| 1. |
- Norberg, Pernilla, 1970-, et al.
(författare)
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Evaluation of reconstruction techniques for lung single photon emission tomography: a Monte Carlo study.
- 2007
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Ingår i: Nuclear medicine communications. - United States : Lippincott Williams & Wilkins. - 0143-3636 .- 1473-5628. ; 28:12, s. 929-36
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: In studies of the distribution of lung function, the image quality of lung single photon emission computed tomography (SPECT) is important and one factor influencing it is the reconstruction algorithm. AIM: To systematically evaluate ordered subsets expectation maximization (OSEM) and compare it with filtered back-projection (FBP) for lung SPECT with Tc. METHODS: The evaluation of the number of iterations used in OSEM was based on the image quality parameter contrast. The comparison between OSEM and FBP was based on trade-off plots between statistical noise and spatial resolution for different filter parameters, collimators and count-levels. A Monte Carlo technique was used to simulate SPECT studies of a digital thorax phantom containing two sets of activity: one with a homogeneous activity distribution within the lungs and the other with superposed high- and low-activity objects. Statistical noise in the reconstructed images was calculated as the coefficient of variation (CV) and spatial resolution as full width at half-maximum (FWHM). RESULTS: For the configuration studied, the OSEM reconstruction in combination with post-filtering should be used in lung SPECT studies with at least 60 MLEM equivalent iterations. Compared to FBP the spatial resolution was improved by about 1 mm. For a constant level of CV, a four-fold increase in count level resulted in an increased resolution of about 2 mm. Spatial resolution and cut-off frequency depends on what value of noise in the image is acceptable also increased by using a low-energy, high-resolution collimator for CV values above 3%. The choice of noise-reducing filter and cut-off frequency depends on what value of noise in the image is acceptable.
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| 2. |
- Almstrand, Ann-Charlotte, et al.
(författare)
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Airway monitoring by collection and mass spectrometric analysis of exhaled particles.
- 2009
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Ingår i: Analytical chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 81:2, s. 662-8
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Tidskriftsartikel (refereegranskat)abstract
- We describe a new method for simultaneously collecting particles in exhaled air for subsequent chemical analysis and measuring their size distribution. After forced exhalation, particles were counted and collected in spots on silicon wafers with a cascade impactor. Several phospholipids were identified by time-of-flight secondary ion mass spectrometric analysis of the collected spots, suggesting that the particles originated from the lower airways. The amount of particles collected in ten exhalations was sufficient for characterizing the phospholipid composition. The feasibility of the technique in respiratory research is demonstrated by analysis of the phospholipid composition of exhaled particles from healthy controls, patients with asthma, and patients with cystic fibrosis. We believe this technology will be useful for monitoring patients with respiratory disease and has a high potential to detect new biomarkers in exhaled air.
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| 3. |
- Almstrand, Ann-Charlotte, et al.
(författare)
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Effect of Airway Opening on Production of Exhaled Particles.
- 2010
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 1522-1601 .- 8750-7587. ; 108:3, s. 584-588
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Tidskriftsartikel (refereegranskat)abstract
- The technique of sampling exhaled air is attractive because it is non-invasive, and so allows repeated sampling with ease and no risk for the patient. Knowledge of the biomarkers' origin is important in order to correctly understand and interpret the data. Endogenous particles, formed in the airways, are exhaled and reflect chemical composition of the respiratory tract lining fluid. However, the formation mechanisms and formation sites of these particles are unknown. We hypothesize that airway opening following airway closure cause production of airborne particles that are exhaled. The objective of this study was to examine production of exhaled particles following varying degrees of airway closure. 10 healthy volunteers performed 3 different breathing manoeuvres in which the initial lung volume preceding an inspiration to total lung capacity was varied between functional residual capacity (FRC) and residual volume (RV). Exhaled particle number concentrations in the size interval 0.30-2.0 mum were recorded. Number concentrations of exhaled particles showed a 2-18 fold increase after exhalations to RV compared to exhalations where no airway closure was shown (8500 (810-28000) vs. 1300 (330-13000) particles/expired litre, p=0.012). The difference was most noticeable for the smaller size range of particles (<1 mum). There were significant correlations between particle concentrations for the different manoeuvres. Our results show that airway reopening following airway closure is an important mechanism for formation of endogenous exhaled particles and that these particles originate from the terminal bronchioles. Key words: exhaled particles, airway closure, breath.
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| 4. |
- Andelid, Kristina, 1953, et al.
(författare)
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Myeloperoxidase as a marker of increasing systemic inflammation in smokers without severe airway symptoms
- 2007
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Ingår i: Respiratory medicine. - : Elsevier BV. - 0954-6111. ; 101:5, s. 888-95
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: There is increasing evidence of systemic inflammation in patients with chronic obstructive pulmonary disease (COPD), but there is very little information on the development of systemic inflammation in smokers without severe airway symptoms. In this longitudinal study, we examined whether smokers with mild or no airway symptoms develop signs of systemic inflammation by assessing inflammatory markers in blood over a 6-year period. METHODS: Forty smokers and 28 male never-smokers were investigated in 1995 (year 0) and 6 years later (year 6). At year 6, 11 smokers had stopped smoking (quitters); these subjects were analysed as a separate group. At year 0 and 6, we measured serum levels of myeloperoxidase (MPO), lysozyme and human neutrophil lipocalin (HNL), regarded as markers of activity in neutrophils plus monocyte-lineage cells, monocyte-lineage cells only and neutrophils only. RESULTS: All systemic markers of inflammation (MPO, HNL and lysozyme) were significantly higher in smokers than in never smokers at year 6. For MPO alone, smokers only displayed a unique pattern compared with the other groups; the concentration of MPO in blood increased among smokers during the 6-year period, and this increase was statistically significant compared with that observed in never-smokers. Even though quitters did not display any clear change in MPO, we observed a statistically significant negative correlation between the change in blood MPO and the duration of smoking cessation in this group. For HNL and lysozyme, the changes over time were similar in smokers and never-smokers, with no statistically significant difference compared with quitters. CONCLUSION: This study provides evidence that male smokers without severe airway symptoms develop an increasing systemic inflammation during a 6-year period. The study forwards both direct and indirect evidence that MPO may be an early marker of this systemic inflammation. However, our study also forwards indirect evidence that ongoing tobacco smoking may "drive" the level of systemic HNL and lysozyme. The origin of the increased MPO and its value as an easily measured predictor for future COPD deserves to be further evaluated.
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| 5. |
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| 6. |
- Bake, Björn, 1939, et al.
(författare)
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Effects of pollen season on central and peripheral nitric oxide production in subjects with pollen asthma
- 2014
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Ingår i: Respiratory Medicine. - : Elsevier BV. - 0954-6111. ; 108:9, s. 1277-1283
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Tidskriftsartikel (refereegranskat)abstract
- Background: Pollen exposure of allergic subjects with asthma causes increased nitric oxide (NO) in exhaled air (FENO) suggestive of increased airway inflammation. It is, however, unclear to what extent NO production in peripheral airways and alveoli are involved. Objectives: The aim of the present investigation was to analyze the relationship between central and peripheral components of FENO to clarify the distribution of pollen induced inflammation in asthma. Subjects and methods: 13 pollen allergic non-smoking subjects with mild-intermittent asthma and 12 healthy non-smoking control subjects were examined with spirometry and FENO at flows between 50 and 270 mL/s during and out of pollen season. Results: Spirometry was normal and unaffected by season in subjects with asthma as well as controls. Out of season subjects with asthma had significantly higher FENO, elevated airway production (JawNO) and preacinar/acinar production (CANO) than controls. Pollen exposure resulted in significantly increased FENO and JawNO but not CANO. FENO among controls were not affected by season. Individual results showed, however, that CANO increased substantially in a few subjects with asthma. The increased CANO in subjects with asthma may be explained by increased NO production in preacinar/acinar airways and back diffusion towards the alveoli. Conclusions: The findings may indicate that subjects with allergic asthma have airway inflammation without alveolar involvement outside the pollen season and pollen exposure causes a further increase of airway inflammation and in a few subjects obstruction of intra acinar airways causing impeded back diffusion. Increased NO production in central airways, unassociated with airway obstruction could be an alternative explanation. These effects were not disclosed by spirometry.
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| 7. |
- Bake, Björn, 1939, et al.
(författare)
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Exhaled Particles After a Standardized Breathing Maneuver
- 2017
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Ingår i: Journal of Aerosol Medicine and Pulmonary Drug Delivery. - : Mary Ann Liebert Inc. - 1941-2711 .- 1941-2703. ; 30:4, s. 267-273
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Tidskriftsartikel (refereegranskat)abstract
- Background: Particles in exhaled air (PEx) provide samples of respiratory tract lining fluid from small airways and offer a new opportunity to monitor pathological changes. The exhaled particles are produced by reopening of closed small airways and contain surfactant. The amount of PEx varies by orders of magnitude among subjects. A standardized breathing pattern reduces the variation, but it remains large and the reasons are unknown. The aim of the present study was to assess to what extent sex, age, body size, and spirometry results explain the interindividual variation of PEx among healthy middle-aged subjects. Methods: The PExA((R)) instrument was used to measure PEx in 126 healthy middle-aged nonsmoking subjects participating in the European Respiratory Community Health Survey (ERCS-III). The subjects performed a standardized breathing maneuver involving expiration to residual volume, a breath-hold of 3 seconds, a full inspiration, and then a full expiration into the PExA instrument. PEx number concentrations were expressed per exhalation and per exhaled liter. Age and anthropometric and spirometric variables were analyzed as potential predictors. Results: PEx/L was consistently and negatively associated to lung size-related variables and accordingly lower in men than in women. PEx/Exhalation was similar in women and men. Increasing age was associated with increasing PEx. Reference equations are presented based on age, weight, and spirometry variables and independent of sex. These predictors explained 28%-29% of the interindividual variation. Conclusions: The interindividual variation of PEx after a standardized breathing maneuver is large and the considered predictors explain a minor part only.
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| 8. |
- Bake, Björn, 1939, et al.
(författare)
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Exhaled particles and small airways
- 2019
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Ingår i: Respiratory Research. - : Springer Science and Business Media LLC. - 1465-993X. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundOriginally, studies on exhaled droplets explored properties of airborne transmission of infectious diseases. More recently, the interest focuses on properties of exhaled droplets as biomarkers, enabled by the development of technical equipment and methods for chemical analysis. Because exhaled droplets contain nonvolatile substances, particles is the physical designation. This review aims to outline the development in the area of exhaled particles, particularly regarding biomarkers and the connection with small airways, i e airways with an internal diameter<2mm.Main bodyGeneration mechanisms, sites of origin, number concentrations of exhaled particles and the content of nonvolatile substances are studied. Exhaled particles range in diameter from 0.01 and 1000m depending on generation mechanism and site of origin. Airway reopening is one scientifically substantiated particle generation mechanism. During deep expirations, small airways close and the reopening process produces minute particles. When exhaled, these particles have a diameter of <4m. A size discriminating sampling of particles <4m and determination of the size distribution, allows exhaled particle mass to be estimated. The median mass is represented by particles in the size range of 0.7 to 1.0m. Half an hour of repeated deep expirations result in samples in the order of nanogram to microgram. The source of these samples is the respiratory tract ling fluid of small airways and consists of lipids and proteins, similarly to surfactant. Early clinical studies of e g chronic obstructive pulmonary disease and asthma, reported altered particle formation and particle composition.ConclusionThe physical properties and content of exhaled particles generated by the airway reopening mechanism offers an exciting noninvasive way to obtain samples from the respiratory tract lining fluid of small airways. The biomarker potential is only at the beginning to be explored.
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| 9. |
- Bake, Björn, 1939, et al.
(författare)
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High tidal end expiratory flow -- an index of dynamic hyperinflation?
- 2007
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Ingår i: Clin Physiol Funct Imaging. - 1475-0961. ; 27:2, s. 116-21
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic hyperinflation is considered an important mechanism behind shortness of breath and reduced exercise capacity in chronic obstructive pulmonary disease (COPD) patients. Prevailing methods to assess dynamic hyperinflation are crude because of the large normal variation of both functional residual capacity and inspiratory capacity (IC). In the present study, we hypothesized that expiratory flow on a relatively high level near the end of tidal expiration is an indication of dynamic hyperinflation. A method to measure tidal end expiratory flow (TEEF), i.e. the flow between 0.6 s and 0.04 s before start of inspiration is presented and evaluated in 15 healthy subjects and 16 COPD patients. The COPD patients had more than twice as high TEEF values compared with the healthy subjects (45.4 +/- 23.8 and 20.4 +/- 7.3 ml s(-1) respectively; mean +/- SD; P = 0.0002, for TEEF at 0.4 s before start of inspiration). TEEF values correlated to IC, e.g. TEEF at 0.4 s before start of inspiration expressed as a fraction of mean expiratory flow, correlated to IC (% pred.) (r = 0.74; P<0.0001). These results justifies further testing of the relationship between TEEF and dynamic hyperinflation.
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| 10. |
- Belfrage, B., et al.
(författare)
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Performance and interpretation of spirometry among Swedish hospitals
- 2016
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Ingår i: Clinical Respiratory Journal. - : Wiley. - 1752-6981 .- 1752-699X. ; 10:5, s. 567-573
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims: It is unclear to what extent spirometric performance and interpretation is standardized in Sweden. The aim of this study was to find out how spirometry is performed and interpreted in large Swedish hospitals. Methods: In telephone interviews, technicians and physicians working with lung function measurements at 21 large Swedish hospitals were interviewed about routines for spirometry. Results: Answers were obtained from 37 of the 42 departments contacted revealing differences in the spirometric routines. Some departments lack a written method description, and three different prediction equations were used among the departments. Different ways of calculating the forced expiratory volume in 1 s (FEV1)/vital capacity (VC) ratio (FEV%) were found and also differences in performance and interpretation of the reversibility test. When diagnosing chronic obstructive pulmonary disease, none of the departments reported using an individualized diagnostic limit of FEV1/VC based on age, sex and height. Conclusion: There is a need for standardization of performance and interpretation of the spirometry test in Sweden and probably also in other countries. © 2014 John Wiley & Sons Ltd
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