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- Hentze, Benjamin, et al.
(author)
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Regional lung ventilation and perfusion by electrical impedance tomography compared to single-photon emission computed tomography
- 2018
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In: Physiological Measurement. - : IOP PUBLISHING LTD. - 0967-3334 .- 1361-6579. ; 39:6
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Journal article (peer-reviewed)abstract
- Objective: Electrical impedance tomography (EIT) is a noninvasive imaging modality that allows real-time monitoring of regional lung ventilation (<(V)over dot>) in intensive care patients at bedside. However, for improved guidance of ventilation therapy it would be beneficial to obtain regional ventilation-to-perfusion ratio (<(V)over dot> / <(Q)over dot>) by EIT.Approach: In order to further explore the feasibility, we first evaluate a model-based approach, based on semi-negative matrix factorization and a gamma-variate model, to extract regional lung perfusion (<(Q)over dot>) from EIT measurements. Subsequently, a combined validation of both <(V)over dot> and <(Q)over dot> measured by EIT against single-photon emission computed tomography (SPECT) is performed on data acquired as part of a porcine animal trial. Four pigs were ventilated at two different levels of positive end-expiratory pressure (PEEP 0 and 15 cm H2O, respectively) in randomized order. Repeated injections of an EIT contrast agent (NaCl 10%) and simultaneous SPECT measurements of <(V)over dot> (81(m)Kr gas) and <(Q)over dot> (99(m)Tc-labeled albumin) were performed.Main results: Both <(V)over dot> and <(Q)over dot> from EIT and SPECT were compared by correlation analysis. Very strong (r(2) = 0.94 to 0.95) correlations were found for <(V)over dot> and <(Q)over dot> in the dorsal-ventral direction at both PEEP levels. Moderate (r(2) = 0.36 to 0.46) and moderate to strong (r(2) = 0.61 to 0.82) correlations resulted for <(V)over dot> and <(Q)over dot> in the right-left direction, respectively.Significance: The results of combined validation indicate that monitoring of <(V)over dot> and <(Q)over dot> by EIT is possible. However, care should be taken when trying to quantify <(V)over dot> / <(Q)over dot> by EIT, as imaging artefacts and model bias may void necessary spatial matching.
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| 2. |
- Muders, Thomas, et al.
(author)
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Individualized Positive End-expiratory Pressure and Regional Gas Exchange in Porcine Lung Injury
- 2020
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In: Anesthesiology. - : LIPPINCOTT WILLIAMS & WILKINS. - 0003-3022 .- 1528-1175. ; 132:4, s. 808-824
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Journal article (peer-reviewed)abstract
- Background: In acute respiratory failure elevated intraabdominal pressure aggravates lung collapse, tidal recruitment, and ventilation inhomogeneity. Low positive end-expiratory pressure (PEEP) may promote lung collapse and intrapulmonary shunting, whereas high PEEP may increase dead space by inspiratory overdistension. The authors hypothesized that an electrical impedance tomography-guided PEEP approach minimizing tidal recruitment improves regional ventilation and perfusion matching when compared to a table-based low PEEP/no recruitment and an oxygenation-guided high PEEP/full recruitment strategy in a hybrid model of lung injury and elevated intraabdominal pressure. Methods: In 15 pigs with oleic acid-induced lung injury intraabdominal pressure was increased by intraabdominal saline infusion. PEEP was set in randomized order: (1) guided by a PEEP/inspired oxygen fraction table, without recruitment maneuver; (2) minimizing tidal recruitment guided by electrical impedance tomography after a recruitment maneuver; and (3) maximizing oxygenation after a recruitment maneuver. Single photon emission computed tomography was used to analyze regional ventilation, perfusion, and aeration. Primary outcome measures were differences in PEEP levels and regional ventilation/perfusion matching. Results: Resulting PEEP levels were different (mean +/- SD) with (1) table PEEP: 11 +/- 3 cm H2O; (2) minimal tidal recruitment PEEP: 22 +/- 3 cm H2O; and (3) maximal oxygenation PEEP: 25 +/- 4 cm H2O; P < 0.001. Table PEEP without recruitment maneuver caused highest lung collapse (28 +/- 11% vs. 5 +/- 5% vs. 4 +/- 4%; P < 0.001), shunt perfusion (3.2 +/- 0.8 l/min vs. 1.0 +/- 0.8 l/min vs. 0.7 +/- 0.6 l/min; P < 0.001) and dead space ventilation (2.9 +/- 1.0 l/min vs. 1.5 +/- 0.7 l/min vs. 1.7 +/- 0.8 l/min; P < 0.001). Although resulting in different PEEP levels, minimal tidal recruitment and maximal oxygenation PEEP, both following a recruitment maneuver, had similar effects on regional ventilation/perfusion matching. Conclusions: When compared to table PEEP without a recruitment maneuver, both minimal tidal recruitment PEEP and maximal oxygenation PEEP following a recruitment maneuver decreased shunting and dead space ventilation, and the effects of minimal tidal recruitment PEEP and maximal oxygenation PEEP were comparable.
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