Human airway narrowing measured using high resolution computed tomography

Exaggerated airway narrowing in response to bronchoconstricting stimuli is a characteristic feature of asthmatic subjects. It is unknown whether the site of airway narrowing differs in asthmatic subjects from that observed in normal subjects. Increased airway wall thickness has been suggested as a contributing cause for airway hyperresponsiveness in asthma, based on histologic measurements. We measured airway wall thickness and the site and magnitude of airway narrowing in response to inhaled methacholine in normal subjects and in patients with mild to moderate asthma using high resolution computed tomography (HRCT). After a comparable decrease in FEV1, there were no differences in the site or magnitude of airway narrowing for any category of airway size in asthmatic subjects and normals. However, the results show that the smaller airways of the asthmatic subjects are significantly thickened and that the airway wall area does not change after bronchoconstriction whereas it decreases in normal subjects. We conclude that airway wall thickening and the lack of a change in airway wall dimensions following bronchoconstricting stimuli could contribute to exaggerated airway narrowing in asthma.

Decreased bronchodilating effect of salbutamol in relieving methacholine induced moderate to severe bronchoconstriction during high dose treatment with long acting beta2 agonists

BACKGROUND

In vitro the long acting beta2 agonist salmeterol can, in contrast to formoterol, behave as a partial agonist and become a partial antagonist to other beta2 agonists. To study this in vivo, the bronchodilating effect of salbutamol was measured during methacholine induced moderate to severe bronchoconstriction in patients receiving maintenance treatment with high dose long acting beta2 agonists.

METHODS

A randomised double blind crossover study was performed in 19 asthmatic patients with mean forced expiratory volume in one second (FEV1) of 88.4% predicted and median concentration of methacholine provoking a fall in FEV1 of 20% or more (PC(20)) of 0.62 mg/ml at entry. One hour after the last dose of 2 weeks of treatment with formoterol (24 microg twice daily by Turbuhaler), salmeterol (100 microg twice daily by Diskhaler), or placebo a methacholine provocation test was performed and continued until there was at least a 30% decrease in FEV1. Salbutamol (50 microg) was administered immediately thereafter, followed by ipratropium bromide (40 microg) after a further 30 minutes. Lung function was monitored for 1 hour after provocation.

RESULTS

There was a significant bronchodilating and bronchoprotective effect after 2 weeks of active treatment. The dose of methacholine needed to provoke a fall in FEV1 of > or = 30% was higher after pretreatment with formoterol (2.48 mg) than with salmeterol (1.58 mg) or placebo (0.74 mg). The difference between formoterol and salmeterol was statistically significant: 0.7 doubling dose steps (95% CI 0.1 to 1.2, p=0.016). The immediate bronchodilating effect of subsequently administered salbutamol was significantly impaired after pretreatment with both drugs (p<0.0003 for both). Three minutes after inhaling salbutamol the increase in FEV1 relative to the pre-methacholine baseline was 15.8%, 7.3%, and 5.5% for placebo, formoterol and salmeterol, respectively (equivalent to increases of 26%, 14%, and 12%, respectively, from the lowest FEV1 after methacholine). At 30 minutes significant differences remained, but 1 hour after completing the methacholine challenge FEV1 had returned to baseline values in all three treatment groups.

CONCLUSION

Formoterol has a greater intrinsic activity than salmeterol as a bronchoprotective agent, indicating that salmeterol is a partial agonist compared with formoterol in contracted human airways in vivo. Irrespective of this, prior long term treatment with both long acting beta2 agonists reduced the bronchodilating effect of an additional single dose of salbutamol equally, indicating that the development of tolerance or high receptor occupancy overshadowed any possible partial antagonistic activity of salmeterol. Patients on regular treatment with long acting beta2 agonists should be made aware that an additional single dose of a short acting beta2 agonist may become less effective.

Heterogeneity of narrowing in normal and asthmatic airways measured by HRCT

Asthmatic airway narrowing is heterogeneous and contributes to airway hyperresponsiveness. The present study compared heterogeneity of narrowing during methacholine challenge in asthmatics and normal subjects using high-resolution computed tomography (HRCT). The current authors defined heterogeneity as variability in narrowing greater than the repeatability of measurement. Airways of <2 mm diameter were compared with larger airways from baseline and postmethacholine HRCT of the right lower lung in 13 normals (seven had repeat baseline scans) and seven asthmatics. The coefficient of repeatability was calculated from repeat scans (RepAi) and was compared with heterogeneity of narrowing measured by the variability in narrowing from pre versus postmethacholine scans (VardeltaAi). Forced expiratory volume in one second decreased 27+/-6% and 24+/-8% in normals and asthmatics, respectively. Airways >2 mm narrowed more heterogeneously in asthmatics (VardeltaAi=+/-0.85 mm) compared with normals (VardeltaAi=+/-0.67 mm), with both being greater than the measure of repeatability (RepAi=+/-0.16 mm). Small airway narrowing was not heterogeneous in asthmatics (VardeltaAi=+/-0.59 mm) or normals (VardeltaAi=+/-0.53 mm) compared with repeatability (RepAi=0.51 mm). It is possible to study heterogeneity of airway narrowing in small and large airways using high resolution computed tomography. Airway narrowing is heterogeneous in the large airways of asthmatics and normals, being greater in asthmatics.

Sputum CD34+IL-5Ralpha+ cells increase after allergen: evidence for in situ eosinophilopoiesis

Eosinophil lineage-committed progenitors increase in the bone marrow of subjects with asthma developing allergen-induced airway hyperresponsiveness and eosinophilia. Also, higher numbers of circulating eosinophil/basophil cfu have been demonstrated 24 hours after allergen inhalation and in bronchial and nasal biopsies of allergic individuals. These cells may undergo in situ eosinophilopoiesis, suggesting that after allergen inhalation, progenitor cells traffic from the bone marrow to the airways, providing an ongoing source of effector cells. To examine this possibility, CD34(+) and CD34(+)IL-5Ralpha(+) cells were measured in induced sputum from allergic subjects with asthma at baseline and at 7 and 24 hours after allergen and diluent inhalation, using flow cytometry. Isolated early responders (n = 9) were contrasted to dual responders (n = 9), who develop allergen-induced sputum and blood eosinophilia and airway hyperresponsiveness, and to normal control subjects. At baseline, there were significantly fewer sputum eosinophils and CD34(+) cells in normal control subjects compared with subjects with asthma. Sputum CD34(+) cells increased at 7 hours after allergen inhalation in both groups of subjects with asthma, which was sustained at 24 hours in the dual responder group only, associated with sustained increases in sputum CD34(+)IL-5Ralpha(+) cells, eosinophils, and interleukin-5. These results indicate that eosinophil progenitors can migrate to the airways and may differentiate toward an eosinophilic phenotype.

Vocal cord dysfunction induced by methacholine challenge testing

STUDY OBJECTIVES

To determine whether methacholine challenge testing (MCT) provokes vocal cord dysfunction (VCD), as evidenced by inspiratory vocal cord closure on direct laryngoscopy, and whether spirometry and flow-volume loops (FVLs) demonstrate any changes that are suggestive of VCD.

DESIGN

Prospective, controlled study.

SETTING

Army medical center.

PATIENTS

Thirty-four subjects all with normal baseline spirometry. Ten subjects had documented evidence of VCD, 12 subjects had exercise-induced asthma (EIA) and reactive MCT, and 12 subjects served as healthy asymptomatic control subjects.

METHODS

Measurement of spirometry with FVLs and direct laryngoscopy of the vocal cords performed immediately before and after subjects had undergone MCT.

RESULTS

Evidence of inspiratory vocal cord adduction was found in four VCD patients. Two patients had adducted vocal cords at baseline, and their conditions were unchanged after undergoing MCT. Two other patients had normal conditions at baseline and demonstrated acute inspiratory vocal cord adduction after undergoing MCT. None of the patients in the EIA or control groups had evidence of VCD at baseline or after undergoing MCT. Truncation of the inspiratory limb of the FVL after MCT was noted in five patients, which correlated with evidence of VCD in 60% of these patients. One EIA patient had truncation of the inspiratory FVL after MCT, and no changes were found in the control group. A comparison of spirometry between EIA patients and VCD patients with and without evidence of inspiratory vocal cord adduction during MCT showed no significant differences.

CONCLUSIONS

The findings suggest that MCT may cause an acute episode of vocal cord adduction and that positive results may not reflect underlying reactive airways disease. However, a flattening or truncation of the inspiratory FVL after the patient undergoes MCT is not diagnostic for the presence of inspiratory vocal cord adduction.

Measuring the prevalence of bronchial hyper-responsiveness in children

BACKGROUND

The aim of this study was to assess the effectiveness of an asthma prevalence video questionnaire (involving the audiovisual presentation of clinical asthma), a standard written questionnaire (based on the IUATLD Bronchial Symptoms Questionnaire) and a new written questionnaire (designed for an international study of asthma and allergies in childhood [ISAAC]) in predicting bronchial hyper-responsiveness (BHR) (PD20 < or = 7.8 mumol methacholine).

METHODS

The IUATLD and video questionnaires were administered to 193 schoolchildren (13-16 years). The ISAAC questionnaire was administered to 87 of these children. All children subsequently underwent bronchial challenge to methacholine.

RESULTS

The sensitivity and specificity for predicting BHR were similar for individual questions from the IUATLD and video questionnaires. The video questions with the highest Youden's index related to moderate wheezing at rest (0.46), severe wheezing at rest (0.38), and nocturnal wheezing (0.37). The ISAAC questionnaire was similar in effectiveness to the IUATLD questionnaire in predicting BHR.

CONCLUSIONS

The video questionnaire is a valid method of assessing the prevalence of BHR, and may be particularly useful when comparing populations with differing languages and cultures. Some video questions appeared more effective than others in relation to predicting BHR. A new written questionnaire (ISAAC) designed for a large international asthma prevalence study in children also is an effective method for measuring the prevalence of BHR.

Attenuation of early and late phase allergen-induced bronchoconstriction in asthmatic subjects by a 5-lipoxygenase activating protein antagonist, BAYx 1005

BACKGROUND

The cysteinyl leukotrienes (LTC4, LTD4 and LTE4) have been implicated in the pathogenesis of allergen-induced airway responses. The effects of pretreatment with BAYx 1005, an inhibitor of leukotriene biosynthesis via antagonism of 5-lipoxygenase activating protein, on allergen-induced early and late asthmatic responses has been evaluated.

METHODS

Eight atopic subjects with mild asthma participated in a two period, double blind, placebo controlled, cross-over trial. Subjects were selected on the basis of a forced expiratory volume in one second (FEV1) of > 70% predicted, a methacholine provocative concentration causing a 20% fall in FEV1 (PC20) of < 32 mg/ ml, a documented allergen-induced early response (EAR, > 15% fall in FEV1 0-1 hour after allergen inhalation) and late response (LAR, > 15% fall in FEV1 3-7 hours after allergen inhalation), and allergen-induced airway hyperresponsiveness (at least a doubling dose reduction in the methacholine PC20 30 hours after allergen inhalation). During the treatment periods subjects received BAYx 1005 (500 mg twice daily) or placebo for 3.5 days; treatment periods were separated by at least two weeks. On the third day of treatment, two hours after administration of medication, subjects performed an allergen inhalation challenge and FEV1 was measured for seven hours.

RESULTS

Treatment with BAYx 1005 attenuated the magnitude of both the allergen-induced early and late asthmatic responses. The mean (SE) maximal fall in FEV1 during the EAR was 26.6 (3.3)% during placebo treatment and 11.4 (3.3)% during treatment with BAYx 1005 (mean difference 15.2 (95% confidence interval (CI) 9.4 to 21.00) with a mean protection afforded by BAYx 1005 of 57.1%. The mean (SE) maximal fall in FEV1 during the LAR was 19.8 (5.7)% during placebo treatment and 10.7 (4.4)% during BAYx 1005 treatment (mean difference 9.2 (95% CI 1.4 to 17.0) with a mean protection afforded by BAYx 1005 of 46.0%. The area under the time response curve (AUC0-3) was also reduced after treatment with BAYx 1005 compared with placebo by 86.5%.h (mean difference 26.3 (95% CI 17.1 to 38.5)) and the AUC3-7 by 59.6%.h (mean difference 26.9 (95% CI-3.8 to 57.6)).

CONCLUSIONS

These results show that antagonism of 5-lipoxygenase activating protein can attenuate allergen-induced bronchoconstrictor responses and support an important role for the cysteinyl leukotrienes in mediating these asthmatic responses.

Effects of bronchial obstruction on lower esophageal sphincter motility and gastroesophageal reflux in patients with asthma

The relationship between gastroesophageal reflux and asthma remains unclear. The aim of this study was to analyze the effect of bronchial obstruction on lower esophageal sphincter (LES) motility and reflux in patients with asthma. LES motility and esophageal pH were assessed in eight subjects with intermittent asthma and eight healthy volunteers during three consecutive 30-minute periods: baseline, methacholine-induced bronchospasm, and after inhalation of the beta2-agonist salbutamol. Healthy subjects inhaled 2 mg of methacholine, whereas subjects with asthma inhaled the dose of methacholine causing a 15% fall in FEV(1), as determined by a previous methacholine challenge. LES motility, esophageal pH, and FEV(1) were not significantly different between the three periods in healthy subjects. In patients with asthma, methacholine induced a 21.9 +/- 2.6% decrease in FEV(1) and a concomitant increase in the rate of transient LES relaxation (TLESR) and reflux episodes. Inhalation of salbutamol decreased the rate of TLESRs but not the number of reflux episodes. We conclude that in patients with asthma, methacholine-induced bronchospasm increases the rate of TLESR and the number of reflux episodes. These results support the belief that, in asthma, bronchial obstruction may be responsible for reflux or may aggravate reflux through a mechanism that remains to be further clarified.

Variants in the vitamin D receptor gene and asthma

BACKGROUND

Early lifetime exposure to dietary or supplementary vitamin D has been predicted to be a risk factor for later allergy. Twin studies suggest that response to vitamin D exposure might be influenced by genetic factors. As these effects are primarily mediated through the vitamin D receptor (VDR), single base variants in this gene may be risk factors for asthma or allergy.

RESULTS

951 individuals from 224 pedigrees with at least 2 asthmatic children were analyzed for 13 SNPs in the VDR. There was no preferential transmission to children with asthma. In their unaffected sibs, however, one allele in the 5' region was 0.5-fold undertransmitted (p = 0.049), while two other alleles in the 3' terminal region were 2-fold over-transmitted (p = 0.013 and 0.018). An association was also seen with bronchial hyperreactivity against methacholine and with specific immunoglobulin E serum levels.

CONCLUSION

The transmission disequilibrium in unaffected sibs of otherwise multiple-affected families seem to be a powerful statistical test. A preferential transmission of vitamin D receptor variants to children with asthma could not be confirmed but raises the possibility of a protective effect for unaffected children.

Sensitivity to methacholine and capsaicin in patients with unclear respiratory symptoms

BACKGROUND

Capsaicin, the pungent ingredient in red pepper, is known to stimulate coughing via the sensory nervous system. Earlier studies showed that patients with airway symptoms induced by chemicals and strong scents cough more after inhalation of capsaicin than healthy control subjects and this has been interpreted as a hyperreactivity of airway sensory nerves. Our aim was to study airway sensitivity to inhaled capsaicin and the occurrence of airway symptoms induced by strong scents in patients who underwent a bronchial methacholine test, primarily because of suspected asthma.

METHODS

Fifty-two consecutive patients referred for testing with methacholine were also provoked with inhaled capsaicin in increasing concentrations. Cough sensitivity to capsaicin was compared with that in 40 healthy control subjects.

RESULTS

The patients coughed significantly more compared with the healthy control subjects with each dose of capsaicin (P < 0.0001). Twelve patients (23%) had a positive methacholine test, and of these, nine were diagnosed with asthma. There was no difference in capsaicin sensitivity between patients sensitive or insensitive to methacholine.

CONCLUSIONS

The majority of the patients had no increased sensitivity to methacholine but did demonstrate sensory hyperreactivity (SHR). SHR appears to be a common diagnosis in investigations of patients with obscure airway symptoms.

Suppression of the asthmatic phenotype by ultraviolet B-induced, antigen-specific regulatory cells

BACKGROUND

Over recent decades, there has been a significant global increase in the prevalence of asthma, an inflammatory disease of the respiratory system. While ultraviolet radiation (UV) has been used successfully in the treatment of inflammatory conditions such as psoriasis, studies of UV-induced regulation of allergic respiratory responses have been rare, and have not analysed in vivo measurements of airway hyperresponsiveness (AHR) or the antigen specificity of the UV-induced effects.

OBJECTIVE

To investigate the regulatory properties of erythemal ultraviolet B (UVB) irradiation of the skin and the induction of allergen-induced airway immunity in a murine asthma model, and to examine the mechanisms involved.

METHODS

BALB/c mice were exposed to a single erythemal dose of UV 3 days before intraperitonial sensitization (day 0) and boost (day 14) with the antigen, ovalbumin (OVA). Airway-associated, asthma-like responses to aerosolized OVA at day 21 were analysed including (a) AHR measured in vivo, (b) OVA-specific proliferative responses and cytokine production by cells from the lung-draining lymph nodes (LDLN), and (c) inflammatory cells and cytokines in the bronchoalveolar lavage fluid. To determine UVB-induced mechanisms of regulation, LDLN cells from UVB irradiated, OVA-sensitized mice were adoptively transferred into naïve BALB/c mice that were subsequently sensitized and challenged with OVA, or a non-specific antigen.

RESULTS

UVB irradiation of skin significantly suppressed AHR to methacholine and OVA-specific responses in the LDLN and in the lung compartment. Reduced OVA-specific responses by LDLN cells from both UVB irradiated mice and mice that received 5 x 10(6) LDLN cells from UVB irradiated, but not from non-irradiated, OVA-sensitized mice suggested that UVB-induced regulatory cells are responsible for many of the asthma-reducing effects of dorsal UVB exposure.

CONCLUSION

UVB irradiation of skin suppresses AHR and cellular responses of the airways to respiratory allergens. Further, this study implicates UVB or its downstream mediators as a potential approach to reducing the severity of asthma.

Dose-dependent effects of inhaled mometasone furoate on airway function and inflammation after allergen inhalation challenge

Comparisons of the potency of different inhaled corticosteroids, delivery devices, and treatment regimens in the management of asthma can only be made when outcome measurements display a dose-dependent effect. These outcomes have been difficult to identify. In this study, we compared in a randomized, double-blind, crossover design, the effects of 6 d treatment with placebo and three doses (50, 100, and 400 microg, twice daily) of mometasone furoate delivered by dry powder inhaler (MF-DPI) on responses after allergen inhalation challenge. Twelve mild asthmatic subjects with dual responses after allergen inhalation were studied. Outcome measurements included early and late asthmatic responses, the change in methacholine airway responsiveness 24 h after challenge, and sputum eosinophilia measured 7 and 24 h after challenge. All three doses of MF-DPI demonstrated similar attenuation of early responses and allergen-induced airway hyperresponsiveness relative to placebo (p < 0.05). The late maximal %fall in FEV(1) after placebo treatment was 23.5% and was significantly reduced in a dose-dependent manner to 12.3%, 11.0%, and 5.9% for the 50-, 100-, and 400-microg twice-daily treatments (p = 0.007). The allergen-induced increase in sputum eosinophilia (x10(4) cells/ml) 24 h after challenge during placebo treatment was 60.2 and was significantly reduced to 24.0, 15.3, and 6.2 for the 50-, 100-, and 400-microg twice-daily treatments. MF-DPI is effective at attenuating allergen-induced early and late responses, airway hyperresponsiveness, and sputum eosinophilia, and dose-response effects exist for the attenuation of the late response.

Bronchoprotective and bronchodilator effects of single doses of (S)-salbutamol, (R)-salbutamol and racemic salbutamol in patients with bronchial asthma

OBJECTIVES

The drug salbutamol is used as a 50: 50 racemic mixture of its two enantiomers, (R)- and (S)-salbutamol. Previous studies suggest that the (R)-enantiomer is active, and the (S)-enantiomer is either inert or may be responsible for adverse effects. The aim of the study was to measure the protection given against methacholine (MCh) and adenosine monophosphate (AMP) by (R)-, (S)- and rac-salbutamol and their bronchodilator effects.

METHODS

A double-blind, placebo-controlled, four-way cross-over study was performed in subjects with mild to moderate asthma. There were three groups: AMP30 (n = 10), MCh30 (n = 13) and MCh180 (n = 10). The groups received AMP or MCh challenges at either 30 min or 180 min after each of four pretreatments: 100 microg (S)-salbutamol, 100 microg (R)-salbutamol, 200 microg rac-salbutamol or placebo (normal saline), each administered via nebuliser. Spirometry was measured at 30, 60, 90, 120, 150 and 180 min in the MCh180 group.

RESULTS

(R)- and rac-salbutamol showed equivalent bronchoprotective effects at 30 min. PC20AMP increased by 3.22 (1.86) and 3.41 (2.15) doubling doses (P < 0.001) and PC20MCh increased by 2.86 (1.09) and 2.75 (0.89) (P < 0.001) respectively. (S)-salbutamol caused no equivalent effect. There was no significant effect at 180 min. No hyper-responsiveness occurred after treatment with (S)-salbutamol. The mean increase in forced expiratory volume in 1 s (FEV1) was 12.4% (6.8%) with (R)- and 12.0%(7.7%) with rac-salbutamol at 90 min. No significant change in FEV1 occurred with (S)-salbutamol.

CONCLUSIONS

These results confirm other recent findings that the bronchoprotective and bronchodilator effects of salbutamol are attributable to its (R)-enantiomer. No adverse effects were noted after single doses of (S)-salbutamol.

Childhood farm environment and asthma and sensitization in young adulthood

BACKGROUND

Farm environment in childhood may protect against sensitization, allergic rhinitis, and asthma.

METHODS

Subjects were obtained from 10 667 Finnish first-year university students who responded to a questionnaire survey on IgE-mediated diseases. Two random samples were selected from 1631 respondents in Turku: subjects with asthma or wheezing, and subjects without asthmatic symptoms. A total of 296 subjects (72%) participated. Skin prick tests (SPT), measurements of IgE-antibodies, methacholine challenge, and bronchodilation tests were performed. Weighted occurrence of current asthma and sensitization among students from "childhood farm" and "childhood nonfarm" environments were analyzed.

RESULTS

Current asthma was found in 3.1% of subjects with childhood farm environment, and in 12.4% with nonfarm environment (odds ratio (OR) 0.22; 95% confidence interval (CI) 0.07-0.70). There were fewer positive SPT to birch (8.3 vs. 24.2%, OR 0.28, 95% CI 0.07-1.15) and timothy pollen (12.6 vs. 30.3%, OR 0.33, 95% CI 0.09-1.20) among subjects with childhood farm environment, but more sensitization to house-dust mite (22.0 vs. 4.9%, OR 5.43, 95% CI 1.60-18.46). Sensitization to cat (RAST class >/= 3) was less common in subjects with farm compared to nonfarm environments in childhood (1.5 vs. 13.1%; OR 0.10, 95% CI 0.02-0.47).

CONCLUSIONS

Farm environment in childhood protects against adult asthma and sensitization-especially to cat-the most important asthma related allergen. In contrast, sensitization to house-dust mite was more common in farming subjects.

Betel-nut chewing and asthma

Two Asian patients admitted to hospital with acute severe asthma had been chewing betel nut immediately before the attacks. Arecoline, a cholinergic alkaloid, is a major constituent of Areca catechu (betel) nut and causes the euphoric effects. We sought an association between betel-nut chewing and bronchoconstriction in asthmatic patients. In vitro, arecoline caused dose-related contraction of human bronchial smooth-muscle strips, with one-tenth the potency of methacholine. In a double-blind challenge study, inhalation of arecoline caused bronchoconstriction in six of seven asthmatic patients and one of six healthy subjects; methacholine caused bronchoconstriction in all the asthmatic patients and in five controls. The geometric mean concentrations of arecoline and methacholine that caused 20% falls in the forced expiratory volume in 1 s (PC20 FEV1) in the asthmatic subjects were 5.2 mg/ml and 1.6 mg/ml, respectively. We then studied four Bengali asthmatic patients, regular users of betel nut, during a betel-nut challenge. Three showed no adverse effects, but one showed a 30% fall in FEV1 by 150 min after chewing; the effect was reproducible. In the UK, the rate of hospital admission for acute asthma is higher among Asians than among other groups in the population; betel-nut chewing may be one of several factors that affect asthma control and severity of attacks.

Changes in methacholine induced bronchoconstriction with the long acting beta 2 agonist salmeterol in mild to moderate asthmatic patients

BACKGROUND

Beta-2 agonists protect against non-specific bronchoconstricting agents such as methacholine, but it has been suggested that the protection afforded by long acting beta 2 agonists wanes rapidly with regular treatment.

METHODS

The changes in airway responsiveness were investigated during and after eight weeks of regular treatment with salmeterol 50 micrograms twice daily in 26 adult asthmatic patients, 19 of whom were receiving maintenance inhaled corticosteroids. The study was of a randomised, placebo controlled, double blind design. Airway responsiveness to methacholine was measured as PD20 by a standardised dosimeter technique 12 hours after the first dose, at four weeks and eight weeks during treatment (12 hours after the last dose of test medication), and at 60 hours, one week and two weeks after stopping treatment.

RESULTS

There were no significant differences between the baseline characteristics of the two groups. A significant improvement in PD20 was seen at all points during treatment with salmeterol compared with the placebo group, with no significant fall off with time. PD20 measurements returned to baseline values after cessation of treatment with no significant difference from the placebo group.

CONCLUSIONS

Salmeterol gave significant protection against methacholine induced bronchoconstriction 12 hours after administration. This protection was of small magnitude, but there was no significant attenuation with eight weeks of regular use and no rebound increase in airway responsiveness on stopping treatment in a group of moderate asthmatic patients, the majority of whom were receiving inhaled corticosteroids.

Glycopyrrolate causes prolonged bronchoprotection and bronchodilatation in patients with asthma

INTRODUCTION

Inhaled anticholinergic drugs are effective bronchodilators in the treatment of COPD, and tiotropium bromide has recently been introduced as a once-daily bronchodilator for use as a maintenance treatment. Racemic glycopyrrolate is an anticholinergic drug that has been used orally to control gastric acidity, parenterally as an antisialogogue and to reverse neuromuscular blockade, and has been studied by inhalation for asthma and COPD.

DESIGN AND OBJECTIVE

We investigated the duration of protection against the constrictor effects of inhaled methacholine of a single dose of inhaled nebulized racemic glycopyrrolate (0.5, 1.0, and 2.0 mg) compared with ipratropium bromide (0.5 mg) and placebo in 10 atopic asthmatic volunteers in a double-blind, five-way, crossover study.

RESULTS

Protection against methacholine-induced bronchospasm after administering glycopyrrolate was maintained to 30 h, the last time point measured. Both bronchodilatation and bronchoprotection were significantly longer with glycopyrrolate than after ipratropium bromide, and bronchoprotection was significant at all time points from 2 to 30 h compared to placebo. Dryness of the mouth and nose was described in 18% of patients after the highest dose of glycopyrrolate.

CONCLUSIONS

The prolonged bronchodilator response and the protection against methacholine-induced bronchospasm demonstrated in asthma suggests that inhaled racemic glycopyrrolate would be superior to ipratropium bromide for treatment of stable COPD.

Recovery of methacholine responsiveness after end of exposure in occupational asthma

Recent data suggest that responsiveness to methacholine continues to improve 2 and more years after cessation of exposure to agents causing occupational asthma (OA). The goal of this study was to characterize further the curve of improvement to methacholine responsiveness in subjects with OA. Eighty subjects with confirmed OA who had at least two assessments of a provocative concentration of histamine causing a 20% drop in FEV(1) (PC(20)) and were seen for at least 2 years after cessation of exposure. The shape of recovery of PC(20) was assessed by CARMA (James K. Lindsey, Liège, Belgium) analysis. Slopes of recovery were compared in the first 2.5 years in 55 subjects and from 2.5 years until the end of observation in 56 subjects. Recovery curves showed progressive improvements in PC(20) significantly influenced by time lapse since end of exposure, sex, baseline PC(20), and FEV(1). The slopes of recovery were significantly different from zero both for the first 2.5 years after cessation of exposure (0.27 +/- 0.05 SEM natural logarithm of PC(20) per year) and later (0.09 +/- 0.008 SEM natural logarithm of PC(20) per year), with the slope significantly steeper for the first 2.5 years. This study shows that improvement in responsiveness to methacholine continues for years after cessation of exposure but that the improvement is more rapid in the first 2.5 years.

Airway reactivity in welders: a controlled prospective cohort study

In a 3-year survey, respiratory symptoms, spirometry, and methacholine reactivity were measured annually in welders (n = 51) and non-welder controls subjects (n = 54) to determine whether welding-related symptoms are associated with accelerated decline in lung function or changes in airway reactivity. In the cross-workshift study, maximal midexpiratory flow rate declined reversibly during a welding day, whereas 1-second forced expiratory volume and forced-vital capacity were unchanged. In the longitudinal study, the welders had significantly more reversible work-related symptoms of cough, phlegm, wheeze, and chest tightness than the non-welder shipyard control subjects. In this group of actively working welders, across-workshift changes in midflow and reversible symptoms were related to the welding occupation, but evidence for chronic irreversible effects on spirometry or airway reactivity was not seen over the 3 years of observation. The short period of observation was not optimal for detecting a chronic effect on lung function. Work practices and engineering controls may be successfully preventing irreversible respiratory effects, but not mild reversible effects, in this group of welders.

Adenosine-mediated bronchoconstriction and lung inflammation in an allergic mouse model

In this study, we studied the role of adenosine on airway responsiveness and airway inflammation using an allergic mouse model. Mice were sensitized by two i.p. injections of ragweed and three consecutive ragweed aerosol challenges. It was found that inhalation of adenosine causes a dose-related bronchoconstriction in this model. Ragweed sensitized and challenged mice showed increased sensitivity to airway challenge to adenosine compared to control animals. Theophylline, a non-selective adenosine receptor antagonist, blocked adenosine-induced bronchoconstriction, but was unable to inhibit bronchoconstrictor response to methacholine. Mice systemically sensitized and airway challenged with allergen showed a marked airway inflammation manifesting increases in eosinophils, lymphocytes and neutrophils, and decrease in macrophages. Twenty-four hours after airway challenge with allergen, aerosolization of adenosine further potentiated the allergen-induced airway inflammation. Cells in bronchoalveolar lavage fluid after adenosine aerosolization increased by 3.07-fold as compared to control mice, and by 1.8-fold compared to ragweed sensitized and challenged mice. The increases in eosinophils, lymphocytes, and neutrophils caused by allergen were potentiated after adenosine challenge. Unexpectedly, macrophages significantly decreased after adenosine challenge. Theophylline attenuated adenosine-enhanced airway inflammation, but could not reverse allergen-induced airway inflammation. These findings suggested that specific adenosine receptors contribute to airway responsiveness and airway inflammation associated with this model of allergic asthma.

A comparison of the speeds of action of salmeterol and salbutamol in reversing methacholine-induced bronchoconstriction

We compared the speed of action of the long acting beta-agonist salmeterol with that of salbutamol in order to assess whether reported in vitro differences are likely to have clinical significance. We used methacholine tests to produce a standardized level of bronchoconstriction and then observed the rate of recovery of FEV1 towards baseline after the administration by metered dose inhaler of salmeterol 50 micrograms or salbutamol 200 micrograms--doses which are considered to have similar bronchodilator potency. Twenty asthmatic subjects participated, and a double-blind, randomized, cross-over study design was followed. Salmeterol showed a significantly slower speed of action with median recovery to 90% and 95% of the baseline FEV1 (pre-methacholine) occurring after 9.6 and 19.4 min, respectively, compared with 4.8 and 8.3 min, respectively, for salbutamol (P less than 0.01). These observations are consistent with in vitro findings and suggest that salmeterol is likely to be less satisfactory than salbutamol as a 'rescue medication' for the treatment of acute episodes of bronchoconstriction.

A trial of nebulized magnesium sulfate to reverse bronchospasm in asthmatic patients

STUDY OBJECTIVE

To test the hypothesis that nebulized magnesium sulfate reverses methacholine-induced bronchospasm in asthmatic patients.

DESIGN

Randomized, double-blind, crossover clinical trial.

SETTING

Center for Asthma and Allergic Diseases, Children's Hospital of Pittsburgh.

TYPE OF PARTICIPANTS

Ten patients who were 21 to 37 years old and had stable asthma.

INTERVENTIONS

Patients withheld asthma medications for 24 hours before each study day. Patients with baseline forced expiratory volume in one second (FEV1) of less than 80% were excluded. All subjects underwent bronchial methacholine challenge to produce bronchospasm. They then received one of three different nebulized treatments: 2.5 mg albuterol in 3 mL saline, 3 mL magnesium sulfate (268 mmol/L, pH 6.4), or 3 mL normal saline. Patients repeated spirometry 15 minutes after completing the study drug and then received albuterol by metered-dose inhaler. Spirometry was repeated after the metered-dose inhaler. Each patient made three separate visits to receive each of the three medications.

MEASUREMENTS AND RESULTS

Methacholine reduced each patient's FEV1 by at least 20% at each testing session. Post-methacholine treatment with nebulized albuterol improved FEV1 by a mean of 56% (SD, 19.6%). Nebulized normal saline led to a mean increase in FEV1 of 29% (SD, 26.5%). Nebulized magnesium sulfate improved FEV1 by a mean of 12% (SD, 12.0%) (P = .054 by paired t-test compared with normal saline).

CONCLUSION

Nebulized magnesium sulfate has a minimal bronchodilatory effect in asthmatic patients with methacholine-induced bronchoconstriction. Responsiveness to magnesium sulfate may be dependent on the mechanism of induction of bronchospasm, and there probably is no role for nebulized magnesium sulfate in the treatment of acute bronchospasm due to cholinergic stimulation.

A comparison of salmeterol and formoterol in attenuating airway responses to short-acting beta2-agonists

In vitro data suggest that salmeterol, contrary to formoterol, can partly antagonise the effect of short-acting beta(2)-agonist rescue medication. To explore whether this occurs in vivo, we compared the effects of increasing doses (200-3200 microg) of fenoterol on the recovery of methacholine induced bronchoconstriction as well as PD(20) methacholine in 23 asthmatic patients, during two-week treatment periods with placebo, and standard doses of salmeterol or formoterol in a double blind, double-dummy, crossover study. Salmeterol showed a slightly higher propensity for the development of bronchodilator tolerance. The recovery of methacholine induced bronchoconstriction was more complete during regular use of formoterol relative to salmeterol. During regular use of both long-acting beta(2)-agonists the bronchoprotective efficacy of fenoterol was attenuated, but this was more pronounced during salmeterol than during formoterol. The mean maximum increase in PD(20) metacholine after the highest dose of fenoterol was 3.97 DD during placebo, 2.47 DD during formoterol (p<0.001) and 1.81 DD during salmeterol treatment (p<0.001). We conclude that in asthmatic patients the efficacy of short-acting beta(2)-adrenoceptor agonists can be significantly attenuated during regular use of long-acting beta(2)-agonists. In this respect, differences were observed between salmeterol and formoterol that may represent the expression of partial antagonism by salmeterol.

Methacholine challenge testing: identifying its diagnostic role, testing, coding, and reimbursement

Methacholine challenge testing (MCT), also sometimes described as bronchoprovocation testing, is widely performed for both research and diagnostic purposes. MCT is clinically useful when the patient presents with a history of symptoms suggesting asthma, but spirometry findings are normal. Typically, MCT is performed in a pulmonary function laboratory, a clinic, or a physician's office. MCT requires time, effort, and understanding. Two standard testing regimes are identified along with proper coding and reimbursement methodologies.

Relationship of skin-prick reactivity to aeroallergens and hyperresponsiveness to challenges with methacholine and adenosine monophosphate

BACKGROUND

Clarification of the relationship between atopy and bronchial hyperresponsiveness (BHR), both key features of asthma, is critical to our understanding of the disease. We therefore investigated the putative relationship between skin-prick reactivity to aeroallergens and BHR to direct and indirect stimuli.

METHODS

We performed a retrospective analysis of data from 332 patients presenting with a diagnosis of asthma. Patients were characterized by skin prick tests (SPT), spirometry and bronchial challenge with methacholine and adenosine monophosphate (AMP).

RESULTS

For patients who had BHR to methacholine but not AMP, the presence of atopy was associated with a lower PD20 (the provocative dose of methacholine producing a fall in FEV1 of 20%), amounting to a geometric mean (95% confidence interval (CI)) of 2.3-fold (1.4-4.0) difference. Furthermore, the number of skin-prick positive (SPP) responses was related to methacholine reactivity: 0-1 SPP, PD20 = 69.9 micro g; 2-4 SPP, PD20 = 47.8 micro g; 5-8 SPP, PD20 = 35.6 micro g. There was a 2.0- fold (1.1-3.6) difference between the groups with a low (0-1 SPP) and high (5-8 SPP) degree of skin-prick reactivity. A similar pattern was seen when data were analyzed including only perennial allergens. Spirometry was unrelated to the degree of skin-prick reactivity.

DISCUSSION

These results suggest that skin-prick reactivity to aeroallergens is associated with BHR to methacholine.