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Background: Some asthmatic patients perceive the severity of their disease rather poorly. These patients may not receive optimal therapy because of underpresentation of their respiratory symptoms. It is therefore important to identify these patients. The present study evaluates a new threshold loading device for measuring the perception of respiratory sensation. This method for measuring the perception of respiratory sensation may be a viable alternative to the bronchial provocation test. The aim of the present study was to investigate whether the assessment of the perception of respiratory sensation based on a threshold loading test (inspiratory and expiratory) identifies the same subjects as poor perceivers as compared to assessment by histamine bronchial provocation test., Method: In 36 subjects, the perception of respiratory sensation through a threshold loading device was compared to the perception of respiratory sensation during a histamine provocation test. Each test was performed with scoring of the magnitude of the respiratory sensation on a visual analog scale (VAS). The magnitude of the stimulus intensity was indicated by the percentage of decrease in FEV(1) during the histamine challenge test and by the percentage of the subject's maximum mouth pressure (percent maximal inspiratory pressure and percent maximal expiratory pressure) during the threshold loading test. The relationship between VAS values and the stimulus intensity was analyzed by determining the linear regression coefficient between the two parameters., Results: No relationship was found between the perception of the sensation induced by the histamine challenge and that during breathing through a threshold loading device for both inspiration (Rs = 0.15; p = 0.40) and expiration (Rs = 0.13; p = 0.47). We did find a significant relation between the perception of respiratory sensation during the inspiratory and expiratory threshold loading test (Rs = 0.67; p = 0. 0001). Furthermore, we defined a subgroup of patients of special interest: those with low symptoms of breathlessness and high bronchial responsiveness. Compared to the inspiratory and expiratory threshold loading test, the histamine challenge test identified more patients in the special interest group as poorest perceivers., Conclusion: The measurement of perception by means of a threshold loading device and a histamine provocation test did not identify the same subjects as poor perceivers, probably because we did not measure the patient's perceptiveness for exactly the same stimuli. In the population with relatively more severe asthma and very low symptoms of breathlessness, the histamine-induced bronchoconstriction test identified more patients as poorest perceivers compared to the threshold loading test.

One of the problems in research on symptom perception during histamine challenge has been the difficulty in finding both a valid and practical parameter of the "perceptiveness" for bronchoconstriction in a subject. The purpose of this study was to validate whether the slope in the linear regression model between stimulus and sensation during histamine challenge is an appropriate index for the "perceptiveness" for bronchoconstriction by comparing it with the classical Stevens' law. One hundred and thirty-four asthmatic patients were included in the study and underwent a bronchial challenge with histamine. The relationship between the change in visual analogue scale (VAS) values and the change in forced expiratory volume in one second (FEV1) as percentage of baseline value was analysed by determining both the exponent n in deltaVAS=k x (%deltaFEV1)n and the slope alpha in deltaVAS=k + alpha(%deltaFEV1). The best-fitting line of both the exponential and the linear regression model were determined by the least-squares method in which the percentage explained variation (R2) was compared. The median value of R2 of the exponential regression line and the linear regression line was 0.76 and 0.83, respectively, and significantly different. The Spearman rank correlation coefficient between exponent n in the exponential model deltaVAS=k x (%deltaFEV1)n and the slope alpha in the linear regression model deltaVAS=k + alpha(%deltaFEV1) was 0.87 (95% confidence interval 0.83-0.91). On the basis of the results, it was concluded that the linear regression coefficient can be used as a valid expression to describe the "perceptiveness" of an asthmatic subject instead of Stevens' power function during histamine challenge.

Background: Inhaled corticosteroids are the most efficacious anti-inflammatory drugs in asthma. International guidelines also advocate the early introduction of inhaled corticosteroids in corticosteroid naive patients. A study was undertaken to assess the effects of inhaled corticosteroids on bronchial hyperresponsiveness in patients with corticosteroid naive asthma by conventional meta-analysis., Methods: A Medline search of papers published between January 1966 and June 1998 was performed and 11 papers were selected in which the patients had no history of treatment with inhaled or oral corticosteroids. Bronchial responsiveness to bronchoconstricting agents was considered as the main outcome parameter. Doubling doses (DD) of histamine or methacholine were calculated., Results: The total effect size of inhaled corticosteroids (average daily dose 1000 microg) versus placebo in the 11 studies was +1.16 DD (95% confidence interval (CI) +0.76 to +1.57). When only the eight short term studies (2-8 weeks) were analysed the effect size of the bronchoconstricting agent was +0.91 DD (95% CI +0.65 to +1.16). No relationship was found between the dose of inhaled corticosteroid used and the effect on bronchial responsiveness., Conclusion: This meta-analysis in patients with corticosteroid naive asthma indicates that, on average, high doses of inhaled corticosteroids decrease bronchial hyperresponsiveness in 2-8 weeks. It remains unclear whether there is a dose-response relationship between inhaled corticosteroids and effect on bronchial hyperresponsiveness.

Background: The role of inhaled corticosteroids in the long term management of chronic obstructive pulmonary disease (COPD) is still unclear. A meta-analysis of the original data sets of the randomised controlled trials published thus far was therefore performed. The main question was: "Are inhaled corticosteroids able to slow down the decline in lung function (FEV1) in COPD?", Methods: A Medline search of papers published between 1983 and 1996 was performed and three studies were selected, two of which were published in full and one in abstract form. Patients with "asthmatic features" were excluded from the original data. Ninety five of the original 140 patients treated with inhaled corticosteroids (81 with 1500 micrograms beclomethasone daily, six with 1600 micrograms budesonide daily, and eight with 800 micrograms beclomethasone daily) and 88 patients treated with placebo (of the initial 144 patients) were included in the analysis. The effect on FEV1 was assessed by a multiple repeated measurement technique in which points of time in the study and treatment effects (inhaled corticosteroids compared with placebo) were investigated., Results: No baseline differences were observed (mean age 61 years, mean FEV1 45% predicted). The estimated two year difference in prebronchodilator FEV1 was +0.034 l/year (95% confidence interval (CI) 0.005 to 0.063) in the inhaled corticosteroid group compared with placebo. The postbronchodilator FEV1 showed a difference of +0.039 l/year (95% CI -0.006 to 0.084). No beneficial effect was observed on the exacerbation rate. Worsening of the disease was the reason for drop out in four patients in the treatment group compared with nine in the placebo group. In the treatment group six of the 95 subjects dropped out because of an adverse effect which may have been related to the treatment compared with two of the 88 patients in the placebo group., Conclusions: This meta-analysis in patients with clearly defined moderately severe COPD showed a beneficial course of FEV1 during two years of treatment with relatively high daily dosages of inhaled corticosteroids.

Background: Patients with a poor perception of their symptoms of asthma seem to have an increased risk of an asthma attack. The influence of factors such as airway calibre, bronchial hyperresponsiveness, age and sex on the "perceptiveness" of a patient are poorly understood. It is of clinical importance to identify patients who are likely to have a poor perception of their symptoms. We have studied the perception of bronchoconstriction by asthmatic patients during a histamine provocation test and analysed the influence of bronchial obstruction, hyperresponsiveness, sex, and age. We were particularly interested to establish whether there was any difference in perception between subjects with a greater or lesser severity of asthma (expressed as bronchial obstruction, hyperresponsiveness)., Methods: One hundred and thirty four patients with allergic asthma underwent a histamine provocation test. The FEV1 was measured after each inhalation of histamine. Subjects were asked to rate subjective quantification of the sensation of breathlessness on a visual analogue scale (VAS). The relationship between changes in VAS values and the reduction in FEV1 as a percentage of the baseline value was analysed by determining the linear regression slope (alpha) between the two parameters and indicates the perception of airway obstruction. Multiple regression analysis was performed to investigate the effect of baseline FEV1, bronchial hyperresponsiveness, sex and age on the "perceptiveness" for bronchoconstriction., Results: The median value of the slope alpha (indicating the perception of airway obstruction) was 0.91 (25-75th percentile: 0.48-1.45). Age and sex had no influence on the perception of bronchoconstriction. Both initial bronchial tone (baseline FEV1) and bronchial hyperresponsiveness (PC20) showed a significant correlation with the perception of bronchoconstriction. The regression coefficients for FEV1 and 2log PC20 in the multiple regression model were 0.20 and 0.10. Patients who had a low baseline FEV1 and/or a high bronchial responsiveness to histamine were more likely to show a low perceptiveness for bronchoconstriction during the challenge test., Conclusions: Low baseline FEV1 and high bronchial responsiveness are associated with a low degree of "perceptiveness" for bronchoconstriction. This suggests that patients with a more severe degree of asthma either show adaptation of "perceptiveness" for airway obstruction or that low perceptiveness leads to more severe asthma.

A novel photoelectrochemical experiment which simultaneously allows the illumination of a TiO2 semiconductor electrode surface and the application of power ultrasound emission is described. The horn probe of an immersion horn transducer is modified by an oxide coated titanium tip and placed in a conventional three electrode electrochemical cell which allows light from a monochromated source to be focussed onto the electrode surface. Well-defined photocurrents are observed in aqueous media and for the photoinduced oxidation of water in acetonitrile and of 2.4-dichlorophenol in acetonitrile. The effect of ultrasound is to shift the observed photocurrent responses to more negative potentials and therefore to enhance the observed processes. Several possible interpretations associated with the complex effects induced by ultrasound are considered and a model based mainly on the extreme change of mass transport at the semiconductor/solution interface is suggested. Considerably enhanced performance for non-Nernstian processes, such as those observed in photoelectrochemical reactions at semiconductor electrodes, can be achieved in the presence of ultrasound.

Recently, spirometers have become available for use within general practice as an alternative to peak flow meters. This study investigates whether practice assistants, after comprehensive training, can effectively carry out spirometry with patients suffering from asthma and other chronic obstructive pulmonary diseases. A scoring system, consisting of 20 items, was devised to determine the effectiveness of the assistants' instructions and to assess the patient's subsequent use of the spirometer. About half the instructions and half the patient performance items were considered to be carried out satisfactorily.

Background: A previous two-year study of continuous and on demand bronchodilator therapy in patients with moderate asthma and chronic bronchitis showed a deterioration in lung function in those on continuous therapy., Aim: A two-year follow-up study was undertaken of patients who had been shown in the previous study to have non-steroid dependent (mild) asthma and chronic bronchitis, in order to investigate the effect of continuous and on-demand treatment with bronchodilator therapy., Method: Patients for the study were drawn from 29 general practices in the catchment area of the University of Nijmegen, the Netherlands. A total of 83 patients (27 with asthma and 56 with chronic bronchitis) were selected from a group of 160 patients who had completed the previous two-year bronchodilator trial. During these first two years the selected subjects had been shown to be non-steroid dependent (no rapid decline in lung function and a low number of exacerbations of their condition per year), and they were followed up for another two years of treatment with bronchodilator therapy. At the start of the four-year study, patients were randomly assigned to one of two parallel treatment groups: continuous treatment (dry powder inhalations of either salbutamol 1600 micrograms or ipratropium bromide 160 micrograms daily) or treatment on demand (only during exacerbations or periods of dyspnoea). Outcome parameters were the annual decline in lung function, changes in peak flow rate, bronchial hyper-responsiveness, exacerbation rate, respiratory symptoms and reported health., Results: After correction for possibly confounding variables and for regression to the mean, the decline in lung function was 49 ml year in patients taking bronchodilators continuously and 51 ml year in patients using bronchodilators on demand, irrespective of the drug use. Continuously treated patients, whether suffering from asthma or chronic bronchitis, did not differ from patients treated on demand with respect to mean morning peak flow rate, diurnal (and week to week) variation of the peak flow rate, bronchial hyper-responsiveness, exacerbation rate and reported health. There was no difference between the long-term effects of salbutamol and ipratropium., Conclusion: Continuous use of bronchodilators over four years in patients with non-steroid dependent asthma or chronic bronchitis does not increase the decline in lung function which had been observed previously in patients with moderate asthma or chronic bronchitis during two years of continuous treatment with bronchodilators.