Capsaicin cough sensitivity in bronchiectasis

Cough in chronic lung disease: a state of the art review

Chronic cough (CC; ≥8 weeks in duration) is a common and burdensome feature of respiratory diseases. The understanding of cough has progressed significantly in recent years, albeit largely in refractory (unexplained) chronic cough (RCC) in the absence of other respiratory conditions. The prevalence of CC in respiratory diseases is poorly described, but estimates have been reported: asthma (8-58%), chronic obstructive pulmonary disease (COPD; 10-74%), bronchiectasis (82-98%), interstitial lung disease (ILD; 50-89%) and sarcoidosis (3-64%). CC in respiratory conditions generally predicts impaired health status and more severe disease. It is associated with increased symptom burden and disease severity in asthma, COPD, bronchiectasis and ILD, higher exacerbation frequency in asthma and bronchiectasis, and increased mortality and lung transplantation in idiopathic pulmonary fibrosis (IPF). Physiologically, heightened cough reflex sensitivity (CRS) has been reported and postulated to be mechanistic in isolated RCC. Cough reflex hypersensitivity (CRH) has also been reported in asthma, COPD, bronchiectasis, ILD and sarcoidosis. Unlike recent advances in isolated RCC, there are limited studies and understanding of central cough neuropathways in other respiratory conditions. Of note, dysfunctional central voluntary cough suppression neuropathways and physiology were observed in isolation in RCC; cough suppression is preserved in COPD. Understanding in the mechanism of RCC cannot be simply extrapolated to other respiratory conditions. The restricted understanding of cough mechanisms in these conditions has limited cough-specific therapeutic options in this context. There is currently an unmet need to expand our understanding of cough in chronic respiratory conditions, both in order to improve the quality of life of patients, and to improve knowledge of cough in general. This review aims to describe the prevalence, impact, pathophysiology and management of CC in asthma, COPD, bronchiectasis, ILD and sarcoidosis.

Cough hypersensitivity and chronic cough

Chronic cough is globally prevalent across all age groups. This disorder is challenging to treat because many pulmonary and extrapulmonary conditions can present with chronic cough, and cough can also be present without any identifiable underlying cause or be refractory to therapies that improve associated conditions. Most patients with chronic cough have cough hypersensitivity, which is characterized by increased neural responsivity to a range of stimuli that affect the airways and lungs, and other tissues innervated by common nerve supplies. Cough hypersensitivity presents as excessive coughing often in response to relatively innocuous stimuli, causing significant psychophysical morbidity and affecting patients' quality of life. Understanding of the mechanisms that contribute to cough hypersensitivity and excessive coughing in different patient populations and across the lifespan is advancing and has contributed to the development of new therapies for chronic cough in adults. Owing to differences in the pathology, the organs involved and individual patient factors, treatment of chronic cough is progressing towards a personalized approach, and, in the future, novel ways to endotype patients with cough may prove valuable in management.

Endobronchial Therapy With Gentamicin and Dexamethasone After Airway Clearance by Bronchoscopy in Exacerbation of Non-Cystic Fibrosis Bronchiectasis: A Real-World Observational Study

Background: The exacerbation of non-cystic fibrosis bronchiectasis (NCFB) may lead to poor prognosis. The objective of this study was to retrospectively analyze the clinical efficacy and safety of endobronchial therapy with gentamicin and dexamethasone after airway clearance by bronchoscopy in the exacerbation of NCFB.

Methods: We retrospectively reviewed 2,156 patients with NCFB between January 2015 and June 2016 and 367 consecutive patients with exacerbation of bronchiectasis who had complete data and underwent airway clearance (AC) by bronchoscopy. The final cohort included 181 cases of intratracheal instillation with gentamicin and dexamethasone after AC (a group with airway drugs named the drug group) and 186 cases of AC only (a group without airway drugs named the control group). The last follow-up was on June 30, 2017.

Results: The total cough score and the total symptom score in the drug group were improved compared to those in the control group during 3 months after discharge (p < 0.001). Re-examination of chest HRCT within 4–6 months after discharge revealed that the improvements of peribronchial thickening, the extent of mucous plugging, and the Bhalla score were all significantly improved in the drug group. Moreover, the re-exacerbations in the drug group were significantly decreased within 1 year after discharge. Univariate analysis showed a highly significant prolongation of the time to first re-exacerbation in bronchiectasis due to treatment with airway drugs compared with that of the control group. Multivariate Cox regression analysis showed that the risk of first re-exacerbation in the drug group decreased by 29.7% compared with that of the control group.

Conclusion: Endobronchial therapy with gentamicin and dexamethasone after AC by bronchoscopy is a safe and effective method for treating NCFB.

Utility of Cough Provocation Tests in Chronic Cough and Respiratory Diseases: A Comprehensive Review and Introduction of New Reference Ranges for the Capsaicin Test

Cough provocation tests (CPTs) are an objective measurement of the sensitivity of the cough reflex arc. However, they are not established in clinical practice because a large variability of response in healthy subjects limits their diagnostic value. There is a paucity of studies that have investigated CPT reference ranges in healthy subjects. This systematic review describes the variability of the responses to CPTs in healthy subjects and factors that influence it. A new analysis of 134 healthy subjects was conducted to create reference ranges for single-breath capsaicin CPT by calculating the interquartile ranges for the provocative concentration of capsaicin to induce 2 and 5 coughs. Female subjects had a more sensitive cough reflex than male counterparts. The ability of CPTs to distinguish various respiratory diseases from healthy subjects was also reviewed. Cough sensitivity was consistently heightened in the following groups: unselected patients with chronic, refractory, or recurrent cough, unexplained chronic cough, gastro-esophageal reflux-associated cough, cough-variant asthma, lower airway symptoms induced by chemical irritants, and fibrotic interstitial lung diseases. In the following groups, hypersensitivity of the cough reflex was present in those individuals whose symptom profile was predominated by cough: asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, and sarcoidosis. In the following conditions, patients usually cough in order to expectorate mucus from their airways, not because of a hypersensitive cough reflex arc: productive cough, asthma, upper airway cough syndrome, COPD, bronchiectasis, cystic fibrosis, and chronic respiratory infections. CPTs have the potential to identify patients with chronic respiratory symptoms due to cough reflex hypersensitivity, thereby providing a targeted approach for therapy.

Nonpharmacological cough control therapy for chronic refractory cough and cough associated with underlying lung disease

Nonpharmacological cough control therapy (CCT) is effective for refractory chronic cough but there is a significant subgroup of nonresponders. CCT appears to be effective in cough associated with underlying disease such as asthma. http://bit.ly/2uCCwu3.

Bronchiectasis and cough: An old relationship in need of renewed attention

Bronchiectasis is an increasingly recognised respiratory condition with limited therapeutic options and a complex spectrum of clinical manifestations that invariably includes chronic cough. As the primary presentation of bronchiectasis in most cases, chronic cough and its mechanistic underpinnings are of central importance but remain poorly understood in this setting. Bronchiectasis is also increasingly identified as an underlying cause of chronic cough highlighting the interrelationship between the two conditions that share overlapping clinical features. Several therapeutic approaches have illustrated positive effects on bronchiectasis-associated cough, however, more focused treatment of heterogeneous cough subtypes may yield better outcomes for patients. A current challenge is the identification of bronchiectasis and cough endophenotypes that may allow improved patient stratification and more targeted therapeutic matching of the right treatment to the right patient. Here we discuss the complex disease phenotypes of bronchiectasis and their interrelationship with cough while considering current and emerging treatment options. We discuss some key cough promoters in bronchiectasis including infection, allergy and immune dysfunction.

Is There a Correlation between New Scoring Systems and Systemic Inflammation in Stable Bronchiectasis?

Aim

The present study aimed to investigate the relation between FACED and BSI scores, which were developed to measure the severity of bronchiectasis, and systemic inflammation in patients with stable bronchiectasis.

Methods

FACED and BSI scores of 117 patients with stable bronchiectasis were calculated. The correlations between mean scores and CRP levels, leukocyte count, and neutrophil/lymphocyte ratio were investigated.

Findings

Mean BSI and FACED scores were 7.2 ± 5.2 and 2.1 ± 1.8, respectively. The severity of bronchiectasis as determined based on BSI and FACED increased significantly with increasing levels of CRP in patients with stable bronchiectasis (p=0.001 and p=0.027, resp.). No significant changes were found in leukocyte count (p=0.72 and p=0.09, resp.) and N/L ratio (p=0.45 and p=0.71, resp.). BSI and FACED scores were significantly correlated with CRP but not with leukocyte count or N/L ratio.

Conclusion

In patients with stable bronchiectasis who are evaluated based on FACED and BSI scores, CRP can be a useful biomarker as a direct indicator of the severity of systemic inflammation.

The Objective Assessment of Cough Frequency in Bronchiectasis

Introduction

Cough in bronchiectasis is associated with significant impairment in health status. This study aimed to quantify cough frequency objectively with a cough monitor and investigate its relationship with health status. A secondary aim was to identify clinical predictors of cough frequency.

Methods

Fifty-four patients with bronchiectasis were compared with thirty-five healthy controls. Objective 24-h cough, health status (cough-specific: Leicester Cough Questionnaire LCQ and bronchiectasis specific: Bronchiectasis Health Questionnaire BHQ), cough severity and lung function were measured. The clinical predictors of cough frequency in bronchiectasis were determined in a multivariate analysis.

Results

Objective cough frequency was significantly raised in patients with bronchiectasis compared to healthy controls [geometric mean (standard deviation)] 184.5 (4.0) vs. 20.6 (3.2) coughs/24-h; mean fold-difference (95% confidence interval) 8.9 (5.2, 15.2); p < 0.001 and they had impaired health status. There was a significant correlation between objective cough frequency and subjective measures; LCQ r = −0.52 and BHQ r = −0.62, both p < 0.001. Sputum production, exacerbations (between past 2 weeks to 12 months) and age were significantly associated with objective cough frequency in multivariate analysis, explaining 52% of the variance (p < 0.001). There was no statistically significant association between cough frequency and lung function.

Conclusions

Cough is a common and significant symptom in patients with bronchiectasis. Sputum production, exacerbations and age, but not lung function, were independent predictors of cough frequency. Ambulatory objective cough monitoring provides novel insights and should be further investigated as an outcome measure in bronchiectasis.

Electronic supplementary material

The online version of this article (doi:10.1007/s00408-017-0038-x) contains supplementary material, which is available to authorized users.

Advances in mechanisms and management of chronic cough: The Ninth London International Cough Symposium 2016

At the Ninth London International Cough Symposium held in June 2016, advances in chronic cough were presented. Chronic cough has been labelled as a cough hypersensitivity syndrome (CHS) with neuroinflammatory mechanisms likely to be the underlying mechanisms. The concept is that there is a stage of peripheral sensitisation induced by inflammatory factors setting up the scene for a central component that can be visualised by functional magnetic resonance imaging. There has also been progress in assessing CHS patients in the clinic in terms of measuring cough, with an increasing interest in assessing different types of cough associated with respiratory diseases such as asthma, COPD, bronchiectasis and pulmonary fibrosis. There is an emerging area of new antitussives in the form of neuromodulators. These advances have been paralleled by improvements in the management of patients with chronic cough. However, more work is needed but the future looks promising.

Validation of a Spanish version of the Leicester Cough Questionnaire in non-cystic fibrosis bronchiectasis

The Leicester Cough Questionnaire (LCQ) has been validated in non-cystic fibrosis bronchiectasis (NCFBC). The present study aimed to create and validate a Spanish version of the LCQ (LCQ-Sp) in NCFBC. The LCQ-Sp was developed following a standardized protocol. For reliability, we assessed internal consistency and the change in score over a 15-day period in stable state. For responsiveness, we assessed the change in scores between visit 1 and the first exacerbation. For validity, we evaluated convergent validity through correlation with the Saint George's Respiratory Questionnaire (SGRQ) and discriminant validity. Two hundred fifty-nine patients (118 mild bronchiectasis, 90 moderate bronchiectasis and 47 severe bronchiectasis) were included. Internal consistency was high for the total scoring and good for the different domains (Cronbach's α: 0.86-0.91). The test-retest reliability shows an intraclass correlation coefficient of 0.87 for the total score. The mean LCQ-Sp score at visit 1 decreased at the beginning of an exacerbation (15.13 ± 4.06 vs. 12.24 ± 4.64; p < 0.001). The correlation between LCQ-Sp and SGRQ scores was -0.66 (p < 0.01). The differences in the LCQ-Sp total score between the different groups of severity were significant (p < 0.001). The LCQ-Sp discriminates disease severity, is responsive to change when faced with exacerbations and is reliable for use in bronchiectasis.

The validity of health-related quality of life questionnaires in bronchiectasis: a systematic review and meta-analysis

BACKGROUND

A range of questionnaires have been used to assess health-related quality of life (HRQOL) in bronchiectasis. A systematic review was conducted to evaluate their psychometric properties and assess associations between HRQOL and clinical measures.

METHODS

Five electronic databases were searched. Studies eligible for inclusion were those that investigated the validity of HRQOL questionnaires and/or their association with other outcomes in adults with bronchiectasis. Patients with cystic fibrosis were excluded. The identified questionnaires were assessed for convergent, discriminant and cross-cultural translation validity; missing data, floor and ceiling effects, internal consistency, responsiveness and test-retest reliability. A meta-analysis was conducted to estimate the strength of associations between HRQOL and clinical measures.

RESULTS

From 1918 studies identified, 43 studies were included in the systematic review, of which 38 were suitable for the meta-analysis. Nine HRQOL questionnaires were identified, with the most widely used being: St George's Respiratory Questionnaire, Leicester Cough Questionnaire, Quality of Life-Bronchiectasis and Short Form-36. HRQOL questionnaires had moderate to good internal consistency and good test-retest reliability. Only 8 of 18 studies that used translated HRQOL questionnaires reported or referred to the validity of the translated questionnaire. There was a stronger correlation (mean r (95% CI)) between HRQOL and subjective outcome measures, such as dyspnoea (0.55 (0.41 to 0.68)) and fatigue (0.42 (0.23 to 0.58)) compared with objective measures; exercise capacity (-0.41 (-0.54 to -0.24)), FEV1% predicted (-0.31 (-0.40 to -0.23)) and extent of bronchiectasis on CT scan (0.35 (0.03 to 0.61)); all p<0.001.

CONCLUSIONS

This review supports most HRQOL questionnaires used in bronchiectasis have good psychometric properties. There was a weak to moderate association between HRQOL and objective outcome measures. This suggests that HRQOL questionnaires assess a unique aspect of health not captured by objective measures.

Predictors of objective cough frequency in pulmonary sarcoidosis

Cough is a common symptom of pulmonary sarcoidosis. This study aimed to quantify cough frequency, and investigate its relationship with cough reflex sensitivity, pulmonary function and health status.32 patients with pulmonary sarcoidosis were compared with 40 healthy controls. Cough reflex sensitivity to capsaicin, objective 24-h cough counts, cough-specific health status, cough severity and cough triggers were measured. The predictors of cough frequency in sarcoidosis were determined in a multivariate analysis.Objective cough frequency was significantly raised in patients with sarcoidosis compared with healthy controls (p<0.001) and patients with cough had an impaired health status. Patients with pulmonary sarcoidosis had a heightened cough reflex sensitivity compared with healthy controls (p<0.001). Only cough reflex sensitivity was significantly associated with objective cough frequency in multivariate analysis, explaining 42% of the variance (p<0.001). There was no association between cough frequency, lung function, number of organs involved, chest radiograph stage or serum angiotensin-converting enzyme levels.Cough is a common and significant symptom in patients with sarcoidosis. Ambulatory objective cough monitoring provides novel insights into the determinants of cough in sarcoidosis, suggesting that cough reflex sensitivity may be more important than lung function and other measures of disease severity, and this should be investigated further.

Capsaicin cough sensitivity and the association with clinical parameters in bronchiectasis

BACKGROUND

Cough hypersensitivity has been common among respiratory diseases.

OBJECTIVE

To determine associations of capsaicin cough sensitivity and clinical parameters in adults with clinically stable bronchiectasis.

METHODS

We recruited 135 consecutive adult bronchiectasis patients and 22 healthy subjects. History inquiry, sputum culture, spirometry, chest high-resolution computed tomography (HRCT), Leicester Cough Questionnaire scoring, Bronchiectasis Severity Index (BSI) assessment and capsaicin inhalation challenge were performed. Cough sensitivity was measured as the capsaicin concentration eliciting at least 2 (C2) and 5 coughs (C5).

RESULTS

Despite significant overlap between healthy subjects and bronchiectasis patients, both C2 and C5 were significantly lower in the latter group (all P<0.01). Lower levels of C5 were associated with a longer duration of bronchiectasis symptoms, worse HRCT score, higher 24-hour sputum volume, BSI and sputum purulence score, and sputum culture positive for P. aeruginosa. Determinants associated with increased capsaicin cough sensitivity, defined as C5 being 62.5 µmol/L or less, encompassed female gender (OR: 3.25, 95%CI: 1.35-7.83, P<0.01), HRCT total score between 7-12 (OR: 2.57, 95%CI: 1.07-6.173, P = 0.04), BSI between 5-8 (OR: 4.05, 95%CI: 1.48-11.06, P<0.01) and 9 or greater (OR: 4.38, 95%CI: 1.48-12.93, P<0.01).

CONCLUSION

Capsaicin cough sensitivity is heightened in a subgroup of bronchiectasis patients and associated with the disease severity. Gender and disease severity, but not sputum purulence, are independent determinants of heightened capsaicin cough sensitivity. Current testing for cough sensitivity diagnosis may be limited because of overlap with healthy subjects but might provide an objective index for assessment of cough in future clinical trials.

Supportive and palliative care of advanced nonmalignant lung disease

Supportive and palliative care is an interdisciplinary challenge with the aims of symptom relief and improvement of quality of life in end-stage patients. Main complaints of patients with advanced nonmalignant lung disease are depression and anxiety, dyspnea, pain, and coughing. The discomfort of many physicians, caregivers, and family members with discussions about end-of-life care is one obstacle for the timely initiation of palliative care and the uncertainty of the short-term prognosis in most advanced nonmalignant respiratory diseases. Early dialog about supportive care already at the onset of the patient's first symptoms and contemporaneous to life-prolonging therapy may overcome these barriers. Furthermore, continuing education for health professionals in palliative care ensures adequate palliative support. Here, we review insights into symptom control and palliative care in patients with advanced nonmalignant respiratory disease.

Does gastroesophageal reflux scintigraphy correlate with clinical findings in children with chronic cough?

OBJECTIVE

Gastroesophageal reflux (GER), a common problem during childhood, leads to chronic troublesome symptoms including chronic respiratory symptoms. Therefore, timely diagnostic work-up for GER is essential in children when GER is suspected. In this study, we aimed to establish whether scintigraphic parameters have clinical importance in investigating the reflux in children.

METHODS

A total of 72 children older than 7 years with chronic cough of unknown etiology were enrolled for this study. The scintigraphic procedure was performed by using technetium-99m tin colloid (37-74 MBq). Cough and GER scores were used for children who were positive for GER both before and after GER treatment.

RESULTS

Of 72 children, 65 children with a mean age of 10.3+/-2.3 (7-19) years had GER on gastroesophageal scintigraphy. Median reflux episode number was 7 (1-14). There was a significantly positive correlation between reflux episode number and cough (r = 0.446, P<0.001) and GER score (r = 0.432, P<0.001). The significant decrease was observed in cough (from 3.5+/-1.9 to 1.6+/-1.3) and GER scores (from 4.1+/-2.5 to 1.3+/-1.1) with GER treatment (P<0.001 for each).

CONCLUSION

Scintigraphy should be used for the detection of GER in children who present with chronic cough. Increasing episode number in gastroesophageal scintigraphy might be a predictor for reflux-related symptom severity.

Postnasal drip and chronic cough: An open interventional study

BACKGROUND

The postnasal drip (PND) syndrome is often linked as a cause of chronic cough although this is disputed.

OBJECTIVES

We examined the effect of specific topical treatment of rhinosinusitis on cough in patients presenting with a chronic cough associated with a postnasal drip or 'nasal catarrh'.

METHODS

Patients presenting with a chronic cough and who complained of PND were enrolled and symptoms of PND and cough were assessed by questionnaire and by a capsaicin cough response. Rhinosinusitis was assessed by questionnaires, direct examination of the nose and by high-resolution computed tomography. In an open study, they were treated with fluticasone nasules, ipratropium bromide and azelastine nasal sprays for 28 days, after which they were re-assessed.

RESULTS

Eighteen out of 21 patients completed the study. All patients reported having the presence of mucus in the throat. Mean cough score improved post-treatment (p<0.05), but there was no significant change in capsaicin cough sensitivity or nasal catarrh questionnaire score. There was improvement in anterior nasal discharge symptom scores (p=0.005) and in endoscopic nasal scores post-treatment (p<0.01), with a tendency to improved PND scores.

CONCLUSION

In a pilot open 'real-life' study treatment targeted towards rhinosinusitis accompanying PND syndrome and chronic cough led to an improvement in cough. A randomised controlled study is now needed to confirm or refute these findings.

Clinical cough VI: the need for new therapies for cough: disease-specific and symptom-related antitussives

Cough is a common symptom that can be self-limiting or persistent. Ideally, treatment of the underlying cause(s) of cough with specific treatments should eliminate cough. This approach may not be successful if no cause can be established or if the treatment of the cause fails. Suppression of cough may be disease-specific or symptom-related. There has been a long tradition in acute cough usually due to upper respiratory tract infections to use symptom-related antitussives. In chronic cough, suppression of cough may be achieved by disease-specific therapies, but in many patients it may be necessary to use symptomatic antitussives. The efficacy of some over-the-counter symptomatic antitussives is often no better than that of a placebo. Currently available cough suppressants include the centrally acting opioids such as morphine, codeine, pholcodeine, and dextromethorphan. Early studies reported success in reducing cough in patients with chronic bronchitis or chronic obstructive pulmonary disease (COPD); however, a carefully conducted blinded controlled study showed no effect of codeine on cough of COPD. Success with these cough suppressants may be achieved at high doses that are associated with side effects. A slow-release preparation of morphine has been shown to have some degree of efficacy, but this should be reserved for the most severe chronic cough patient, and for patients with terminal cancer who may also benefit from its analgesic effects. There are case reports of the success of centrally acting drugs such as amitriptyline, paroxetine, gabapentin, and carbamezepine in chronic cough. New agents derived from basic research such as new opioids such as nociceptin or antagonists of transient receptor potential vanniloid-1 may turn out to have antitussive effects. Efficacy of symptomatic cough suppressants must be tested in double-blind randomized trials using validated measures of cough in patients with chronic cough not responding to specific treatments. Patients with chronic cough need effective antitussives that could be used either on demand or on a long-term basis.

Management of chronic cough

Cough that remains unexplained after basic clinical assessment is a common reason for referral to secondary care. Much of the evidence about management of isolated chronic cough is derived from case series; this evidence suggests that isolated chronic cough is usually due to asthma, gastro-oesophageal reflux disease, and upper airway conditions, and that it can be cured in most people by treatment of these conditions. However, there is increasing recognition that satisfactory control of chronic cough is not achieved in a substantial number of patients seen in secondary care. Moreover, there is a concern that perpetuation of the belief that chronic cough is solely due to the effects of comorbid conditions is inhibiting research into the pathophysiology of an abnormally heightened cough reflex, and jeopardising development of improved treatments. We advocate a change in emphasis, which makes a clear distinction between cough due to corticosteroid-responsive eosinophilic airway diseases and corticosteroid-resistant non-eosinophilic cough. We recommend that some factors with weak evidence of an association with cough are best viewed as potential aggravating factors of an intrinsic abnormality of the cough reflex, rather than the cause. We call for more research into the basic mechanisms and pharmacological control of an abnormally heightened cough reflex, and recommend ways to assess the effects of potentially antitussive treatments.

Prevalence, pathogenesis, and causes of chronic cough

Cough is a reflex action of the respiratory tract that is used to clear the upper airways. Chronic cough lasting for more than 8 weeks is common in the community. The causes include cigarette smoking, exposure to cigarette smoke, and exposure to environmental pollution, especially particulates. Diseases causing chronic cough include asthma, eosinophilic bronchitis, gastro-oesophageal reflux disease, postnasal drip syndrome or rhinosinusitis, chronic obstructive pulmonary disease, pulmonary fibrosis, and bronchiectasis. Doctors should always work towards a clear diagnosis, considering common and rare illnesses. In some patients, no cause is identified, leading to the diagnosis of idiopathic cough. Chronic cough is often associated with an increased response to tussive agents such as capsaicin. Plastic changes in intrinsic and synaptic excitability in the brainstem, spine, or airway nerves can enhance the cough reflex, and can persist in the absence of the initiating cough event. Structural and inflammatory airway mucosal changes in non-asthmatic chronic cough could represent the cause or the traumatic response to repetitive coughing. Effective control of cough requires not only controlling the disease causing the cough but also desensitisation of cough pathways.

Chronic cough: future directions in chronic cough: mechanisms and antitussives

Cough is an important defensive reflex of the respiratory tract needed to clear and protect the upper airways; however, it may become exaggerated and interfere with quality of life. Although chronic cough may be successfully treated when associated with the common causes such as asthma and eosinophilic bronchitis, gastrooesophageal reflux disease and post-nasal drip syndrome or rhinosinusitis, increasingly, idiopathic cough or cough with no associated cause is recognised. Chronic cough is often associated with an increased response to tussive agents such as capsaicin, used as an index of the cough reflex. Some airway receptors mediate or influence cough through activation of vagal afferent pathways which converge on brain stem respiratory networks and of supramedullary centres. Plastic changes in intrinsic and synaptic excitability at the brain stem, spinal or ganglionic level may be the mechanism by which the cough reflex is enhanced in chronic cough. Subjective and objective measurements of cough in the clinic are now available but a major unmet need in chronic cough is the availability of effective antitussives. Future directions in chronic cough include the pathophysiological mechanisms of the enhanced cough reflex, and the discovery of effective antitussives that can successfully alleviate chronic cough.

Impact of cough across different chronic respiratory diseases: comparison of two cough-specific health-related quality of life questionnaires

BACKGROUND

Cough is a prominent symptom across a range of common chronic respiratory diseases and impacts considerably on patient health status.

METHODS

We undertook a cross-sectional comparison of scores from two cough-specific health-related quality of life (HRQoL) questionnaires, the Leicester Cough Questionnaire (LCQ), and the Cough Quality of Life Questionnaire (CQLQ), together with a generic HRQoL measure, the EuroQol. Questionnaires were administered to and spirometry performed on 147 outpatients with chronic cough (n = 83), COPD (n = 18), asthma (n = 20), and bronchiectasis (n = 26).

RESULTS

There was no significant difference in the LCQ and CQLQ total scores between groups (p = 0.24 and p = 0.26, respectively). Exploratory analyses of questionnaire subdomains revealed differences in psychosocial issues and functional impairment between the four groups (p = 0.01 and p = 0.05, respectively). CQLQ scores indicated that chronic coughers have more psychosocial issues than patients with bronchiectasis (p = 0.03) but less functional impairment than COPD patients (p = 0.04). There was a significant difference in generic health status across the four disease groups (p = 0.04), with poorest health status in COPD patients. A significant inverse correlation was observed between CQLQ and LCQ in each disease group (chronic cough r = - 0.56, p < 0.001; COPD r = - 0.49, p = 0.04; asthma r = - 0.94, p < 0.001; and bronchiectasis r = - 0.88, p < 0.001). There was no correlation between cough questionnaire scores and FEV(1) in any group, although a significant correlation between EuroQol visual analog scale component and FEV(1) (r = 0.639, p = 0.004) was observed in COPD patients.

CONCLUSION

Cough adversely affects health status across a range of common respiratory diseases. The LCQ and CQLQ can each provide important additional information concerning the impact of cough.

Currently Available Cough Suppressants for Chronic Cough

Chronic cough is a common symptom but only a fraction of patients seek medical attention. Addressing the causes of chronic cough may lead to control of cough; however, this approach is not always successful since there is a certain degree of failure even when the cause(s) of cough are adequately treated; in idiopathic cough, there is no cause to treat. Persistent cough may be associated with deterioration of quality of life, and treatment with cough suppressants is indicated. Currently available cough suppressants include the centrally acting opioids such as morphine, codeine, and dextromethorphan. Peripherally acting antitussives include moguisteine and levodropropizine. Early studies report success in reducing cough in patients with chronic bronchitis or COPD; however, a carefully conducted study showed no effect of codeine on cough of COPD. Success with these cough suppressants can be achieved at high doses that are associated with side effects. Slow-release morphine has been reported to be useful in controlling intractable cough with good tolerance to constipation and drowsiness. There have been case reports of the success of centrally acting drugs such as amitryptiline, paroxetine, gabapentin, and carbamezepine in chronic cough. New opioids such as nociceptin or antagonists of TRPV1 may turn out to be more effective. Efficacy of cough suppressants must be tested in double-blind randomised trials using validated measures of cough in patients with chronic cough not responding to specific treatments. Patients with chronic cough are in desperate need of effective antitussives that can be used either on demand or on a long-term basis.

Effective antitussives for the cough patient: an unmet need

Chronic cough is a prevalent symptom in the community but it is likely that only a small fraction of chronic coughers seek medical attention. Chronic cough can be controlled by addressing the 'cause' of the cough, but not all cough is controlled using this approach; an 'idiopathic' cough or cough of unknown aetiology is becoming more well-recognized. In these patients and in those whose cough has not responded to treatment of the cause(s), there is a lack of efficacious antitussive therapies ('non-specific' antitussives). Even in those whose cough is controlled by treatment of the cause, an efficacious antitussive for symptomatic relief would be useful for breakthrough symptoms. It is necessary to address the mechanisms underlying chronic cough, particularly the process of sensitization, both peripherally and centrally, that is the basis of chronic cough; such a process may persist even in the absence of the initiating event that first induced the cough. Currently-available antitussives in both acute and chronic cough are not very effective. Novel targets that may result in effective antitussives have been identified and with the development of clinical tools to measure cough accurately and reliably (e.g. cough counts and cough-specific quality-of-life questionnaires) and the evoked cough response (e.g. citric acid or capsaicin challenges), clinical trials should be performed. The chronic cough population is clinically heterogeneous but is characterized by an enhanced cough reflex; this should be the target population for study. Patients with chronic cough are in desperate need of effective antitussives that can be used either on demand or on a long-term basis.