Home-based exercise is capable of preserving hospital-based improvements in severe chronic obstructive pulmonary disease

We examined the feasibility of home-based walking training to maintain the benefits of a short-term exercise training in patients with severe chronic obstructive pulmonary disease (COPD). After initial recovery from an exacerbation, 46 patients were randomized into a training and a control group, and 30 patients completed the programme (mean +/- SD FEV1, 36 +/- 7% predicted). The training group performed a 10-day walking training programme in the hospital, followed by a 6-month programme of supervised walking training at home, integrated into daily activities. The control group did not have exercise training in the hospital or at home. Until 6 months after discharge, lung function, exercise performance and symptom scores were assessed. Six-minute walking distance in the training group improved from day 1 to day 10 (P<0.001) and this effect was maintained over 6 months (P<0.001). On average, daily walking distance at home was 2308 m and walking was reported on 157 days. Quality of life (QoL) scores changed significantly over 6 months (P<0.001). The control group showed no significant changes in exercise performance or QoL scores throughout the whole study period. Therefore, (i) significant improvements in exercise performance and Chronic Respiratory Disease Questionnaire (CRQ) scores could be achieved after recovery from an exacerbation and (ii) these improvements were maintained after discharge, when supported by a home-based walking training.

The therapeutic effect of theophylline in mild obstructive sleep Apnea/Hypopnea syndrome: results of repeated measurements with portable recording devices at home

Theophylline has been recommended in the literature as a therapeutic option in mild OSAHS. In mild obstructive sleep apnea/hypopnea syndrome (OSAHS), night-to-night variability of parameters of sleep-disordered breathing has been determined rarely, we therefore compared the results of serial measurements of sleep apnea/hypopnea parameters under the effects of placebo and theophylline. To this end, we measured the individual variability of the apnea-hypopnea index (AHI) for seven consecutive nights using a portable sleep apnea recording device, in 14 subjects (2 women, 12 men, mean age +/- [standard deviation] 50 +/- 8 years), treated with placebo or theophylline in a double blind, randomized crossover fashion, whose polysomnographically measured AHI was 13 +/- 5 /hour. Under theophylline treatment in comparison with placebo we observed a small but significant decrease in mean (of seven days) AHI at home (9.2 +/- 7.7 to 6.7 +/- 6.1 /hour), which was independent of body position. The night-to-night variability of AHI at home was high (9. 2 +/- 8.9 /hour; range: 0-31.4 /hour) and proved to be independent of body position and alcohol consumption. - In mild OSAHS, repeated measurements of sleep related breathing events should be performed. Theophylline showed a small but clinically insignificant potencial to reduce AHI.

Monitoring central and peripheral airway inflammation in asthma

Invasive methods involving bronchoscopy allow identification of the site of airway inflammation, although within the peripheral airways further distinctions are difficult. The method of induced sputum refers only to the central airways, and the analysis of exhaled NO to the airways as a whole. Therefore there is still a need for more refined tools to asses airway inflammation.

Modelling the production of nitric oxide within the human airways

The measurement of exhaled nitric oxide (NO) is well established for monitoring of airway inflammation in bronchial asthma. It is known that the concentration of NO determined as steady state (plateau) value at a constant expiratory flow rate depends on the flow rate chosen. This suggests that the exhaled NO is released within the conducting airways, whereas alveolar NO levels are negligible. The processes involved can be described through a lung model comprising an alveolar compartment and an airway compartment thought of as a pipe. This concept has been formulated mathematically and the models proposed in the literature are essentially equivalent. NO plateau levels obtained at different flow rates allow the estimation of 1) an effective airway wall NO concentration that represents the driving force for NO release, 2) an airway diffusing capacity for NO which depends on factors impeding or facilitating NO transport, including an increase in NO-producing surface area. Clinical studies will have to assess whether the knowledge of these or related parameters offers a significant advantage over the determination of exhaled NO at a single flow rate.

Flow cytometric analysis of the effect of dithiothreitol on leukocyte surface markers

Pretreatment with dithiothreitol (DTT) is necessary to dissolve mucus in samples of induced sputum prior to analysis. However, DTT may affect cell surface markers which are essential for lymphocyte subtyping. Therefore, the aim of this study was to evaluate the effect of DTT on an appropriate panel of surface markers. Peripheral blood leukocytes were used because these cells, in contrast to sputum cells, could be obtained without DTT treatment. Peripheral blood from healthy donors was incubated with either DTT according to standard sputum procedures or phosphate-buffered saline (PBS), washed and incubated with fluorochrome-labelled antibodies. After lysis of erythrocytes, analysis was performed using a calibrated flow cytometer. Leukocyte populations were identified by their light scattering properties. For analysis, fluorescence intensity was compared between DTT- and PBS-treated samples. After treatment with DTT, fluorescence intensity was significantly increased in CD16-positive granulocytes; it was reduced in CD2-positive lymphocytes, CD45-positive lymphocytes and CD14-positive monocytes (p < or = 0.001). These changes occurred in all samples. The fluorescence intensity of CD3-, CD4-, CD8-, CD19-, CD56- and histocompatibility leukocyte antigen DR-positive lymphocytes was not altered by DTT. However, there were statistically significant (p<0.001), although small, changes in the percentages of leukocytes. The present data demonstrate that, although dithiothreitol as used in sputum analysis affects some surface markers of peripheral blood leukocytes, comparability between samples concerning lymphocyte surface markers is preserved. Therefore, it is suggested that treatment of sputum samples with dithiothreitol does not invalidate the immunocytochemical analysis of lymphocytes.

Trends in bronchial hyperresponsiveness, respiratory symptoms and lung function among adults: West and East Germany. INGA Study Group. Indoor Factors and Genetics in Asthma

Previous studies have shown higher prevalences of bronchial hyperresponsiveness (BHR), respiratory symptoms and atopic sensitization among adults in Western Germany than in Eastern Germany. One of the aims of the joint project INGA (INdoor Factors and Genetics in Asthma) is to assess incidence, prevalence and trends for asthma, BHR and atopic diseases over a time period of 11 years (1990-2001) in the former West (Hamburg) and East Germany (Erfurt), with special reference to indoor exposure. INGA was designed as a case-control study following a cross-sectional study performed from 1990 to 1992 within the European Community Respiratory Health Survey (ECRHS). The database consisted of 1159 subjects in Hamburg and 731 subjects in Erfurt from the ECRHS (age 20-44). In 1995-1996, 107 cases (diagnosed asthma, positive specific serum IgE, positive skin prick or PD20FEV1< or =2.0 mg methacholine at ECRHS) and 106 controls (none of the previous findings) participated in Hamburg (115 cases and 109 controls in Erfurt). The methodology was identical to the ECRHS and dose-response slopes (DRS) of the methacholine challenge were calculated as an index of responsiveness. In the control group, median values of DRS were 0.028% mg(-1) (1990-1992) and 0.044 (1995-1996) (P<0.01) in Erfurt. Corresponding values for Hamburg were 0.028 and 0.022 (NS). Corresponding values within the case groups were 0.041 and 0.049 (NS) for Erfurt, and 0.069 and 0.052 (P<0.05) for Hamburg. Thus, 4 years after the first survey, we found an increased BHR in the Erfurt control group while the bronchial responsiveness remained unchanged for the Hamburg group. These trends in BHR, which indicate the expected converging tendency between East and West Germany, have to be confirmed within the next INGA-survey in 2000-2001.

Factor analysis of changes in dyspnea and lung function parameters after bronchodilation in chronic obstructive pulmonary disease

Expiratory airway collapse is a characteristic feature in patients with chronic obstructive pulmonary disease (COPD). We hypothesized that this collapse might mask the effects of bronchodilators during forced expiration but not during forced inspiration, and that accordingly, the improvement in forced inspiration and not that in forced expiration with bronchodilator therapy would be related to changes in the perception of dyspnea. In order to investigate this, we conducted lung function measurements, including measurements of forced inspiration and expiration before and 30 min after inhalation of 400 microg salbutamol, in 61 patients with COPD (mean FEV(1): 38. 3 L; range: 12.9 to 79.5% predicted). The change in dyspnea from baseline was assessed with a standard visual analogue scale (VAS) ranging from -100 to +100. To delineate the relationship between parameters, we used the statistical procedure of factor analysis. Salbutamol induced an improvement of 0.16 +/- 0.02 L (mean +/- SD) in FEV(1), 0.36 +/- 0.04 L in forced inspiratory volume in one second (FIV(1)), 0.30 +/- 0.04 L in inspiratory capacity (IC), and -0.34 +/- 0.07 L in intrathoracic gas volume; the mean VAS score was 36.4 +/- 3.2. Factor analysis demonstrated that the reduction in dyspnea at rest was primarily associated with changes in parameters describing forced inspiration and not with those of forced expiration or lung hyperinflation, including IC. Our data indicate that in patients with COPD, the reduction in dyspnea after inhalation of a beta(2)-adrenoreceptor agonist is closely correlated with the change in parameters of forced inspiration, and particularly FIV(1), but not with changes in parameters of forced expiration or lung hyperinflation.

The effect of repeated ozone exposures on inflammatory markers in bronchoalveolar lavage fluid and mucosal biopsies

The aim of this study was to investigate the cellular and biochemical events associated with repeated exposures to ozone. Twenty-three healthy subjects underwent single exposures to 200 ppb ozone and to filtered air (FA), as well as repeated exposures to 200 ppb ozone on 4 consecutive days, each for 4 h of intermittent exercise. Bronchoalveolar lavage was performed and mucosal biopsies were taken 20 h after the single or the last of the repeated exposures. As compared with FA, the single exposure to ozone caused a decrease in FEV(1), an increase in the percentages of neutrophils and lymphocytes, the concentrations of total protein, IL-6, IL-8, reduced glutathione, urate, and ortho-tyrosine in BAL fluid (BALF), but no changes in the cellular composition of biopsy. After the repeated exposure, the effect on lung function was abolished and differential cell counts in BALF were not significantly different from those after FA. However, the concentrations of total protein, IL-6, IL-8, reduced glutathione, and ortho-tyrosine were still increased. IL-10 could only be detected in BALF after repeated ozone exposures. Furthermore, macroscopic scores for bronchitis, erythema, and hypervulnerability of airway mucosa were increased, as well as numbers of neutrophils in bronchial mucosal biopsies. Our data demonstrate that airway inflammation persists after repeated ozone exposure, despite attenuation of some inflammatory markers in BALF and adaptation of lung function.

Efficacy and duration of action of the antileukotriene zafirlukast on cold air-induced bronchoconstriction

The objectives of the study were to assess the magnitude of the effect of the leukotriene receptor antagonist, zafirlukast, against cold air-induced bronchoconstriction following the first dose and to assess magnitude and duration after 5 days of dosing. Nineteen patients with asthma were included. In a randomized cross-over design, either zafirlukast 20 mg or 80 mg b.d. or placebo were given over 5 days. Challenges were performed 3 h post first dose and 3, 8, 12 and 24 h post last dose. The authors assessed the provocative ventilation rate necessary to achieve a 10% (PV10) and 20% (PV20) fall in forced expiratory volume in one second. The median PV20 3 h post first dose was 69.1 L x min-1 for zafirlukast 80 mg compared to 40 L x min-1 for placebo (p=0.004). The corresponding median value for zafirlukast 20 mg was 59.9 L x min-1 (p=0.06). At steady state the differences in PV20, between zafirlukast 80 mg and placebo were significant at 8 h and 12 h post last dose. The corresponding difference for zafirlukast 20 mg was statistically significant at 8 h post last dose. The analysis of PV10 yielded compatible results. There was no significant protection 24 h after last dose. This study has demonstrated that zafirlukast offers significant protection against cold air-induced bronchoconstriction in asthma. The degree and duration of protection were dose-dependent. However, there was a large interindividual variability for the protective effect of this leukotriene receptor antagonist.

Sequentially induced sputum in patients with asthma or chronic obstructive pulmonary disease

It has been demonstrated that consecutive samples of induced sputum may differ with respect to cellular composition. The aim of this study was to compare two sequential sputum samples in patients with chronic obstructive pulmonary disease (COPD) and asthma with different severity. Two sputum inductions were performed 30 min apart and processed separately in healthy subjects (n=11), patients with moderate to severe COPD (n=10), asthmatics treated with beta2-agonists alone (group 1, n=11), inhaled steroids (group 2, n=12) or systemic steroids (group 3, n=7). In healthy subjects and asthma group 2, percentages of neutrophils decreased significantly between the two sputum inductions but did not change in COPD and asthma group 3. Percentages of eosinophils did not change significantly in any group of patients. Concentrations of interleukin (IL)-8 decreased significantly in the control group and asthma groups 1 and 2 but not in asthma group 3 and the COPD group. These data demonstrate differences in sputum composition between two consecutive samples which were most pronounced in healthy subjects. Therefore, pooling of sputum samples may affect the results, particularly in healthy subjects, in contrast to subjects with more severe asthma or chronic obstructive pulmonary disease. These findings may be suggestive of differences in the distribution of inflammation along the airways between distinct airway diseases.

Ozone-induced airway inflammatory changes differ between individuals and are reproducible

To study whether the individual inflammatory response to ozone was reproducible, dose-dependent, and time-dependent, we performed two exposures to 250 ppb ozone, one to 125 ppb and one to filtered air, each for 3 h of intermittent exercise and separated by at least 1 wk. Twenty-one healthy and 15 asthmatic subjects participated in the study. One hour after the two exposures to 250 ppb ozone we observed a mean increase in sputum neutrophils of 17.9 and 17.9% in healthy and of 20.3 and 15.2% in asthmatic subjects (p < 0.05 each). Twenty-four hours after exposure, the respective values were 11.9 and 14.8%, and 9.1 and 16.1% (p < 0.05 each). In the whole group of subjects, individual changes in the percentage of neutrophils were significantly correlated between the two exposure days 1 h (r = 0.87, p < 0.001; intraclass correlation coefficient [Ri] = 0.86) as well as 24 h (r = 0.79, p < 0.001; Ri = 0.71) after exposure. The percentages of lymphocytes were increased 24 h after exposures (all subjects combined: p < 0.05). The decrease in FEV1 in both groups (p < 0.01), was also reproducible (r = 0.77, p < 0.001), but there were no correlations between changes in sputum parameters and lung function. Exposure to 125 ppb ozone caused a small increase (p < 0. 05) in the percentage of neutrophils in asthmatic subjects and in the concentrations of interleukin-8 in both groups combined. Our data demonstrate that inflammatory and lung function responses to ozone differ between individuals and are reproducible but not related to each other. Therefore, these responses appear to represent two independent factors underlying the airway response to ozone.

Oxidant-induced lung injury in anticancer therapy

Lung injury is one of the most frequent side effects in anticancer therapy. Especially simultaneous application of high doses of ionising radiation and radiosensitising cytotoxic drugs is considered to cause deleterious pneumonitis and pulmonary fibrosis. Growing evidence indicates that reactive oxygen species (ROS) play a key role in the development of these disorders. They are capable of causing cell component alterations and changing cellular protein expression. Observing these disease mechanisms reveals an impressive self-amplifying cascade of secondary ROS generation. Through intricate interactions between cells, cytokines and growth factors, fibroblasts are activated and thus pulmonary matrix content is massively increased. - As clinical appearance is uniform and unspecific, an early, reliable diagnosis of therapy-associated lung damage is not possible so far. However, improving this situation could enable us to take advantage of new multimodal therapeutic facilities. This review discusses mechanisms of ROS generation during radio-chemotherapy in the lung, antioxidant defense strategies and responses to oxidants, thereby assessing current diagnostic tools.

Exercise training improves recovery in patients with COPD after an acute exacerbation

Clinical experience suggests that exercise is beneficial for recovery after an acute exacerbation in patients with severe chronic obstructive pulmonary disease (COPD). The aim of this study was to quantify the clinical benefit of exercise in these patients. Twenty-nine inpatients were randomly assigned to a training group (n = 15, FEV1 34% pred) or a control group (n = 14, FEV1 38% pred). On ten consecutive days, patients in the training group performed a 6-min treadmill walking test and, in addition, five walking sessions per day at > or = 75% of the respective treadmill walking distance. Patients in the control group performed only treadmill walking tests on days 1, 5, and 10. To directly compare the possible benefit of exercise training all patients had an exercise test on day 11 at the same work load as on day 1. In the training group, 6-min walking distance increased from 237 to 420 m, in the control group from 230 to 255 m over the 10 day period which was significantly different (P < 0.0001). Minute ventilation and oxygen uptake increased significantly (P < 0.05) in the training but not in the control group. When comparing exercise tests on days 1 and 11, minute ventilation, oxygen uptake, PaCO2, lactic acid concentration, and Borg scale were significantly reduced to achieve the same work load (P < 0.01) only in the training group. Intrathoracic gas volume and residual volume decreased, and FEV1 and vital capacity increased in the training (P < 0.05) but not in the control group. Our data demonstrate that exercise training significantly improves the exercise capacity in patients with severe COPD after an acute exacerbation of their disease.

Assessment of accuracy and applicability of a new electronic peak flow meter and asthma monitor

The aim of this study was to assess the accuracy and applicability of a portable electronic peak flow meter combined with an asthma monitor (AM1, Jaeger, Germany) which measures peak expiratory flow (PEF), forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). The technical accuracy in PEF, FEV1 and FVC measurement was tested according to American Thoracic Society (ATS) criteria for monitoring devices using a flow generator. In addition, the effect of connecting a heated screen pneumotachograph (PT) to the AM1 was determined and the accuracy in FEV1 determinations was evaluated by simultaneous measurements in 49 normal volunteers. The devices tested fulfilled all ATS criteria for monitoring devices with respect to the accuracy of PEF, FEV1, and FVC measurements. The conditions of intra- and interdevice variability were satisfied in all cases. Compared with the PT, the AM1 showed about 4% lower values in FEV1, as measured in the 49 subjects. In conclusion, the electronic peak flow meter and asthma monitor AM1 yielded valid measurements of peak expiratory flow and forced expiratory volume in one second, which matched the accuracy criteria of the American Thoracic Society standards for monitoring devices.

Interactions between human bronchoepithelial cells and lung fibroblasts after ozone exposure in vitro

Long-term exposure to ozone has been shown to cause lung fibrosis and increased collagen synthesis by fibroblasts in experimental animals. As the bronchial epithelium appears to play a major regulatory role in inflammatory processes, we investigated whether ozone induces bronchoepithelial cells in vitro to increase gene expression of procollagens and other fibrogenic mediators in human lung fibroblasts. Membrane cultures of human airway epithelial cells (BEAS-2B) in the presence or absence of lung fibroblast (HFL-1) cultures were exposed to air or 500 ppb ozone for 1 h, followed by (co-)incubation periods of 11 and 23 h. After ozone exposure of the co-cultures, there were substantial increases of steady-state mRNA levels of both alpha1 procollagens type I and III as well as TGF beta1 in the fibroblasts above the corresponding air control levels. In the absence of ozone, the presence of epithelial cells always caused significant decreases in the basal steady-state mRNA levels of both procollagens as compared to their absence. There were no significant effects of ozone on the secretion or gene expression of TGF beta2, PDGF or IL-8 in any cell type. In contrast, co-culture condition induced altered patterns of IL-8 gene expression or of PDGF production in fibroblasts and bronchoepithelial cells, respectively, both in the absence or presence of ozone. In summary, our data demonstrate that the effect of ozone on fibroblasts was mediated by epithelial cells and that mutual regulatory interactions between the different cell types occur. Thus, our co-cultivation system in vitro appears to be able to mimic the in vivo situation providing insight into the nature of cellular interactions and modulation by ozone, which may occur in the whole organism after long-term exposure.

Changes in sputum composition during sputum induction in healthy and asthmatic subjects

BACKGROUND

Induced sputum is increasingly used to characterize the cellular and biochemical composition of the airways.

OBJECTIVE

We studied whether the composition of induced sputum is different between samples obtained sequentially during one sputum induction.

METHODS

Subjects with mild asthma (n=7) or healthy subjects (n=6) produced sputum during and after three consecutive 10 min periods of hypertonic saline inhalation. Samples were analysed separately for the three periods. To determine the reproducibility of the cellular composition, sputum induction was repeated on another two days.

RESULTS

The mean percentage of neutrophils decreased significantly (P<0.01) during sputum induction in asthmatic (36.9, 29.8, 16.3%) and healthy subjects (43.6, 17.2, 18.0%). Correspondingly, percentages of macrophages increased and percentages of eosinophils were 4.9, 3.5, and 3.7% in the asthmatic and 0.6, 0.7, and 0.5% in the healthy subjects, without significant change over the three periods; mean eosinophil numbers were significantly higher in the subjects with asthma (P< 0.05). Reproducibility of percentage cell counts did not markedly depend on sampling periods in terms of coefficients of variation. The concentration of eosinophil cationic protein decreased in both groups during sputum induction (P<0.01), geometric mean values being 579, 143, 57.4 microg L(-1) in the asthmatic and 130, 47.3, 28.4 microg L(-1) in the healthy subjects. Similar changes were seen for lactate dehydrogenase.

CONCLUSION

The separate analysis of induced sputum from three consecutive sampling periods of a single induction procedure demonstrated significant changes in their cellular and biochemical composition, both in healthy and mild asthmatic subjects.

Changes in sputum composition between two inductions performed on consecutive days

BACKGROUND

Sputnum induction is a non-invasive method for obtaining cellular and biochemical material from the airways and appears to be particularly suited for repeated testing. However, it has not been clarified whether repeated inductions lead to a change in sputum composition. The aim of this study was to compare induced sputum results between two inductions performed 24 hours apart.

METHODS

Ten subjects with mild asthma and 19 healthy subjects were included. Sputum was obtained during three consecutive 10 minute periods of hypertonic saline inhalation. Samples were analysed separately for the three inhalation periods. Corresponding pooled values were computed, taking into account total cell numbers of each inhalation period.

RESULTS

In the three consecutive inhalation periods mean (SE) percentages of neutrophils increased from 29.2 (4.2)%, 22.0 (4.6)% and 14.5 (2.9)% on day 1 to 43.1 (5.3)%, 34.8 (5.5)% and 25.7 (5.3)% on day 2 in healthy subjects and from 21.3 (4.3)%, 24.1 (5.9)% and 15.9 (3.7)% to 35.9 (6.9)%, 30.7 (7.1)% and 31.8 (6.5)% in asthmatic subjects. This parallel shift corresponded to a mean (95% CI) increase in the pooled percentages of neutrophils of 17.4 (11.6) to 23.3)% in healthy and 14.6 (1.2 to 28.0)% in asthmatic subjects. In contrast to neutrophils, the percentage of macrophages decreased from day 1 to day 2, while eosinophil and lymphocyte percentages did not change significantly.

CONCLUSION

These results suggest that the induction procedure itself causes a change in the composition of sputum detectable after 24 hours. This effect has to be taken into account when repeated sputum induction is performed.

Age-dependent differences in the prevalence of allergic rhinitis and atopic sensitization between an eastern and a western German city

Recent studies have found a higher prevalence of allergic rhinitis and atopic sensitization among adults living in eastern than those living in western Germany. We hypothesize that prevalence rates were similar before Germany was divided and diverged after the division. Because there are no historical data comparing atopic status between the two parts of Germany, we tested this hypothesis by comparing the prevalence of atopy among persons who were born during different decades. As part of the EC Respiratory Health Survey, a respiratory health questionnaire was mailed to a population-based sample of 8363 subjects aged 20-44 years from a city in the former West Germany (Hamburg) and a city in the former East Germany (Erfurt). Of the target population, 6428 (77%) subjects responded. Subsamples of 731 subjects from Erfurt and 1159 subjects from Hamburg participated in medical examinations, including skin prick tests and specific IgE measurements. Prevalence rates of allergic sensitization were similar in Hamburg and Erfurt for those born in the periods 1946-51 and 1952-61, respectively, but differed between Hamburg and Erfurt subjects born in the period 1962-71. After adjustment for several potential predictors, the younger subjects from Hamburg had a higher odds ratio (OR) of sensitization than those Hamburg subjects born before 1952 (skin prick test reactivity: OR 2.06, any specific IgE > 0.35 kU/l: OR 1.61). The younger subjects from Erfurt were not more frequently sensitized than the older subjects (skin prick test reactivity: OR 1.05, any specific IgE > 0.35 kU/l: OR 0.79). No single allergen could be identified as responsible for the observed difference. We conclude that factors related to a "Western lifestyle", which were prevalent in the West German city during the 1960s and 1970s, may be responsible for the higher prevalence of allergic sensitization observed in Hamburg.

Airway responsiveness to sulfur dioxide in an adult population sample

We determined the prevalence of airway hyperresponsiveness to sulfur dioxide (SO2) in an adult population sample of 790 subjects 20 to 44 yr of age. Subjects were drawn randomly from the population of Hamburg, Northern Germany, within the framework of the European Community Respiratory Health Survey. In addition, we analyzed the relationship between SO2 responsiveness and a number of risk factors, such as a history of respiratory symptoms, methacholine responsiveness, and atopy derived from skin-prick test results. SO2 inhalation challenges were performed during isocapnic hyperventilation at constant rate (40 L x min(-1), for 3 min) with doubling concentrations of SO2 up to a maximum concentration of 2.0 ppm. If subjects achieved a 20% decrease in FEV1 from baseline during the challenge, they were considered to be hyperresponsive to SO2. The raw prevalence of SO2 hyperresponsiveness within the population sample studied was 3.4% (95% confidence interval [CI]: 2.3 to 5.0%). Adjustment for nonparticipation led to an estimated prevalence of SO2 hyperresponsiveness of 5.4%. Among subjects with hyperresponsiveness to methacholine, 22.4% (95% CI: 20.1 to 25.3) demonstrated hyperresponsiveness to SO2. There was no significant correlation between the degrees of hyperresponsiveness to methacholine and SO2. Predictors of a positive SO2 response were hyperresponsiveness to methacholine (p < 0.0001), a positive history of respiratory symptoms (p < 0.05), and a positive skin-prick test to at least one common allergen (p < 0.05). We conclude from these data that airway hyperresponsiveness to SO2 can be found in about 20 to 25% of subjects within the 20- to 44-yr age range who are hyperresponsive to methacholine.

Citric acid-induced cough thresholds in normal subjects, patients with bronchial asthma, and smokers

Several challenge procedures have been developed to characterize the cough reflex in patients with airway diseases. This study was performed to compare the interindividual range of cough sensitivity in asthmatic and normal subjects as well as smokers using an identical method. Sixteen normal subjects, 20 patients with mild bronchial asthma, 6 patients with moderate to severe bronchial asthma, 9 current smokers, and 7 occasional smokers were included. In all subjects, methacholine challenges and standardized citric acid challenges were performed. Sensitivity of the cough reflex was expressed as cough threshold, i.e., as concentration at which coughing occurred. Reproducibility was assessed in 23 subjects. Within a concentration range of 0.625-320.0 mg/ml, inhaled citric acid caused cough in all subjects. Geometric mean (range) cough threshold was 13 (2.5-160) in normal subjects, 14 (5-40) in patients with mild, and 32 (20-40) mg/ml in patients with moderate to severe asthma, 40 (20-80) in current smokers, and 119 (80-160) in occasional smokers. Cough thresholds were reproducible within one doubling concentration. In normal subjects and patients with mild bronchial asthma, thresholds were not significantly different from each other but lower than those of the other groups (p<0.05 each). Cough thresholds in smokers and patients with moderate to severe asthma did also not differ significantly and were lower than in occasional smokers (p<0.05). There was no significant correlation between cough threshold, baseline FEV subset1 , and methacholine responsiveness. Our data indicate that (1) subjects with mild asthma showed on average similar cough thresholds as normal subjects, (2) there was a large variation in cough thresholds within groups, (3) the reproducibility of cough thresholds was within one doubling concentration, (4) cough thresholds did not correlate with methacholine responsiveness or baseline airway tone. In view of the prevalence of cough as a symptom of bronchial asthma, it appears that the determination of citric acid-induced cough thresholds does not yield additional diagnostic information in these subjects.

Effect of a nasal challenge with endotoxin-containing swine confinement dust on nasal nitric oxide production

Inhalation of swine confinement dust containing endotoxin causes an inflammatory response in the nose as reflected by an influx of neutrophils 3 hrs after exposure (Am J Respir Crit Care Med 149: A401(1994)). As there is evidence that nitric oxide (NO) in exhaled air indicates cellular activation, we studied whether endotoxin causes an increase in nasal NO production in human subjects. Seven healthy subjects underwent a nasal challenge in which 50 mg swine confinement dust was given into each nostril (endotoxin concentration, 23.6 microg . g-1). Exhaled NO was measured before and during 3 hrs after the challenge and was compared to control values measured over the same period of time. Endotoxin produced a slight but statistically significant (p = 0.017) increase in nasal NO concentrations, mean (+/-SEM) values over 3 hrs being 367.5 +/- 7.5 ppb after endotoxin and 342.1 +/- 7.2 ppb under control conditions. The difference was most pronounced during the first hour after the challenge. We conclude that nasal administration of endotoxin causes a short-term increase in NO production which must precede cell influx or upregulation of transcription.

A short protocol for methacholine provocation testing adapted to the Rosenthal-Chai dosimeter technique

BACKGROUND

The purpose of this study was to develop a rapid and safe methacholine provocation protocol equivalent to the standard dosimeter technique.

METHODS

The rapid protocol comprised a short and a long subprotocol. The challenge was started with one of these subprotocols according to the subject's answers to a questionnaire and baseline lung function. If FEV1 dropped by 10% during the short subprotocol, the test was continued with the long subprotocol. The concentrations of methacholine and numbers of inhalations were chosen to match the concentrations of the standard method as closely as possible. To verify the protocol, we compared both methods in 38 subjects with asthma and 10 control subjects.

RESULTS

The provocative concentrations of methacholine (PC20FEV1) obtained with the standard method and the rapid method were within one doubling concentration in 38 of 40 subjects. None of the subjects who were normoreactive according to the standard method (PC20FEV1 > 8 mg/mL) responded in the rapid protocol. The standard method required, on average (+/-SD), 34+/-11 min; the rapid method required 15+/-3 min.

CONCLUSIONS

The rapid provocation protocol is equivalent to the standard method, without loss in precision and safety, but with considerable saving in time. Therefore, it appears to be particularly suited for studies that require comparability with provocative concentrations obtained with the Rosenthal-Chai dosimeter method.

[Comparison of nasal and bronchial production of nitric oxide in healthy probands and patients with asthma]

Nitric oxide (NO) appears to play an important role in the pathophysiology of airway diseases as suggested from measurements of NO in exhaled air, animal and in vitro experiments. As NO is produced in variable amounts within the bronchial system and the nose, we studied the relationship between nasal and bronchial production of NO in patients with asthma and determined to which extent these productions were increased compared to healthy subjects. The nasal and bronchial production rates of NO as a function of breathholding time were assessed in 10 healthy subjects, 7 patients with asthma without inhaled corticosteroids, and 5 patients with asthma and a therapy of inhaled corticosteroids. After a breathhold of 10 s bronchial NO concentrations were elevated in the patients with asthma without steroids by the factor 3.5 (p < 0.005) and nasal concentrations by the factor 1.2 (n.s.) compared to healthy subjects. NO concentrations increased with time. Correspondingly, bronchial production rates were increased by factor 2.7 (p < 0.01) and nasal production rates by factor 1.1 (n.s.) in asthmatic compared to healthy subjects. The asthmatic patients with steroids showed lower production rates than those without steroids. We conclude from these data that in patients with asthma as compared to normal subjects bronchial production of NO is markedly increased, whereas the corresponding relative increase in nasal production is lower.