether lung stress and strain remained below 27 mbar and 2.0, respectively. Results Prospective optimization of mechanical ventilation with EIT led to higher PEEP levels (16.5 [14–18] mbar vs. 10 [8–10] mbar before optimization; p = 0.0001) and similar VT (5.7 ± 0.92 ml/kg vs. 5.8 ± 0.47 ml/kg before optimization; p = 0.96). Global lung stress remained below 27 mbar in all patients and global strain below 2.0 in 19 out of 20 patients. Compliance remained similar, while oxygenation was significantly improved and alveolar cycling was reduced after EIT-based optimization. Conclusions Adjustment of PEEP and VT using the EIT-based protocol led to individualization of ventilator settings with improved oxygenation and reduced alveolar cycling without promoting global overdistension. Trial registrationThis study was registered at clinicaltrials.gov (NCT02703012) on March 9, 2016 before including the first patient.

Download Full-text

Individualization of PEEP and Tidal Volume in ARDS Patients with Electrical Impedance Tomography

10.21203/rs.3.rs-115065/v1 ◽

2020 ◽

Author(s):

Tobias Hermann Becher ◽

Valerie Buchholz ◽

Daniel Hassel ◽

Timo Alexander Meinel ◽

Dirk Schädler ◽

...

Keyword(s):

Tidal Volume ◽

Electrical Impedance Tomography ◽

Electrical Impedance ◽

Predicted Body Weight ◽

Impedance Tomography ◽

Mechanically Ventilated ◽

Lung Overdistension ◽

Fraction Of Inspired Oxygen ◽

Ventilator Settings ◽

Lung Stress

Abstract BackgroundIn mechanically ventilated patients with acute respiratory distress syndrome (ARDS), electrical impedance tomography (EIT) provides information on alveolar cycling and overdistension as well as assessment of recruitability at the bedside. We developed a protocol for individualization of positive end-expiratory pressure (PEEP) and tidal volume (VT) utilizing EIT-derived information on recruitability, overdistension and alveolar cycling. The aim of this study was to assess whether the EIT-based protocol allows individualization of ventilator settings without causing lung overdistension, and to evaluate its effects on respiratory system compliance, oxygenation and alveolar cycling. Methods20 patients with ARDS were included. Initially, patients were ventilated according to the recommendations of the ARDS-Network with a VT of 6 ml per kg predicted body weight and PEEP adjusted according to the fraction of inspired oxygen. Subsequently, ventilator settings were adjusted according to the EIT-based protocol once every 30 minutes for a duration of 4 hours. To assess global overdistension, we determined whether lung stress and strain remained below 27 and 2.0, respectively. ResultsWe found that prospective optimization of mechanical ventilation with EIT led to global lung stress below 27 mbar in all patients and global strain below 2.0 in 19 out of 20 patients. Compliance remained similar while oxygenation was significantly improved and alveolar cycling was reduced after EIT-based optimization.ConclusionsAdjustment of PEEP and VT using the EIT-based protocol led to individualization of ventilator settings with improved oxygenation and reduced alveolar cycling without promoting global overdistension. Trial registrationThis study was registered at clinicaltrials.gov (NCT02703012) on March 9, 2016 before including the first patient.

Download Full-text

Identification of lung overdistension caused by tidal volume and positive end-expiratory pressure increases based on electrical impedance tomography

British Journal of Anaesthesia ◽

10.1016/j.bja.2021.01.026 ◽

2021 ◽

Author(s):

Zhanqi Zhao ◽

Ling Sang ◽

Yimin Li ◽

Inéz Frerichs ◽

Knut Möller ◽

...

Keyword(s):

Tidal Volume ◽

Electrical Impedance Tomography ◽

Electrical Impedance ◽

Positive End Expiratory Pressure ◽

Impedance Tomography ◽

Lung Overdistension

Download Full-text

Influence of overdistension/recruitment induced by high positive end-expiratory pressure on ventilation–perfusion matching assessed by electrical impedance tomography with saline bolus

Critical Care ◽

10.1186/s13054-020-03301-x ◽

2020 ◽

Vol 24 (1) ◽

Author(s):

Huaiwu He ◽

Yi Chi ◽

Yun Long ◽

Siyi Yuan ◽

Inéz Frerichs ◽

...

Keyword(s):

Electrical Impedance Tomography ◽

Electrical Impedance ◽

High Peep ◽

Perfusion Image ◽

Impedance Tomography ◽

Mechanically Ventilated ◽

Mechanically Ventilated Patients ◽

R Ratio ◽

Lung Overdistension ◽

Ventilated Patients

Abstract Background High positive end-expiratory pressures (PEEP) may induce overdistension/recruitment and affect ventilation–perfusion matching (VQMatch) in mechanically ventilated patients. This study aimed to investigate the association between PEEP-induced lung overdistension/recruitment and VQMatch by electrical impedance tomography (EIT). Methods The study was conducted prospectively on 30 adult mechanically ventilated patients: 18/30 with ARDS and 12/30 with high risk for ARDS. EIT measurements were performed at zero end-expiratory pressures (ZEEP) and subsequently at high (12–15 cmH2O) PEEP. The number of overdistended pixels over the number of recruited pixels (O/R ratio) was calculated, and the patients were divided into low O/R (O/R ratio < 15%) and high O/R groups (O/R ratio ≥ 15%). The global inhomogeneity (GI) index was calculated to evaluate the ventilation distribution. Lung perfusion image was calculated from the EIT impedance–time curves caused by 10 ml 10% NaCl injection during a respiratory pause (> 8 s). DeadSpace%, Shunt%, and VQMatch% were calculated based on lung EIT perfusion and ventilation images. Results Increasing PEEP resulted in recruitment mainly in dorsal regions and overdistension mainly in ventral regions. ΔVQMatch% (VQMatch% at high PEEP minus that at ZEEP) was significantly correlated with recruited pixels (r = 0.468, P = 0.009), overdistended pixels (r = − 0.666, P < 0.001), O/R ratio (r = − 0.686, P < 0.001), and ΔSpO2 (r = 0.440, P = 0.015). Patients in the low O/R ratio group (14/30) had significantly higher Shunt% and lower VQMatch% than those in the high O/R ratio group (16/30) at ZEEP but not at high PEEP. Comparable DeadSpace% was found in both groups. A high PEEP caused a significant improvement of VQMatch%, DeadSpace%, Shunt%, and GI in the low O/R ratio group, but not in the high O/R ratio group. Using O/R ratio of 15% resulted in a sensitivity of 81% and a specificity of 100% for an increase of VQMatch% > 20% in response to high PEEP. Conclusions Change of ventilation–perfusion matching was associated with regional overdistention and recruitment induced by PEEP. A low O/R ratio induced by high PEEP might indicate a more homogeneous ventilation and improvement of VQMatch. Trial registration ClinicalTrials.gov, NCT04081155. Registered on 9 September 2019—retrospectively registered.

Download Full-text