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- Kretzschmar, Moritz, et al.
(författare)
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Effect of Bronchoconstriction-induced Ventilation-Perfusion Mismatch on Uptake and Elimination of Isoflurane and Desflurane
- 2017
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Ingår i: Anesthesiology. - 0003-3022 .- 1528-1175. ; 127:5, s. 800-812
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Increasing numbers of patients with obstructive lung diseases need anesthesia for surgery. These conditions are associated with pulmonary ventilation/perfusion (VA/Q) mismatch affecting kinetics of volatile anesthetics. Pure shunt might delay uptake of less soluble anesthetic agents but other forms of VA/Q scatter have not yet been examined. Volatile anesthetics with higher blood solubility would be less affected by VA/Q mismatch. We therefore compared uptake and elimination of higher soluble isoflurane and less soluble desflurane in a piglet model.METHODS: Juvenile piglets (26.7 ± 1.5 kg) received either isoflurane (n = 7) or desflurane (n = 7). Arterial and mixed venous blood samples were obtained during wash-in and wash-out of volatile anesthetics before and during bronchoconstriction by methacholine inhalation (100 μg/ml). Total uptake and elimination were calculated based on partial pressure measurements by micropore membrane inlet mass spectrometry and literature-derived partition coefficients and assumed end-expired to arterial gradients to be negligible. VA/Q distribution was assessed by the multiple inert gas elimination technique.RESULTS: Before methacholine inhalation, isoflurane arterial partial pressures reached 90% of final plateau within 16 min and decreased to 10% after 28 min. By methacholine nebulization, arterial uptake and elimination delayed to 35 and 44 min. Desflurane needed 4 min during wash-in and 6 min during wash-out, but with bronchoconstriction 90% of both uptake and elimination was reached within 15 min.CONCLUSIONS: Inhaled methacholine induced bronchoconstriction and inhomogeneous VA/Q distribution. Solubility of inhalational anesthetics significantly influenced pharmacokinetics: higher soluble isoflurane is less affected than fairly insoluble desflurane, indicating different uptake and elimination during bronchoconstriction.
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| 2. |
- Bachmann, M. Consuelo, et al.
(författare)
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Electrical impedance tomography in acute respiratory distress syndrome
- 2018
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Ingår i: Critical Care. - : BioMed Central. - 1364-8535 .- 1466-609X. ; 22
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Forskningsöversikt (refereegranskat)abstract
- Acute respiratory distress syndrome (ARDS) is a clinical entity that acutely affects the lung parenchyma, and is characterized by diffuse alveolar damage and increased pulmonary vascular permeability. Currently, computed tomography (CT) is commonly used for classifying and prognosticating ARDS. However, performing this examination in critically ill patients is complex, due to the need to transfer these patients to the CT room. Fortunately, new technologies have been developed that allow the monitoring of patients at the bedside. Electrical impedance tomography (EIT) is a monitoring tool that allows one to evaluate at the bedside the distribution of pulmonary ventilation continuously, in real time, and which has proven to be useful in optimizing mechanical ventilation parameters in critically ill patients. Several clinical applications of EIT have been developed during the last years and the technique has been generating increasing interest among researchers. However, among clinicians, there is still a lack of knowledge regarding the technical principles of EIT and potential applications in ARDS patients. The aim of this review is to present the characteristics, technical concepts, and clinical applications of EIT, which may allow better monitoring of lung function during ARDS.
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| 7. |
- Batista Borges, João, 1966-
(författare)
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The Plausibility of "Bronchiolotrauma"
- 2018
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Ingår i: American Journal of Respiratory and Critical Care Medicine. - : AMER THORACIC SOC. - 1073-449X .- 1535-4970. ; 197:8, s. 1086-1087
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Tidskriftsartikel (refereegranskat)
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| 9. |
- Borges, João Batista, 1966-
(författare)
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Regional Lung Kinetics of Ventilator-Induced Lung Injury and Protective-Ventilation Strategies Studied by Dynamic Positron Emission Tomography
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mechanical ventilation in itself can harm the lung and cause ventilator-induced lung injury (VILI), which can induce or aggravate acute respiratory distress syndrome (ARDS). Much debate remains over pivotal concepts regarding the pathophysiology of VILI, especially about the precise contribution, kinetics, and primary role of potential VILI mechanisms. Consequently, it remains largely unknown how best to design a well-timed and full-bodied mechanical ventilation strategy. Little is known also about small airways dysfunction in ARDS. Dynamic positron emission tomography (PET) with [18F]fluoro-2-deoxy-D-glucose (18F-FDG) can be used to image cellular metabolism, which during lung inflammation mainly reflects neutrophil activity, allowing the study of regional lung inflammation in vivo. We studied the regional evolution of inflammation using dynamic PET/CT imaging of 18F-FDG in VILI and during different lung-protective mechanical ventilation strategies. By dynamic CT we investigated also the location and magnitude of peripheral airway closure and alveolar collapse under high and low distending pressures and high and low inspiratory oxygen fraction. Piglets were submitted to an experimental model of early ARDS combining repeated lung lavages and injurious mechanical ventilation. The animals were subsequently studied during sustained VILI, or submitted to distinct approaches of lung-protective mechanical ventilation: the one recommended by the ARDS Network (ARDSNet), or to one defined as open lung approach (OLA). The normally and poorly aerated regions - corresponding to intermediate gravitational zones - were the primary targets of the inflammatory process accompanying early VILI, which may be attributed to the small volume of the aerated lung that receives most of ventilation. The ARDSNet strategy did not attenuate global pulmonary inflammation during 27h and led to a concentration of inflammatory activity in the upper and poorly aerated lung regions. The OLA, in comparison with the ARDSNet approach, resulted in sustained and better gas exchange and lung mechanics. Moreover, the OLA strategy resulted in less global and regional inflammation. Dynamic CT data suggested that a significant amount of airway closure and related reabsorption atelectasis occurs in acute lung injury. Whether potential distal bronchioles injury (“bronchiolotrauma”) is a critical and decisive element in ventilator-associated lung injury is a matter for future studies.
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| 10. |
- Broche, Ludovic, et al.
(författare)
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Dynamic Mechanical Interactions Between Neighboring Airspaces Determine Cyclic Opening and Closure in Injured Lung
- 2017
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Ingår i: Critical Care Medicine. - 0090-3493 .- 1530-0293. ; 45:4, s. 687-694
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Positive pressure ventilation exposes the lung to mechanical stresses that can exacerbate injury. The exact mechanism of this pathologic process remains elusive. The goal of this study was to describe recruitment/derecruitment at acinar length scales over short-time frames and test the hypothesis that mechanical interdependence between neighboring lung units determines the spatial and temporal distributions of recruitment/derecruitment, using a computational model. Design: Experimental animal study. Setting: International synchrotron radiation laboratory. Subjects: Four anesthetized rabbits, ventilated in pressure controlled mode. Interventions: The lung was consecutively imaged at - 1.5-minute intervals using phase-contrast synchrotron imaging, at positive end expiratory pressures of 12, 9, 6, 3, and 0 cm H2O before and after lavage and mechanical ventilation induced injury. The extent and spatial distribution of recruitment/derecruitment was analyzed by subtracting subsequent images. In a realistic lung structure, we implemented a mechanistic model in which each unit has individual pressures and speeds of opening and closing. Derecruited and recruited lung fractions (F-derecruaed, F-recruited) were computed based on the comparison of the aerated volumes at successive time points. Measurements and Main Results: Alternative recruitment/derecruitment occurred in neighboring alveoli over short-time scales in all tested positive end-expiratory pressure levels and despite stable pressure controlled mode. The computational model reproduced this behavior only when parenchymal interdependence between neighboring acini was accounted for. Simulations closely mimicked the experimental magnitude of F-derecruited and F-recruited when mechanical interdependence was included, while its exclusion gave F-recruited values of zero at positive end -expiratory pressure greater than or equal to 3 cm H2O. Conclusions: These findings give further insight into the microscopic behavior of the injured lung and provide a means of testing protective-ventilation strategies to prevent recruitment/derecruitment and subsequent lung damage.
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