Prevalence, pathogenesis, and causes of chronic cough

Recent progress in the management of chronic cough

Chronic cough is a common clinical condition with significant impact on quality of life and for which effective therapy remains an unmet clinical need. Over the past decade, there has been a major shift in how we approach this problem, driven by better appreciation of the clinical manifestation of chronic cough and an improved understanding of the associated neurobiology. "Cough hypersensitivity syndrome" has been proposed as a new diagnostic term for chronic cough, encompassing different phenotypes of the condition. Accumulating evidence suggests that this new concept is clinically relevant. However, while it is gaining widespread endorsement within the allergy and respiratory community, raising its profile in routine clinical practice is a priority. Thus, the present paper reviews recent progress in our understanding and management of chronic cough, with focus on mechanistic and clinical studies. It also provides detail on knowledge gaps and future research directions.

Giant cell arteritis manifested by chronic dry cough

A 77-year-old man visited the hospital with a chronic cough persisting for 2.5 months accompanied with night sweats, weight loss (3.5 kg) and elevated C-reactive protein level. Chest CT of the lung field was normal, but aortic wall thickening accompanied by a contrast effect was noted. Positron emission tomography-CT (PET-CT) showed that the aorta and subclavian artery were inflamed, suggesting large-vessel vasculitis. Ultrasonography showed thickening of the superficial temporal artery wall (macaroni sign). Biopsy revealed lymphocytic infiltration in the tunica media and foreign-body giant cell reaction with the elastic lamina, resulting in a diagnosis of giant cell arteritis (GCA). The cough was considered a symptom of GCA as it resolved following prednisolone administration. Cough may rarely be an initial GCA symptom. However, for chronic cough accompanied with elevated inflammatory findings but with a normal lung field, imaging studies such as PET-CT are useful for the differential diagnosis.

Ethnobotanical Survey of Plants Used for Treating Cough Associated with Respiratory Conditions in Ede South Local Government Area of Osun State, Nigeria

In many developing countries, community members depend on their local flora for treating diverse ailments including those affecting the respiratory system. This is often attributed to the high cost and limited access to health care facilities. This present study focused on the documentation of plant species used against cough associated with the respiratory diseases in Ede South Local Government Area of Osun State. The survey was conducted using semi-structured interviews among 100 participants. Information obtained was analyzed using different ethno-botanical indices including relative frequency of citation (RFC) and fidelity level (FL). A total of 87 plant species from 39 families, which was mostly represented by Fabaceae, were reported in the study area. Crinum jagus was the most popular plant used against cough and approximately 32% of the plants have been reported as cough remedies for the first time. However, some of the documented plants have been reported for the treatment of cough and related respiratory diseases in several countries. In terms of the life-form, trees constituted the highest proportion of the medicinal plants (37%), while leaves (36%) were the predominant plant part prescribed for cough. Decoction was the main method of preparing the plants, which were all administered orally. Approximately 63% of the plants were exclusively sourced from the wild. The current study revealed the richness and widespread use of plant species for managing cough associated with respiratory diseases in the study area. The generated inventory contributes to the expanding database of valuable plant resources with medicinal potential in Nigeria and Africa.

Tracheal Irrigation Without Bronchoscopy as an Alternative Emergent Treatment of Blood Aspiration

BACKGROUND

Tracheobronchial foreign body aspiration can cause mild symptoms but may also become dangerous enough to cause death. Bronchoscopy is the first choice for the diagnosis and the removal of aspirated foreign bodies. So, when bronchoscopy is not available, the situation might get challenging.

CASE REPORT

A 62-year-old man was waiting for emergent surgery for traumatic epidural hematoma in the Emergency Department (ED). Endotracheal intubation was performed for surgery and airway maintenance. However, oxygen saturation dropped and respiratory arrest was expected. As emergent bronchoscopy could not be performed, the emergency physician decided to irrigate the trachea by using 0.9% normal saline in the ED. After three rounds of irrigation, vital signs including oxygen saturation improved and the patient could undergo neurosurgical surgery. The patient was subsequently discharged with improved health. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Bronchoscopy is the first choice for the treatment and diagnosis in cases of bronchial aspiration of blood, such as that caused by epistaxis. However, in emergency situations, such as deteriorating vital signs due to aspiration of life-threatening amounts of blood from epistaxis, using blind tracheal irrigation as an alternative tool when bronchoscopy is not available can help in achieving clinically acceptable results.

Assessment of the Efficacy and Safety of Ivy Leaf (Hedera helix) Cough Syrup Compared with Acetylcysteine in Adults and Children with Acute Bronchitis

Introduction

Acute bronchitis is defined as a sudden inflammation of the bronchial tubes in the lung mainly caused by viral infection. It is characterized by a persistent cough which can be productive or dry. It is the most common disease in industrialized countries, and thus herbal expectorants enjoy a high popularity in many European countries due to their favorable risk-benefit ratio.

Objective

The present noninterventional study was intended to gain further data on the application of a cough syrup containing ivy leaf extract EA 575® by evaluating its efficacy and safety in children and adults with symptoms of acute bronchitis. Acetylcysteine (ACC) was chosen as comparator drug (common mono preparations). Material and Methods. The study was conducted at 25 medical practices throughout Switzerland as prospective, open, noninterventional study.

Results

At entry visit, all clinical assessments including coughing fits, sputum, dyspnoea, rales, severity of the diseases, and coughing quality were rated with moderate intensity in both groups. At the final visit after seven days of treatment, there was a comparable improvement in both groups for all assessments except dyspnoea and number of cough attacks which showed a higher improvement in the EA 575® group compared with ACC. Further, cough-associated sleeping disorders improved more in the EA 575® group. Both, physicians and patients described the efficacy of EA 575® comparable with acetylcysteine. Observations of the tolerability were comparable for both products. The study results indicate that ivy leaf extract might be an effective alternative to acetylcysteine with respect to the improvement of respiratory function in children and adults at a slightly better evaluation of efficacy.

The Wide-Ranging Spectrum of Cough-Induced Complications and Patient Harm

Cough is one of the most common complaints encountered in every setting; however, complications associated with coughing have received relatively little attention. An exhaustive systematic review of the English literature revealed an exceedingly large and varied spectrum of cough-induced complications affecting many systems, including upper airways, chest wall and thorax, abdominal wall, heart and aorta, central nervous system, eye, gastrointestinal tract, urogenital system, and emotional and psychological harm. Prospective studies and prevalence data are conspicuously missing. Reported cough-induced pathology ranges from rare (the majority) to common and from trivial (eg, lightheadedness, subconjunctival hemorrhage) to severe and life-threatening (eg, cervical artery dissection, rupture of a normal spleen). Other seemingly benign entities may mask a serious underlying pathology (eg, cough headache, cough syncope). A substantial proportion of patients experience anxiety and insomnia, and their quality of life is affected. Thus, the wide spectrum of cough-induced pathology need to be recognized and considered in patients complaining of cough. Suppression of cough must not be neglected in patients at risk, and areas of uncertainty need to be clarified by future prospective studies.

Electronic cigarette use among Italian smokers: patterns, settings, and adverse events

OBJECTIVE

Information is scanty on the patterns and settings of electronic cigarette use and on its possible adverse events. To fill the knowledge gap on these issues, we conducted a survey among ever-smokers attending smoking cessation services (SCS) in Italy.

METHODS

In 2016-2018, we enrolled 395 ever-smokers aged ⩾18 years who were current or former electronic cigarette users in 12 SCS from northern, central, and southern Italy.

RESULTS

In all, 12.4% of ever smokers were regular, 9.4% occasional, and 78.2% past users of electronic cigarettes. Of all users, 93.8% consumed electronic cigarettes with nicotine, 95.9% used refillable devices, and 76.6% purchased electronic cigarette devices or liquids in vape shops. The mean duration of use was 3.7 months and the mean number of puffs per day was 86. Among users, 71.5% used electronic cigarettes in at least 1 smoke-free indoor environment, 53.7% in workplaces, 49.5% in restaurants and bars, 33.5% in train/metro stations or airports, and 18.4% in public transports. The use of electronic cigarettes in smoke-free environments significantly decreased with age and increased with duration of use and nicotine dependence. In our sample, 47.1% reported at least 1 adverse event attributable to electronic cigarette use: 19.5% dry cough, 12.0% dry mouth, 7.6% throat or mouth irritation, and 6.8% sore throat.

CONCLUSION

In Italy, most conventional cigarette smokers use electronic cigarettes where smoking conventional cigarettes is prohibited. About half of users reported 1 or more symptoms attributable to electronic cigarettes, despite the relatively short duration of use.

Association of cough with asthma in chronic rhinosinusitis patients

OBJECTIVE

To determine whether the complaint of cough in chronic rhinosinusitis (CRS) patients is associated with asthma and if there is a potential predictive value for asthma diagnosis.

METHOD

Consecutive patients presenting for initial evaluation at a tertiary rhinology clinic who were diagnosed with CRS were considered for inclusion in a cross-sectional study. The presence and severity of cough was determined using the 22-item Sinonasal Outcome Test (SNOT-22). Subgroup analysis included asthma diagnosis confirmed by pulmonary function testing (PFT) in our institution, and for chronic rhinosinusitis patients with (CRSwNP) and without nasal polyps (CRSsNP).

RESULTS

The total study population included 297 patients with a diagnosis of CRS, with 63.9% of patients reporting cough. Physician-confirmed diagnosis of asthma was made in 38.7% of patients, and confirmed in 69.6% by PFT. Cough was more frequently reported by CRS patients diagnosed with asthma (relative risk [RR] = 1.60, 95% confidence interval [CI], 1.13-2.25), with sensitivity of 73.9% (95% CI, 65.0%-81.1%). This remained significant in the CRSsNP subgroup (RR = 2.65, 95% CI, 1.32-5.30), with sensitivity of 83.3% (95% CI, 70.4%-91.3%) and specificity of 41.2% (95% CI, 33.2%-49.8%). Cough was not associated with asthma in CRSwNP patients (RR = 1.26, 95% CI, 0.89-1.79). Cough severity had poor predication for asthma diagnosis (AUC = 0.60, 95% CI, 0.54-0.65).

CONCLUSIONS

Complaint of cough is associated with diagnosis of asthma in CRS patients. In CRSsNP, complaint of cough was sensitive for asthma diagnosis, although specificity was low. Cough in CRS patients can be multifactorial and asthma may be an important diagnostic consideration.

LEVEL OF EVIDENCE

4.

A new simple score of chronic cough: cough evaluation test

Background

Chronic cough has an important impact on physical, social and psychological aspects. A simple and effective method to assess different aspects of chronic cough severity is required. We aimed to develop a simple, self-completed test, Cough Evaluation Test (CET), to evaluate cough severity and its impact on health.

Method

The items of preliminary CET were generated based on literature review and clinical practice. Items reduction was conducted by modified Delphi method. Patients with chronic cough were recruited to complete CET, Cough Visual Analog Scales (VAS), Mandarin Chinese version of the Leicester Cough Questionnaire (LCQ-MC), and Cough Symptom Score (CSS). Reassessments were performed at 1 week apart before treatment, and after more than 2 weeks treatments. Concurrent validation, internal consistency, repeatability, responsiveness and the minimal important difference (MID) were determined.

Results

CET consists of five items with a 5-point Likert scale (1–5 scaling of items, 5–25 score range). The Cronbach’s alpha values for CET was 0.80. CET showed a stronger correlation with LCQ-MC (r = − 0.74) compared to that between LCQ-MC with VAS (r = − 0.61). CET also showed a stronger correlation with VAS (r = 0.70) compared to that between VAS with other measures. Intraclass correlation coefficients for CET was 0.84. In patients undergoing treatment, CET scores significantly changed (p < 0.0001). The MID of CET was 2.

Conclusion

Cough Evaluate Test is a reliable, valid and responsive tool to simply evaluate impact of cough on physical, social and psychological aspects.

Evidence of Possible Irritable Larynx Syndrome in Obstructive Sleep Apnea: An Epidemiologic Approach

OBJECTIVE

"Irritable larynx syndrome" (ILS) often refers to a constellation of laryngeal-based symptoms including chronic cough (CC), diurnal dyspnea, and dysphonia. In patients with OSA, we examined: (1) the frequency, severity, comorbidity, risks and triggers of each problem, (2) whether these symptoms were compatible with stereotypic ILS and (3) the role of CPAP in their expression.

STUDY DESIGN

Cross-sectional, descriptive epidemiology study.

SETTING

Sleep-Wake Center at University of Utah Health Care, Salt Lake City, UT.

SUBJECTS AND METHODS

Ninety-four individuals with OSA (53 men, 41 women; mean age 54.7 ± 12.8 yrs.) underwent an extensive telephone interview that addressed study objectives.

RESULTS

Long-term CC, daytime breathing and voice problems were common, especially among women despite less severe OSA. Women, more than men, reported all three chronic conditions alone or in combination: CC (44% vs 11.3%), diurnal dyspnea (41.5% vs 13.2%) and voice disorders (41.5% vs 13.2%). Symptoms were not associated with age, BMI or Apnea Hypopnea Index after adjusting for sex. Although evidence supporting stereotypic ILS symptomatology was inconsistent, those participants with a voice disorder were 3.3 (95% CI = 1.8-6.0) times more likely to report CC and 2.4 (95% CI = 1.3-4.4) times more likely to experience diurnal dyspnea. Esophageal reflux, post-nasal drip, and frequent sinus infections were significantly associated with all three conditions. Triggers that provoked or made symptoms worse varied by condition and sex. Nightly, humidified CPAP use was associated with fewer symptoms overall and improved quality of life.

CONCLUSIONS

Symptoms suggestive of possible ILS are common in OSA, especially among women, and lessened by nightly CPAP use.

Automatic Identification of Cough Events from Acoustic Signals

Cough is a common symptom of numerous respiratory diseases. In certain cases, such as asthma and COPD, early identification of coughs is useful for the management of these diseases. This paper presents an algorithm for automatic identification of cough events from acoustic signals. The algorithm is based on only four features of the acoustic signals including LPC coefficient, tonality index, spectral flatness and spectral centroid with a logistic regression model to label sound segments into cough and non-cough events. The algorithm achieves sensitivity of of 86.78%, specificity of 99.42%, and F1-score of 88.74%. Its high performance despite its small size of feature-space demonstrate its potential for use in remote patient monitoring systems for automatic cough detection using acoustic signals.

Chronic Cough in Individuals With COPD: A Population-Based Cohort Study

BACKGROUND

The role and impact of chronic cough in individuals with COPD have not been described in the general population. This study hypothesized that comorbid chronic cough is a marker of disease severity in individuals with COPD.

METHODS

This study identified individuals with COPD and chronic cough, and recorded respiratory symptoms, health-care utilizations, lung function, and inflammatory biomarkers in blood in a nested cohort of 43,271 adults from the Copenhagen General Population Study (CGPS).

RESULTS

Among 43,271 individuals from the general population, 8,181 (19%) experienced COPD, of whom 796 (10%) had chronic cough. Individuals with COPD and chronic cough had a Leicester Cough Questionnaire median (25th-75th percentiles) total score of 17.7 (16.0-18.9), corresponding to 5.9 (5.3-6.3) for the physical domain, 5.6 (4.9-6.3) for the psychological domain, and 6.3 (5.8-6.8) for the social domain. Among individuals with COPD, those with chronic cough vs those without chronic cough more often experienced sputum production (60% vs 8%), wheezing (46% vs 14%), dyspnea (66% vs 38%), chest pain/tightness (9% vs 4%), nighttime dyspnea (8% vs 3%), episodes of acute bronchitis/pneumonias in the last 10 years (45% vs 25%), and ≥ 3 general practitioner visits in the past 12 months (53% vs 37%). Furthermore, these individuals had lower FEV₁ % predicted (81% vs 89%) and FEV₁/FVC (0.64 vs 0.66), as well as higher levels of high-sensitivity C-reactive protein, fibrinogen, leukocytes, neutrophils, eosinophils, and IgE in blood.

CONCLUSIONS

Comorbid chronic cough in individuals with COPD is associated with a more severe disease in terms of more respiratory symptoms and health-care utilizations, lower lung function, and increased inflammation in blood.

Exploring the clinical relevance of cough hypersensitivity syndrome

Introduction: Knowledge of the pathophysiology of cough has continued to advance over recent decades. Establishing anatomic-diagnostic protocols, based on the anatomy and distribution of vagus nerve pathways regulating the cough reflex, was the first breakthrough in modern clinical medicine for chronic cough. The unmet clinical need has prompted revised thinking regarding the pathophysiology of and the clinical approach to chronic cough.Areas covered: The paradigm of cough hypersensitivity syndrome (CHS) has been recently proposed, wherein aberrant neuro-pathophysiology is a common etiology. This review covers major findings on chronic cough and cough hypersensitivity, particularly focused on recently-published studies and explores the clinical relevance and applicability of CHS based on current knowledge and discuss knowledge gaps and future research directions.Expert opinion: This paradigm has provided new opportunities in managing chronic cough and evidence is accumulating to support the validity of CHS. It also warrants the re-appraisal of existing clinical evidence and investigation of how to refine our clinical strategy. While CHS highlights the importance of clinical thinking from the viewpoint of cough, the value of anatomic-diagnostic protocols should remain. Moreover, given the considerable heterogeneity in clinical presentation, cough-associated disease conditions, and treatment responses across different patients, precise molecular endotyping remains key to making further to advancing clinical practice .

Arnold Nerve Reflex: Vagal Hypersensitivity in Chronic Cough With Various Causes

BACKGROUND

A higher incidence of Arnold nerve reflex (ANR) has been observed in patients with chronic cough. However, the different ANR response in various causes of chronic cough remains unclear. Furthermore, it is unknown whether ANR will change after effective treatment.

METHODS

Patients with chronic cough were enrolled in the Guangzhou Institute of Respiratory Health. The causes of chronic cough were diagnosed via a validated management algorithm. Patients underwent an assessment of ANR response before and after 1 month of etiologic treatment.

RESULTS

A total of 127 patients with chronic cough and 55 healthy control subjects were enrolled. The positive response, defined as cough-only ANR or urge-to-cough (UTC), was present in 14.8% of patients with cough variant asthma (CVA), 11.1% of patients with upper airway cough syndrome, 15.4% of patients with gastroesophageal reflex related cough (GERC), 4.8% of patients with eosinophilic bronchitis, and 26.9% of patients with unexplained cough (UC). No ANR or UTC was found in the healthy control subjects. The incidence of the positive response was higher in subjects with CVA, GERC, and UC compared with healthy control subjects (all P < .05). No difference was observed among the different causes of chronic cough (all P > .05). After 1 month of treatment, 87.5% of patients identified with a positive response changed to a negative response. In a subgroup analysis, an increased cough sensitivity to capsaicin was found in the patients with a positive response compared with the patients with a negative response (P < .05).

CONCLUSIONS

A positive ANR appears to be a sign of vagal hypersensitivity and can be reversed after effective treatment of chronic cough. However, although various causes of chronic cough share a similar feature of an elevated ANR response in a minority of patients, there appears to be limited usefulness in assessing ANR because it does not appear to be a valid predictor of etiology of chronic cough or outcome of treatment.

Nonmetastatic renal cell carcinoma presenting with persistent cough: Case report with literature review

Renal cell carcinomas (RCC), constitute 80– 85% of primary renal neoplasms. The classic triad of RCC (flank pain, hematuria, and a palpable abdominal renal mass) occurs in approximately 9% of patients; it strongly suggests locally advanced disease. RCC may also be associated with a number of paraneoplastic syndromes. These are typically due to ectopic production of various hormones. We present a 69-year-old male patient previously healthy presented to the emergency department with recurrent persistent cough. A non-metastatic RCC was incidentally discovered. Eventually, he underwent left radical nephrectomy. One year has passed with no cough. This is a rare and unusual presentation of RCC that falls under the category of paraneoplastic syndrome with review of similar reported cases and summary of all paraneoplastic syndromes associated with RCC in literature.

Cough: A Practical and Multifaceted Approach to Diagnosis and Management

Cough is a common symptom often confronted in the clinical setting. Time and resources attributed to cough place an undue burden on patients and the health care system. One characteristic of cough that likely contributes to this is the multifactorial nature of cough. Physicians are trained to find a single diagnosis to explain symptoms. With cough, if all factors contributing are not identified and treated together, the cough often remains unresolved. This article provides a practical approach to treatment and management of cough, emphasizing causes and potentiators.

Joint analysis of multiple phenotypes using a clustering linear combination method based on hierarchical clustering

Emerging evidence suggests that a genetic variant can affect multiple phenotypes, especially in complex human diseases. Therefore, joint analysis of multiple phenotypes may offer new insights into disease etiology. Recently, many statistical methods have been developed for joint analysis of multiple phenotypes, including the clustering linear combination (CLC) method. Due to the unknown number of clusters for a given data, a simulation procedure must be used to evaluate the p-value of the final test statistic of CLC. This makes the CLC method computationally demanding. In this paper, we use a stopping criterion to determine the number of clusters in the CLC method. We have named our method, hierarchical clustering CLC (HCLC). HCLC has an asymptotic distribution, which is very computationally efficient and makes it applicable for genome-wide association studies. Extensive simulations together with the COPDGene data analysis have been used to assess the type I error rates and power of our proposed method. Our simulation results demonstrate that the type I error rates of HCLC are effectively controlled in different realistic settings. HCLC either outperforms all other methods or has statistical power that is very close to the most powerful method with which it has been compared.

Impact of Chronic Cough on Health-Related Quality of Life in the Korean Adult General Population: The Korean National Health and Nutrition Examination Survey 2010-2016

Purpose

Chronic cough is a prevalent condition in the community and may pose considerable impairment to quality of life (QoL). However, its disease burden remains largely undefined in the general population. The present study investigated the relationship between chronic cough and health-related QoL in a Korean nationwide population database, with an emphasis on clinical conditions which may confound the impact of cough.

Methods

This study analyzed cross-sectional datasets of adults (aged ≥ 40 years) in the Korean National Health and Nutrition Examination Survey 2010–2016. Health-related QoL was assessed using the 3-level EuroQoL 5-dimension component (EQ-5D-3L) index score. The presence of chronic cough and other conditions were defined using structured questionnaires.

Results

The prevalence of chronic cough was 3.48% ± 0.17% among adults aged ≥ 40 years. The overall EQ-5D-3L index score was significantly lower in subjects with than without chronic cough (0.79 ± 0.01 vs. 0.86 ± 0.00, P < 0.001). In subgroup analyses by age and sex, chronic cough had a notably large impact on QoL in women aged ≥ 65 years (vs. those without chronic cough: 0.55 ± 0.04 vs. 0.70 ± 0.01, P < 0.001), although the mean difference in the scores exceeded the minimally important difference score of 0.05 in all subgroups. In multivariate analyses, chronic cough was significantly associated with QoL, independent of confounders including depression, arthritis, asthma, and chronic obstructive pulmonary disease. In dimension analyses, chronic cough was more associated with anxiety/depression, pain/discomfort, and usual activities than with self-care or mobility in the EQ-5D.

Conclusions

The present study demonstrated significant associations between chronic cough and health-related QoL in a nationwide large general adult population aged ≥ 40 years, which were independent of clinical confounders. The impact of chronic cough was greater in women aged ≥ 65 years. These findings indicate a considerable burden of chronic cough in the general population and warrant further investigations to assess the disease burden of chronic cough in a global scale.

Clinical Characteristics of Chronic Cough in Korea

BACKGROUND

Chronic cough is defined as a cough lasting more than 8 weeks and socio-economic burden of chronic cough is enormous. The characteristics of chronic cough in Korea are not well understood. The Korean Academy of Tuberculosis and Respiratory Diseases (KATRD) published guidelines on cough management in 2014. The current study evaluated the clinical characteristics of chronic cough in Korea and the efficacy of the KATRD guidelines.

METHODS

This was a multi-center, retrospective observational study conducted in Korea. The participants were over 18 years of age. They had coughs lasting more than 8 weeks. Subjects with current pulmonary diseases, smokers, ex-smokers with more than 10 pack-years or who quit within the past 1 year, pregnant women, and users of cough-inducing medications were excluded. Evaluation and management of cough followed the KATRD cough-management guidelines.

RESULTS

Participants with chronic cough in Korea showed age in the late forties and cough duration of more than 1 year. Upper airway cough syndrome was the most common cause of cough, followed by cough-variant asthma (CVA). Gastro-esophageal reflux diseases and eosinophilic bronchitis were less frequently observed. Following the KATRD cough-management guidelines, 91.2% of the subjects improved after 4 weeks of treatment. Responders were younger, had a longer duration of cough, and an initial impression of CVA. In univariate and multivariate analyses, an initial impression of CVA was the only factor related to better treatment response.

CONCLUSION

The causes of chronic cough in Korea differed from those reported in other countries. The current Korean guidelines proved efficient for treating Korean patients with chronic cough.

Clinical significance of self-reported cough intensity and frequency in patients with interstitial lung disease: a cross-sectional study

Background

The intensity and frequency of cough remain unclear in interstitial lung disease (ILD). The aim of this study was to evaluate the intensity and frequency of cough in idiopathic interstitial pneumonias (IIPs), connective tissue disease-associated interstitial lung disease (CTD-ILD), and chronic hypersensitivity pneumonia (CHP), and examine their associations with clinical indices.

Methods

In this cross-sectional study, the intensity and frequency of cough were evaluated using a 100-mm visual analogue scale. Scores on the Leicester Cough Questionnaire, chronic dyspnoea scale, and a frequency scale for symptoms of gastro-oesophageal reflux disease (FSSG) were collected. The correlations of cough intensity and frequency with potential predictor variables were tested using bivariate and multiple logistic regression analysis.

Results

The study included 70 patients with IIPs, 49 with CTD-ILD, and 10 with CHP. Patients with IIPs had the most severe cough intensity among the three patient groups. In patients with IIPs, both the intensity and frequency of cough were negatively associated with the diffusing capacity of the lung for carbon monoxide and positively with the Composite Physiologic Index (CPI). In CTD-ILD, both the intensity and frequency of cough were correlated with a higher FSSG score. In multivariate analysis of patients with ILD, IIPs and the FSSG score were independently associated with both components of cough, and CPI tended to be independently associated with cough frequency. Finally, we examined the features of the differences between cough intensity and frequency in all patients with ILD. Patients in whom cough frequency was predominant had a greater impairment of health status relative to other patients.

Conclusions

Cough intensity was greater in IIPs than in other ILDs. Different clinical indices were associated with patient-reported cough intensity and frequency according to the subtype of ILD. Cough frequency was more strongly associated with health status than was cough intensity. These findings suggest that medical staff could manage patients with ILD by considering cough-related factors when assessing the intensity and frequency of cough.

Gastroesophageal reflux disease and chronic cough: A possible mechanism elucidated by ambulatory pH-impedance-pressure monitoring

BACKGROUND

The pathophysiological mechanism(s) of gastroesophageal reflux disease (GERD)-related chronic cough (CC) is unclear. We aimed to determine the mechanism of reflux-induced cough by synchronous monitoring of reflux episodes, esophageal motility, and cough.

METHODS

Patients with GERD were prospectively enrolled and classified into GERD with CC (GERD-CC) and without CC (GERD) groups. Twenty-four-hour ambulatory pH-impedance-pressure monitoring was performed; the reflux patterns, esophageal motility during prolonged exposure to acid and characteristics of reflux episodes that induced coughing paroxysms were analyzed.

KEY RESULTS

Thirty-one patients with GERD-CC and 47 with GERD were enrolled; all of whose monitoring results fulfilled the criteria for diagnosis of GERD. Patients with GERD-CC had higher reflux symptom scores, longer exposure to acid, higher DeMeester scores, and more frequent reflux episodes, proximal extent reflux detected by impedance, and higher percentage of strongly acidic reflux than patients in the GERD group (all P < .05). Of 63 reflux-cough episodes identified in the GERD-CC group, 74.6% of distal reflux and 67.0% of proximal reflux episodes were acidic. More patients had low pan-esophageal pressure in primary peristalsis (48.5% vs 11.8%, P = .000) and synchronous contraction in secondary peristalsis during prolonged exposure to acid in the GERD-CC than in the GERD group (63.9% vs 9.1%, P = .000).

CONCLUSIONS & INFERENCES

Proximal acidic reflux and distal reflux-reflex are jointly associated with reflux-induced cough in patients with GERD. Low pan-esophageal pressure in primary peristalsis and synchronous contraction in secondary peristalsis may play important roles in GERD-associated chronic cough.

The Mechanisms Involved in Morphine Addiction: An Overview

Opioid use disorder is classified as a chronic recurrent disease of the central nervous system (CNS) which leads to personality disorders, co-morbidities and premature death. It develops as a result of long-term administration of various abused substances, along with morphine. The pharmacological action of morphine is associated with its stimulation of opioid receptors. Opioid receptors are a group of G protein-coupled receptors and activation of these receptors by ligands induces significant molecular changes inside the cell, such as an inhibition of adenylate cyclase activity, activation of potassium channels and reductions of calcium conductance. Recent data indicate that other signalling pathways also may be involved in morphine activity. Among these are phospholipase C, mitogen-activated kinases (MAP kinases) or β-arrestin. The present review focuses on major mechanisms which currently are considered as essential in morphine activity and dependence and may be important for further studies.

The management of chronic cough

Chronic cough is a common presentation to primary care and constitutes a significant volume of referrals to secondary care. It affects around 10% of the adult population and has a plethora of respiratory and non-respiratory causes. It can have a significant impact on the quality of life of affected individuals. In many patients, minimal baseline investigations lead to an easily identifiable and treatable cause. In others, no cause can be identified even after extensive investigations in specialized cough clinics. This evidence-based review article outlines the approach to the adult patient presenting with chronic cough and focuses upon current management strategies in those with chronic idiopathic cough. It includes results from trials of speech and language therapies, and the emerging concept of chronic idiopathic cough as a neuropathic disorder with its own bespoke approach to management including the use of neuromodulatory agents.

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.

Changing etiological frequency of chronic cough in a tertiary hospital in Shanghai, China

Background

The frequency distributions of the etiologies of chronic cough have changed over time. This study aimed to investigate the changing etiological frequency of chronic cough in a tertiary hospital in Shanghai, China, and to explore the clinical significance.

Methods

Medical records of 1,311 patients with chronic cough who visit our hospital between January 2009 and December 2016 were retrospectively reviewed. The etiologies of chronic cough were identified according to a standardized step-by-step diagnostic protocol and the changes in the etiological frequency of chronic cough over the years were using the Chi-squared (χ²) test.

Results

Cough variant asthma (CVA) (449/1,311, 34.2%), gastroesophageal reflux-related chronic cough (GERC) (374/1,311, 28.5%), upper airway cough syndrome/postnasal drip syndrome (UACS/PNDs) (241/1,311, 18.4%), atopic cough (AC) (188/1,311, 14.3%), and non-asthmatic eosinophilic bronchitis (NAEB) (147/1,311, 11.2%) were the common causes of chronic cough in descending order. The post-infectious cough (PIC) (39/1,311, 3.0%) and angiotensin-converting enzyme inhibitor (ACEI)-induced cough (25/1,311, 1.9%) were less common. During the 8-year period, the proportion of CVA (χ²=72.86, P<0.0001) and UACS/PNDs (χ²=68.80, P<0.0001) decreased, while those of NAEB (χ²=51.38, P<0.0001), GERC (χ²=55.95, P<0.0001) and AC (χ²=39.09, P<0.0001) increased.

Conclusions

The etiological frequency of chronic cough varies over time, and it may encourage the adjustment of the current diagnostic and therapeutic strategies for chronic cough.

Effect of anti-reflux treatment on gastroesophageal reflux-associated chronic cough: Implications of neurogenic and neutrophilic inflammation

Objective: Gastroesophageal reflux disease (GERD) is an important cause of chronic cough. Substance P (SP) has been implicated in the pathophysiology of cough. Proton pump inhibitors (PPIs) and prokinetic agents are the current treatment for GER-associated cough. The aim was to evaluate the effects of anti-reflux treatment and its associations with cellular and neurogenic inflammation.Methods: Thirty-seven patients with GER-associated cough suspected based on characteristic symptoms such as heartburn and worsening of cough by phonation and rising were recruited. A PPI, rabeprazole 20 mg daily, and a prokinetic agent, itopride 50 mg t.i.d., were administered for 4 weeks in a prospective, observational manner. Before and after treatment, subjective cough measures [visual analog scale (VAS) and the Japanese version of the Leicester Cough Questionnaire (J-LCQ)], the modified frequency scale for the symptoms of GERD [FSSG, consisting of 2 domains: acid-reflux (AR) and functional dyspepsia symptoms], sputum and plasma SP levels, and sputum cell differentials were examined. Patients with good response to treatment [Δ (decrease of) VAS >15 mm; n = 21) were compared with poor responders (ΔVAS ≤15 mm).Results: Anti-reflux treatment significantly improved the cough VAS, J-LCQ, and AR symptoms, and ΔVAS and ΔAR were significantly correlated. Decreases of plasma and sputum SP levels and sputum neutrophil counts were significantly greater in responders than in poor responders. Both baseline values and post-treatment changes of plasma SP and sputum neutrophils were significantly correlated for all patients.Conclusions: Successful treatment of GER-associated cough may be associated with the attenuation of neurogenic and neutrophilic inflammation.

Naringin and Naringenin Relax Rat Tracheal Smooth by Regulating BKCa Activation

Naringin and its aglycone, naringenin, occur naturally in our regular diet and traditional Chinese medicines. This study aimed to detect an effective therapeutic approach for cough variant asthma (CVA) through evaluating the relaxant effect of these two bioactive herbal monomers as antitussive and antiasthmatic on rat tracheal smooth muscle. The relaxant effect was determined by measuring muscular tension with a mechanical recording system in rat tracheal rings. Cytosolic Ca²⁺ concentration was measured using a confocal imaging system in primary cultured tracheal smooth muscle cells. In rat tracheal rings, addition of both naringin and naringenin could concentration dependently relax carbachol (CCh)-evoked tonic contraction. This epithelium-independent relaxation could be suppressed by BaCl₂, tetraethylammonium, and iberiotoxin (IbTX), but not by glibenclamide. After stimulating primary cultured tracheal smooth muscle cells by CCh or high KCl, the intracellular Ca²⁺ increase could be inhibited by both naringin and naringenin, respectively. This reaction was also suppressed by IbTX. These results demonstrate that both naringin and naringenin can relax tracheal smooth muscle through opening big conductance Ca²⁺-activated K⁺ channel, which mediates plasma membrane hyperpolarization and reduces Ca²⁺ influx. Our data indicate a potentially effective therapeutic approach of naringin and naringenin for CVA.

Characteristics of Chinese chronic cough patients

Chronic cough is one of the most common complains for patients seeking medical attention in both general practice and respiratory specialist clinics. Cough variant asthma, eosinophilic bronchitis, upper airway cough syndrome, as well as gastro-esophageal reflux disease are common conditions associated with chronic cough, and cough variant asthma, eosinophilic bronchitis account for a higher proportion of patients with chronic cough in China than in Western countries. An older female predominance has been reported in most Western countries, which may be attributed to a higher cough reflex sensitivity in females, especially those post-menopausal females. However, studies conducted in China showed that patients with chronic cough have a nearly similar gender distribution and most of them are in their late 30s or early 40s, despite the similar gender and age difference in cough reflex sensitivity as Western countries. Environmental and occupational exposures, cigarette smoking, unhealthy lifestyle might play a role in the distinct age and gender distribution of Chinese chronic cough patients, yet further study is needed to clarify it.

Heterogeneity of cough hypersensitivity mediated by TRPV1 and TRPA1 in patients with chronic refractory cough

Background

The differential sensitivity of cough to antitussive therapies implies the existence of heterogeneity in cough hypersensitivity, but how such heterogeneity is expressed across individual patients is poorly understood. We investigated the phenotypes of cough hypersensitivity by examining transient receptor potential ankyrin 1 (TRPA1)- and transient receptor potential vanilloid 1 (TRPV1)-mediated cough sensitivity in patients with chronic refractory cough.

Methods

Using a selective TRPA1 agonist, allyl isothiocyanate (AITC), we established an AITC cough challenge as a measure of TRPA1-mediated cough sensitivity. The AITC cough challenge and the widely used capsaicin (a selective TRPV1 agonist) cough challenge were performed with 250 patients with chronic refractory cough and 56 healthy subjects. The concentration of AITC or capsaicin solution causing at least two (C2) and five coughs (C5) was recorded. Cough sensitivity was expressed as the mean (95% confidence interval) of log C5, and cough hypersensitivity was defined as a log C5 value lower than that of healthy subjects.

Results

A distinct concentration–response effect of inhaled AITC was identified both in patients with chronic refractory cough and in healthy subjects. Cough sensitivity to AITC and capsaicin was significantly higher in patients than in healthy subjects (AITC: 2.42 [2.37–2.48] vs 2.72 [2.66–2.78] mM, p = 0.001; capsaicin: 1.87 [1.75–1.98] vs 2.53 [2.36–2.70] μM, p = 0.001) and was higher in females than in males for both healthy subjects and patients (all p < 0.05). Among the 234 patients who completed both challenges, 25 (10.7%) exhibited hypersensitivity to both AITC and capsaicin, 44 (18.8%) showed hypersensitivity to AITC only, 28 (11.9%) showed hypersensitivity to capsaicin only, and 137 (58.6%) exhibited hypersensitivity to neither. Those with TRPA1- and/or TRPV1-mediated hypersensitivity were predominantly female, while those without TRPA1- and TRPV1-mediated hypersensitivity were mainly male.

Conclusions

Four phenotypes of cough hypersensitivity were identified by the activation of TRPV1 and TRPA1 channels, which supports the existence of heterogeneity in cough pathways and provides a new direction for personalized management of chronic refractory cough.

Trial registration

ClinicalTrials.gov NCT02591550.

Effect of pregabalin for the treatment of chronic refractory cough: A case report

RATIONALE

Chronic refractory cough (CRC) is a common clinical problem which is more likely associated with some physical problems. Although many patients have received satisfactory treatment, there were still many patients suffered from long-term cough symptoms after standardized treatment.

PATIENT CONCERNS

A patient suffered from postherpetic neuralgia (PHN) and also he complained CRC for more than 20 years.

DIAGNOSIS

The patient was diagnosed with PHN and CRC.

INTERVENTIONS

Pregabalin was originally administered to treat PHN.

OUTCOMES

pregabalin not only alleviated her pain of PHN but also relieved chronic cough.

LESSONS

This report demonstrated the surprising effect of pregabalin on the treatment of CRC.

Exhaled nitric oxide in chronic cough: A good tool in a multi-step approach

INTRODUCTION

The impact of fractional exhaled nitric oxide (FENO) on the management of chronic cough (CC) is still inconclusive. The aim of the present study was to assess whether FENO is a good tool to predict the response to inhaled corticosteroids (ICS) in patients with CC.

METHODS

Patients, referred for investigation of CC, had a FENO measurement determined as part of their first-line assessment. A methacholine test was performed as part of a second-line assessement. Patients were assigned to two groups according to their FENO values: a high FENO level group (Ⱕ25 ppb) and a normal FENO level group (<25 ppb).

RESULTS

One hundred patients were included in the study. High FENO levels were found in 25 patients (25%). The proportion of patients who responded to ICS was significantly greater in the high FENO group compared to the normal FENO level group (86.4% vs 46.3%, P<0.05). FENO is a good tool to predict ICS response in patients with high FENO levels but a response to ICS cannot be ruled out in patients with normal FENO levels. In patients with normal FENO values, a methacholine test could be an interesting tool for a second-line assessment. Among the 13 patients with a positive methacholine test result, 11 responded to ICS whilst 2 did not. Of the patients with a negative methacholine test result, 3 responded to ICS whilst 13 did not.

CONCLUSION

FENO may be a more reliable predictor of ICS response when used as part of a multi-step assessment procedure.

The Spectrum of Non-asthmatic Airway Diseases Contributing to Cough in the Adult

PURPOSE OF REVIEW

Cough becomes a pathologic reflex when the airways are inflamed and overwhelmed with excessive mucus. The goal of this review is to discuss acute and chronic cough syndromes caused by non-asthmatic airway diseases.

RECENT FINDINGS

Acute cough syndrome is short-lived and self-limited. Acute bronchitis and diffuse acute infectious bronchiolitis (DAIB) are examples. The former is usually caused by a viral illness; the latter by Mycoplasma pneumoniae, influenza, and Haemophilus influenzae. Causes of chronic cough in the adult include chronic bronchitis, non-infectious bronchiolitis, and non-cystic fibrosis bronchiectasis.

SUMMARY

Supportive measures are recommended for acute bronchitis and antibiotic use is discouraged. Antibiotics may be needed for DAIB. Smoking cessation and bronchodilators can control cough in chronic bronchitis. Therapeutic approaches for non-infectious bronchiolitis depend on the varied etiology. The hallmark of bronchiectasis is a chronic infection of the airways, and antibiotics, mucus clearance measures, and bronchodilators are all supportive.

[From acute cough to chronic cough in adults: Overview on a common reason for consultation]

Cough is divided into two categories: acute cough lasting less than 3 weeks, and chronic cough lasting more than 8 weeks. Acute cough is usually triggered by a viral infection of the upper airways. Evidence of treatment effectiveness is low and management of acute cough is complex in clinical practice. Chronic cough is a common reason for consultation in medicine. The most frequent causes are upper airway diseases, gastroesophageal reflux disease, asthma, eosinophilic bronchitis, and drugs. Before investigation, smoking cessation and drug withdrawal must be achieved for 4 to 6 weeks. Once this step is completed, simple investigations have to be performed in order to find common causes of chronic cough (questioning, physical examination, spirometry, chest X-ray). If no causes have been identified or cough remains despite optimal treatment, exhaustive exploration has to be performed to rule out rare causes. A chronic cough hypersensitivity syndrome is suggested if any causes have been found despite exhaustive assessment or if cough remains with optimal treatments. This syndrome is characterized by an increase in the sensitivity of cough peripheral receptors and is not sensitive to usual therapies. The therapeutic options are limited but innovative treatments such as P2X3 receptor antagonists are in development.

Update on the clinical development of gefapixant, a P2X3 receptor antagonist for the treatment of refractory chronic cough

Chronic cough, or cough lasting >8 weeks, is often associated with underlying medical conditions (ie, asthma, gastroesophageal reflux disease, nonasthmatic eosinophilic bronchitis, and upper-airway cough syndrome). In some patients with chronic cough, treatment of these underlying conditions does not resolve the cough (refractory chronic cough [RCC]), or none of these conditions are present (unexplained chronic cough [UCC]). Despite appropriate medical evaluation, patients with RCC or UCC frequently experience cough persisting for many years, as there are currently no targeted pharmacological approaches approved for the treatment of these conditions. However, the adenosine triphosphate (ATP)-gated P2X3 receptor, a key modulator of the activation of sensory neurons central to the cough reflex, has recently garnered attention as a potential therapeutic target for the treatment of chronic cough. Gefapixant, a first-in-class, non-narcotic, selective antagonist of the P2X3 receptor, recently demonstrated efficacy and was generally well tolerated in phase 2 clinical trials in patients with RCC, validating the utility of targeting this receptor in patients with chronic cough. On the basis of these data, 2 global phase 3 trials, with combined anticipated enrolment exceeding 2000 patients and with treatment durations of up to 1 year, have been initiated. Together, these trials will further evaluate efficacy and safety of gefapixant in the control of cough in patients with RCC or UCC.

Chronic Cough in Adults: Make the Diagnosis and Make a Difference

Chronic cough is common and impactful, frustrating both patients and clinicians. An empirical trial of therapy is often done with inhaled corticosteroids, but this practice should be replaced with attempting to make an accurate diagnosis. The three most common causes are upper airway cough syndrome, asthma, and gastroesophageal reflux disease (GERD), but there are often multiple causes involved. Minimal investigations after history, physical exam, travel history, and drug history include a chest radiograph and spirometry. Empirical trial of therapy with inhaled corticosteroids is reasonable if there is evidence of eosinophilic inflammation. Empiric therapy for GERD may also be reasonable in those with symptoms. Red flags should especially be considered an urgency to make the correct diagnosis.

A 3D Human Airway Model Enables Prediction of Respiratory Toxicity of Inhaled Drugs In Vitro

Respiratory tract toxicity represents a significant cause of attrition of inhaled drug candidates targeting respiratory diseases. One of the key issues to allow early detection of respiratory toxicities is the lack of reliable and predictive in vitro systems. Here, the relevance and value of a physiologically relevant 3D human airway in vitro model (MucilAir) were explored by repeated administration of a set of compounds with (n = 8) or without (n = 7) respiratory toxicity following inhalation in vivo. Predictability for respiratory toxicity was evaluated by readout of cytotoxicity, barrier integrity, viability, morphology, ciliary beating frequency, mucociliary clearance and cytokine release. Interestingly, the data show that in vivo toxicity can be predicted in vitro by studying cell barrier integrity by transepithelial electrical resistance (TEER), and cell viability determined by the Resazurin method. Both read-outs had 88% sensitivity and 100% specificity, respectively, while the former was more accurate with receiver operating characteristic (ROC) AUC of 0.98 (p = .0018) compared with ROC AUC of 0.90 (p = .0092). The loss of cell barrier integrity could mainly, but not fully, be attributed to a loss of cell coverage in 6 out of 7 compounds with reduced TEER. Notably, these effects occurred only at 400 µM, at concentration levels significantly above primary target cell potency, suggesting that greater attention to high local lung concentrations should be taken into account in safety assessment of inhaled drugs. Thus, prediction of respiratory toxicity in 3D human airway in vitro models may result in improved animal welfare and reduced attrition in inhaled drug discovery projects.

A retrospective study of clinical features of cough variant asthma in Chinese adults

Background

Clinical features of cough variant asthma (CVA) in Chinese adults are largely uncertain.

Methods

A total of 303 patients newly diagnosed as uncontrolled asthma (symptom control and future risk of adverse outcomes), including 175 CVA and 128 classic asthma (CA), were enrolled in this retrospective survey. Clinical features including basic characteristics, pulmonary function, airway hyperresponsiveness (AHR) and cell counts of induced sputum, were compared retrospectively. All patients were classified into four inflammatory subtypes based on the counts of induced sputum eosinophils and neutrophils as eosinophilic (E), neutrophilic (N), mixed granulocytic (M), and paucigranulocytic (P) subtypes. Inflammatory subtype distribution was also compared.

Results

Compared with CA patients, CVA patients were younger (P = 0.009), had a higher prevalence of female patients (P = 0.001), higher parameter values of baseline pulmonary function (P ≤ 0.01 for all), shorter duration of disease (P = 0.002), lower AHR (P = 0.001) and lower sputum eosinophil% (P = 0.009). There was a difference in the AHR distribution as the percentage of moderate and severe AHR in CVA was significantly lower than in CA (41.72% VS 64.70%, P = 0.001). The inflammatory subtype distribution was different as the proportion of E and M subtypes in CVA was lower than in CA (56.0% vs 67.19%, P = 0.049). The proportion of subtype P was the lowest and subtype M was the highest in both CVA and CA patients. There was a similar negative correlation of sputum eosinophil% with AHR in CVA and CA (r = − 0.337, P < 0.0001 and r = − 0.27, P = 0.026, respectively), and a positive correlation between sputum eosinophil% and improvement rate of FEV₁ after inhalation of bronchodilator (ΔFEV₁%) (r = 0.33, P = 0.01).

Conclusions

CVA patients showed a better pulmonary function and lower airway inflammation in contrast to CA patients, which may participate in the pathogenesis of chronic cough in CVA.

Traffic-related air pollution induces non-allergic eosinophilic airway inflammation and cough hypersensitivity in guinea-pigs

BACKGROUND

The pathogenesis and pathophysiology of eosinophilia-related chronic cough such as non-asthmatic eosinophilic bronchitis and cough variant asthma are still not clear.

OBJECTIVE

This study is to examine the potential role of traffic-related air pollution (TRAP) in eosinophilic inflammation and cough responses.

METHODS

Non-sensitized guinea-pigs were exposed to TRAP in an urban traffic tunnel or kept in a filtered air environment for 7 or 14 days. Reflexive cough was measured using citric acid and allyl isothiocyanate (AITC) challenges, respectively. Spontaneous cough counting was determined using audio recording and a waveform analysis. Airway inflammation was evaluated using differential cells in bronchoalveolar lavage fluid (BALF) and lung histopathology. To further elucidate the relationship between airway inflammation and cough hypersensitivity, a subgroup of those exposed for 14 days received a dexamethasone treatment.

RESULTS

Compared to reflexive cough count (mean (95% confidence interval) in 10 minutes) provoked by the AITC challenge for the unexposed animals (3.1 (1.7-4.5)), those were increased significantly following both the 7-day (12.0 (6.8-17.2), P < 0.01) and the 14-day (12.0 (6.4-17.6), P < 0.01) TRAP exposure. The effect provoked by the citric acid challenge was more profound following the 14-day exposure (26.0 (19.5-32.5) vs 3.8 (1.5-6.0) for the control, P < 0.001). TRAP exposures enhanced spontaneous cough events, caused a significant increase of eosinophils and neutrophils in BALF and resulted in a dramatic eosinophilic infiltration in submucosal layer of trachea and bronchus, which can be inhibited significantly by dexamethasone treatment.

CONCLUSIONS & CLINICAL RELEVANCE

TRAP exposures induced cough hypersensitivity and non-allergic eosinophilic inflammation of airways in guinea-pigs. This study highlights the potential mechanisms of eosinophilia-related chronic cough that can be induced by traffic-related air pollution.

Age and Sex Distribution of Chinese Chronic Cough Patients and Their Relationship With Capsaicin Cough Sensitivity

PURPOSE

An older female predominance has been reported among chronic cough patients in Western countries, which is considered to be associated with a higher cough sensitivity in females. However, the characteristics of Chinese chronic cough patients remain unclear. This study aimed to explore the age and sex distribution as well as their relationship with cough reflex sensitivity to capsaicin in Chinese chronic cough patients.

METHODS

We analyzed the demographic features of 1,882 consecutive chronic cough patients who attended our cough clinic in Guangzhou, China. Cough sensitivity to capsaicin, which was defined as the lowest concentration of capsaicin causing 5 coughs or more (C5), was measured in 539 of the 1,882 patients and 68 healthy volunteers.

RESULTS

The mean age of the patients was 43.0 ± 13.7 years and patients aged <50 years accounted for more than two-thirds of the study population. Around 87% of the patients were never-smokers. The proportion of females (51.5%) was almost equal to that of males (48.5%). The pattern of the age and sex distribution was consistently reflected within most common causes of chronic cough, while a female predominance was shown in patients with cough-variant asthma and patients aged ≥50 years. Female patients had higher cough sensitivity to capsaicin than male patients (log C5: 1.58 ± 0.84 vs. 2.04 ± 0.84 μmol/L, P = 0.001), and patients aged ≥50 years had higher cough sensitivity to capsaicin than patients aged <50 years.

CONCLUSIONS

In China, patients with chronic cough have a roughly equal sex distribution and a middle-aged predominance, irrespective of a higher cough sensitivity to capsaicin in females and older patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02591550.

Altering cough reflex sensitivity with aerosolized capsaicin paired with behavioral cough suppression: a proof-of-concept study

Background

The purpose of this prospective, quasi-experimental, single cohort proof-of-concept study was to determine feasibility and proof-of-concept of programmatically decreasing cough sensitivity through use of cough suppression strategies following inhalation of aerosolized capsaicin, in gradually increasing doses, across repeated treatment sessions.

Methods

Five healthy adults, ages 20-32 years of age, enrolled and completed the study. The study commenced in three phases. Phase I consisted of baseline cough sensitivity testing using pharmaceutical-grade aerosolized capsaicin, delivered via a Koko DigiDoser with nebulizer. The single-inhale, dose-response method was used. Doses that elicited two coughs (C2) and five coughs (C5) were recorded. Testing ceased when participants met the C5 threshold or when they had been given the maximum dose of 1,000 µmol/L. Phase II consisted of 5-6 treatment sessions, during which participants were exposed to increasing doses of aerosolized capsaicin while implementing behavioral cough suppression strategies. In phase III, cough sensitivity was re-tested at 1 and 3 weeks post-treatment. Participants were given explicit instructions to not try to suppress their cough. Participants who did not reach the C2 or C5 threshold at 1,000 µmol/L were assigned a score of 1,250 µmol/L.

Results

Each participant demonstrated a gradual increase in maximum capsaicin dose suppressed during each treatment session, with each successfully suppressing at 1,000 µmol/L by the final treatment session. C2 was greater than baseline in 4 of the 5 participants at 1 week post-treatment, and in 3 of the 5, at 3 weeks post-treatment. C5 was greater in all 5 participants at both post-treatment time points. In fact, 4 of the 5 participants did not reach the C5 threshold during either post-treatment testing sessions. Wilcoxon's Signed Rank Test, using the logC2 and logC5 values, revealed a significant difference relative to baseline in logC5 at 1 week (z=-2.02, P=0.04) and 3 weeks (z=-2.03, P=0.04) post-treatment. The difference in logC2 neared significance at 1 week post-treatment (z=-1.77, P=0.077), but was insignificant at 3 weeks post-treatment (z=-1.46, P=0.144).

Conclusions

This study demonstrates the potential of treating patients with refractory chronic cough (RCC), due to cough hypersensitivity, with a progressive desensitization approach paired with behavioral cough suppression. Additional research is needed using a randomized, placebo-controlled trial with patients with RCC.