Bronchoconstriction-triggered cough is impaired in typical asthmatics

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Methacholine-Induced Cough in the Absence of Asthma: Insights From Impulse Oscillometry

Introduction

The pathophysiologic differences between methacholine-induced cough but normal airway sensitivity (COUGH) and healthy individuals (CONTROL) are incompletely understood and may be due to differences in the bronchodilating effect of deep inspirations (DIs). The purpose of this study is to compare the bronchodilating effect of DIs in individuals with classic asthma (CA), cough variant asthma (CVA), and COUGH with CONTROL and to assess impulse oscillometry (IOS) measures as predictors of the bronchodilating effect of DIs.

Methods

A total of 43 adults [18 female; 44.8 ± 12.3 years (mean ± SD); n = 11 CA, n = 10 CVA, n = 7 COUGH, n = 15 CONTROL] underwent modified high-dose methacholine challenge, with IOS and partial/maximal expiratory flow volume (PEFV/MEFV) maneuvers (used to calculate DI Index) to a maximum change (Δ) in FEV₁ of 50% from baseline (MAX). Cough count and dyspnea were measured at each dose. The relation between IOS parameters and DI Index was assessed at baseline and MAX using multivariable linear regression analysis.

Results

Cough frequency, dyspnea intensity, and baseline peripheral resistance (R5-R20) were significantly greater in COUGH compared with CONTROL (p = 0.006, p = 0.029, and p = 0.035, respectively). At MAX, the DI Index was significantly lower in COUGH (0.01 ± 0.36) compared with CA (0.67 ± 0.97, p = 0.008), CVA (0.51 ± 0.73, p = 0.012), and CONTROL (0.68 ± 0.45, p = 0.005). Fres and R5-R20 were independent IOS predictors of the DI Index.

Conclusion

The bronchodilating effect is impaired in COUGH and preserved in mild CA, CVA, and CONTROL. Increased peripheral airway resistance and decreased resonant frequency are associated with a decreased DI Index. COUGH is a clinical phenotype distinct from healthy normals and asthma.

Repeated bronchoconstriction attenuates the cough response to bronchoconstriction in naïve guinea pigs

BACKGROUND

Cough variant asthma (CVA) is recognized as a precursor of bronchial asthma (BA). However, the cough response to bronchoconstriction differs between these similar diseases. Repeated bronchoconstriction and the resulting imbalance of endogenous lipid mediators may impact the cough response.

METHODS

We investigated the influence of repeated bronchoconstriction on the cough response to bronchoconstriction using naïve guinea pigs. Bronchoconstriction was induced for 3 consecutive days and changes in the cough response and lipid mediators, such as PGE₂, PGI₂, and cysteinyl-LTs (Cys-LTs), in BAL fluid (BALF) were assessed. We investigated the effect of endogenous PGI₂ on the cough response by employing a PGI₂ receptor antagonist. In order to investigate the cough response over a longer period, we re-evaluated the cough response 2 weeks after repeated bronchoconstriction.

RESULTS

The number of coughs induced by bronchoconstriction were significantly decreased by repeated bronchoconstriction. The levels of PGE₂, PGI₂, and Cys-LTs, and the ratio of PGI₂/PGE₂ were significantly increased, following repeated bronchoconstriction. This decrease in the cough response was suppressed by pretreatment with a PGI₂ receptor antagonist. Two weeks after repeated bronchoconstriction, the cough response returned to the same level as before repeated bronchoconstriction along with a concomitant return of lipid mediators, such as PGE₂, PGI₂, and Cys-LTs and the ratio of PGI₂/PGE₂.

CONCLUSIONS

Our results suggest that repeated bronchoconstriction and the resulting imbalance of endogenous lipid mediators contribute to the difference in cough responses to bronchoconstriction in CVA and BA.

Role of prostaglandin I2 in the bronchoconstriction-triggered cough response in guinea pigs

Purpose/Aim of the study: Methacholine chloride (MCh) inhalation causes bronchoconstriction and cough. Following MCh-induced bronchoconstriction, metabolic products of prostaglandin I₂ (PGI₂) increase in bronchoalveolar lavage fluid (BALF), suggesting that PGI₂ plays a role in the cough response. Accordingly, we used an experimental guinea pig model to evaluate the role of PGI₂ in the bronchoconstriction-triggered cough response.

MATERIALS AND METHODS

Experiment 1: The concentration of PGF_1α, a stable metabolite of PGI₂, in BALF was assessed in animals exposed to nebulized MCh and animals exposed to nebulized saline. Experiment 2: Bronchoconstriction and cough were assessed in 3 groups of animals after MCh inhalation (a saline group, low-dose PGI₂ group, and high-dose PGI₂ group). Enhanced pause (Penh) was used as a measure of bronchoconstriction. Experiment 3: Bronchoconstriction and cough were assessed in 3 groups of animals (groups administered saline, a low dose of a specific antagonist of the PGI₂ receptor (IP antagonist), and a high dose of a specific IP antagonist).

RESULTS

The PGF_1α concentration in BALF was significantly higher in the bronchoconstriction group than in the control group. In animals administered high-dose PGI₂, the MCh-induced increase in Penh was significantly suppressed, and the number of coughs induced by bronchoconstriction was significantly decreased. In animals treated with a high dose of an IP antagonist, the MCh-induced increase in Penh was not affected, and the number of coughs increased.

CONCLUSIONS

Our results suggest that PGI₂ ameliorates a bronchoconstriction-triggered cough. The measurement and administration of PGI₂ may assist in the diagnosis and treatment, respectively, of the cough response triggered by bronchoconstriction.

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

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

Role of prostaglandin E2 in bronchoconstriction-triggered cough response in guinea pigs

A feature of cough variant asthma is a heightened cough response to bronchoconstriction. The mediators of this response are unknown. This study was designed to elucidate the role of lipid mediators in bronchoconstriction-triggered cough response in an experimental animal model. We examined the influence of bronchoconstriction on cell components and mediators including prostaglandin E₂ (PGE₂) in bronchoalveolar lavage fluid (BALF). We studied the cough response to bronchoconstriction (CRB) by measuring the correlation between the increase in enhanced pause (Penh), an index of bronchoconstriction, and cough counts induced by methacholine (Mch) inhalation in conscious guinea pigs. We then examined the effects of intraperitoneal pretreatment with 16, 16-dimethyl-prostaglandin E₂ (dm-PGE₂) on CRB and cough counts. The total number of cells and cell components in the BALF were not influenced by bronchoconstriction. While levels of PGE₂, prostaglandin I₂, and cysteinyl leukotrienes were significantly increased, levels of prostaglandin D₂, thromboxane B₂, and substance P in the BALF were not. Dm-PGE₂ significantly decreased the Mch-induced increase in Penh. Following bronchoconstriction by additional Mch inhalation, dm-PGE₂ produced an increase in CRB and cough counts in a dose-dependent manner. Additionally, the heightened CRB following dm-PGE₂ treatment was suppressed by pretreatment with PGE₂ receptor (E-prostanoid EP) -1 and EP-3 antagonists in a dose-dependent manner, but not by EP-2 and EP-4 antagonists. The EP-1 antagonist also decreased cough counts. These results suggest that PGE₂ acts as an exacerbating factor for bronchoconstriction-triggered cough. EP1 and EP3 may provide new therapeutic targets for cough variant asthma.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Bronchodilator therapy for chronic cough

Experimental studies indicate that airway calibre increases the sensitivity of the afferents involved in the cough reflex but it has proved difficult to demonstrate that airway calibre increases the sensitivity of the afferents involved in the cough reflex. Therefore, bronchodilators might have a role, although rather minor, in the treatment of cough. However, although bronchodilators represent the standard of care in the treatment of airway obstruction associated with asthma or COPD, controversy persists regarding the mechanism(s) by which these agents alleviate cough. Furthermore, the available evidence indicates that the effects of bronchodilators on cough are rather inconsistent in humans and casts doubt on the appropriateness of the common practice of using bronchodilators in the treatment of patients with cough without any other evidence of airway obstruction. Regrettably, appropriate long-term trials specifically aimed at evaluating the clinical efficacy of bronchodilators in pathologic cough have not yet been performed. Therefore, properly executed clinical studies of bronchodilators in various types of acute and chronic pathologic cough are required.

Bronchoconstriction-triggered cough in atopic cough: A retrospective study

BACKGROUND

Atopic cough (AC) and cough variant asthma (CVA) were identified as major causes of chronic non-productive cough in a Japanese study. A characteristic feature of CVA is the presence of a heightened cough response to bronchoconstriction. On the other hand, the cough response to bronchoconstriction in AC remains unclear.

METHODS

Methacholine (Mch)-induced cough in AC was measured and compared with that in CVA. Diagnoses of AC and CVA were made based on patient history, physical examination, response to bronchodilator therapy, cough reflex sensitivity to capsaicin, spirometry, and airway responsiveness to methacholine.

RESULTS

Thirteen AC patients and 12 CVA patients in whom the criteria were met were recruited to the study. After inhalation of Mch at PC35-PEF40 that means milder bronchoconstriction than PC20-FEV1, cough was triggered a few times in AC. [cough number: 1/ 32 min (0-40)]. Conversely, significantly greater number of coughs was provoked in CVA, compared with AC [cough number: 35.5/ 32 min (25-125), p < 0.05].

CONCLUSIONS

The cough response to bronchoconstriction is reduced in AC compared to CVA. This feature may be useful in the diagnosis of chronic cough.

Bronchodilating effect of deep inspirations in asthma and chronic cough

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

Atopic cough and fungal allergy

We have shown that some patients presenting with chronic bronchodilator-resistant non-productive cough have a global atopic tendency and cough hypersensitivity without nonspecific bronchial hyperresponsiveness, abbreviated as atopic cough (AC). The cough can be treated successfully with histamine H1 antagonists and/or glucocorticoids. Eosinophilic tracheobronchitis and cough hypersensitivity are pathological and physiological characteristics of AC. Fungus-associated chronic cough (FACC) is defined as chronic cough associated with basidiomycetous (BM) fungi found in induced sputum, and recognition of FACC has provided the possibility of using antifungal drugs as new treatment strategies. Bjerkandera adusta is a wood decay BM fungus, which has attracted attention because of its potential role in enhancing the severity of cough symptoms in FACC patients by sensitization to this fungus. Before making a diagnosis of "idiopathic cough" in cases of chronic refractory cough, remaining intractable cough-related laryngeal sensations, such as "a sensation of mucus in the throat (SMIT)," which is correlated with fungal colonization, should be evaluated and treated appropriately in each patient. The new findings, i.e., the detection of environmental mushroom spores that should not be present in the human airways in addition to the good clinical response of patients to antifungal drugs, may lead to the development of novel strategies for treatment of chronic cough.

Heightened cough response to bronchoconstriction in cough variant asthma

BACKGROUND AND OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cough in asthma

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

Chronic cough and irritable larynx

BACKGROUND

Perennial rhinitis (PR), chronic rhinosinusitis (CRS), or both, asthma, and gastroesophageal reflux disease (GERD) are the most frequent triggers of chronic cough (CC). Extrathoracic airway receptors might be involved in all 3 conditions because asthma is often associated with PR/CRS and gastroesophageal refluxate might reach the upper airway. We previously found that most patients with rhinosinusitis, postnasal drip, and pharyngolaryngitis show laryngeal hyperresponsiveness (LHR; ie, vocal cord adduction on histamine challenge) that is consistent with an irritable larynx.

OBJECTIVE

We sought to evaluate the role of LHR in patients with CC.

METHODS

LHR and bronchial hyperresponsiveness (BHR) to histamine were assessed in 372 patients with CC and in 52 asthmatic control subjects without cough (asthma/CC-). In 172 patients the challenge was repeated after treatment for the underlying cause of cough.

RESULTS

The primary trigger of CC was PR/CRS in 208 (56%) patients, asthma in 41 (11%) patients (asthma/CC+), GERD in 62 (17%) patients, and unexplained chronic cough (UNEX) in 61 (16%) patients. LHR prevalence was 76% in patients with PR/CRS, 77% in patients with GERD, 66% in patients with UNEX, 93% in asthma/CC+ patients, and 11% in asthma/CC- patients. Upper airway disease was found in most (95%) asthma/CC+ patients and in 6% of asthma/CC- patients. BHR discriminated asthmatic patients and atopy discriminated patients with PR/CRS from patients with GERD and UNEX. Absence of LHR discriminated asthmatic patients without cough. After treatment, LHR resolved in 63% of the patients and improved in 11%, and BHR resolved in 57% and improved in 18%.

CONCLUSIONS

An irritable larynx is common in patients with CC and indicates upper airway involvement, whether from rhinitis/sinusitis, gastric reflux, or idiopathic sensory neuropathy.