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- Robinson, Paul, et al.
(författare)
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Consensus statement for inert gas washout measurement using multiple and single breath tests.
- 2013
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Ingår i: The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology. - : European Respiratory Society (ERS). - 1399-3003. ; 41:3, s. 507-522
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Tidskriftsartikel (refereegranskat)abstract
- Inert gas washout tests, performed using the single or multiple breath washout technique (SBW and MBW, respectively), were first described over 60 years ago. As measures of ventilation distribution inhomogeneity, they offer complementary information to standard lung function tests such as spirometry as well as improved feasibility across wider age ranges and improved sensitivity in the detection of early lung damage. These benefits have led to a resurgence of interest in these techniques from manufacturers, clinicians and researchers, yet detailed guidelines for washout equipment specifications, test performance and analysis are lacking. This manuscript provides recommendations about these aspects, applicable to both the paediatric and adult testing environment, whilst outlining the important principles that are essential for the reader to understand. These recommendations are evidence-based where possible but in many places represent expert opinion from a working group with a large collective experience in the techniques discussed. Finally, the important issues that remain unanswered are highlighted. By addressing these important issues and directing future research, the hope is to facilitate the incorporation of these promising tests into routine clinical practice.
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- 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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- Verbanck, S, et al.
(författare)
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Pulmonary tissue volume, cardiac output, and diffusing capacity in sustained microgravity
- 1997
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Ingår i: Journal of applied physiology (Bethesda, Md. : 1985). - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 83:3, s. 810-816
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Tidskriftsartikel (refereegranskat)abstract
- Verbanck, Sylvia, Hans Larsson, Dag Linnarsson, G. Kim Prisk, John B. West, and Manuel Paiva. Pulmonary tissue volume, cardiac output and diffusing capacity in sustained microgravity. J. Appl. Physiol. 83(3): 810–816, 1997.—In microgravity (μG) humans have marked changes in body fluids, with a combination of an overall fluid loss and a redistribution of fluids in the cranial direction. We investigated whether interstitial pulmonary edema develops as a result of a headward fluid shift or whether pulmonary tissue fluid volume is reduced as a result of the overall loss of body fluid. We measured pulmonary tissue volume (Vti), capillary blood flow, and diffusing capacity in four subjects before, during, and after 10 days of exposure to μG during spaceflight. Measurements were made by rebreathing a gas mixture containing small amounts of acetylene, carbon monoxide, and argon. Measurements made early in flight in two subjects showed no change in Vti despite large increases in stroke volume (40%) and diffusing capacity (13%) consistent with increased pulmonary capillary blood volume. Late in-flight measurements in four subjects showed a 25% reduction in Vti compared with preflight controls ( P < 0.001). There was a concomittant reduction in stroke volume, to the extent that it was no longer significantly different from preflight control. Diffusing capacity remained elevated (11%; P< 0.05) late in flight. These findings suggest that, despite increased pulmonary perfusion and pulmonary capillary blood volume, interstitial pulmonary edema does not result from exposure to μG.
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- Verbanck, S, et al.
(författare)
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Specific ventilation distribution in microgravity
- 1996
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Ingår i: Journal of applied physiology (Bethesda, Md. : 1985). - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 80:5, s. 1458-1465
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Tidskriftsartikel (refereegranskat)abstract
- We studied the contribution of inter- and intraregional inhomogeneities of specific ventilation (delta V/Vo) from the rebreathing inert gas trace in microgravity and on Earth. The rebreathing tests were carried out by four astronauts before, during, and after the 10-day Spacelab D-2 mission. Starting from functional residual capacity, the rebreathing maneuver consisted of eight reinspirations from a bag filled with 1.8-2.2 liters of test gas mixtures containing approximately 5% argon. The rate of argon equilibration in the rebreathing bag, termed RBeq, was quantified by determining the logarithm of the actual minus the equilibrated argon concentrations normalized to the inspired minus the equilibrated argon concentrations. A compartmental model of the lung (S. Verbanck and M. Paiva. J. Appl. Physiol. 76: 445-454, 1994) was used to validate the method for determining RBeq and to simulate the influence of intra- and interregional delta V/Vo inhomogeneities on the RBeq curve. The comparison between the experimental Earth-based and microgravity RBeq curves and model simulations shows that gravity-independent delta V/Vo inhomogeneity is at least as large as gravity-dependent delta V/Vo inhomogeneity.
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