Effects of Support Pressure and Peep on the Asynchrony Index Evaluated by Electrical Impedance Tomography in Mechanically Ventilated Critical Patients of a University Hospital

2019 ◽  
Author(s):  
D. Arellano ◽  
R.A. Cornejo ◽  
M. Lazo
Keyword(s):  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
University Hospital ◽  
Support Pressure ◽  
Impedance Tomography ◽  
Asynchrony Index ◽  
Mechanically Ventilated ◽  
Critical Patients

scholarly journals Unmatched ventilation and perfusion measured by electrical impedance tomography predicts the outcome of ARDS

Critical Care ◽  
2021 ◽  
Vol 25 (1) ◽  
Author(s):  
Elena Spinelli ◽  
Michael Kircher ◽  
Birgit Stender ◽  
Irene Ottaviani ◽  
Maria C. Basile ◽  
...  
Keyword(s):  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Prospective Observational Study ◽  
Distress Syndrome ◽  
Regional Distribution ◽  
Impedance Tomography ◽  
Mechanically Ventilated ◽  
Risk Of Death ◽  
Ventilation Induced Lung Injury ◽  
Ventilation And Perfusion

Abstract Background In acute respiratory distress syndrome (ARDS), non-ventilated perfused regions coexist with non-perfused ventilated regions within lungs. The number of unmatched regions might reflect ARDS severity and affect the risk of ventilation-induced lung injury. Despite pathophysiological relevance, unmatched ventilation and perfusion are not routinely assessed at the bedside. The aims of this study were to quantify unmatched ventilation and perfusion at the bedside by electrical impedance tomography (EIT) investigating their association with mortality in patients with ARDS and to explore the effects of positive end-expiratory pressure (PEEP) on unmatched ventilation and perfusion in subgroups of patients with different ARDS severity based on PaO2/FiO2 and compliance. Methods Prospective observational study in 50 patients with mild (36%), moderate (46%), and severe (18%) ARDS under clinical ventilation settings. EIT was applied to measure the regional distribution of ventilation and perfusion using central venous bolus of saline 5% during end-inspiratory pause. We defined unmatched units as the percentage of only ventilated units plus the percentage of only perfused units. Results Percentage of unmatched units was significantly higher in non-survivors compared to survivors (32[27–47]% vs. 21[17–27]%, p < 0.001). Percentage of unmatched units was an independent predictor of mortality (OR 1.22, 95% CI 1.07–1.39, p = 0.004) with an area under the ROC curve of 0.88 (95% CI 0.79–0.97, p < 0.001). The percentage of ventilation to the ventral region of the lung was higher than the percentage of ventilation to the dorsal region (32 [27–38]% vs. 18 [13–21]%, p < 0.001), while the opposite was true for perfusion (28 [22–38]% vs. 36 [32–44]%, p < 0.001). Higher percentage of only perfused units was correlated with lower dorsal ventilation (r =  − 0.486, p < 0.001) and with lower PaO2/FiO2 ratio (r =  − 0.293, p = 0.039). Conclusions EIT allows bedside assessment of unmatched ventilation and perfusion in mechanically ventilated patients with ARDS. Measurement of unmatched units could identify patients at higher risk of death and could guide personalized treatment.

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

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tobias Becher ◽  
Valerie Buchholz ◽  
Daniel Hassel ◽  
Timo Meinel ◽  
Dirk Schädler ◽  
...  
Keyword(s):  
Tidal Volume ◽  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Predicted Body Weight ◽  
Impedance Tomography ◽  
Mechanically Ventilated ◽  
Global Strain ◽  
Lung Overdistension ◽  
Ventilator Settings ◽  
Lung Stress

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.

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

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.

scholarly journals 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 ◽  
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.

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