Bronchoalveolar lavage findings in patients with chronic nonproductive cough

Airway inflammation and remodelling changes in patients with chronic cough: do they tell us about the cause of cough?

Airway mucosal changes have been reported in chronic cough. In cough variant asthma and in eosinophilic bronchitis, there is evidence of eosinophil infiltration and sub-basement membrane thickening. In non-asthmatic cough, an increase of bronchoalveolar mast cells, mucosal mononuclear cells, and epithelial shedding have been reported. In a more recent study, evidence of airway wall remodelling has been observed in both asthmatic and non-asthmatic cough, such as an increase in sub-basement membrane thickness, goblet cell area, vascularity and vessel size. Smooth muscle area was increased in non-asthmatic coughers. Heightened cough sensitivity in non-asthmatic coughers was related to the degree of goblet cell hyperplasia and epithelial shedding. Cough reflex may be heightened by increased production of growth factors that might be further enhanced by the physical effects of cough on the airways. Mast cells may participate in the cough pathophysiology through release of growth factors as well as tussive mediators. Changes in the airway wall mucosa and epithelium may be important in the pathogenesis of cough receptor sensitization.

Attenuating effect of H+K+ATPase inhibitors on airway cough hypersensitivity induced by allergic airway inflammation in guinea-pigs

BACKGROUND

Gastrooesophageal reflux (GER) is a frequent cause of chronic cough. Several investigators have indicated that inhibitors of H(+)K(+)ATPase (proton pump inhibitors; PPIs) could relieve coughing via inhibition of acid reflux. However, we considered that PPIs might directly inhibit increased cough reflex sensitivity.

OBJECTIVE

The present study was designed to examine whether PPIs directly inhibit antigen-induced increase in cough reflex sensitivity and to elucidate the mechanism.

METHODS

Actively sensitized guinea-pigs were challenged with aerosol antigen (ovalbumin, OVA) and cough reflex sensitivity to inhaled capsaicin was measured 24 h later. The PPIs (omeprazole and rabeprazole) or the histamine H(2) blocker cimetidine were administered intraperitoneally 1 h before OVA challenge and before measuring cough reflex sensitivity, then bronchoalveolar lavage fluid (BALF) was immediately collected. The pH of the fluid obtained by bronchial washing was determined after examining the effect of rabeprazole on the cough response to capsaicin.

RESULTS

The number of coughs elicited by capsaicin was significantly increased 24 h after challenge with OVA compared with saline, indicating antigen-induced increase in cough reflex sensitivity. Both PPIs dose dependently and significantly inhibited antigen-induced cough hypersensitivity. Omeprazole did not influence the antigen-induced increase in the total number of cells or ratio (%) of eosinophils in BALF. Cimetidine did not affect the antigen-induced cough hypersensitivity or cellular components of BALF. The pH of the bronchial washing fluid was significantly decreased in antigen-challenged animals. Rabeprazole did not affect the antigen-induced decrease in the pH of bronchial washing fluid.

CONCLUSION

These findings show that PPIs, but not histamine H(2) blockers, can directly decrease antigen-induced cough reflex hypersensitivity, while the mechanism remains unclear.

Idiopathic cough, prevalence and underlying mechanisms

A number of authors have reported a significant percentage of patients whose cause of cough remains undetermined despite a systematic evaluation as recommended in a number of International Guidelines. This subset of patients, which may be regarded as having an idiopathic cough, are often female and of peri or postmenopausal age. Sex hormones may influence the cough reflex in disease or contribute to the chronic lymphocytic airway inflammation seen in some cases and to the association with organ specific autoimmune disease reported. This paper seeks to investigate some of the possible causes of idiopathic cough.

Reduced pH and chloride levels in exhaled breath condensate of patients with chronic cough

BACKGROUND

Increased hydrogen and reduced chloride ionic environments of the airways are conducive to the stimulation of cough. However, the constituents of the local milieu of the airways of patients with chronic cough are unknown.

METHODS

The pH and chloride levels in exhaled breath condensate and capsaicin cough threshold (C5) were measured in 50 patients with chronic cough and in 16 healthy controls. pH and chloride measurements were repeated after capsaicin challenge in those with cough. The cause of cough was asthma (n = 13), postnasal drip/rhinitis (n = 7), gastro-oesophageal reflux (n = 5), bronchiectasis (n = 5), but remained unidentified in 20.

RESULTS

Compared with controls, patients with chronic cough had lower pH (mean 7.9 v 8.3, 95% CI of difference -0.5 to -0.2, p<0.0001), chloride levels (median 4 v 6 mmol/l, 95% CI -3.1 to -0.2, p = 0.007), and C5 (median 3.9 v 125 micro M, 95% CI -270.0 to -17.6, p = 0.002). The pH levels were different in the six subgroups including controls, and were reduced in all diagnostic subgroups of patients with cough compared with controls but did not differ between them. Chloride levels were significantly different in the six subgroups but were lower than controls in only the gastro-oesophageal reflux subgroup. There was a weak but significant correlation between chloride levels and C5 when all participants were analysed together, but not between pH and C5 or chloride levels. pH and chloride levels did not change after capsaicin challenge.

CONCLUSIONS

The epithelial lining fluid of patients with chronic cough has a reduced pH and reduced chloride levels which could contribute to the enhanced cough reflex.

Eosinophil degranulation in the allergic lung of mice primarily occurs in the airway lumen

Eosinophil degranulation is thought to play a pivotal role in the pathogenesis of allergic disorders. Although mouse models of allergic disorders have been used extensively to identify the contribution of eosinophils to disease, ultrastructural evidence of active granule disassembly has not been reported. In this investigation, we characterized the degree of eosinophil activation in the bone marrow, blood, lung tissue, and airways lumen [bronchoalveolar lavage fluid (BALF)] of ovalbumin-sensitized and aero-challenged wild-type and interleukin-5 transgenic mice. Degranulation was most prominent in and primarily compartmentalized to the airways lumen. Eosinophils released granule proteins by the process of piecemeal degranulation (PMD). Accordingly, recruitment and activation of eosinophils in the lung correlated with the detection of cell-free eosinophil peroxidase in BALF and with the induction of airways hyper-reactivity. As in previous studies with human eosinophils, degranulation of isolated mouse cells did not occur until after adherence to extracellular matrix. However, higher concentrations of exogenous stimuli appear to be required to trigger adherence and degranulation (piecemeal) of mouse eosinophils when compared with values reported for studies of human eosinophils. Thus, mouse eosinophils undergo PMD during allergic inflammation, and in turn, this process may contribute to pathogenesis. However, the degranulation process in the allergic lung of mice is primarily compartmentalized to the airway lumen. Understanding the mechanism of eosinophil degranulation in the airway lumen may provide important insights into how this process occurs in human respiratory diseases.

Idiopathic chronic cough: association with organ specific autoimmune disease and bronchoalveolar lymphocytosis

BACKGROUND

We have recently reported a strong association between organ specific autoimmune disease and idiopathic chronic cough and have suggested that cough may be caused by airway inflammation secondary to aberrant homing of activated lymphocytes to the lung. An immunopathological study was undertaken to test the hypothesis that idiopathic chronic cough is associated with lymphocytic airway inflammation.

METHODS

Bronchoscopy, bronchial biopsies, bronchoalveolar lavage (BAL), and peripheral blood and BAL flow cytometry were performed in 19 patients with idiopathic chronic cough, 14 with explained chronic cough, and 11 normal subjects.

RESULTS

Organ specific autoimmune disease or positive autoantibodies were present in eight of the 19 patients with idiopathic cough, in one of the 14 patients with explained cough, and in one of the 11 normal subjects. Median BAL fluid differential lymphyocyte counts were significantly higher in patients with idiopathic cough (10.0%) than in normal subjects (6.3%, 95% confidence interval of difference 1.5 to 11.9, p = 0.01) or patients with explained cough (5.2%, 95% CI of difference 2.0 to 10.4, p = 0.001). There were no differences in bronchial biopsy T lymphocyte counts between the groups. The mean (SE) proportion of CD3+ peripheral blood mononuclear cells expressing CD4 was significantly higher in normal subjects than in patients with idiopathic cough (69 (3)% v 58 (3)%, mean difference 11%, 95% CI of difference 2 to 20, p<0.02) but not than those with explained chronic cough (63 (2)%). There were no differences in BAL T lymphocyte phenotype between groups.

CONCLUSION

BAL fluid lymphocytosis occurs in some patients with idiopathic chronic cough. The association of idiopathic chronic cough with organ specific autoimmune disease raises the possibility that this might be caused by lymphocyte homing from the primary site of autoimmune inflammation or the result of an autoimmune process in the lung.

Cough. 1: Chronic cough in adults

The investigation and treatment of chronic cough in adults is generally rewarding, provided there is an understanding of its aetiology, particularly when it arises from sites outside the respiratory tract.

Induced sputum inflammatory mediator concentrations in chronic cough

Previous studies have shown evidence of airway inflammation in patients with chronic cough and have suggested that the cough may be due to release of tussive mediators and activation of afferent sensory nerve endings. We measured the concentration of various proinflammatory and tussive mediators in induced sputum supernatants from 20 patients with cough variant asthma or eosinophilic bronchitis, 20 patients with nonasthmatic chronic cough, 22 patients with idiopathic chronic cough, and 18 healthy control subjects. We measured histamine, cysteinyl-leukotrienes, prostanoids (prostaglandin D2 and prostaglandin E2), and interleukin-8 by enzyme immunoassay. The median sputum histamine concentrations were significantly higher in patients with idiopathic chronic cough (8.0 ng/ml) and cough variant asthma/eosinophilic bronchitis (10.2 ng/ml) than in normal subjects (2.6 ng/ml; 95% confidence interval of difference from idiopathic chronic cough, 0.8 to 25.8 [p = 0.009] and 95% confidence interval of difference from cough variant asthma/eosinophilic bronchitis, 1.1 to 20.1 [p = 0.01]). Median sputum prostaglandin D2 and prostaglandin E2 concentrations were significantly higher in all categories of chronic cough. Our findings support the view that there is release of inflammatory and tussive mediators in patients with chronic cough and suggest that there might be similarities in the mechanism of cough in a diverse range of conditions.

Eosinophilic bronchitis as a cause of chronic cough

Eosinophilic bronchitis is a recently described condition in patients with chronic cough, sputum eosinophilia, normal spirometry and no evidence of bronchial hyperreactivity. The aim of the study was to assess the causes of chronic cough and to identify the prevalence of eosinophilic bronchitis as a cause of chronic cough. Thirty-six patients [mean age 45.4 +/- 14.3 years (range 16-69 years), M/F: 4/32] with an isolated chronic cough lasting for more than 4 weeks were recruited from the outpatient clinic. In all patients, after a full history and physical examination, blood eosinophil count, eosinophilic cationic protein (ECP), serum total and specific IgE levels were measured. Spirometry, methacholine provocation test, skin prick tests, ear, nose and throat examination, induction of sputum and esophageal pH testing were performed. The mean duration of cough was 31.3 +/- 52.3 months. Sputum eosinophilia greater than 3% was present in 12 (33.3%) patients and they were diagnosed as eosinophilic bronchitis. Their induced sputum had a mean eosinophil count of 8.3% and a mean ECP level of 98.5 mg x l(-1), which were higher than the others (P=0.003, both). The diagnosis of the remaining patients were postnasal drip syndrome in eight, gastroesophageal reflux disease in eight, post-infectious cough in two and cough-variant asthma in one patient. In conclusion, eosinophilic bronchitis is an important cause of chronic cough and should be considered in the assessment of patients before regarding them as having idiopathic chronic cough.

Assessment and measurement of cough: the value of new tools

On systematic investigation, patients with persistent cough are often diagnosed as having asthma, gastro-oesophageal reflux (GOR) and post-nasal drip; often, there is no associated diagnosis. Cough-variant asthma and eosinophilic bronchitis are conditions presenting with cough, usually associated with airway eosinophilia and responding well to corticosteroids. These conditions including asthma are best grouped as 'eosinophil-associated cough'. Analysis of induced sputum for eosinophils is an important tool in the investigation of chronic persistent cough. Reliable ambulatory counters for cough have been developed and the contribution of cough count and intensity to the severity of cough have been partly evaluated, and used in assessing antitussive therapies. Self-scoring evaluations are still widely used, but the inclusion of quality of life tools specifically adapted to the evaluation of cough appears to be a useful tool that can directly measure the impact of chronic cough. We need a greater assessment and evaluation of all these tools.

Sex-related differences in cough reflex sensitivity in patients with chronic cough

Among patients attending specialist cough clinics there is an excess of females, but the reason for this sex difference is unknown. We tested the hypothesis that the sensitivity of the cough reflex is greater in female compared with male patients with chronic cough. Inhalation cough challenges with capsaicin and citric acid were performed in a large group of patients with chronic cough. The concentrations of tussive agent causing two (C2) and five (C5) coughs were calculated. Measurements of capsaicin cough reflex sensitivity (median [interquartile range]) were significantly lower for female patients compared with male patients (C2: 1.9 [0.5 to 5.5] versus 5.3 [2.2 to 11.5] micro M, p = 0.0026; C5: 8.6 [2.2 to 34.0] versus 51.2 [7.2 to > 100] micro M, p = 0.0007). Similarly for citric acid challenge, values were significantly lower for female compared with male patients (C2: 53.5 [17.3 to 145.4] versus 118.1 [41.4 to 381.7] mM, p = 0.0064; C5: 300.0 [97.1 to > 1,000] versus 830.4 [300.0 to > 1,000] mM, p = 0.032). There were significant correlations between capsaicin and citric acid C2 values (r(s) = 0.54, p < 0.0001) and C5 values (r(s) = 0.57, p < 0.0001). These findings indicate a sex difference in cough sensitivity in patients with chronic cough, as previously reported in healthy volunteers. This may explain the female preponderance in cough clinics.

Extrathoracic airway responsiveness in children with asthma-like symptoms, including chronic persistent cough

Asthma-like symptoms, including chronic persistent cough, are not always specific for classical asthma. In order to investigate whether assessment of extrathoracic airway hyperresponsiveness (EAHR) during methacholine bronchial challenge helped in the evaluation of pediatric patients with asthma-like symptoms such as chronic cough, we examined 133 consecutive, unselected patients (mean age, 10.06 +/- 2.16 years) who had neither established asthma nor bronchial obstruction previously. We recorded the forced mid-inspiratory flow (FIF(50)) as an index of extrathoracic airway narrowing. In addition, a 25% decrease in FIF(50) (PD(25)FIF(50)) below the cutoff concentration of < or = 8 mg/mL methacholine was assumed to indicate EAHR. According to the methacholine response, 81 patients had EAHR, and 41 of them had combined EAHR and bronchial hyperresponsiveness (BHR); 39 patients had only BHR. Airway hyperresponsiveness was not demonstrated in 13 patients and not in any of the control children. When patients with cough as the sole presenting symptom (60.9%) were compared with those with cough and wheeze (20.3%), those with cough alone had a significantly greater probability of having EAHR (OR, 4.16; 95% CI, 1.32-13.13) and a lower probability of having BHR (OR, 0.70; CI, 0.25-1.95) than those with cough and wheeze. Patients with cough, wheeze, and dyspnea (18.8%) had a significantly greater chance of having BHR than those with cough alone (OR, 5.08; CI, 1.55-16.64). Patients with cough and wheeze as compared with those with cough, wheeze, and dyspnea had significantly greater probability of having both EAHR and BHR (OR, 4.71; CI, 1.94-11.47). In order to ascertain the clinical relevance of EAHR, we assessed in the second part of the study whether the effects of treatment of the underlying disease would result in relief of airway hyperresponsiveness. Rhinosinusitis and perennial allergic rhinitis accounted for EAHR in 71 patients, and 34 of them also demonstrated BHR. They received specific therapy for their upper airway diseases for 4 weeks. Compared with values before treatment, FIF(50) and forced expiratory volume in 1 sec (FEV(1)) did not change significantly. The dose of methacholine causing a 20% fall in FEV(1) (PD(20)FEV(1)) and PD(25)FIF(50) values were significantly increased from 2.40 +/- 1.39 to 4.22 +/- 1.13 mg /mL (P < 0.001) and from 1.03 +/- 1.75 to 8.71 +/- 1.21 mg /mL (P < 0.0001), respectively. We conclude that measurements of EAHR and BHR are the most important ways to evaluate children with asthma-like symptoms, including chronic persistent cough when chest X-rays and pulmonary function tests remain within normal limits. Therefore, empirical treatment is not necessary when these investigations are available. Our results suggest that specific treatment of inflammation in the upper airways reversed persistant cough, and may play an important role in modulating lower airways responsiveness in patients with concomitant BHR.

Eosinophilic bronchitis: clinical manifestations and implications for treatment

Airway inflammation with eosinophils is now reported to occur not only in asthma but in other airway diseases such as cough variant asthma, chronic cough, atopic cough, episodic symptoms without asthma, allergic rhinitis, and COPD. Although the prevalence of eosinophilic bronchitis (EB) is less than in asthma, the causes, mechanisms and treatment of EB in these conditions appears to be similar to asthma where allergen induced IL-5 secretion and symptoms are readily responsive to inhaled corticosteroids. The prognosis of EB without asthma is not known but it may be a precursor for asthma and, if so, recognition of this syndrome may permit effective treatment and reduction in the rising prevalence of asthma. Induced sputum analysis allows recognition of EB in clinical practice. The place of the asthma treatment paradigm with early and sustained corticosteroid treatment needs to be defined in EB without asthma. Airway wall remodelling can occur in rhinitis, COPD, and cough variant asthma with EB. The mechanisms and long term implications of this complication in EB without asthma need to be clarified.

The relation between peripheral blood leukocyte counts and respiratory symptoms, atopy, lung function, and airway responsiveness in adults

STUDY OBJECTIVES

Eosinophils and neutrophils play major roles, respectively, in the pathogenesis of asthma and COPD, and it is well recognized that levels of these cells in peripheral blood are increased in relation to their pulmonary involvement. However, the relation between peripheral blood cell counts of the other major leukocyte groups and these lung diseases or markers of allergy or airflow obstruction is less clear. We have therefore investigated the association between peripheral blood levels of eosinophils, neutrophils, basophils, monocytes, and lymphocytes and the occurrence of chronic respiratory symptoms, atopy, lung function, and bronchial hyperresponsiveness, and the modifying effect of age, in adults.

DESIGN

A cross-sectional general population study.

SETTING

Data on > 2,000 British adults, who originally participated in a study of diet and lung health, were analyzed using multiple linear and logistic regression to adjust for potential confounders, including age, sex, and smoking history.

RESULTS

We found that, like eosinophils, the peripheral basophil count was increased in relation to asthma and associated symptoms, and to airway hyperreactivity and increased total IgE, but differed from eosinophils in that basophils were unrelated to atopy. Monocytes were predominantly associated with symptoms indicative of obstructive airway disease, in similar relation to neutrophils, but both of these leukocyte counts were also increased in asthma patients in older age groups. Lymphocyte counts were unrelated to any objective or subjective marker of disease.

CONCLUSIONS

If peripheral blood cell counts reflect pulmonary involvement of these leukocyte groups, basophils and monocytes may play a distinct role in the pathogenesis of allergic and nonallergic respiratory disease.