| 1. |
- Bitzén, Ulrika, et al.
(författare)
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Dynamic elastic pressure-volume loops in healthy pigs recorded with inspiratory and expiratory sinusoidal flow modulationRelationship to static pressure-volume loops.
- 2004
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Ingår i: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 30:3, s. 481-488
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The objective was to analyse relationships between inspiratory and expiratory static and dynamic elastic pressure-volume (P-el/V) curves in healthy pigs. Design: The modulated low flow method was developed to allow studies also of the expiratory P-el/V curves. Static P-el/V (P-el,P-st/V) and dynamic P-el/V (P-el,P-dyn/V) loops were studied in healthy pigs. Setting: Animal research laboratory in a university hospital. Material: Ten healthy anaesthetised and paralysed pigs. Interventions and measurements: A computer controlled a Servo Ventilator 900C with respect to respiratory rate, inspiratory flow and expiratory pressure to achieve a sinusoidal modulation of inspiration and expiration for determination of P-el,P-dyn/V loops from zero end-expiratory pressure (ZEEP) and from a positive end-expiratory pressure (PEEP) of 6 cmH(2)O to 20, 35 and 50 cmH(2)O. The same system was used for studies of P-el,P-st/V loops with the flow-interruption method from ZEEP and PEEP to 35 cmH(2)O. Recordings were analysed with an iterative technique. Results: The feasibility of automated determination of P-el,P-dyn/V loops was demonstrated. Differences between P-el,P-dyn/V and P-el,P-st/V loops were explained by viscoelastic behaviour. P-el,P-st/V loops recorded from PEEP to 35 cmH(2)O showed no significant hysteresis, indicating a non-significant surface tension hysteresis. P-el,P-dyn/V loops from PEEP and both P-el,P-st/V and P-el,P-dyn/V loops from ZEEP to 35 cmH(2)O showed hysteresis. This indicates that lung collapse/re-expansion caused P-el/V loop hysteresis which, in P-el,P-dyn/V loops, was augmented by viscoelastic behaviour. Conclusions: Viscoelasticity influences P-el,P-dyn/V curves. Hysteresis caused by surface tension merits re-evaluation. Lung collapse and re-expansion may be indicated by hysteresis of P-el/V loops.
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| 3. |
- Uttman, Leif, et al.
(författare)
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Computer simulation allows goal-oriented mechanical ventilation in acute respiratory distress syndrome
- 2007
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Ingår i: Critical Care. - : Springer Science and Business Media LLC. - 1364-8535. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Introduction To prevent further lung damage in patients with acute respiratory distress syndrome ( ARDS), it is important to avoid overdistension and cyclic opening and closing of atelectatic alveoli. Previous studies have demonstrated protective effects of using low tidal volume ( VT), moderate positive end-expiratory pressure and low airway pressure. Aspiration of dead space ( ASPIDS) allows a reduction in VT by eliminating dead space in the tracheal tube and tubing. We hypothesized that, by applying goal-orientated ventilation based on iterative computer simulation, VT can be reduced at high respiratory rate and much further reduced during ASPIDS without compromising gas exchange or causing high airway pressure. Methods ARDS was induced in eight pigs by surfactant perturbation and ventilator-induced lung injury. Ventilator resetting guided by computer simulation was then performed, aiming at minimal VT, plateau pressure 30 cmH(2)O and isocapnia, first by only increasing respiratory rate and then by using ASPIDS as well. Results VT decreased from 7.2 +/- 0.5 ml/kg to 6.6 +/- 0.5 ml/kg as respiratory rate increased from 40 to 64 +/- 6 breaths/min, and to 4.0 +/- 0.4 ml/kg when ASPIDS was used at 80 +/- 6 breaths/min. Measured values of arterial carbon dioxide tension were close to predicted values. Without ASPIDS, total positive end-expiratory pressure and plateau pressure were slightly higher than predicted, and with ASPIDS they were lower than predicted. Conclusion In principle, computer simulation may be used in goal-oriented ventilation in ARDS. Further studies are needed to investigate potential benefits and limitations over extended study periods.
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| 4. |
- Aboab, J., et al.
(författare)
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CO2 elimination at varying inspiratory pause in acute lung injury
- 2007
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961. ; 27:1, s. 2-6
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies have indicated that, during mechanical ventilation, an inspiratory pause enhances gas exchange. This has been attributed to prolonged time during which fresh gas of the tidal volume is present in the respiratory zone and is available for distribution in the lung periphery. The mean distribution time of inspired gas (MDT) is the mean time during which fractions of fresh gas are present in the respiratory zone. All ventilators allow setting of pause time, T-P, which is a determinant of MDT. The objective of the present study was to test in patients the hypothesis that the volume of CO2 eliminated per breath, VTCO2, is correlated to the logarithm of MDT as previously found in animal models. Eleven patients with acute lung injury were studied. When T-P increased from 0% to 30%, MDT increased fourfold. A change of T-P from 10% to 0% reduced VTCO2 by 14%, while a change to 30% increased VTCO2 by 19%. The relationship between VTCO2 and MDT was in accordance with the logarithmic hypothesis. The change in VTCO2 reflected to equal extent changes in airway dead space and alveolar PCO2 read from the alveolar plateau of the single breath test for CO2. By varying T-P, effects are observed on VTCO2, airway dead space and alveolar PCO2. These effects depend on perfusion, gas distribution and diffusion in the lung periphery, which need to be further elucidated.
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| 8. |
- Aksyutina, Yu, et al.
(författare)
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Lithium isotopes beyond the drip line
- 2008
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 666:5, s. 430-434
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Tidskriftsartikel (refereegranskat)abstract
- The unbound isotopes 10Li, 12Li and 13Li have been observed after nucleon-knockout reactions at relativistic energies with 11Li and 14Be beams impinging on a liquid hydrogen target. The channels , and were analysed in the ALADIN-LAND setup at GSI. The 10Li data confirm earlier findings, while the 12Li and 13Li nuclei were observed for the first time. The relative-energy spectrum shows that the ground state of 12Li can be described as a virtual s-state with a scattering length of -13.7(1.6) fm. A broad energy spectrum was found for the channel. Based on the assumption that the relative-energy spectrum is dominated by a correlated background presumably stemming from initial correlations in the 14Be ground-state, evidence for a 13Li resonance at 1.47(31) MeV above the threshold with a width around 2 MeV has been found.
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| 9. |
- Aksyutina, Yuliya, 1983, et al.
(författare)
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Properties of the 7He ground state from 8He neutron knockout
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 679:3, s. 191 - 196
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Tidskriftsartikel (refereegranskat)abstract
- The unbound nucleus 7He, produced in neutron-knockout reactions with a 240 MeV/u 8He beam in a liquid-hydrogen target, has been studied in an experiment at the ALADIN-LAND setup at GSI. From an R-matrix analysis the resonance parameters for 7He as well as the spectroscopic factor for the 6He(0+) + n configuration in its ground-state have been obtained. The spectroscopic factor is 0.61 confirming that 7He is not a pure single-particle state. An analysis of 5He data from neutron-knockout reactions of 6He in a carbon target reveals the presence of an s-wave component at low energies in the α+n relative energy spectrum. A possible low-lying exited state in 7He observed in neutron knockout data from 8He in a carbon target and tentatively interpreted as a Iπ=1/2− state, could not be observed in the present experiment. Possible explanations of the shape difference between the 7He resonance obtained in the two knockout reactions are discussed in terms of target-dependence or different reaction mechanisms at relativistic energies.
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| 10. |
- Alcorta, M., et al.
(författare)
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Nuclear Structure of C-12 from Break-up Studies in Complete Kinematics
- 2009
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735407022 ; 1165, s. 27-30 461
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Konferensbidrag (refereegranskat)abstract
- A complete kinematics study of the B-10(He-3,p alpha alpha alpha) and B-11(He-3,d alpha alpha alpha) reactions has been performed to study the multi-particle break-up of C-12 resonances above the triple-alpha threshold. Four-particle coincidence detection gives us complete information on the direction and energy of the individual alpha particles from the decay of C-12, allowing us to extract new information on the structure of C-12 which we shall present in this contribution. We have observed gamma de-excitation of the T=1 15.11 MeV resonance using charged particle detectors, and have constructed Dalitz plots of the individual resonances in C-12 using the complete kinematics information of the alpha particles which come from their break-up.
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