| 1. |
- Almgren, Birgitta, 1958-
(författare)
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Endotracheal Suction a Reopened Problem
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During mechanical ventilation, patients are connected to the ventilator by an endotracheal tube. The tube needs to be cleaned from mucus by suction, which can cause negative effects such as lung collapse, hypoxemia and desaturation. These can be avoided by preoxygenation, change of ventilator settings, use of closed suction systems and recruitment manoeuvres. The aim of the study was to investigate the effects of endotracheal suction during different ventilator settings and by different suction methods. A method to reverse side effects was investigated.In anaesthetized pigs, the effect of suction during volume and pressure-controlled ventilation was investigated, and the effect of different suction systems and catheter sizes were compared. Suction efficacy was investigated in a bench study. The effect of recruitment manoeuvre added after suction, i.e. post-suction recruitment manoeuvre was evaluated.Endotracheal suction causes lung volume loss leading to impaired gas exchange, an effect that is more severe in pressure-controlled ventilation than in volume-controlled ventilation. When 14 French suction catheters were used more side effects were found compared to 12 French catheters, but no difference was found between open and closed suction system in pressure-controlled ventilation. Open suction system was more effective to remove mucus compared to closed system. Post-suction recruitment manoeuvre restored the side effects after the first recruitment when it was applied directly after suction.In conclusion, open endotracheal suction causes impairment in gas exchange and lung mechanics, and more so in pressure-controlled than in volume-controlled mode. These changes can be minimized if smaller suction catheters are used. A post-suction recruitment manoeuvre applied directly after suction restores lung function. It is obvious that the recruitment manoeuvre should be added directly after suction, because if the manoeuvre is delayed and the lung is collapsed and left collapsed, it will be more difficult to recruit the lung.
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| 2. |
- Almgren, Mats, et al.
(författare)
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Contrast Variation SANS Investigation of Composition Distributions in Mixed Surfactant Micelles
- 2007
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 111:25, s. 7133-7141
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Tidskriftsartikel (refereegranskat)abstract
- Small angle neutron scattering measurements have been performed on three systems (HFDeP-d5-C (N-1(1,1,2,2-tetrahydroperfluorodecanoyl)pyridinium-d5 chloride)/C16PC in 63 mM NaCl; HFDeP-d5-C/C12PC in 200 mM NaCl, and as an example of an ideally mixed system, SDS/SDS-d25 in 200 mM NaCl) contg. micelles formed in a binary mixt. of surfactants, in order to investigate the compn. distribution of the mixed micelles. The exptl. data were collected varying the contrast between the av. scattering length d. of micelles and aq. solvent by changing the H2O/D2O ratio. Anal. of data includes a model-independent approach-the indirect Fourier transformation method and direct modeling-simultaneous fit at all contrasts by the scattering from micelles of equal size and shape with compn. distribution and an effective interaction. It has earlier been shown (Almgren, M.; Garamus, V. M. J. Phys. Chem. B 2005, 109, 11348) that for micelles of equal size, independent of the compn., and with negligible intermicellar interactions, the scattered intensity at zero angle varies quadratically with the contrast, with the min. intensity at the nominal match point proportional to s2, the variance of the micelle compn. distribution. Within the regular soln. framework, the compn. distribution and its variance are uniquely defined by the value of the interaction parameter and the micelle aggregation no. At 25 DegC, the first system gave s = 0.37, corresponding to a broad, bimodal compn. distribution, the second s = 0.22, a broad distribution with a shallow min. at the midpoint. For SDS/SDS-d25, we found s = 0.006 +- 0.030, which is a smaller value than that of the binominal compn. distribution expected for an ideally mixed system.
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| 3. |
- Almgren, Mats, et al.
(författare)
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Dispersed lipid liquid crystalline phases stabilized by a hydrophobically modified cellulose
- 2007
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 23:5, s. 2768-2777
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous dispersions of monoolein (MO) with a commercial hydrophobically modified ethyl hydroxyethyl cellulose ether (HMEHEC) have been investigated with respect to the morphologies of the liquid crystalline nanoparticles. Only very low proportions of HMEHEC are accepted in the cubic and lamellar phases of the monoolein−water system. Due to the broad variation of composition and size of the commercial polymer, no other single-phase regions were found in the quasi-ternary system. Interactions of MO with different fractions of the HMEHEC sample induced the formation of lamellar and reversed hexagonal phases, identified from SAXD, polarization microscopy, and cryogenic TEM examinations. In excess water (more than 90 wt %) coarse dispersions are formed more or less spontaneously, containing particles of cubic phase from a size visible by the naked eye to small particles observed by cryoTEM. At high polymer/MO ratios, vesicles were frequently observed, often oligo-lamellar with inter-lamellar connections. After homogenization of the coarse dispersions in a microfluidizer, the large particles disappeared, apparently replaced by smaller cubic particles, often with vesicular attachments on the surfaces, and by vesicles or vesicular particles with a disordered interior. At the largest polymer contents no proper cubic particles were found directly after homogenization but mainly single-walled defected vesicles with a peculiar edgy appearance. During storage for 2 weeks, the dispersed particles changed toward more well-shaped cubic particles, even in dispersions with the highest polymer contents. In some of the samples with low polymer/MO ratio, dispersed particles of the reversed hexagonal type were found. A few of the homogenized samples were freeze-dried and rehydrated. Particles of essentially the same types, but with a less well-developed cubic character, were found after this treatment.
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| 5. |
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| 6. |
- Almgren, Mats
(författare)
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Vesicle transformations resulting from curvature tuning in systems with micellar, lamellar, and bicontinuous cubic phases
- 2007
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Ingår i: Journal of Dispersion Science and Technology. - : Informa UK Limited. - 0193-2691 .- 1532-2351. ; 28:1, s. 43-54
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Tidskriftsartikel (refereegranskat)abstract
- LCNP, liquid crystalline nanoparticles, are dispersions of liquid crystalline phases in excess solvent, usually water. Vesicles are the ones derived from the lamellar phase, and are characterized by a spontaneous monolayer curvature close to zero, or a surfactant packing parameter close to one. By changing the composition of amphiphile mixtures, the spontaneous curvature may be changed. This results in a change of the phase behavior as well as in the stability and morphology of the dispersed particles. This article reviews such changes mainly for systems based on polar lipid amphiphiles such as lecithins and glycerylmonooleate mixed with surfactants or amphiphilic block copolymers. Perforated vesicles, stomatosomes, are paid particular attention, not because of their importance as LCNP, but simply because they are least well known. As a tribute to Per Ekwall, some cryoTEM micrographs of vesicles from the “holy system,” sodium caprylate-decanol-water, are presented. Stomatosomes were not found in that system.
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| 7. |
- Almgren, Sara, 1979, et al.
(författare)
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Gamma radiation doses to people living in Western Sweden.
- 2008
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Ingår i: Journal of environmental radioactivity. - : Elsevier BV. - 0265-931X. ; 99:2, s. 394-403
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Tidskriftsartikel (refereegranskat)abstract
- Indoor environments contribute to gamma radiation in the general population. The aims of the present study were to investigate average gamma radiation doses in a rural and an urban area of Sweden, compare indoor dose rates with personal exposure, and study the effects of building characteristics on radiation levels. Radiation was measured with thermoluminescence dosimeters (TLDs). Repeated measurements were performed with TLDs worn by participants (n=46) and placed in their dwellings. Personal dose rates were 0.092microSv/h (rural) and 0.096microSv/h (urban). The mean effective gamma dose rates in dwellings were 0.091microSv/h (rural) and 0.11microSv/h (urban), which are higher than the world average. Dose rates in apartments were higher than in detached houses and higher for concrete than wooden dwellings. Personal dose rates were strongly associated with dwelling dose rates (r(p)=0.68, p<0.01) and could be modelled. Within-participant variability was low.
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| 8. |
- Almgren, Sara, 1979, et al.
(författare)
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GIS supported calculations of (137)Cs deposition in Sweden based on precipitation data.
- 2006
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Ingår i: The Science of the total environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 368:2-3, s. 804-13
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Tidskriftsartikel (refereegranskat)abstract
- It is of interest to know the spatial variation and the amount of (137)Cs e.g. in case of an accident with a radioactive discharge. In this study, the spatial distribution of the quarterly (137)Cs deposition over Sweden due to nuclear weapons fallout (NWF) during the period 1962-1966 was determined by relating the measured deposition density at a reference site to the amount of precipitation. Measured quarterly values of (137)Cs deposition density per unit precipitation at three reference sites and quarterly precipitation at 62 weather stations distributed over Sweden were used in the calculations. The reference sites were assumed to represent areas with different quarterly mean precipitation. The extent of these areas was determined from the distribution of the mean measured precipitation between 1961 and 1990 and varied according to seasonal variations in the mean precipitation pattern. Deposition maps were created by interpolation within a geographical information system (GIS). Both integrated (total) and cumulative (decay corrected) deposition densities were calculated. The lowest levels of NWF (137)Cs deposition density were noted in north-eastern and eastern parts of Sweden and the highest levels in the western parts of Sweden. Furthermore the deposition density of (137)Cs, resulting from the Chernobyl accident was determined for an area in western Sweden based on precipitation data. The highest levels of Chernobyl (137)Cs in western Sweden were found in the western parts of the area along the coast and the lowest in the east. The sum of the deposition densities from NWF and Chernobyl in western Sweden was then compared to the total activity measured in soil samples at 27 locations. Comparisons between the predicted values of this study show a good agreement with measured values and other studies.
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| 9. |
- Almgren, Sara, 1979, et al.
(författare)
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Long-term investigation of anthropogenic and naturally occurring radionuclides at reference sites in western Sweden.
- 2009
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Ingår i: Journal of environmental radioactivity. - : Elsevier BV. - 1879-1700 .- 0265-931X. ; 100:7, s. 599-604
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Tidskriftsartikel (refereegranskat)abstract
- In case of an accidental release of radioactive substances into the environment, it is important to quickly and reliably estimate the radiation dose received by people in the affected area, and to determine the extent of the contamination. Measurements of the extent of the release and the subsequent contamination can be facilitated if there are predetermined reference sampling sites with known background radiation and inventory of radionuclides. Since 1996, 34 reference sites for soil sampling, field gamma, and intensimeter measurements have been established in western Sweden. Time series data for dose rates and radioisotope inventory have been collected at these sites, allowing for the investigation of changes in these parameters over time. The mass activity densities for the uranium and thorium series elements varied approximately between 10 and 50 Bq/kg and between 10 and 40 Bq/kg, respectively. The mass activity density of (40)K was approximately in the range 300-800 Bq/kg. The radiation exposure due to (137)Cs was rather small in this area. The dose rates calculated from in situ measurement data showed that the contribution to the total dose rate was almost entirely due to naturally occurring radionuclides. The measured dose rate was about twice as high as the calculated rate, even after subtracting the contribution from cosmic radiation. This may be explained by the fact that intensimeters generally are calibrated to measure the quantity ambient dose equivalent, which should not underestimate the effective dose.
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| 10. |
- Almgren, Sara, 1979, et al.
(författare)
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Measurements and comparisons of gamma radiation doses in a high and a low (137)Cs deposition area in Sweden.
- 2008
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Ingår i: Journal of environmental radioactivity. - : Elsevier BV. - 0265-931X. ; 99:11, s. 1750-5
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Tidskriftsartikel (refereegranskat)abstract
- Sweden is one of the countries affected by the Chernobyl fallout. The aim of the present study was to investigate the average radiation dose to people living in a high-deposition area (the parish of Hille) in Sweden for comparison with dose rates previously measured in a low-deposition area in western Sweden. Individual measurements (personal and dwelling dose rates) were performed using thermoluminescence dosimeters in 24 randomly chosen individuals. Dwelling and personal dose rates in Hille were 0.12 and 0.11 microSv/h, respectively. The dose rates in Hille were slightly higher than in western Sweden (difference for detached houses=0.024 microSv/h for personal and 0.030 microSv/h for dwelling dose rates), partly because of the higher (137)Cs deposition. In wooden houses, the difference was somewhat greater. Our results indicate a current contribution to personal gamma radiation in this area of about 0.2 mSv per year from the Chernobyl fallout.
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