scholarly journals Gravitational distribution of regional opening and closing pressures, hysteresis and atelectrauma in ARDS evaluated by electrical impedance tomography

Critical Care ◽  
2020 ◽  
Vol 24 (1) ◽  
Author(s):  
Gaetano Scaramuzzo ◽  
Elena Spinelli ◽  
Savino Spadaro ◽  
Alessandro Santini ◽  
Donatella Tortolani ◽  
...  
Keyword(s):  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Regional Distribution ◽  
Low Flow ◽  
Dependent Lung ◽  
Impedance Tomography ◽  
Lung Physiology ◽  
Volume Curve ◽  
Opening And Closing ◽  
Closing Pressure

Abstract Background The physiological behavior of lungs affected by the acute respiratory distress syndrome (ARDS) differs between inspiration and expiration and presents heterogeneous gravity-dependent distribution. This phenomenon, highlighted by the different distribution of opening/closing pressure and by the hysteresis of the pressure–volume curve, can be studied by CT scan, but the technique expose the patient to radiations, cannot track changes during time and is not feasible at the bedside. Electrical impedance tomography (EIT) could help in assessing at the bedside regional inspiratory and expiratory mechanical properties. We evaluated regional opening/closing pressures, hysteresis and atelectrauma during inspiratory and expiratory low-flow pressure–volume curves in ARDS using electrical impedance tomography. Methods Pixel-level inspiratory and expiratory PV curves (PVpixel) between 5 and 40 cmH2O were constructed integrating EIT images and airway opening pressure signal from 8 ARDS patients. The lower inflection point in the inspiratory and expiratory PVpixel were used to find opening (OPpixel) and closing (CPpixel) pressures. A novel atelectrauma index (AtI) was calculated as the percentage of pixels opening during the inspiratory and closing during the expiratory PV curves. The maximal hysteresis (HysMax) was calculated as the maximal difference between normalized expiratory and inspiratory PV curves. Analyses were conducted in the global, dependent and non-dependent lung regions. Results Gaussian distribution was confirmed for both global OPpixel (r2 = 0.90) and global CPpixel (r2 = 0.94). The two distributions were significantly different with higher values for OPpixel (p < 0.0001). Regional OPpixel and CPpixel distributions were Gaussian, and in the dependent lung regions, both were significantly higher than in the non-dependent ones (p < 0.001). Both AtI and the HysMax were significantly higher in the dependent regions compared to the non-dependent ones (p < 0.05 for both). Conclusions Gravity impacts the regional distribution of opening and closing pressure, hysteresis and atelectrauma, with higher values in the dorsal lung. Regional differences between inspiratory and expiratory lung physiology are detectable at the bedside using EIT and could allow in-depth characterization of ARDS phenotypes and guide personalized ventilation settings. Graphic abstract

scholarly journals The effects of prone and supine positions on the regional distribution of ventilation in infants and children using electrical impedance tomography

2015 ◽  
Vol 71 (1) ◽  
Author(s):  
Alison Lupton-Smith ◽  
Andrew Argent ◽  
Peter Rimensberger ◽  
Brenda Morrow
Keyword(s):  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Regional Distribution ◽  
Head Position ◽  
Infants And Children ◽  
Dependent Lung ◽  
Impedance Tomography ◽  
Left And Right ◽  
Head Positions ◽  
Spontaneously Breathing

Background: Positioning of ill children is often used to optimise ventilation–perfusion matching, thereby improving oxygenation. Objectives: To determine the effects of supine and prone positions, and different head positions, on the distribution of ventilation in healthy, spontaneously breathing infants and children between the ages of 6 months and 9 years.Methods: Electrical impedance tomography measurements were recorded from participants in supine and prone positions. Head positions included the head turned to the left and right in supine and prone positions, and in the midline in the supine position. Distribution of ventilation was described using end-expiratory–end-inspiratory relative impedance change.Results: A total of 56 participants (boys = 31 [55%]; girls = 25 [45%]) were studied. The dorsal lung was significantly better ventilated than the ventral lung (P < 0.001) in both body positions. The majority of participants (83%) had greater ventilation in the dorsal lung in both positions, whilst five participants (10%) demonstrated consistently better ventilation in the non-dependent lung in both positions. Head position had no effect on the distribution of ventilation.Conclusions: This study demonstrates that the distribution of ventilation in healthy, spontaneously breathing infants and children in supine and prone positions is not as straightforward as previously thought, with no clear reversal of the adult pattern evident.

What hinders pulmonary gas exchange and changes distribution of ventilation in immobilized white rhinoceroses (Ceratotherium simum) in lateral recumbency?

2020 ◽  
Vol 129 (5) ◽  
pp. 1140-1149
Author(s):  
Martina Mosing ◽  
Andreas D. Waldmann ◽  
Muriel Sacks ◽  
Peter Buss ◽  
Jordyn M. Boesch ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Breath Holding ◽  
Dependent Lung ◽  
Regional Ventilation ◽  
Impedance Tomography ◽  
Ventilation And Perfusion ◽  
Lateral Recumbency ◽  
Nondependent Lung

Electrical impedance tomography measurements of regional ventilation and perfusion applied to etorphine-immobilized white rhinoceroses in lateral recumbency revealed a pronounced disproportional shift of the measured ventilation and perfusion toward the nondependent lung. The dependent lung was minimally ventilated and perfused, but still aerated. Perfusion was found primarily around the hilum of the nondependent lung. These shifts can explain the gas exchange impairments found in this study. Breath holding can redistribute ventilation.

Combined effects of body positioning and noninvasive ventilation on the regional distribution of pulmonary ventilation evaluated by electrical impedance tomography in the young and the elderly

2019 ◽  
Author(s):  
Liegina Silveira Marinho ◽  
Andrea Nobrega Cirino Nogueira Da Nobrega Cirino Nogueira ◽  
Juliana Arcanjo Lino ◽  
Gabriela De Carvalho Gomes Frota ◽  
Renata Dos Santos Vasconcelos ◽  
...  
Keyword(s):  
Electrical Impedance Tomography ◽  
Noninvasive Ventilation ◽  
Electrical Impedance ◽  
Pulmonary Ventilation ◽  
Regional Distribution ◽  
The Elderly ◽  
Combined Effects ◽  
Impedance Tomography ◽  
Body Positioning

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 Effect of the number of electrodes on the reconstructed lung shape in electrical impedance tomography

2016 ◽  
Vol 2 (1) ◽  
pp. 499-502 ◽  
Author(s):  
Benjamin Schullcke ◽  
Sabine Krueger-Ziolek ◽  
Bo Gong ◽  
Knut Moeller
Keyword(s):  
Image Quality ◽  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Regional Distribution ◽  
Current Injection ◽  
The Body ◽  
Voltage Measurement ◽  
Impedance Tomography ◽  
The Impact ◽  
Stimulation Pattern

AbstractElectrical impedance tomography (EIT) is used to monitor the regional distribution of ventilation in a transversal plane of the thorax. In this manuscript we evaluate the impact of different quantities of electrodes used for current injection and voltage measurement on the reconstructed shape of the lungs. Results indicate that the shape of reconstructed impedance changes in the body depends on the number of electrodes. In this manuscript, we demonstrate that a higher number of electrodes do not necessarily increase the image quality. For the used stimulation pattern, utilizing neighboring electrodes for current injection and voltage measurement, we conclude that the shape of the lungs is best reconstructed if 16 electrodes are used.

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