Airway calibre as a confounder in interpreting bronchial responsiveness in asthma

Bronchial Reactivity and Lung Function After World Trade Center Exposure

BACKGROUND

World Trade Center (WTC)-exposed rescue/recovery workers endured massive respiratory insult from inhalation of particulate matter and gases, resulting in respiratory symptoms, loss of lung function, and, for many, bronchial hyperreactivity (BHR). The persistence of respiratory symptoms and lung function abnormalities has been well-documented, whereas persistence of BHR has not been investigated.

METHODS

A total of 173 WTC-exposed firefighters with bronchial reactivity measured within 2 years after September 11, 2001 (9/11) (baseline methacholine challenge test), were reevaluated in 2013 and 2014 (follow-up methacholine challenge test). FEV1 measurements were obtained from the late pre-9/11, early post-9/11, and late post-9/11 periods. Respiratory symptoms and corticosteroid treatment were recorded.

RESULTS

Bronchial reactivity remained stable (within 1 doubling dilution) for most (n = 101, 58%). Sixteen of 28 (57%) with BHR (provocative concentration of methacholine producing a 20% decline in FEV1 <8 mg/mL) at baseline had BHR at follow-up, and an additional 27 of the 145 (19%) without BHR at baseline had BHR at follow-up. In multivariable models, we found that BHR baseline was strongly associated with BHR follow-up (OR, 6.46) and that BHR at follow-up was associated with an estimated 15.4 mL/y greater FEV1 decline than experienced by those without BHR at follow-up. Annual FEV1 decline was moderated by corticosteroid use.

CONCLUSIONS

Persistent BHR and its deleterious influence on lung function suggest a role for airway inflammation in perpetuation of WTC-associated airway disease. In future massive occupational exposure to inorganic dust/gases, we recommend early and serial pulmonary function testing, including measurements of bronchial reactivity, when possible, and inhaled corticosteroid therapy for those with symptoms or pulmonary function tests consistent with airway disease.

Outcome in adulthood of asymptomatic airway hyperresponsiveness in childhood: a longitudinal population study

The clinical outcome of asymptomatic airway hyperresponsiveness (AHR) first detected in childhood is sparsely reported, with conflicting results. We used a birth cohort of 1,037 children followed to age 26 years to assess the clinical outcome of asymptomatic AHR to methacholine first documented in study members at age 9 years. Of 547 study members who denied wheezing symptoms ever at age 9 years, 41 (7.5%) showed AHR. Forty showed methacholine responsiveness, with a provocation concentration of methacholine that elicited a 20% drop in forced expired volume in 1 sec (PC(20)) < or = 8 mg/mL, and one had baseline airway obstruction with a bronchodilator response exceeding 10%. Of these 41 study members, 18 (44%), 11 (27%), and 4 (10%) maintained AHR in 1, 2, and 3 later assessments, respectively, while 23 (56%) manifested AHR only at age 9. Compared with asymptomatic study members without AHR, those with asymptomatic AHR at age 9 years were more likely to report asthma and wheeze at any subsequent assessment, were more likely to have high IgE levels and eosinophils at ages 11 and 21, and more often demonstrated positive responses to skin allergen testing at ages 13 and 21 years. Persistent AHR at later assessments increased these likelihoods further.In conclusion, asymptomatic children with AHR are more likely to develop asthma and atopy later in life compared with asymptomatic children without AHR. Persistent AHR, even though initially asymptomatic, was associated with an even greater increased risk of development of asthma. We suggest that rather than considering AHR as a marker of asthma, it should be regarded as a parallel pathological process that may lead to subsequent symptoms and clinical evidence of asthma.

The relationship between airway hyper-responsiveness, markers of inflammation and lung function depends on the duration of the asthmatic disease

BACKGROUND

The combination of airway hyper-responsiveness, eosinophilic airway inflammation, and lung function impairment is considered as a hallmark of bronchial asthma. Since airway function might change with time in chronic asthma, the association between parameters which are characteristic of asthma could be different in subjects with different durations of the disease.

OBJECTIVE

We assessed whether in patients with asthma the relationship between airway hyperresponsiveness, non-invasive markers of airway inflammation, and baseline lung function depended on the duration of the disease.

METHODS

Sixty-six non-smoking patients with mild to moderate allergic asthma without corticosteroids were assigned to two groups, according to a duration of the disease (time interval since doctor's diagnosis) of either < or = 16 years (median 8 years; mean FEV1, 92.6% pred.; n = 34) or > 16 year (median 25 years; mean FEV1, 87.9% pred.; n = 32).

RESULTS

Groups did not differ statistically in PC20FEV1 of methacholine, sputum composition, levels of exhaled nitric oxide (NO), lung function parameters, or history of treatment. There were significant correlations between PC20FEV1, eosinophils and NO in patients with a duration of the disease < or = 16 year, but no relation to lung function. In contrast, patients with a duration > 16 year showed a correlation between PC20FEV1 of methacholine and lung function but not eosinophils or NO. In both groups, eosinophils and NO were associated with each other. These results were corroborated by the statistical procedure of factor analysis that revealed 'inflammation' and 'lung function' as major entities and found 'responsiveness' to be associated with only one of them in each group.

CONCLUSION

Our data demonstrate that with a shorter duration of the asthmatic disease airway hyper-responsiveness is associated with airway inflammation, whereas with a longer duration it is associated with impaired lung function, suggesting that in chronic asthma ongoing alterations become the primary determinant of functional characteristics.

Lung deposition and protective effect of terbutaline delivered from pressurized metered-dose inhalers and the Turbuhaler in asthmatic individuals

We investigated the relationship between pulmonary deposition of terbutaline and bronchoprotection against methacholine and histamine with the Turbuhaler (AstraZeneca, Lund, Sweden) and a pressurized metered dose inhaler (pMDI) in 13 asthmatic patients. The study was done with a randomized, double blind, double dummy, and crossover design. On different days, the provocative concentration of histamine causing a 20% decrease in FEV(1) (PC(20) histamine) and PC(20) methacholine were determined before and at 1.5, 3, and 6 h after inhalation of 0.25 or 0.5 mg of terbutaline sulfate. The Turbuhaler delivered significantly more drug than did the pMDI (% of the nominal metered dose and 95% confidence interval): 20.8% (16.4 to 26.6%) and 16.9% (13.2 to 21.7%) versus 4.8% (3.8 to 6.1%) and 7.4% (5.8 to 9.5%), respectively. Average protection against histamine over 6 h was 0.66 (95% CI: 0.45 to 0.87) doubling concentrations (DC) after inhalation of 0.25 mg and 1.08 (95% CI: 0.87 to 1.29) DC after 0.5 mg terbutaline via pMDI, and 1.07 (95% CI: 0.87 to 1.29) DC after 0.25 mg and 1.24 (95% CI: 1.03 to 1.45) DC after 0.50 mg via Turbuhaler. Protection against methacholine was also dose- and device-dependent. The dose needed to obtain the same pulmonary deposition with the pMDI was 3.14 times greater than with the Turbuhaler, and that needed for the same protective effect was 2.1 and 3.2 times greater for histamine and methacholine, respectively. We conclude that pulmonary deposition of terbutaline was predictive of the clinical response.

Differential diagnosis of chronic airflow obstruction

Chronic obstructive pulmonary disease is a syndrome including illnesses such as asthma, chronic bronchitis, and emphysema. Although these diseases share a common obstructive component, their optimal treatment and prognosis differ. This article examines the salient features of the history, physical exam, pulmonary function tests, and radiological evaluation which may allow the clinician to differentiate the various diseases that make up COPD; thus allowing the clinician to better target the multiple therapeutic modalities available.

The importance of serum IgE for level and longitudinal change in airways hyperresponsiveness in COPD

BACKGROUND

Airways hyperresponsiveness (AHR) is an important feature of patients with chronic obstructive pulmonary disease (COPD). Little is known about factors that modulate AHR in COPD.

OBJECTIVE

To study these factors, we performed a long-term, double-blind, parallel intervention study in 58 male, non-allergic patients with COPD.

METHODS

During a period of 2 years, patients were treated with inhaled budesonide (1600 microg/day), inhaled budesonide (1600 microg/day) plus oral prednisolone (5 mg/day), or placebo. PC20 histamine was measured at 4-monthly intervals. The influence of treatment, smoking, age, level of lung function, initial serum IgE level and peripheral blood eosinophils on level and longitudinal change of PC20 histamine was analysed.

RESULTS

During follow-up, PC20 decreased in our group, and this decrease was not influenced by treatment. PC20 tended to decrease faster in current smokers than in ex-smokers. PC20 was significantly associated with pre-challenge FEV1 at each time point. Level nor decline of PC20 were significantly related to age. A higher initial serum IgE level was independently associated with a lower PC20. Moreover, a higher initial serum IgE level was associated with a slower annual decline of PC20, regardless of treatment, pre-challenge FEV1, and other modulating factors. No significant associations were found between initial blood eosinophils and level or decline of PC20.

CONCLUSION

We conclude that AHR increases over time in non-allergic patients with COPD. Treatment with an inhaled corticosteroid alone or in combination with oral prednisolone does not change this increase. Our study suggests an important role for IgE in the course of the disease, since a higher initial serum IgE level predicts a more favourable course with regard to annual decline of PC20 histamine.

Determinants of bronchial responsiveness in the European Community Respiratory Health Survey in Italy: evidence of an independent role of atopy, total serum IgE levels, and asthma symptoms

The aim of the analysis was to test whether total serum IgE levels, specific serum IgE levels, and asthma symptoms are independent predictors of bronchial hyperresponsiveness (BHR), after controlling for known risk factors or potential confounders. The study was carried out on a sample of 875 young adults, 20-44 years old, who took part in the European Community Respiratory Health Survey in Italy. The subjects underwent a dose-response methacholine challenge test. We also measured airway caliber as the baseline FEV1 in absolute terms and as percentage of forced vital capacity (FVC); skin wheal response to 11 common environmental allergens; and total and specific serum IgE levels to mites, molds, pets, and respiratory symptoms by means of a standardized questionnaire. Atopy (positive skin prick test and/or positive specific IgE assay), total IgE, asthma symptoms, airway caliber, and age appeared to be independent predictors of BHR. When all the other risk factors were taken into account, atopy and total IgE were associated with a threefold increase in BHR risk and thus emerged as the main determinants of BHR. The importance of symptom status as a determinant of BHR decreased remarkably after controlling for atopy and IgE: the odds ratio of current asthmatics to asymptomatic subjects decreased from 15.3 to 8.8. When controlling for symptoms and atopy, a family history of allergic diseases and early respiratory infections was not found to be associated with BHR. Both FEV1 and FEV1/FVC were strongly and inversely associated with BHR. When airway caliber was taken into account, older age was associated with decreased responsiveness, and the level of responsiveness did not differ significantly between males and females and between smokers and nonsmokers. The results from this analysis indicate that at any given age, irrespective of sex and smoking habits, total serum IgE, specific IgE, airway caliber, and asthma symptoms are the main independent factors influencing the occurrence of BHR in a young adult sample.