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- Andersson, Mikael, 1979-
(författare)
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Assessing Physical Activity and Physical Capacity in Subjects with Chronic Obstructive Pulmonary Disease
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis was to assess measurement properties of methods suitable for screening or monitoring of physical capacity and physical activity in subjects with chronic obstructive pulmonary disease (COPD), and to explore factors associated with physical activity levels.Methods: Four observational studies were conducted. Participants in studies I-III (sample sizes) (n=49, n=15, n=73) were recruited from specialist clinics, and in study IV from a population-based cohort (COPD n=470 and Non-COPD n=659). Psychometric properties of methods assessing physical capacity (study I) and physical activity (study II) were investigated in laboratory settings. Daily physical activity and clinical characteristics were assessed with objective methods (study III) and with subjective methods (study IV).Results: Physical capacity as measured by walking speed during a 30-metre walk test displayed high test-retest correlations (ICC>0.87) and small measurement error. The accuracy for step count and body positions differed between activity monitors and direct observations. In study III 92% of subjects had an activity level below what is recommended in guidelines. Forty five percent of subjects’ activity could be accounted for by clinical characteristics with lung function (22.5%), walking speed (10.1%), quadriceps strength (7.0%) and fat-free mass index (3.0%) being significant predictors. In study IV, low physical activity was significantly more prevalent in COPD subjects from GOLD grade ≥II than among Non-COPD subjects (22.4 vs. 14.6%, p = 0.016). The strongest factors associated with low activity in COPD subjects were a history of heart disease, OR (CI 95%) 2.11 (1.10-4.08) and fatigue, OR 2.33 (1.31-4.13) while obesity was the only significant factor in Non-COPD subjects, OR 2.26 (1.17-4.35).Conclusion: The 30 meter walk test and activity monitors are useful when assessing physical capacity and physical activity, respectively in patients with COPD. Impaired physical activity in severe COPD is related to low lung function, low walking speed, low muscle strength and altered body composition, whereas comorbidities and fatigue are linked to insufficient physical activity in patients with moderately severe COPD.
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- Andersson, Mikael, 1964-
(författare)
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Characterisation of Chromatography Media Aimed for Purification of Biomolecules
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chromatography media (resins) are very important for and widely used by the biopharma industry in large scale production of biopharmaceuticals, e.g. monoclonal antibodies. Today there are several hundred biopharmaceuticals released globally on the healthcare market. This thesis discusses various strategies and methods for the characterisation of chemical and functional stability of chromatography media. In addition, various analytical techniques used in these areas were evaluated and applied. Further, more specific physical and chemical characterisation methods were evaluated and applied to explore different properties of various chromatography media.In Papers I-III, established methodologies for performing chemical and functional stability studies were used. Mainly agarose-based chromatography media were investigated. For fast screening of the chemical stability, the total organic carbon analysis technique was evaluated and applied. This technique that measures the carbon leakage from the chromatography media at different conditions, proved to be very suitable and robust. For detection and/or identification of leakage compounds responsible for or for part of the measured carbon leakage, different methods such as (high performance) liquid chromatography and gas chromatography mass spectrometry were used.In Papers IV-VII, different properties (i.e. functional performance, ligand content and surface chemistry) were evaluated for different agarose-based chromatography media. Standard chromatographic methods (ion exchange chromatography) and spectroscopic methods (e.g. Fourier transform infrared spectroscopy and time-of-flight secondary ion mass spectrometry) were evaluated and applied. Chemometric methods were used for efficient evaluation of data.Information of chemical, functional and leakage data of chromatography media are valuable and important for the biopharmaceutical companies to be able to fulfil the regulatory requirements of biopharmaceuticals. In addition, information of various chemical, functional and physical properties of chromatography media is likewise important during development and set up of new biopharmaceutical processes.
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- Appelberg, Jonas, 1964-
(författare)
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Ventilation and Lung Volume During Sleep and in Obstructive Sleep Apnea
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Obstructive sleep apnea (OSA) appears to affect up to 5% of the population. The extent to what pulmonary function awake and during sleep relates to obstructive breathing and hypoxemia during sleep in these patients is unclear. The aim of this study was to investigate respiratory function in patients with varying degree of snoring and OSA and to analyse regional lung aeration during sleep.In all, 35 healthy subjects and 90 patients with snoring and OSA were studied. The ventilatory response to CO2 (VRCO2) was measured. Lung function tests were performed. A technique based on computed tomography was developed to study lung aeration during sleep.Patients with OSA displayed a higher VRCO2 in comparison to healthy subjects and snorers (p<0.01). Increased closing volume and reduced expiratory reserve volume (ERV) were found in patients with OSA (p<0.001). In a multiple regression analysis, ERV was an independent predictor of nocturnal apnea (R2=0.13; p=0.001) and desaturation frequency (R2=0.11; p<0.01). In both healthy subjects and OSA patients, lung aeration was reduced during sleep by 0.10 ml gas/g tissue in the dorsal lung region (p<0.05 and p<0.01). OSA patients had a significantly lower gas/tissue ratio in comparison to healthy subjects both awake (-23%; p<0.04) and during sleep (-25%; p<0.04). In a univariate analysis, functional residual capacity (FRC) correlated with the change in lung aeration from wakefulness to sleep (r=-0.78; p<0.001). In patients with OSA, ERV (r=-0.69; p<0.05) and sleep time (r=0.69; p<0.05) correlated with the fall in lung aeration. In conclusion, patients with OSA display an increased ventilatory response to CO2, reduced ERV and increased closing volume. ERV predicts nocturnal apnea and desaturation frequency to a similar extent as obesity. Lung aeration is reduced in the dorsal region during sleep and patients with OSA display a lower amount of gas in comparison to healthy subjects. Decrease in lung volumes, promoting airway closure, and loss of muscle tone contributed to the altered lung function during sleep.
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