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Biomedical subjects

G Bylin

Publications and source records attributed to G Bylin.

36 records · Page 2Linked to original sources
PubMed1993

Deposition in asthmatics of particles inhaled in air or in helium-oxygen.

Ten subjects with asthma inhaled 3.6 micron particles labeled with 111In in air and in a helium-oxygen mixture (He-O2) at 0.5 and at 1.2 L/s. Lung retention was measured after zero and after 24 h, and the percentage 24-h retention (Ret24) was taken to represent the fraction deposited in the alveolar part of the lung. For both inhalation rates, Ret24 was significantly higher when particles were inhaled with He-O2 than with air. The increase in Ret24 seemed to be larger in subjects with asthma than in healthy persons earlier studied. Ret24 was correlated with changes in both large and small airways, especially when the particles were inhaled with He-O2. Our data suggest that inhalation of drugs in He-O2 might be of therapeutic value when treating patients with severely obstructed airways.

Administration, Inhalation↗
PubMed1992

Relationships among gas exchange, spirometry and symptoms in asthma.

OBJECTIVES: The severity of asthma is usually evaluated by clinical examination and spirometry. In a small study of asthmatics considerable ventilation/perfusion (VA/Q) inequality was found, however, despite essentially normal flow rates. These findings prompted the current study. METHODS: We prospectively examined symptoms, spirometry and VA/Q inequality in 26 patients with chronic, symptomatic asthma once a week for 9 consecutive weeks. VA/Q measurements were made using a less invasive approach of the multiple inert gas elimination technique and symptoms were scored. RESULTS: Correlation coefficients between indices for VA/Q inequality (log SDQ), spirometry (FEV1.0/VC, MEF25) and symptom scores were only in the range 0.24-0.29. CONCLUSION: We conclude that even at the individual level, symptoms, spirometry and VA/Q inequality are so poorly correlated that one cannot evaluate any of these aspects of asthma without measuring each. The data support the notion that spirometric and gas exchange abnormalities in asthma are caused by different pathophysiologic events.

Asthma↗
PubMed1991

Regional deposition of 3.6-micron particles and lung function in asthmatic subjects.

In a group of moderately severe asthmatic subjects, regional deposition of 3.6-microns (aerodynamic diameter) monodispersed Teflon particles labeled with 111In was studied twice. The particles were inhaled with maximally deep inhalation at 0.5 l/s. Lung retention was measured at 0, 6, 24, and 48 h by use of a profile scanner equipped with two 13 x 5-cm NaI crystals. The retentions at 24 (Ret24) and 48 h were highly correlated (r = 0.96 with a slope of the regression line close to 1). There was a poor correlation between retention at 6 h and Ret24 (r = 0.54). The Ret24 values at the two exposures were well correlated (r = 0.86). There were significant correlations between airway resistance as well as single-breath nitrogen test phase III and Ret24 (r = 0.70 and 0.67, respectively). The correlation between single-breath nitrogen test phase III and Ret24 persisted also when only subjects within a narrow interval of airway resistance were included. The study indicates that regional deposition can be studied by measurements of Ret24 in subjects with moderately severe asthma and that it is dependent on changes in both large and small airways.

Administration, Inhalation↗
PubMed1988

Ambient nitrogen dioxide concentrations increase bronchial responsiveness in subjects with mild asthma.

Twenty subjects with mild asthma were exposed at rest in a body plethysmograph, to NO2 at 0, 260, 510 and 1,000 micrograms.m3, for 30 min on four separate days. Bronchial responsiveness (histamine inhalation test) was measured after each exposure session. Airway resistance (Raw), thoracic gas volume (TGV) and specific airway resistance (sRaw) were measured before, during and after exposure, and the breathing pattern was monitored during the whole session. Bronchial responsiveness increased significantly after 30 min exposure to 510 micrograms.m3 NO2 (p less than 0.01). There were also tendencies to an increased bronchial responsiveness after exposure to 260 and 1,000 micron.m3 NO2, but these changes were not statistically significant. Effects on airway resistance and breathing pattern were not demonstrated by exposure to 0-1,000 micrograms.m3 NO2. We conclude that short-term NO2 exposure at about 500 micrograms.m3 slightly affects human bronchial responsiveness in subjects with mild asthma.

Adult↗
PubMed1987

Reproducibility of the multiple inert gas elimination technique.

Although measurement errors in the multiple inert gas elimination technique have a coefficient of variation of approximately 3%, small biological fluctuations in ventilation, blood flow, or other variables must contribute additional variance to this method of assessing ventilation-perfusion (VA/Q) mismatch. To determine overall variance of computed indices of VA/Q mismatch, an analysis of variance was carried out using a total of 400 duplicate pairs of inert gas samples obtained from canine (N = 118) and human (N = 282) studies in the past 2 years. In both sets VA/Q mismatch ranged from minimal (2nd moment of ventilation and blood flow distributions, log SDV and log SDQ, respectively approximately equal to 0.3 each) to severe (log SDV and log SDQ approximately equal to 2.0). Differences between duplicate log SD values were computed and found to be a constant fraction of the mean log SD of each duplicate pair, averaging 13% for both canine and human ventilation and blood flow data. The resultant coefficient of variation for a single measurement of log SD about its mean averaged 8.6% for all data combined. This analysis demonstrates excellent reproducibility of these dispersion indices over a wide range of conditions, and if the mean of duplicate values is used, thus reducing variability by square root 2 to 6.1%, log SD can be estimated with an approximately 95% confidence limit of +/- 12%.

Animals↗
PubMed1987

Ventilation-perfusion inequality in chronic asthma.

The prevalence and variability of ventilation-perfusion (VA/Q) inequality was examined in 26 stable, symptomatic, asthmatic subjects (mean FEV1/FVC, 79% predicted; mean FEF75, 43% predicted) studied once a week for 9 consecutive weeks. We used a recent modification of the multiple inert gas elimination technique allowing frequent serial studies without the need for sampling arterial blood. The VA/Q inequality was expressed as log SD (the second moment) of the distributions of blood flow (Q) and ventilation (V) on a log scale. Log SDQ averaged 0.74, and in every patient log SDQ exceeded the 95% upper limit of normal (0.60) in 2 wk or more. In only 5 patients was mean log SDQ less than 0.6. The ventilation distribution was less abnormal, with mean log SDV exceeding the 95% normal upper limit in only 4 patients. Bimodal blood-flow distributions containing low VA/Q units were observed at some point in 24 of 26 subjects, but occurrence was variable, and in only one third of all measurements was bimodality found. Analysis of variance showed that 70 to 75% of the total variance of log SD was due to intersubject differences, about 20% was due to random changes over time, and the remaining 7 to 9% was not explained by either and was due mostly to experimental error. Arterial PO2 measured 3 times in each subject was inversely related to log SDQ (r = 0.76), but only 60% of the variance in PaO2 was explained by VA/Q mismatch, the rest being due presumably to variation in mixed venous PO2 and similar extrapulmonary factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Asthma↗
PubMed1987

No influence of acetylcysteine on gas exchange and spirometry in chronic asthma.

Non-smoking patients (n:25) with stable symptomatic asthma were investigated with regard to the pulmonary effects of N-acetylcysteine (NAC), peroral dose 200 mg three times daily, in a crossover double-blind study. They were studied once a week for 9 weeks, with a run-in period and periods with NAC and placebo (3 weeks each). Functional residual capacity and specific airway resistance were 19 and 53% larger, respectively, and forced expiratory variables (FEV%, MEF25) were 20 and 53% lower than reference values. Distribution of ventilation-perfusion ratios (VA/Q), assessed by multiple inert gas elimination technique with peripheral venous sampling, was abnormal, although arterial PO2 and PCO2 were within normal limits. NAC medication had no effect on any spirometric, lung mechanic or gas exchange variable, nor on the frequency of pulmonary symptoms.

Acetylcysteine↗
PubMed1985

Effects of short-term exposure to ambient nitrogen dioxide concentrations on human bronchial reactivity and lung function.

Eight normal and 8 asthmatic subjects were exposed to NO2 in a modified body box for plethysmography during 20 min at 0,230,460 and 910 micrograms/m3 on 4 separate days. Bronchial reactivity (histamine inhalation test) was measured after exposure to air alone and to 910 micrograms/m3NO2. Airway resistance (Raw), thoracic gas volume (TGV) and specific airway resistance (SRaw) were measured before, during and after exposure. The bronchial reactivity of the asthmatic subjects increased significantly (p = 0.04) by 20 min exposure to 910 micrograms/m3 NO2. In the non-asthmatic group the airway resistance increased significantly (p = 0.03) after 20 min exposure to 460 micrograms/m3 NO2 and decreased significantly (p = 0.01) after 20 min exposure to 910 micrograms/m3 NO2. In the asthmatic group the trend in airway resistance was the same but not statistically significant. In the latter group TGV was significantly decreased (p = 0.02) during exposure to 910 micrograms/m3 NO2. Short term NO2-exposure in concentrations even below 1000 micrograms/m3 seems to have effects on human bronchial reactivity and lung function.

Adolescent↗
PubMedDate not supplied

Personal NO2 exposure monitoring shows high exposure among ice-skating schoolchildren.

A method for measuring personal nitrogen dioxide (NO2) exposure, using passive samplers, was tested among schoolchildren. Activity patterns and NO2 exposure levels were studied in relation to urban and rural living. Stationary air monitoring data indicated that the urban children were supposed to be exposed to NO2 levels that were among the highest in Sweden. It was shown that NO2 levels measured at the stationary air monitoring station were not representative for the children's exposure. The children spent 90% of their time indoors; only a small percentage of their time was spent in transit. The median daily NO2 exposure level in the urban area (13 micrograms NO2/m3, 7 ppb) was significantly higher (p < .001) than in the rural area (7 micrograms NO2/m3, 4 ppb). The most important source of exposure was the indoor ice-skating arenas, where levels up to 8,000 micrograms NO2/m3 (4 240 ppb) were measured during 1-h periods.

Air Pollutants↗
PubMedDate not supplied

Measurement of personal exposure to NO2 in Sweden--evaluation of a passive sampler.

A passive (filter badge) sampler for personal NO2 exposure measurements was tested in a laboratory setting (exposure chamber), and in the field--outdoors, during periods of high relative humidity (mean 85%) and low temperature (-5 to +10 degrees C), and indoors, in an ice-hockey arena--using chemiluminescence as a reference method. Parallel measurements of NO2 in the exposure chamber (concentration range 100-825 micrograms NO2/m3) for 15, 30, and 60 min sampling periods, showed good agreement between methods. The concentrations obtained with passive samplers were 78 to 122% (mean 94%, SD +/- 11, N = 39) of those obtained with chemiluminescence, using a sampling rate (K'OG) of 0.14 cm/sec. The detection limits were 320, 160, and 80 micrograms NO2/m3 for 15, 30, and 60 minutes of sampling, respectively. Outdoors (concentration range 15-102 micrograms NO2/m3, concentrations obtained with passive samplers were consistently lower than concentrations obtained with chemiluminescence (mean 79%, SD +/- 9.3%, range 61-95%, N = 25), using the K'OG of 0.14 of cm/sec (Passive samplerNO2 = 0.67ChemilumNO2 + 4.5). A better agreement between concentrations obtained with passive samplers and chemiluminescence was achieved with a K'OG of 0.11 cm/sec (mean 100%, SD +/- 12%, range 78-121%, Passive samplerNO2 = 0.84 ChemilumNO2 + 6.4). Indoors (concentration range 210-3895 micrograms NO2/m3), concentrations obtained with passive samplers were 70 to 113% (mean 90%, SD +/- 16%) of the concentrations obtained with chemiluminescence (Passive samplerNO2 = 1.00ChemilumNO2 - 93) using a K'OG of 0.10 cm/sec. Duplicate samples collected indoors N = 18) and outdoors (N = 31) showed a variability (coefficient of variation, or CV) of less than 6%. It was concluded that the passive sampler is useful for measuring personal daily exposure as well as peak exposure. It is necessary to determine sampling rates for various environmental conditions.

Air Pollutants↗
PubMedDate not supplied

Specific airway conductance and airway conductance-lung volume curves in normal and asthmatic subjects.

Airway conductance (Gaw) depends on lung volume (TGV). An approximate correction for this volume dependence can be obtained by calculating specific airway conductance (sGaw = Gaw-TGV). In this study, Gaw-TGV curves were compared with sGaw in 30 healthy and 20 asthmatic subjects who were studied by body plethysmography. Gaw, TGV and sGaw were measured five times at three to five different lung volumes. sGaw was dependent on TGV, the regression having a negative slope (-0.24 and -0.27 kPa-1.s-1.l-1, in the group without and with asthma, respectively). A change in TGV by 1 l caused a 9 and 11% decrease in sGaw, respectively. Bronchial obstruction induced by histamine inhalation in the asthmatic subjects increased the dependence on TGV by sGaw, now with a positive slope. Thus, a change in TGV by 1 l caused a 20-100% increase in sGaw, depending on the degree of airway obstruction. The Gaw-TGV curve was approximately linear around the resting lung volume. The coefficient of variation in determining the slope of the Gaw-TGV curve was as high as 110 and 153% in health and asthmatic subjects, respectively. It is concluded that sGaw, although rapidly determined, has a systematic error in its correction of lung volume dependence, which the Gaw-TGV curve does not. The Gaw-TGV curve therefore has advantages in research work, but since its construction is time consuming it is hardly suitable in clinical practice.

Adult↗