Features of cough variant asthma and classic asthma during methacholine-induced brochoconstriction: a cross-sectional study

Impulse oscillometry bronchodilator response in preschool children

BACKGROUND

In preschoolers, performing an acceptable spirometry and measuring bronchodilator response (BDR) is challenging; in this context, impulse oscillometry (IOS) represents a valid alternative. However, more studies on the standardization of BDR for IOS in young children are required.

OBJECTIVE

The objective of the study was to identify optimal thresholds to define a positive BDR test with IOS in preschoolers with suspected asthma.

METHODS

Children aged 3-6 years with suspected asthma and their lung function investigated with both IOS and spirometry pre- and post-BDR were retrospectively analyzed. The spirometric BDR was defined as positive when the change of FEV1 was ≥12% or ≥200 mL. The oscillometric BDR was defined as positive in case of change of at least -40% in R5, +50% in X5, and -80% in AX.

RESULTS

Among 72 patients, 36 (age 5.2 ± 1 years; 64% boys) were selected for the subsequent analysis according to ATS/ERS quality criteria of measurements; specifically, 19 patients did not meet IOS and 36 did not meet spirometry criteria. The spirometric BDR was found positive in seven subjects (19.4%); conversely, a positive oscillometric BDR was identified in four patients (11.1%). No patient presented a positive BDR response with both methods. In IOS, the mean decrease in R5 and AX was 19.9% ± 10% and 44% ± 22.1%, and the mean increase in X5 was 23.3% ± 17.8%, respectively. A decrease in R5 of 25.7% (AUC 0.77, p = .03) and an increase in X5 of 25.7% (AUC 0.75, p = .04) showed the best combination of sensitivity and specificity to detect an increase of FEV1 ≥ 12% and/or ≥200 mL.

CONCLUSION

The IOS represents a valid alternative to spirometry to measure BDR in preschool children and should be the gold standard in this age group. We are considering a decrease of 26% in R5 and an increase of 26% in X5 as diagnostic threshold for BDR.

Bronchial thermoplasty improves cough hypersensitivity and cough in severe asthmatics

BACKGROUND

Cough is a troublesome symptom of asthma because it is associated with disease severity and poor asthma control. Bronchial thermoplasty (BT) may be effective in improving cough severity and cough-related quality of life in severe uncontrolled asthma.

OBJECTIVE

To evaluate the efficacy of BT for cough in severe uncontrolled asthma.

METHODS

Twelve patients with severe uncontrolled asthma were enrolled in this study between 2018 May and March 2021 and arbitrarily divided into cough-predominant [cough severity Visual Analog Scale (VAS) ≥ 40 mm, n = 8] and typical asthma (cough VAS <40 mm, n = 4) groups. Clinical parameters, such as capsaicin cough sensitivity [C-CS: the concentrations to inhaled capsaicin required to induce at least two (C2) and five (C5) coughs], lung function, and type-2-related biomarkers (fractional nitric oxides and absolute eosinophil counts) and cough-related indices [cough severity VAS and the Leicester Cough Questionnaire (LCQ)] were evaluated before and 3 months after performing BT.

RESULTS

BT significantly improved both cough-related indices and C-CS in the cough-predominant group. Changes in C-CS were significantly correlated with changes in the LCQ scores (C5: r = 0.65, p = 0.02 for all patients, and r = 0.81, p = 0.01 for the cough-predominant group).

CONCLUSIONS

BT may be effective for cough in severe uncontrolled asthma by improving C-CS. However, further larger cohort studies are necessary to confirm the effect of BT for cough in asthma.

CLINICAL TRIAL REGISTRATION

This study was registered in the UMIN Clinical Trials Registry (Registry ID UMIN: 000031982).

The Reaction of Airways of Employees Working in the Environments Polluted with Heavy Metals in Mine Kosovo

This paper is studied the respiratory function as a result of the impact of air pollution in the environment of the sector of exploitation of heavy minerals such Pb, Zn, Au, Ag, Bi, Cd, PM in the mines of Trepça, Kosovo. Lung function parameters are determined by Body plethysmography. Airway resistance (Raw) was recorded and Intra-Thoracic Gas Volume (ITGV) was measured and specific resistance (SRaw) and airway specific conductance (SGaw) were calculated. The research was done in two groups, the control group and the experimental one. The control group consisted of 24 healthy people, while the experimental one is made up of 52 mining workers for the exploitation of minerals in the Trepçamine, Kosovo. The results obtained from this research indicate that the mean value of specific resistance (SRaw) is significantly higher in the experimental group (p<0.01), compared to the control group (p>0.1). Also, in this study it was confirmed that smoking favors the negative effects of air contamination in the mineral exploitation sector, the changes are significant (p<0.01). Respiratory system parameters of the control group and the experimental group were measured before and after bronchoprovocation with histamine-aerosol (1 mg/ml). The differences between these two groups after provocation were statistically significant (p<0.01). Respiratory changes from air pollution with noxae in mines where metals are mined, it takes a long time for changes in respiratory function to appear. Therefore, exposure of workers to these conditions poses a risk to their health, causing bronchial reactivity, bronchial asthma or, obstructive pulmonary syndrome.

Narrative Review of the Mechanisms and Treatment of Cough in Asthma, Cough Variant Asthma, and Non-asthmatic Eosinophilic Bronchitis

Chronic cough is a debilitating condition affecting 10-12% of the general population and is one of the leading causes for referral to secondary care. Many conditions have been associated with chronic cough, including asthma, gastro-esophageal reflux disease and upper airways cough syndrome. Inflammatory airway conditions including cough variant asthma (CVA) and non-asthmatic eosinophilic bronchitis (NAEB) contribute to a significant proportion of presentations with chronic cough, with differing diagnostic criteria and different responses to commonly used asthma therapy for their respective diagnoses. Mechanistic studies in both animal models and humans have identified increased neuronal sensitivity and subsequent central sensitization. These mechanisms include inflammatory-mediated nociceptor sensitization and alterations of afferent nerve terminal excitability, phenotypic changes in the vagal afferent neurons over time, and central neuroplasticity resulting from increased synaptic signalling from peripheral afferents. The aim of this review is to discuss the mechanisms, neurophysiology, and management approaches currently available for patients presenting with chronic cough with underlying asthma, CVA, and NAEB and to shed a light on areas of further research required to elucidate the mechanisms of cough in this patient population.

Retrospective Study of the Effects of Post-nasal Drip Symptoms on Cough Duration

BACKGROUND/AIM

The aim of this study was to elucidate the significance of allergic rhinitis and post-nasal drip symptoms in patients with cough-variant and cough-predominant asthma.

PATIENTS AND METHODS

We conducted a retrospective analysis of 91 patients who had cough-variant or cough-predominant asthma and first visited the Nakajima Medical Clinic in Japan between June 2012 and July 2015.

RESULTS

Post-nasal drip symptoms were reported in 58 (63.7%) patients. The patients with post-nasal drip symptoms (19.5±8.3 days) had a significantly longer time until cough disappearance than those without post-nasal drip symptoms (11.0±4.8 days) (p=0.000034). Multivariate analysis showed that post-nasal drip symptoms are independent prolonged factors of cough duration.

CONCLUSION

Post-nasal drip symptoms may affect cough control in patients with cough-variant and cough-predominant asthma.

Narrative Review: how long should patients with cough variant asthma or non-asthmatic eosinophilic bronchitis be treated?

The causes of chronic cough can be categorized into eosinophilic and noneosinophilic disorders, and approximately 30% to 50% of people with chronic cough have eosinophilic airway inflammation, the presence of which can be confirmed by sputum eosinophilia or elevated exhaled nitric-oxide levels. Cough variant asthma (CVA) is a phenotype of asthma which lacks wheezing or dyspnea, and consistently one of the most common causes of chronic cough worldwide. CVA and non-asthmatic eosinophilic bronchitis (NAEB) shares common feature such as chronic dry cough, eosinophilic inflammation, and development of chronic airflow obstruction (CAO) and asthma in a subset of patients. The distinctive characteristic of these conditions is the presence of airway hyperresponsiveness in CVA but not in NAEB. Coughing is responsive to bronchodilators such as beta-agonists in CVA, but such feature has not been clarified in NAEB. Inhaled corticosteroids (ICSs) are the first-line treatment, and leukotriene receptor antagonists are also effective, in patients with both CVA and NAEB. This review will give an outline of clinical and physiological features, and prognosis and its determinants of CVA and EBNA. Further, the rationale and evidence, despite limited, for the need of long-term treatment will be discussed. The development of airway remodeling due to mechanical stress to the airways exerted by long-standing coughing will also be discussed.

The Japanese respiratory society guidelines for the management of cough and sputum (digest edition)

Cough and sputum are common complaints at outpatient visits. In this digest version, we provide a general overview of these two symptoms and discuss the management of acute (up to three weeks) and prolonged/chronic cough (longer than three weeks). Flowcharts are provided, along with a step-by-step explanation of their diagnosis and management. Most cases of acute cough are due to an infection. In chronic respiratory illness, a cough could be a symptom of a respiratory infection such as pulmonary tuberculosis, malignancy such as a pulmonary tumor, asthma, chronic obstructive pulmonary disease, chronic bronchitis, bronchiectasis, drug-induced lung injury, heart failure, nasal sinus disease, sinobronchial syndrome, eosinophilic sinusitis, cough variant asthma (CVA), atopic cough, chronic laryngeal allergy, gastroesophageal reflux (GER), and post-infectious cough. Antibiotics should not be prescribed for over-peak cough but can be considered for atypical infections. The exploration of a single/major cause is recommended for persistent/chronic cough. When sputum is present, a sputum smear/culture (general bacteria, mycobacteria), cytology, cell differentiation, chest computed tomography (CT), and sinus X-ray or CT should be performed. There are two types of rhinosinusitis. Conventional sinusitis and eosinophilic rhinosinusitis present primarily with neutrophilic inflammation and eosinophilic inflammation, respectively. The most common causes of dry cough include CVA, atopic cough/laryngeal allergy (chronic), GER, and post-infectious cough. In the last chapter, future challenges and perspectives are discussed. We hope that the clarification of the pathology of cough hypersensitivity syndrome will lead to further development of "pathology-specific non-specific therapeutic drugs" and provide benefits to patients with chronic refractory cough.

Manifestation of bronchial hyperreactivity from exposure to heavy and precious metal vapors among the ore smeltery workers of Zveçan, Kosovo

Context:

Kosovo is a region in the Western Balkans that is rich in minerals and coal, so pollution is a serious public health problem there. Workers in the heavy and precious metal smeltery in Zveqan, Kosovo, were studied with regard to the roles that vapor from the smelting of metals (Pb, Zn, Au, Ag, P, and Cu) and particulate matter play in causing bronchial hyperreactivity.

Objectives:

The purpose of the article was to measure the parameters of lung function as determined by body plethysmography, diagnosis of respiratory diseases, and assessment of respiratory function using a histamine bronchoprovocation test.

Settings and Design:

The present study was conducted in two groups of participants: A control group, which included 25 healthy persons, and a smeltery worker group, which included 45 mine workers (15 smokers and 30 nonsmokers) holding permanent jobs in the mineral foundry of Zvecan, Kosovo.

Subjects and Methods:

Pulmonary function parameters (specific airway resistance [Raw] and intrathoracic gas volume) were measured and used to calculate the specific resistance (SRaw)and specific conductance (SGaw) of the airways, and a histamine bronchoprovocation test was conducted.

Statistical Analysis Used:

The data were entered and analyzed using the Microsoft Excel and INSTAT 3 software.

Results:

Airway specific resistance (SRaw) was significantly higher in the smeltery worker group (P < 0.01) as compared to the control group (P > 0.1).

Conclusion:

These results suggest that occupational exposure to vapors during the metal refining process poses a risk to the workers' health and can cause bronchial hyperreactivity, bronchial asthma, or chronic obstructive pulmonary disease.

Suhuang Zhike Capsules for the Treatment of Cough Variant Asthma: A Meta-analysis

Cough variant asthma (CVA) is a unique type of asthma characterized by cough as the only or primary clinical presentation. Inhaled glucocorticoid is the main treatment in clinical practice currently, but its efficacy remains relatively unsatisfactory. Traditional Chinese medicine has certain advantages in the treatment of CVA, and at present, the most commonly used traditional Chinese medicine is Suhuang Zhike Capsule (SZC). The aim of this study was to systematically evaluate the efficacy and safety of SZC in the treatment of CVA using a meta-analysis. A comprehensive search of papers published in the PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Chinese Biomedical Literature database (CBM), Wanfang Database, and VIP Information (VIP) from January 2018 to June 2019 was conducted. Review Manager 5.3 was used to carry out a meta-analysis of 10 studies that fulfilled the inclusion criteria. In a total of 10 randomized controlled trials, 896 CVA patients were included. The results showed the following: (1) compared with conventional Western medicine, SZC can effectively increase the efficacy rate of CVA (RR 1.25, 95% CI, 1.16-1.35, P < 0.00001) and (2) compared with other traditional Chinese medicines, SZC can effectively increase the efficacy rate of CVA (RR 1.44, 95% CI, 1.01-2.05, P=0.05), In conclusion, our study builds on existing clinical evidence showing that SZC is safe and effective in treating CVA. However, larger randomized controlled trials are required for further validation.

Inflammatory Subtypes in Classic Asthma and Cough Variant Asthma

Background

Measurement of sputum is used to define airway inflammatory phenotypes. Cough variant asthma (CVA) is considered to be the initial stage of classic asthma (CA). The aim of this study was to describe the association between the different subtypes of CVA and CA.

Methods

A total of 459 patients with CVA and CA were screened for the study. All included patients performed spirometry, underwent a bronchial challenge with methacholine and induced sputum according to the guidelines.

Results

A higher frequency of female patients were found with CVA and the eosinophilic airway inflammation of CVA than in CA and the noneosinophilic airway inflammation of CA (p=0.004 and p=0.024, respectively). Bronchial hyper-responsiveness (BHR) was lower in eosinophilic CVA and CA (p=0.006), while no difference was found in noneosinophilic CVA and CA. Association between the percentage of sputum eosinophils and the FEV₁ level fell below 20% of the baseline value (PD₂₀) in CVA and CA (r= −0.1245, p=0.0357 and r= −0.2148, p=0.0014, respectively).

Conclusion

Eosinophilia may be associated with more severe disease, yet there was no difference in spirometry between the eosinophilic and noneosinophilic groups, and the BHR difference was not dramatic.

A multicenter, prospective, observational study on montelukast monotherapy or montelukast-based combinations treating cough variant asthma

Background

Evidence of treatment against cough variant asthma (CVA) is insufficient for the clinical practice in China. We aimed at evaluating the real-world effectiveness of montelukast (MONT) alone or in combination with low-dose inhaled corticosteroids (ICS) and low-dose ICS plus long-acting beta-2-agonists (LABA) for Chinese CVA patients in a multicentre, prospective, cohort study.

Methods

Adult patients diagnosed with CVA defined as chronic cough >8 weeks with a positive bronchial provocation test and normal chest X-ray findings were enrolled at respiratory clinics. Study treatment followed routine clinical practice. The investigators initiated MONT by 10 mg/day alone or in combination with a low-dose ICS +/− LABA and followed up treatment outcomes for 4 weeks. The primary outcome measure was the change in cough score (CS) from baseline.

Results

The study enrolled 247 patients (MONT =146, MONT + ICS =38, MONT + ICS/LABA =63). In the primary analysis, the mean change (95% CI) in CS at the end of the study was −1.2 (−1.6, −0.9), −0.9 (−1.5, −0.4), and −1.3 (−1.7, −0.8) in the three groups, respectively. MONT monotherapy had a satisfactory rate of weekly asthma control at the end of the study (83.5%, 95% CI: 75.1%, 89.4%) in the per-protocol analysis. Rates of weekly asthma control were similar in two MONT-based combination regimens (83.9%, 81.4%). Short-acting beta-2-agonist (SABA) user (≥2 times per week) was 16.8% in the MONT group.

Conclusions

The real-world effectiveness of MONT alone or in combination with ICS or ICS and LABA was acceptable for CVA short-term control.

Methacholine-induced cough as an indicator of bronchodilator-responsive cough

BACKGROUND

Cough variant asthma (CVA) is the most common cause of chronic cough and responds well to bronchodilator therapy. Previous studies on methacholine -induced cough have shown that heightened cough response due to bronchoconstriction is a feature of CVA. The aim of this study was to assess Mch-induced cough as an indicator of bronchodilator-responsive cough (BRC).

METHODS

This was a single-center retrospective study of prolonged/chronic cough cases who underwent evaluation via spirometry, FeNO and bronchial challenge testing using Mch and capsaicin (C5). Resultant bronchoconstriction after Mch challenge was assessed by flow-volume curves measuring the expiratory flow of the partial flow-volume curve 40% above residual volume (PEF₄₀) and FEV₁. BRC was defined as a decrease in cough with bronchodilator therapy by 30% or more on a visual analog scoring scale.

RESULTS

Of the 100 patients evaluated, 63 were diagnosed with BRC. Mch-induced cough at a decrease in PEF₄₀ of 35% (PC₃₅-PEF₄₀) was predictive of BRC on AUROC analysis with an AUC of 0.82 (95% CI 0.73-0.90) and cut-off of 24. The AUC for C5, FeNO and PC₂₀-FEV₁ were 0.65, 0.47, and 0.58, respectively.

CONCLUSION

Compared to C5, FeNO and PC₂₀-FEV₁, Mch-induced cough better supports a diagnosis of BRC.

Exploring the role of nerves in asthma; insights from the study of cough

Cough in asthma predicts disease severity, prognosis, and is a common and troublesome symptom. Cough is the archetypal airway neuronal reflex, yet little is understood about the underlying neuronal mechanisms. It is generally assumed that symptoms arise because of airway hyper-responsiveness and/or airway inflammation, but despite using inhaled corticosteroids and bronchodilators targeting these pathologies, a large proportion of patients have persistent coughing. This review focuses on the prevalence and impact of cough in asthma and explores data from pre-clinical and clinical studies which have explored neuronal mechanisms of cough and asthma. We present evidence to suggest patients with asthma have evidence of neuronal dysfunction, which is further heightened and exaggerated by both bronchoconstriction and airway eosinophilia. Identifying patients with excessive coughing with asthma may represent a neuro-phenotype and hence developing treatment for this symptom is important for reducing the burden of disease on patients' lives and currently represents a major unmet clinical need.

Interfering with airway nerves in cough associated with asthma

Cough is a troublesome and often refractory symptom of asthma, which is associated with poor control of disease. The pathogenesis of asthmatic cough has mainly been attributed to bronchoconstriction, but recent evidence indicate that cough reflex hypersensitivity or neuronal dysfunction is a feature of asthma, even in those with mild stable disease. This is likely resistant to the mainstay treatment ICS/LABA which inhibits classic asthmatic response. Such refractory cough might manifest more predominantly in the day-time rather than night-time. Treatment options of such refractory cough or cough reflex hypersensitivity in asthma targeting the nerves (LTRAs, tiotropium, and potentially bronchial thermoplasty) are discussed.

Clinical Characteristics of Cough Frequency Patterns in Patients with and without Asthma

BACKGROUND

Cough is a frequent symptom of asthma. Cough frequency (CoFr) monitoring devices are now available to objectively measure cough counts and offer a novel endpoint to assess asthma. However, little is known about CoFr in asthma.

OBJECTIVE

The aims were, first, to determine whether unique features of CoFr exist in asthmatic and nonasthmatic patients and, secondly, to evaluate relationships between CoFr and pathophysiological parameters of asthma.

METHODS

In the current study, 73 asthmatic and 63 nonasthmatic patients suffering from persistent cough were enrolled. At study entry, the Leicester Cough Questionnaire (LCQ health status), cough visual analog scale (VAS), Leicester Cough Monitor (LCM), fractional exhaled nitric oxide (FeNO) measurements, and spirometry were performed. In asthmatic patients, the bronchial hyperresponsiveness (BHR) test was conducted if applicable. In 28 asthmatic and 17 nonasthmatic patients, LCQ, VAS, and LCM were examined before and after treatment.

RESULTS

CoFr during nighttime (asleep) was significantly higher in asthmatic patients than in nonasthmatic patients. Twenty-four-hour CoFr significantly decreased after appropriate treatment and was correlated with changes in VAS and LCQ in all patients. The improvement in cough in asthmatic patients was greater during nighttime than during daytime (awake). CoFr in asthmatic patients was significantly correlated with BHR, but not with FeNO.

CONCLUSIONS

In asthmatic patients, nocturnal CoFr can be associated with BHR, was significantly higher before treatment, but improved more after treatment compared with nonasthmatic patients. Monitoring nocturnal CoFr may provide unique and valuable information on making an early prediction of therapeutic effects in asthma.

Small-airway obstruction, dynamic hyperinflation, and gas trapping despite normal airway sensitivity to methacholine in adults with chronic cough

The clinical relevance of cough during methacholine challenge in individuals with normal airway sensitivity is unknown. We compared responses of individuals with chronic cough who cough during high-dose methacholine bronchoprovocation and have normal versus increased airway sensitivity to healthy controls. Fifteen healthy participants (CONTROL) aged 26 ± 7 yr (mean ± SD) and 32 participants aged 42 ± 14 yr with chronic cough and suspected asthma completed high-dose methacholine challenge testing. Three participants who did not cough and had normal airway sensitivity were excluded. Spirometry and lung volumes were compared at the maximum response (MAX) among 1) ASTHMA [ n = 15, provocative concentration of methacholine causing a 20% fall in forced expiratory volume in 1 s (FEV₁) from baseline (PC₂₀) 4.71 ± 1.37 mg/ml], 2) methacholine-induced cough with normal airway sensitivity (COUGH, n = 14, PC₂₀ 41.2 ± 18.7 mg/ml for 3 participants with a measurable PC₂₀), and 3) CONTROL ( n = 15; PC₂₀ 93.4 ± 95.4 mg/ml for 4 participants with a measurable PC₂₀). Esophageal pressure-derived pulmonary mechanics were compared at MAX for the ASTHMA and COUGH groups. From baseline to MAX, FEV₁ and forced expiratory flow between 25% and 75% of forced vital capacity decreased more in ASTHMA (-36.2 ± 3.8 %pr; -47.1 ± 6.9 %pr, respectively) than COUGH (-12.2 ± 3.0 %pr ( P < 0.001); -24.7 ± 6.5 %pr ( P < 0.001), respectively) and CONTROL (-13.7 ± 2.0 %pr ( P < 0.001); -32.8 ± 5.4 %pr ( P < 0.017), respectively). In both ASTHMA and COUGH, inspiratory capacity decreased by 500-800 ml, and functional residual capacity and residual volume increased by ~800 ml. Individuals with COUGH develop dynamic hyperinflation and gas trapping comparable to individuals with ASTHMA despite less bronchoconstriction and smaller reductions in mid-to-late expiratory flows, which leads us to believe that COUGH is a distinct phenotype. NEW & NOTEWORTHY Healthy individuals and individuals with chronic cough who demonstrate normal airway sensitivity but cough during methacholine bronchoprovocation bronchoconstrict less than individuals with mild asthma. However, those who cough and have normal airway sensitivity develop dynamic hyperinflation and gas trapping comparable to individuals with mild asthma. Thus, methacholine-induced cough with normal airway sensitivity may be clinically relevant, related to reversible small airway obstruction and preservation of the bronchodilating and/or bronchoprotective effects of deep inspirations.

Pattern of Response to Bronchial Challenge with Histamine in Patients with Non-Atopic Cough-Variant and Classic Asthma

Background: The aim of this study was to establish whether non-atopic patients with cough variant asthma (CVA) have different pattern of response to direct bronchoconstrictors than non-atopic patients with classic asthma (CA). Method: A total of 170 patients of both sexes with stable CVA and CA were screened for the study and 153 were included. Patients with proven atopy were not included and 17 patients with worsening of their condition or with verified bronchial obstruction during screening were excluded. All included patients performed spirometry and underwent a bronchial challenge with histamine according to long-standing protocol in our laboratory. Results: Significantly higher frequency of bronchial hyper-responsiveness (BHR) was found in patients with CA than in patients with CVA (63.9% vs. 44.9%, respectively; p < 0.05). Sensitivity was significantly lower in patients with CVA (p < 0.05), while no significant difference was found in maximal response and responsiveness. Only patients with positive challenge tests were included in the analysis. Conclusion: Adult non-atopic patients with CVA and CA have a pattern of response to non-specific bronchial stimuli similar to atopic patients with same conditions, with the exception of similar maximal response, which may reflect the efficacy of previous treatment. We believe that further studies are needed to clarify the mechanisms involved in airway response to non-specific stimuli in CVA and CA, especially in non-atopic patients. Further studies should also clarify whether this response pattern has any implications on clinical presentation or on treatment options.

Tiotropium Attenuates Refractory Cough and Capsaicin Cough Reflex Sensitivity in Patients with Asthma

BACKGROUND

Asthmatic cough is often refractory to standard treatments such as inhaled corticosteroids (ICS) and long-acting β₂ agonists (LABA). Tiotropium may modulate cough reflex sensitivity of acute viral cough, but its efficacy in asthmatic cough remains unknown.

OBJECTIVE

To evaluate whether tiotropium improves cough and cough reflex sensitivity in patients with asthma refractory to ICS/LABA.

METHODS

Seventeen consecutive patients with asthma with chronic cough despite the use of ICS/LABA (13 women; 43.4 ± 19.0 years; average ICS dose, 651 ± 189 μg/d; fluticasone equivalent) were additionally treated with tiotropium (5 μg/d) for 4 to 8 weeks to examine its effects on pulmonary function and capsaicin cough reflex sensitivity (cough thresholds C2 and C5). Cough severity, cough-specific quality of life, and asthma control were also evaluated using cough visual analog scales (VASs), the Japanese version of Leicester Cough Questionnaire (J-LCQ), and Asthma Control Test (ACT), respectively. Patients with an improved cough VAS score of 15 mm or more were considered responders to tiotropium.

RESULTS

Tiotropium significantly improved cough VAS, J-LCQ, and ACT scores, but not FEV₁. Changes in cough VAS score correlated with those in C2 (r = -0.58; P = .03), C5 (r = -0.58; P = .03), and ACT scores (r = -0.62; P = .02), but not in FEV₁ in the overall patients. When analyses were confined to the 11 responders, tiotropium significantly improved capsaicin cough reflex sensitivity within the subgroup (C2: P = .01 and C5: P = .02) and versus the nonresponders (C2: P = .004 and C5: P = .02).

CONCLUSION

Tiotropium may alleviate asthmatic cough refractory to ICS/LABA by modulating cough reflex sensitivity but not through bronchodilation.

The measurement of cough response to bronchoconstriction induced by methacholine inhalation in healthy subjects: An examination using the Astograph method

BACKGROUND

We demonstrated that heightened cough response to bronchoconstriction is a fundamental feature of cough variant asthma (CVA). To evaluate this physiological feature of CVA in daily clinical practice, it is necessary to clarify the cough response to bronchoconstriction in healthy subjects. We evaluated cough response to methacholine (MCh)-induced bronchoconstriction in healthy subjects. A forced oscillometry technique was used to measure airway resistance changes with Mch.

METHODS

Healthy never-smokers (21 men, 20 women; mean 22.3 ± 3.7 years) participated. None had a >3-week cough history, clinically significant respiratory or cardiovascular disorders, or disorders that might put subjects at risk or influence the study results or the subjects' ability to participate. Twofold increasing concentrations of Mch chloride diluted in phosphate-buffered saline (0.039 to 160 mg/mL) were inhaled from nebulizers at 1-minute intervals during subjects' tidal breathing after the baseline respiratory resistance (Rrs) was recorded. Mch inhalation continued until Rrs reached twice the baseline value and forced expiratory volume in 1 second (FEV₁) decreased to <90% of baseline value. Spirometry was measured before Mch inhalation and immediately after Rrs had increased twofold. Coughs were counted during and for 30 minutes after Mch inhalation. The cough reflex sensitivity to capsaicin was also examined.

RESULTS

The number of coughs was 11.1 ± 14.3 (median, 7.0; range, 0 to 71; reference range, 0 to 39.7). There was no significant difference in the cough response between the sexes. The reproducibility of the cough response to bronchoconstriction was sufficient. No correlation existed between the bronchoconstriction-induced cough response and capsaicin cough-reflex sensitivity.

CONCLUSIONS

Using the Astograph method, cough response to bronchoconstriction could be measured easily, safely and highly reproducibly in healthy subjects.

[Comparison of functional parameters of small airways between patients with typical asthma and cough-variant asthma]

OBJECTIVE

To compare the functional parameters of the small airways and clinical characteristics between patients with typical asthma (TA) and cough-variant asthma (CVA).

METHODS

Forty-three newly diagnosed asthmatic patients were enrolled, including 15 with TA and positive bronchial provocation test [TA BPT(+)], 12 with TA and positive bronchial dilation test [TA BDT(+)] and 16 with CVA, and 27 healthy subjects served as the control group. All the subjects were required to complete data acquisition, asthma control test, asthma control test scale, fractional exhaled nitric oxide, airway resistance and pulmonary function tests, BPT or BDT.

RESULTS

The interval from onset to a definite diagnosis of TA BDT(+) was longer than that of TA BPT(+), while that of CVA was the shortest (P=0.022). The pulmonary functional parameters of TA BDT (+) was significantly lower than those of the other 3 groups (P<0.05). MMEF, MEF75, MEF50, and MEF25 in patients with TA BDT(+), TA BPT(+) and CVA were significantly lower than those in the control group (P<0.01). The resonant frequency, respiratory impedance, resistance at 5 Hz, resistance at 20 Hz, and reactance at 5 Hz were significant higher in patients with TA BDT (+) than in the control subjects, while these parameters showed no significant differences among TA BPT (+), CVA and control groups. The airway resistance in TA BPT(+), CVA, and control groups increased after BPT, and the patients with TA BPT(+) showed greater changes in airway resistance than those in CVA and control groups. In CVA patients, FeNO showed a strong positive correlation with respiratory impedance (r=0.523, P=0.038), resistance at 5 Hz (r=0.542, P=0.030), and resistance at 20 Hz (r=0.524, P=0.037), and the airway responsiveness showed a strong positive correlation with resistance at 20 Hz (Rho=-0.512, P=0.043).

CONCLUSION

CVA is the early stage of TA, and CVA, TA BPT(+), and TA BDT(+) may represent different stages of asthma. Uncontrolled, prolonged CVA may evolve into TA BPT (+), whose further progression can cause damages of the pulmonary function and small airway function and leads eventually to TA BDT (+).

[Comparison of functional parameters of small airways between patients with typical asthma and cough-variant asthma]

OBJECTIVE

To compare the functional parameters of the small airways and clinical characteristics between patients with typical asthma (TA) and cough-variant asthma (CVA).

METHODS

Forty-three newly diagnosed asthmatic patients were enrolled, including 15 with TA and positive bronchial provocation test [TA BPT(+)], 12 with TA and positive bronchial dilation test [TA BDT(+)] and 16 with CVA, and 27 healthy subjects served as the control group. All the subjects were required to complete data acquisition, asthma control test, asthma control test scale, fractional exhaled nitric oxide, airway resistance and pulmonary function tests, BPT or BDT.

RESULTS

The interval from onset to a definite diagnosis of TA BDT(+) was longer than that of TA BPT(+), while that of CVA was the shortest (P=0.022). The pulmonary functional parameters of TA BDT (+) was significantly lower than those of the other 3 groups (P<0.05). MMEF, MEF₇₅, MEF₅₀, and MEF₂₅ in patients with TA BDT(+), TA BPT(+) and CVA were significantly lower than those in the control group (P<0.01). The resonant frequency, respiratory impedance, resistance at 5 Hz, resistance at 20 Hz, and reactance at 5 Hz were significant higher in patients with TA BDT (+) than in the control subjects, while these parameters showed no significant differences among TA BPT (+), CVA and control groups. The airway resistance in TA BPT(+), CVA, and control groups increased after BPT, and the patients with TA BPT(+) showed greater changes in airway resistance than those in CVA and control groups. In CVA patients, FeNO showed a strong positive correlation with respiratory impedance (r=0.523, P=0.038), resistance at 5 Hz (r=0.542, P=0.030), and resistance at 20 Hz (r=0.524, P=0.037), and the airway responsiveness showed a strong positive correlation with resistance at 20 Hz (Rho=-0.512, P=0.043).

CONCLUSION

CVA is the early stage of TA, and CVA, TA BPT(+), and TA BDT(+) may represent different stages of asthma. Uncontrolled, prolonged CVA may evolve into TA BPT (+), whose further progression can cause damages of the pulmonary function and small airway function and leads eventually to TA BDT (+).

"Cold air" and/or "talking" as cough triggers, a sign for the diagnosis of cough variant asthma

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is considered an alternative marker of eosinophilic airway inflammation and is sometimes incorporated in the diagnosis of asthma. However, many patients with cough variant asthma (CVA) demonstrate an FeNO in the normal range. Therefore, additional information is needed to confirm the diagnosis of CVA, particularly in patients with low FeNO levels. We aimed to investigate the feasibility of using cough triggers to help diagnose CVA.

METHODS

We studied 163 patients presenting with prolonged/chronic cough alone (including 104 CVA patients) who underwent FeNO measurements and an airway responsiveness test, and answered a questionnaire listing 18 cough triggers. The sensitivity and specificity of FeNO levels and cough triggers for the diagnosis of CVA were determined.

RESULTS

CVA patients showed higher FeNO levels than non-CVA patients. When the cut-off value of FeNO levels for the diagnosis of CVA was set at 22ppb, its sensitivity was 57%. CVA patients more frequently responded to "cold air" and "talking" as cough triggers than non-CVA patients. When the analysis was confined to those with a low FeNO (<22ppb) group, the sensitivity and positive predictive values of "cold air" and "talking" for the diagnosis of CVA were 36% and 70% for "cold air", and 44% and 74% for "talking", respectively. Their specificity was 81%. "Cold air" was associated with airway hyperresponsiveness in all patients with an emphasis on those with low FeNO levels.

CONCLUSION

"Cold air" and/or "talking" as cough triggers could be signs for the diagnosis of CVA, particularly when FeNO levels are low.

Gastroesophageal dysmotility is associated with the impairment of cough-specific quality of life in patients with cough variant asthma

BACKGROUND

Gastroesophageal reflux disease (GERD) is known as a common comorbidity of asthma and chronic cough. The impact of GERD symptoms on cough-specific quality of life (QoL) in patients with asthmatic cough is poorly understood. The aim of this study is to determine the association of GERD symptoms with cough-specific quality of life in patients with cough variant asthma (CVA) using the Leicester Cough Questionnaire (LCQ).

METHODS

A total of 172 consecutive patients (121 females) with mean cough duration of 45.1 months (range 2-480 months) completed the Japanese version of the LCQ. The Frequency Scale for the Symptoms of Gastroesophageal reflux was administered to assess symptoms of acid-reflux and dysmotility. A range of clinical variables that may determine cough-specific QoL (LCQ) were estimated.

RESULTS

The mean LCQ scores was 12.9 (SD 3.5), consistent with severe impairment in QoL. Female gender, symptoms of gastroesophageal dysmotility, sensitization to allergens (house dust and Japanese cedar pollen) and the number of sensitized allergens were associated with lower LCQ scores (i.e. impaired cough-specific QoL) in univariate regression analysis. Acid-reflux symptoms, airway hyperresponsiveness, fractional exhaled nitric oxide, and sensitization to molds were unrelated to the LCQ score. After adjustment for gender, symptoms of gastroesophageal dysmotility was the only significant determinant of impaired cough-specific QoL accounting for 23% of the variance.

CONCLUSIONS

Cough-specific QoL is severely impaired in patients with CVA. Symptoms of gastroesophageal dysmotility are an independent predictor of cough-specific QoL of patients with CVA.

Trigger of bronchial hyperresponsiveness development may not always need eosinophilic airway inflammation in very early stage of asthma

Background:

Cough variant asthma (CVA), a suggested precursor of standard bronchial asthma (SBA), is characterized by positive bronchial hyperresponsiveness (BHR) and a chronic cough response to bronchodilator that persists for >8 weeks.

Objective:

Airway inflammation, BHR, and airway obstructive damage were analyzed to assess whether CVA represents early or mild-stage SBA.

Methods:

Patients with newly diagnosed CVA (n = 72) and SBA (n = 84) naive to oral or inhaled corticosteroids and without exacerbated asthma were subjected to spirometry, impulse oscillometry, BHR tests, sputum induction, and fractional exhaled nitric oxide measurements.

Results:

In the patients with CVA, spirometry demonstrated higher forced expiratory volume in 1 second (FEV₁) to forced vital capacity ratio, FEV₁ percent predicted, flow volume at 50% of vital capacity % predicted, and flow volume at 25% of vital capacity % predicted values, and impulse oscillometry demonstrated lower R₅–Z₂₀, AX, and Fres, and higher X₅ values. In addition, the fractional exhaled nitric oxide and sputum eosinophil numbers were lower and the PC₂₀ was higher than in patients with moderate SBA. However, these factors were similar in the patients with CVA and in the patients with intermittent mild SBA. A significantly smaller proportion of the patients with CVA had increased sputum eosinophils than the patients with intermittent mild SBA (p < 0.0001). However, interestingly, among the patients with CVA, no significant differences in the PC₂₀ values were found between the patients with and those without increased sputum eosinophils.

Conclusions:

All measures of central and peripheral airway obstruction, eosinophilic inflammation, and airway hyperresponsiveness in patients with CVA were milder than in patients with moderate SBA but were similar to those of patients with intermittent mild SBA. In CVA, the BHR was not affected by airway eosinophilic inflammation, which indicated that the very early development of BHR may not always need airway eosinophilic inflammation.

Bronchodilating effect of deep inspirations in asthma and chronic cough

The pathophysiologic processes distinguishing classic asthma (CA), cough-variant asthma (CVA), and methacholine (MCh)-induced cough but normal airway sensitivity (COUGH) are inadequately understood and may be a result of differences in the ability to bronchodilate following a deep inspiration (DI). The purpose of this study was to compare the bronchodilating effect of DIs in individuals with CA, CVA, and COUGH using high-dose MCh. Individuals aged 18-65 yr with CA or suspected CVA completed high-dose MCh testing to a maximum change in forced expiratory volume in 1 s (FEV1) of 50% from baseline (MAX). Impulse oscillometry (IOS) measurements and partial and maximal-flow volume curves (used to calculate a DI index) were recorded at baseline and at each dose of MCh. Body plethysmography was performed at baseline and MAX. Twenty-eight subjects [25 women, 39.8 ± 11.9 yr (means ± SD)] were studied (n = 11 CA, n = 10 CVA, and n = 7 COUGH). At MAX, the percent change in FEV1 was greater in subjects with CA compared with those with CVA (P < 0.001) and COUGH (P < 0.001), and the percent change in forced vital capacity was greater in those with CA than with COUGH (P = 0.017). Subjects with CA and CVA developed dynamic hyperinflation and gas trapping. In subjects with CA and CVA, all IOS parameters were significantly increased from baseline to MAX, except for central respiratory resistance (R20). In individuals with COUGH, total respiratory resistance, R20, and resonant frequency were significantly increased from baseline. At MAX, the DI index was positive in all groups, suggesting preserved bronchodilation (CA, 0.67 ± 0.97; CVA, 0.51 ± 0.73; COUGH, 0.01 ± 0.36; P = 0.211). We conclude that the bronchodilating effect of DIs is preserved in individuals with CA, CVA, and borderline with COUGH; however, hyperinflation and gas trapping are avoided in subjects with COUGH alone.

Therapeutic effects of naringin in a guinea pig model of ovalbumin-induced cough-variant asthma

Naringin, a well known component isolated from Exocarpium Citri Grandis, has significant antitussive effects. Recently, Naringin exhibited novel anti-inflammatory effect in chronic inflammatory diseases. In this work, we firstly evaluated the effects of naringin on enhanced cough, airway hyper-responsiveness (AHR), and airway inflammation in an ovalbumin-induced experimental cough-variant asthma (CVA) model in guinea pigs. We investigated the effect of naringin (18.4 mg/kg, per os, single dose or consecutively) on cough to inhaled capsaicin after challenge with an aerosolized antigen in actively sensitized guinea pigs. The effect of naringin on AHR to inhaled methacholine was evaluated 24 h after cough determination. Airway inflammation was assessed via bronchoalveolar lavage fluid (BALF) cytology and lung histopathology. Naringin, given consecutively, significantly reduced ovalbumin-induced enhanced cough and AHR, inhibited the increases in the leukocytes, interleukin-4 (IL-4), IL-5, and IL-13 in BALF compared with the model group. Moreover, the pathologic changes in lung tissues were clearly ameliorated by naringin treatment. These results suggest that naringin may be a beneficial agent for CVA treatment.

Prevalence and clinical relevance of allergic rhinitis in patients with classic asthma and cough variant asthma

BACKGROUND

A clinically relevant relationship between classic asthma and allergic rhinitis has been reported. However, the possible link between cough variant asthma (CVA) and allergic rhinitis remains unknown.

OBJECTIVES

To clarify the prevalence and clinical relevance of perennial allergic rhinitis or seasonal allergic rhinitis in CVA patients compared to classic asthma patients.

METHODS

We retrospectively studied adult patients with classic asthma (n = 190) and those with CVA (n = 83). The prevalence of perennial allergic rhinitis or seasonal allergic rhinitis and associations of concomitant perennial or seasonal allergic rhinitis with asthma severity, forced expiratory volume in 1 s (% predicted), fractional exhaled nitric oxide (FeNO) levels, and eosinophil proportions in sputum and blood were analyzed in the two groups.

RESULTS

The prevalence of perennial allergic rhinitis and/or seasonal allergic rhinitis was significantly higher in classic asthma patients than in CVA patients (all p < 0.05). Concomitant perennial allergic rhinitis was associated with higher FeNO levels and eosinophil proportions in sputum and blood in classic asthma patients (p = 0.035, p = 0.036, and p = 0.008, respectively) and with higher asthma severity, FeNO levels, and sputum eosinophil proportions in CVA patients (p = 0.031, p = 0.007, and p = 0.010, respectively). Concomitant seasonal allergic rhinitis was only associated with higher sputum eosinophil proportions in CVA patients with active rhinitis symptoms during the sensitized pollen season (p = 0.025).

CONCLUSIONS

Perennial allergic rhinitis may be relevant for CVA patients as well as classic asthma patients by consistently augmenting eosinophilic lower airway inflammation.

Cough in asthma is due to eosinophilic airway inflammation: a pro/con debate

Multiple prospective studies have demonstrated that asthma is among the most common etiologies of chronic cough, along with upper-airway cough syndrome (formerly known as postnasal drip syndrome) and gastroesophageal reflux disease. More recently, the entity of nonasthmatic eosinophilic bronchitis has been appreciated as a significant cause of chronic cough worldwide. Chronic cough associated with both of these conditions typically responds well to therapy with systemic or inhaled corticosteroids, thus leading to a general assumption that the suppression of eosinophilic airway inflammation explains the improvement in cough. However, some recent studies challenge a causal relationship between eosinophilic airway inflammation and cough in asthmatics. The 4th American Cough Conference, held in New York in June 2013, provided an ideal forum for discussion and debate of this issue between two internationally recognized experts in the field of asthma and chronic cough.

A network-based systematic study for the mechanism of the treatment of zhengs related to cough variant asthma

Traditional Chinese medicine (TCM) has shown significant efficacy in the treatment of cough variant asthma (CVA), a special type of asthma. However, there is shortage of explanations for relevant mechanism of treatment. As Zhengs differentiation is a critical concept in TCM, it is necessary to explain the mechanism of treatment of Zhengs. Based on TCM clinical cases, this study illustrated the mechanism of the treatment of three remarkably relevant Zhengs for CVA: “FengXieFanFei,” “FeiQiShiXuan”, and “QiDaoLuanJi.” To achieve this goal, five steps were carried out: (1) determining feature Zhengs and corresponding key herbs of CVA by analyses of clinical cases; (2) finding out potential targets of the key herbs and clustering them based on their functional annotations; (3) constructing an ingredient-herb network and an ingredient network; (4) identifying modules of the ingredient network; (5) illustrating the mechanism of the treatment by further mining the latent biological implications within each module. The systematic study reveals that the treatment of “FengXieFanFei,” “FeiQiShiXuan,” and “QiDaoLuanJi” has effects on the regulation of multiple bioprocesses by herbs containing different ingredients with functions of steroid metabolism regulation, airway inflammation, and ion conduction and transportation. This network-based systematic study will be a good way to boost the scientific understanding of mechanism of the treatment of Zhengs.

Cough, asthma, and cysteinyl-leukotrienes

Asthma is a chronic inflammatory disease of the lower airways, involving various cells such as eosinophils, and cytokines and mediators. Cyteinyl-leukotrienes (cys-LTs) are one of the chemical mediators that play major pathophysiological roles in asthma. They are produced by eosinophils and mast cells, and induce bronchoconstriction, mucous hypersecretion, microvascular leakage, eosinophil chemotaxis and airway remodeling. Anti-leukotrienes, including leukotriene receptor antagonists (LTRAs) which block cysLT1 receptors, exert both bronchodilatory and anti-inflammatory effects and are utilized as second- to third-line controller medication of persistent asthma. Cough is a major symptom of asthma, and cough variant asthma (CVA) is an asthma phenotype that solely presents with coughing. Sputum levels of cys-LTs are increased in patients with CVA. Antitussive effects of monotherapy with LTRAs in patients with CVA have been reported. We have recently demonstrated that 4 weeks' treatment with an LTRA montelukast exerted anti-inflammatory effect as proved by a decrease of sputum eosinophils, in addition to attenuation of cough VAS and capsaicin cough sensitivity, as reported previously. Spirometry, airway responsiveness, and impulse oscillation indices (respiratory resistance and reactance) were unchanged. These results suggested that the antitussive effect of montelukast in CVA might be attributable to its anti-inflammatory ability rather than bronchodilation. The treatment did not affect sputum levels of mediators (cys-LTs, LTB4, PGD2, PGE2, PGF2α, and TXB2). Since inhaled corticosteroid does not seem to affect cough sensitivity while attenuating cough in patients with CVA, LTRAs may involve different mechanism(s) from that of corticosteroid. LTRAs must theoretically be effective against cough of asthmatic subjects through its "anti-asthma" effects, while evidence supporting direct antitussive effects of cys-LTs on "cough receptors" is scarce. An important clinical question is that whether LTRAs involve non-specific antitussive effects. While a definite answer is not available yet, this possibility seems unlikely at the moment, although some secondary anti-inflammatory properties have been reported for montelukast. This issue needs to be clarified by future research to avoid overuse of this expensive class of medication.

The fractional exhaled nitric oxide and serum high sensitivity C-reactive protein levels in cough variant asthma and typical bronchial asthma

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is known to be a good marker of airway eosinophilic inflammation in bronchial asthma. Recently, serum high sensitivity C-reactive protein (hs-CRP) has been shown to be also useful to detect the airway inflammation.

METHODS

Newly diagnosed 90 cough variant asthma and 92 bronchial asthma patients were enrolled. FeNO, serum hs-CRP, pulmonary function tests, bronchial hyperresponsiveness, IgE and sputum eosinophils ratio were compared. Ninety healthy control subjects were set for FeNO and serum hs-CRP normal range reference. We have compared the clinical utilities of FeNO and serum hs-CRP to differentiate bronchial asthma and cough variant asthma.

RESULTS

FeNO was significantly higher in bronchial asthma (92.6 ± 85.5ppb) than in cough variant asthma (35.6 ± 43.3; p < 0.001) and both were significantly higher than normal range (18.0 ± 6.4, p < 0.001, respectively), and in differentiating between the two groups showed a sensitivity of 0.69 and a specificity of 0.73 at the cutoff value of 28 ppb. Serum hs-CRP did not differ significantly between bronchial asthma (723 ± 1162ng/ml) and cough variant asthma (558 ± 758) even if both were significantly higher than normal range (345 ± 401, p < 0.01 and p < 0.05 respectively).

CONCLUSIONS

FeNO is more useful than serum hs-CRP in differentiating patients with bronchial asthma from those with cough variant asthma, and healthy persons.

Heightened cough response to bronchoconstriction in cough variant asthma

BACKGROUND AND OBJECTIVE

The pathophysiology of cough variant asthma (CVA) is poorly understood. We compared bronchoconstriction-triggered cough between CVA patients and normal control (NC) subjects.

METHODS

There were two protocols in the study. We measured bronchial responsiveness to methacholine (MCh) and counted the number of coughs in nine CVA patients and seven NC subjects (study A). Using partial and full flow-volume curves, expiratory flow of the partial flow-volume curve at 40% above residual volume level (PEF40) and FEV(1) were used to measure bronchoconstriction. Mild bronchoconstriction was defined as a 35% fall in PEF40 (PC(35) -PEF40), and more severe bronchoconstriction as a 20% fall in FEV1 (PC20) -FEV(1) ). In study B, the same measurements were obtained in six CVA patients before and after therapy.

RESULTS

In study A, more coughs were provoked at PC35 -PEF40 in CVA patients (median, 60 coughs/32 min post challenge; range, 12-135) than in NC subjects (median, 0/32 min; range, 0-13; P < 0.05). At PC20 -FEV1 , more coughs were provoked in CVA patients (median, 60/32 min; range, 12-150) than in NC subjects (median, 20/32 min; range, 0-54; P < 0.05). In study B, the six CVA patients who underwent re-examination after treatment had less coughs at PC35 -PEF40 (median, 3/32 min; range, 0-14) and PC(20) -FEV1 (median, 13/32 min; range, 3-26) after therapy than before therapy (median, 54/32 min; range, 33-125 and 52/32 min, 45-96, respectively; P < 0.05).

CONCLUSIONS

We identified heightened cough response to bronchoconstriction as a feature of CVA.

Cough triggers and their pathophysiology in patients with prolonged or chronic cough

BACKGROUND

The character or timing of chronic cough is considered to be unpredictable for diagnosing its cause. However, the associations of cough triggers with cough pathophysiology remains unknown.

METHODS

We developed a closed questionnaire listing 18 triggers that were reported by ≥1% of 213 patients in a retrospective survey. Using this questionnaire, patients with cough-predominant or cough-variant asthma (n = 140) and those with non-asthmatic cough (54) were asked whether their cough was induced by the listed triggers. Associations of triggers with causes of cough, airway sensitivity to inhaled methacholine, exhaled nitric oxide (NO) levels, number of sensitizing allergens, and scores from gastroesophageal reflux (GER) questionnaires were examined. Factor analysis was used to categorize variables, including the 12 most common cough triggers, diagnosis of asthmatic cough, airway sensitivity, and exhaled NO levels.

RESULTS

"Cold air" and "fatigue/stress" induced cough more often in asthmatic coughers than in non-asthmatic coughers. "Spices" and "meals" induced cough more frequently in GER-coughers (n = 19). Patients who marked "cold air" as the trigger were more sensitive to inhaled methacholine and showed higher exhaled NO levels than those who did not mark this trigger. The "post-nasal drip" trigger was associated with elevated exhaled NO levels, and this association was mainly exhibited by patients with cough-predominant asthma. The triggers "pollen" and "mold smell" were associated with a number of sensitizing allergens. The number of triggers was weakly associated with GER scores. By factor analysis, "cold air," "fatigue/stress," asthmatic cough, airway hypersensitivity, and elevated NO levels were categorized into the same factor.

CONCLUSIONS

Several cough triggers may reflect the pathophysiology of prolonged or chronic cough.

Cough variant asthma: lessons learned from deep inspirations

The pathophysiology of cough variant asthma is poorly understood. In particular, the mechanisms that cause different symptoms in typical asthma (in which wheeze predominates) compared with cough variant asthma (in which cough predominates) have not been determined. Traditional explanations include higher wheezing thresholds, differences in cough sensitivity, and/or differences in small airway function. Recent studies using high-dose methacholine challenge testing suggest that altered small-airway function plays a role. Preservation or loss of the bronchoprotective effect of a deep inspiration may be a fundamental pathophysiologic difference between asthma, cough variant asthma, methacholine-induced cough with normal sensitivity, and eosinophilic bronchitis.

Cough in asthma

Asthma is one of the most common causes of chronic cough, and cough may be the sole or predominant symptom of asthma. The mechanisms of cough in asthma are complex and presumbably multi-factorial. In particular, the pathophysiologic basis of cough variant versus classic asthma is poorly understood. Recent research utilizing various inhalation challenge tests suggests that preservation of the bronchodilating and bronchoprotective effects of deep inspirations is a distinguishing feature of cough variant asthma. This review outlines the tussive agents used in cough research (including tussive and direct, indirect and combined bronchoconstrictive stimuli), their mechanisms of action, the receptors involved in eliciting cough, and characteristic responses in classic asthma and cough variant asthma.

Cough and Asthma

Cough is the most common complaint for which patients seek medical attention. Cough variant asthma (CVA) is a form of asthma, which presents solely with cough. CVA is one of the most common causes of chronic cough. More importantly, 30 to 40% of adult patients with CVA, unless adequately treated, may progress to classic asthma. CVA shares a number of pathophysiological features with classic asthma such as atopy, airway hyper-responsiveness, eosinophilic airway inflammation and various features of airway remodeling. Inhaled corticosteroids remain the most important form of treatment of CVA as they improve cough and reduce the risk of progression to classic asthma most likely through their prevention of airway remodeling and chronic airflow obstruction.

Structural changes in the airways: cause or effect of chronic cough?

Patients with a chronic cough have asthma or "asthma-related" diagnoses such as cough variant asthma or non-asthmatic eosinophilic bronchitis usually responsive to inhaled corticosteroid therapy, or non-asthma-related diagnoses including "idiopathic" or "unexplained" cases. Both of these conditions involve airway inflammation. More recently, structural changes or remodeling of the lower airways, which have been considered characteristic of classic asthma with wheezing, have also been demonstrated in patients with chronic cough, irrespective of its cause. In this article, the presence, pathogenesis, and possible consequences of such structural changes in patients with chronic cough are reviewed. Although whether chronic cough leads to structural changes or structural changes is a cause of chronic cough is difficult to determine, the concomitance of both mechanisms may lead to a positive feedback mechanism or a vicious cycle of cough persistence.

Within breath ventilatory responses to mechanical tracheal stimulation in anaesthetised rabbits

Ventilatory responses to airway mechanical stimulation usually consist in mixed cough (CR) and expiration (ER) reflexes. The stimulus characteristics that would favour either reflex may vary with breathing, but the issue cannot be addressed with the usual long lasting stimulus. The aim of the study was to describe respiratory responses evoked by a punctuate tracheal stimulus and their relationship to inspiration and expiration. Experiments were repeated after bronchoconstriction. Eight anesthetized tracheotomized rabbits were stimulated in the trachea by 150 ms probing before and after methacholine inhalation (248 tests). CR and ER were evaluated from tidal volume and expiratory flow. The overall incidence of responses was larger in inspiration than expiration (p < 0.0001). A majority of responses were single CR or ER, also strongly related to breathing: 93% CR occurred with the stimulus in inspiration and 78% ER with the stimulus in expiration (p = 0.001). Bronchoconstriction did not change the incidence of single efforts, increased that of mixed responses and decreased the amplitude of preparatory and expulsive phases of CR. The study demonstrates the strong dependence of CR and ER on the phase of breathing and adds to the current evidence that regulating mechanisms clearly differ for each reflex.

Bronchoconstriction-triggered cough is impaired in typical asthmatics

BACKGROUND AND OBJECTIVE

Cough is an essential innate protective behavior, which is experienced by even healthy individuals. The mechanism of cough triggered by bronchoconstriction is not yet clear. The aim of this study was to investigate the relation between bronchoconstriction and cough caused by methacholine (Mch) inhalation in typical asthmatics and normal healthy subjects.

METHODS

We measured bronchial responsiveness to Mch and counted the number of coughs induced by Mch inhalation in 15 typical asthmatics and 20 normal subjects.

RESULTS

After inhalation of Mch at the concentration causing 20% or more decrease in forced expiratory volume in 1 second (FEV(1)) (PC(20)-FEV(1)), coughs were provoked in normal subjects (number of cough: 22.5/32 min, range: 3.3-45). Conversely, coughs were hardly provoked in typical asthmatics (median number of cough: 2/32 min, range: 0-4).

CONCLUSIONS

Although typical asthmatics have increased airway responsiveness, their cough response to bronchoconstriction is impaired.