| 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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| 11. |
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| 12. |
- Bodin, Per, et al.
(författare)
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Breathing patterns during breathing exercises in persons with tetraplegia
- 2003
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Ingår i: Spinal Cord. ; 41:5
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Tidskriftsartikel (refereegranskat)abstract
- STUDY DESIGN: Cross-sectional, observational, controlled study. OBJECTIVES: To survey breathing patterns during breathing at rest, ordinary deep breathing (DB), positive expiratory pressure (PEP) and inspiratory resistance-positive expiratory pressure (IR-PEP) among individuals with a cervical spinal cord lesion (SCL) compared with able-bodied controls. SETTING: Sahlgrenska University Hospital, Goteborg, Sweden. METHOD: Participants consisted of 20 persons with a complete SCL at the C5-C8 level (at least 1 year postinjury) and 20 matched, able-bodied controls. Breathing patterns and static lung volumes were measured using a body plethysmograph. RESULTS: Compared to the controls, breathing patterns at rest among the people with tetraplegia were characterised by a decreased tidal volume, stable respiratory rate and total cycle duration resulting in decreased mean inspiratory and expiratory flow, and alveolar ventilation. All volume and flow parameters increased except respiratory rate, which decreased during DB and PEP. During IR-PEP, tidal volume increased less compared to PEP, and combined with a decreased respiratory rate the alveolar ventilation was lower than during breathing at rest. The functional residual capacity increased during PEP and IR-PEP in people with tetraplegia. CONCLUSION: DB exercises with or without resistance during expiration or the whole breathing cycle affect the breathing pattern in persons with tetraplegia. DB was superior in increasing volumes and flow. PEP and IR-PEP increased FRC but IR-PEP decreased volumes and flows. However, large interindividual differences in the SCL group indicate the need for caution in generalising the results. SPONSORSHIP: This work was supported in part by grants from the Memorial Foundation of the Swedish Association of registered Physiotherapists and the Association of Cancer and Road Accident Victims.
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| 13. |
- Bodin, Per, et al.
(författare)
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Effects of abdominal binding on breathing patterns during breathing exercises in persons with tetraplegia
- 2005
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Ingår i: Spinal Cord. - : Springer Science and Business Media LLC. - 1362-4393 .- 1476-5624. ; 43, s. 117-122
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Tidskriftsartikel (refereegranskat)abstract
- Study design: Cross-sectional, experimental. Objectives: To investigate and compare static lung volumes and breathing patterns in persons with a cervical spinal cord lesion during breathing at rest, ordinary deep breathing, positive expiratory pressure (PEP) and inspiratory resistance-positive expiratory pressure (IR-PEP) with and without an abdominal binder (AB). Setting: The outpatient clinic at the Spinal Unit at Sahlgrenska University Hospital, Göteborg, Sweden. Method: The study group consisted of 20 persons with complete cervical cord lesion at C5–C8 level. Breathing patterns and static lung volumes with and without an AB were measured using a body plethysmograph. Results: With an AB, static lung volumes decreased, vital capacity increased, breathing patterns changed only marginally and functional residual capacity remained unchanged during PEP and IR-PEP. Conclusion: Evidence supporting the general use of an AB to prevent respiratory complications by means of respiratory training is questionable. However, the interindividual variation in our results indicates that we cannot rule out that some patients may benefit from the treatment. Sponsorship: This work was supported by grants from the Memorial Foundation of the Swedish Association of registered Physiotherapists and the Association of Cancer and Road Accident Victims, Sweden.
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| 14. |
- Brisman, Jonas, 1954, et al.
(författare)
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Spirometric reference equations for Swedish adults
- 2017
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Ingår i: Clinical Physiology and Functional Imaging. - : Wiley. - 1475-0961. ; 37:6, s. 640-645
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Tidskriftsartikel (refereegranskat)abstract
- New spirometric reference equations for Swedish adults are required. Three different older sets of reference equations clinically used in Sweden have various drawbacks and the recently published 'The Global Lung Function 2012 (GLI) equations' have been shown not to be adequate for Swedish normal, healthy non-smokers. We have recently concluded that a piecewise linear model presented by Lubinski and Golczewski accurately describes the distribution of spirometric variables in a large Swedish random population sample. This piecewise linear model also offers the important advantage of implementing easily physiologically interpretable coefficients. The present study aimed at presenting piecewise linear reference equations for Swedish adults based on a random population sample of 6685 individuals aged 25-75years. Predicted normal values by the piecewise linear reference equations and lower limit normal (LLN) were compared with the three reference equations frequently used clinically in Sweden and the GLI equations. We found predicted normal values according to the present piecewise linear reference equations close to 100% predicted normal as expected, whereas the other equations either overestimated or underestimated normal subjects. Concerning LLN, the present equations, i.e. 1.645 x RSD, showed the least deviation from the expected 5% and, e.g., the GLI equations systematically identified too few subjects below LLN. We conclude that the present piecewise linear reference equations, based on a relatively large general population sample, ought to be considered for clinical use in Sweden. Application of 1.645 x RSD below predicted value gave an acceptably accurate LLN.
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| 15. |
- Carneskog, Jan, et al.
(författare)
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The red cell mass, plasma erythropoietin and spleen size in apparent polycythaemia.
- 1999
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Ingår i: European journal of haematology. - 0902-4441. ; 62:1, s. 43-8
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Tidskriftsartikel (refereegranskat)abstract
- It has been shown previously that measurement of the spleen size and plasma erythropoietin (EPO) concentration are valuable adjuncts in the diagnostic work-up of patients with polycythaemia vera. The aim of the present work was to evaluate their value in the assessment of apparent polycythaemia (AP). Therefore, over a 24-month period we routinely performed bone marrow biopsies, measurement of red cell mass (RCM) and plasma volume (PV), spleen size determination by gamma camera scintigraphy and determination of the plasma EPO concentration in consecutive patients referred to us because of elevated values for packed cell volume (>0.48 in females and >0.51 in males). After having excluded patients with clonal and secondary polycythaemias we were left with 38 patients (27 males and 11 females) with AP. In all of them the measured RCM was within normal range, i.e. <36 ml/kg for males and <32 ml/kg for females. The subjects were characterized by moderate increase in RCM and a concomitant moderate decrease in PV. Thus, as an average the measured RCM exceeded the predicted values by 14% in males and by 12% in females; conversely, as compared to the predicted values the average measured value for PV was reduced by 17% in males and by 8% in females. The average RCM for males was 29+/-3 ml/kg; the corresponding figure for females was 23+/-4 ml/kg. It was shown that 86% of the subjects had plasma EPO concentrations within the control range; the remaining had values slightly above or below the control range. The mean posterior spleen scan area was 57+/-16 cm2 and mean left lateral area 57+/-17 cm2; the reference value for spleen scan area (for both projections) is 57+/-12 cm2. Of the patients 35/38 (92%) had a spleen scan area within the mean+2SD for controls and 38 subjects (100%) had values within the mean+3SD. It is concluded that measurement of plasma EPO and a careful assessment of the spleen size should always be considered in the evaluation of patients with elevated values for venous packed cell volume.
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| 16. |
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| 17. |
- Ekberg-Jansson, Ann, 1960, et al.
(författare)
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Bronchial mucosal mast cells in asymptomatic smokers relation to structure, lung function and emphysema
- 2005
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Ingår i: Respir Med. - : Elsevier BV. - 0954-6111 .- 1532-3064. ; 99:1, s. 75-83
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Tidskriftsartikel (refereegranskat)abstract
- The pathologic mechanisms of chronic obstructive pulmonary disease (COPD) most certainly involves neutrophil granulocytes, cytotoxic T-cells, macophages and mast cells. The aim of this study was to investigate the relation between the number of mast cells in different compartments in bronchial biopsies of central proximal airways to structural changes, lung function tests and emphysema detected by high resolution computed tomography (HRCT). Twenty nine asymptomatic smoking and 16 never-smoking men from a population study were recruited. Central bronchial biopsies were stained to identify mast cells by immunohistochemistry. The number of mast cells in the epithelium, lamina propria and smooth muscle as well as epithelial integrity and thickness of the tenascin and laminin layer were determined. Smokers had increased numbers of mast cells in all compartments (P<0.001). Structural changes were correlated to mast cell numbers with the closest associations to mast cell numbers in the smooth muscle [epithelial integrity (R(S)=-0.48, P=0.008), laminin layer (R(S)=0.63, P=0.0002), tenascin layer (R(S)=0.40, P=0.03)]. Similar correlations between mast cells and lung function tests were seen [functional residual capacity (FRC) (R(S)=0.60, P=0.0006), total lung capacity (TLC) (R(S)=0.44, P=0.02) and residual volume (RV) (R(S)=0.41, P=0.03)]. No correlations could be detected between mast cells and FEV1 or to emphysema. Smoking is associated with an increase of mast cells in all compartments of the bronchial mucosa, including smooth muscle, and this is related to altered airway structure and function.
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| 18. |
- Ekström, Magnus, et al.
(författare)
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Absolute lung size and the sex difference in breathlessness in the general population
- 2018
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Ingår i: Plos One. - San Francisco, USA : Public Library of Science (PLoS). - 1932-6203. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Breathlessness is associated with major adverse health outcomes and is twice as common in women as men in the general population. We evaluated whether this is related to their lower absolute lung volumes. Cross-sectional analysis of the population-based Swedish CardioPulmonarybioImage Study (SCAPIS) Pilot, including static spirometry and diffusing capacity (n = 1,013; 49% women). Breathlessness was measured using the modified Medical Research Council (mMRC) scale and analyzed using ordinal logistic regression adjusting for age, pack-years of smoking, body mass index, chronic airway limitation, asthma, chronic bronchitis, depression and anxiety in all models. Breathlessness was twice as common in women as in men; adjusted odds ratio (OR) 2.20 (95% confidence interval, 1.32-3.66). Lower absolute lung volumes were associated with increased breathlessness prevalence in both men and women. The sex difference in breathlessness was unchanged when adjusting for lung function in %predicted, but disappeared when controlling for absolute values of total lung capacity (OR 1.12; 0.59-2.15), inspiratory capacity (OR 1.26; 0.68-2.35), forced vital capacity (OR 0.84; 0.42-1.66), forced expiratory volume in one second (OR 0.70; 0.36-1.35) or lung diffusing capacity (OR 1.07; 0.58-1.97). In the general population, the markedly higher prevalence of breathlessness in women is related to their smaller absolute lung volumes.
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| 19. |
- Gustafsson, Agnetha, et al.
(författare)
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Evaluation of various attenuation corrections in lung SPECT in healthy subjects
- 2003
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Ingår i: Nuclear Medicine Communications. - : Ovid Technologies (Wolters Kluwer Health). - 0143-3636 .- 1473-5628. ; 24:10, s. 1087-1095
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Tidskriftsartikel (refereegranskat)abstract
- The effect of increasingly more sophisticated attenuation correction methods on image homogeneity has been studied in seven healthy subjects. The subjects underwent computed tomography (CT), single photon emission computed tomography (SPECT) and transmission computed tomography (TCT) of the thorax region in the supine position. Density maps were obtained from the CT and TCT studies. Attenuation corrections were performed using five different methods: (1) uniform correction using only the body contour; (2) TCT based corrections using the average lung density; (3) TCT based corrections using the pixel density; (4) CT based corrections using average lung density; and (5) CT based corrections using the pixel density. The isolated attenuation effects were assessed on quotient images generated by the division of images obtained using various attenuation correction methods divided by the non-uniform attenuation correction based on CT pixel density (reference method). The homogeneity was calculated as the coefficient of variation of the quotient images (CVatt), showing the isolated attenuation effects. Values of CVatt were on average 12.8% without attenuation correction, 10.7% with the uniform correction, 8.1% using TCT map using the average lung density value and 4.8% using CT and average lung density corrections. There are considerable inhomogeneities in lung SPECT slices due to the attenuation effect. After attenuation correction the remaining inhomogeneity is considerable and cannot be explained by statistical noise and camera non-uniformity alone. ((C) 2003 Lippincott Williams Wilkins).
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| 20. |
- Hamnegård, Carl-Hugo, 1954, et al.
(författare)
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Does undernutrition contribute to diaphragm weakness in patients with severe COPD?
- 2002
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Ingår i: Clinical Nutrition. ; 21:3, s. 239-243
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND AIMS: The assumption that undernourishment contributes to diaphragm weakness in chronic obstructive pulmonary disease (COPD) remains unproven. METHODS: We, therefore, studied diaphragm strength, measured as transdiaphragmatic pressure during a maximal voluntary sniff (Sn P(di)) and cervical magnetic stimulation (Tw P(di)), in two groups of 10 patients with severe COPD. The groups had equally severe COPD as judged by FEV(1) and thoracic gas volume (V(tg)). The malnourished group had a mean body mass index (BMI) of 17.3 kg/m(2) compared with 27 kg/m(2) for the normally nourished group (mean difference -9.7 kg/m(2); 95% confidence intervals -6.8 to -12.6 kg/m(2),P <0.0001). RESULTS: There was no significant difference between Tw P(di) (mean difference 2.1 cm H(2)O; 95% CI-3 to + 7.4 cm H(2)O, P=0.39) or Sn P(di) (mean difference -2.4 cm H(2)O; 95% CI-21 cm H(2)O to +16 cm H(2)O,P =0.8). CONCLUSION: We conclude that undernourishment of the severity studied does not contribute to diaphragm weakness in severe COPD.
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| 21. |
- Hamnegård, Carl-Hugo, 1954, et al.
(författare)
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Effect of lung volume reduction surgery for emphysema on diaphragm function
- 2006
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Ingår i: Respir Physiol Neurobiol.. ; 150:2-3
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Tidskriftsartikel (refereegranskat)abstract
- Preoperative prediction of a successful outcome following lung volume reduction surgery (LVRS) for emphysema is imperfect. One mechanism could be improvement in respiratory muscle function yet controversy exists regarding the magnitude and mechanism of such an improvement. Therefore, we measured diaphragm strength in 18 patients before and after LVRS. Mean (S.D.) FRC fell from 6.53 to 5.40l (p=0.0001). Mean sniff transdiaphragmatic pressure increased from 76 to 87cmH(2)O (14%, p<0.03) and mean twitch transdiaphragmatic pressure (Tw Pdi) increased by 2.5cmH(2)O at 3 months (12%, p=0.03). There was a highly significant increase in twitch esophageal pressure (Tw Pes) (60%, p<0.0001), which was maintained at 12 months (46% increase, p=0.0004). No change was observed in quadriceps twitch tension in nine subjects in whom it was measured. After LVRS the ratio Tw Pes:Tw Pdi increased from 0.24 to 0.37 at 3 months (p=0.0003) and 0.36 at 12 months (p=008). Low values of Sn Pdi, Sn Pes, Tw Pes and a high RV/TLC ratio were the preoperative variables most predictive of improvement in shuttle walking distance. We conclude that LVRS improves diaphragm function primarily by alteration of lung volume. Patients with poor diaphragm function and high RV/TLC ratio preoperatively are most likely to benefit from the procedure.
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| 22. |
- Hamnegård, Carl-Hugo, 1954, et al.
(författare)
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Quadriceps strength assessed by magnetic stimulation of the femoral nerve in normal subjects
- 2004
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Ingår i: Clin Physiol Funct Imaging. ; 24:5
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Tidskriftsartikel (refereegranskat)abstract
- Summary Magnetic stimulation of the femoral nerve is a new technique for assessment of quadriceps strength by measurement of twitch tension (TwQ), a test that is independent of subject motivation. In this study, we sought to establish better define normal values by measurement of TwQ in 45 normal subjects. Supramaximal stimulation, as judged by TwQ, was achieved in 43 of 45 subjects at a mean of 90% of maximum stimulator output. The mean TwQ was 7.3 kilograms force (kgf) (SD 2.3) for women and 9.8 kgf (SD 2.5) for men. The mean maximal voluntary contraction (MVC) force was 48.0 kgf (SD 9.2) for women and 70.1 kgf (15.2) for men. The mean TwQ/MVC ratio was 0.15 for both women and men. Significant correlations were observed between TwQ and weight (r = 0.33, P<0.03) and height (r = 0.32, P<0.03) but these were weak and only partially explained observed variance. Our data confirm that magnetic femoral nerve stimulation is generally acceptable to naive subjects. Values are provided as a function of weight in normal subjects.
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| 23. |
- Holmgren, Helene, 1981, et al.
(författare)
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Effects of breath holding at low and high lung volumes on amount of exhaled particles
- 2013
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Ingår i: Respiratory Physiology & Neurobiology. - : Elsevier BV. - 1569-9048. ; 185:2, s. 228-234
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Tidskriftsartikel (refereegranskat)abstract
- Exhaled breath contains particles originating from the respiratory tract lining fluid. The particles are thought to be generated during inhalation, by reopening of airways closed in the preceding expiration. The aim here was to explore processes that control exhaled particle concentrations. The results show that 5 and 10 s breath holding at residual volume increased the median concentration of particles in exhaled air by 63% and 110%, respectively, averaged over 10 subjects. An increasing number of closed airways, developing on a timescale of seconds explains this behaviour. Breath holds of 5, 10 and 20 s at total lung capacity decreased the concentration to 63%, 45% and 28% respectively, of the directly exhaled concentration. The decrease in particle concentration after breath holding at total lung capacity is caused by gravitational settling in the alveoli and associated bronchioles. The geometry employed here when modelling the deposition is however not satisfactory and ways of improving the description are discussed.
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| 24. |
- Holmgren, Helene, 1981, et al.
(författare)
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Relation Between Humidity and Size of Exhaled Particles
- 2011
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Ingår i: Journal of Aerosol Medicine and Pulmonary Drug Delivery. - : Mary Ann Liebert Inc. - 1941-2711 .- 1941-2703. ; 24:5, s. 253-260
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Tidskriftsartikel (refereegranskat)abstract
- Background: Aerosol particles are generated in human airways, and leave the body with exhaled air. These particles may carry indicators of various lung conditions. To fully utilize the information provided by endo- genously produced exhaled particles, it is important to understand their formation mechanism and physical properties. The scope of this work was to measure number size distributions of exhaled aerosol particles at various surrounding relative humidities (RH) in order to gain some knowledge of the size distribution at the point of particle generation. Methods: Number size distributions of exhaled particles were measured at various RHs, using an optical particle counter. Breathing with airway closure was employed. Results: A relation between particle volume and RH was fitted to experimental data and used to predict how exhaled droplets behave at RHs not easily accessible by experiments. The diameter of an exhaled particle is reduced by a factor of 0.42 when the RH is changed from 99.5 to 75% at 309 K. Calculations also show that the droplets are concentrated solutions near saturation at 75% RH. Conclusions: It is concluded that the particles are supersaturated liquid particles, rather than crystalline solids, in ambient air with RH below 75%. A size distribution related to the aerosol at the moment of formation is given. A successful detailed formation mechanismshould be able to accommodate the size distribution predicted at 99.5%RH.
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| 25. |
- Holmgren, Helene, 1981, et al.
(författare)
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Size Distribution of Exhaled Particles in the Range from 0.01 to 2.0 µm
- 2010
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502 .- 1879-1964. ; 41:5, s. 439-446
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the number size distribution of endogenously produced exhaled particles during tidal breathing and breathing with airway closure. This is the first time that the region below 0.4 µm has been investigated. The particle concentration was generally lower for tidal breathing than for airway closure, although the inter-individual variation was large. During tidal breathing, the size distribution peaks at around 0.07 µm. This peak is still present during the airway closure manoeuvre, but an additional broad and strong peak is found between 0.2 and 0.5 µm. This suggests that different mechanisms govern the generation of particles in the two cases. The particles produced from airway closure may be attributed to formation of film droplets in the distal bronchioles during inhalation. It is speculated that the very small particles are film droplets originating from the alveolar region.
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