Tussive effect of capsaicin in patients with gastroesophageal reflux without cough

Tracheobronchial-esophageal reflex initiates esophageal hypersensitivity and aggravates cough hyperreactivity in guinea pigs with esophageal acid infusion

Esophageal-tracheobronchial reflex is considered the main mechanism underlying cough due to gastroesophageal reflux, and is associated with esophageal hypersensitivity. We hypothesized that tracheobronchial-esophageal reflex may also exist, and may be related to esophageal hypersensitivity. To test this hypothesis, conscious and ether-anesthetized guinea pigs were subjected to repetitive capsaicin inhalation to establish models of cough (conscious) and cough-free (anesthetized) airway injury, respectively, followed by esophageal acid infusion. Recurrent capsaicin inhalation induced similar cough hyperreactivity to inhaled capsaicin after esophageal acid infusion in guinea pigs with cough and guinea pigs with cough-free airway injury during recurrent capsaicin inhalation. Cough hyperreactivity, along with overexpression of transient receptor potential vanilloid 1 (TRPV1) receptors in esophageal mucosa and in nerve fibers of tracheal mucosa of guinea pigs were blocked by pretreatment with esophageal infusion of capsazepine, but not atropine. Thus, recurrent airway nociceptive stimuli induce esophageal hyperreactivity via a tracheobronchial-esophageal reflex mediated by vagal C afferents expressing TRPV1, and enhance cough due to reflux.

Cough reflex sensitization from esophagus and nose

The diseases of the esophagus and nose are among the major factors contributing to chronic cough although their role in different patient populations is debated. Studies in animal models and in humans show that afferent C-fiber activators applied on esophageal or nasal mucosa do not initiate cough, but enhance cough induced by inhaled irritants. These results are consistent with the hypothesis that activation of esophageal and nasal C-fibers contribute to cough reflex hypersensitivity observed in chronic cough patients with gastroesophageal reflux disease (GERD) and chronic rhinitis, respectively. The afferent nerves mediating cough sensitization from the esophagus are probably the neural crest-derived vagal jugular C-fibers. In addition to their responsiveness to high concentration of acid typical for gastroesophageal reflux (pH < 5), esophageal C-fibers also express receptors for activation by weakly acidic reflux such as receptors highly sensitive to acid and receptors for bile acids. The nature of sensory pathways from the nose and their activators relevant for cough sensitization are less understood. Increased cough reflex sensitivity was also reported in many patients with GERD or rhinitis who do not complain of cough indicating that additional endogenous or exogenous factors may be required to develop chronic coughing in these diseases.

Anatomy and neurophysiology of cough: CHEST Guideline and Expert Panel report

Bronchopulmonary C-fibers and a subset of mechanically sensitive, acid-sensitive myelinated sensory nerves play essential roles in regulating cough. These vagal sensory nerves terminate primarily in the larynx, trachea, carina, and large intrapulmonary bronchi. Other bronchopulmonary sensory nerves, sensory nerves innervating other viscera, as well as somatosensory nerves innervating the chest wall, diaphragm, and abdominal musculature regulate cough patterning and cough sensitivity. The responsiveness and morphology of the airway vagal sensory nerve subtypes and the extrapulmonary sensory nerves that regulate coughing are described. The brainstem and higher brain control systems that process this sensory information are complex, but our current understanding of them is considerable and increasing. The relevance of these neural systems to clinical phenomena, such as urge to cough and psychologic methods for treatment of dystussia, is high, and modern imaging methods have revealed potential neural substrates for some features of cough in the human.

Menthol suppresses laryngeal C-fiber hypersensitivity to cigarette smoke in a rat model of gastroesophageal reflux disease: the role of TRPM8

Patients with gastroesophageal reflux disease (GERD) display enhanced laryngeal reflex reactivity to stimuli that may be due to sensitization of the laryngeal C-fibers by acid and pepsin. Menthol, a ligand of transient receptor potential melastatin-8 (TRPM8), relieves throat irritation. However, the possibility that GERD induces laryngeal C-fiber hypersensitivity to cigarette smoke (CS) and that menthol suppresses this event has not been investigated. We delivered CS into functionally isolated larynxes of 160 anesthetized rats. Laryngeal pH 5-pepsin treatment, but not pH 5-denatured pepsin, augmented the apneic response to CS, which was blocked by denervation or perineural capsaicin treatment (a procedure that blocks the conduction of C fibers) of the superior laryngeal nerves. This augmented apnea was partially attenuated by capsazepine [an transient receptor potential vanilloid 1 (TRPV1) antagonist], SB-366791 (a TRPV1 antagonist), and HC030031 [a transient receptor potential ankyrin 1 (TRPA1) antagonist] and was completely prevented by a combination of TRPV1 and TRPA1 antagonists. Local application of menthol significantly suppressed the augmented apnea and this effect was reversed by pretreatment with AMTB (a TRPM8 antagonist). Our electrophysiological studies consistently revealed that laryngeal pH 5-pepsin treatment increased the sensitivity of laryngeal C-fibers to CS. Likewise, menthol suppressed this laryngeal C-fiber hypersensitivity and its effect could be reversed by pretreatment with AMTB. Our results suggest that laryngeal pH 5-pepsin treatment increases sensitivity to CS of both TRPV1 and TRPA1, which are presumably located at the terminals of laryngeal C-fibers. This sensory sensitization leads to enhanced laryngeal reflex reactivity and augmentation of the laryngeal C-fiber responses to CS, which can be suppressed by menthol acting via TRPM8.

Sensory nerves in lung and airways

Sensory nerves innervating the lung and airways play an important role in regulating various cardiopulmonary functions and maintaining homeostasis under both healthy and disease conditions. Their activities conducted by both vagal and sympathetic afferents are also responsible for eliciting important defense reflexes that protect the lung and body from potential health-hazardous effects of airborne particulates and chemical irritants. This article reviews the morphology, transduction properties, reflex functions, and respiratory sensations of these receptors, focusing primarily on recent findings derived from using new technologies such as neural immunochemistry, isolated airway-nerve preparation, cultured airway neurons, patch-clamp electrophysiology, transgenic mice, and other cellular and molecular approaches. Studies of the signal transduction of mechanosensitive afferents have revealed a new concept of sensory unit and cellular mechanism of activation, and identified additional types of sensory receptors in the lung. Chemosensitive properties of these lung afferents are further characterized by the expression of specific ligand-gated ion channels on nerve terminals, ganglion origin, and responses to the action of various inflammatory cells, mediators, and cytokines during acute and chronic airway inflammation and injuries. Increasing interest and extensive investigations have been focused on uncovering the mechanisms underlying hypersensitivity of these airway afferents, and their role in the manifestation of various symptoms under pathophysiological conditions. Several important and challenging questions regarding these sensory nerves are discussed. Searching for these answers will be a critical step in developing the translational research and effective treatments of airway diseases.

Gastro-oesophageal reflux treatment for prolonged non-specific cough in children and adults

BACKGROUND

Gastroesophageal reflux disease (GORD) is said to be the causative factor in up to 41% of adults with chronic cough. Treatment for GORD includes conservative measures (diet manipulation), pharmaceutical therapy (motility or prokinetic agents, H(2)-antagonist and proton pump inhibitors (PPI)) and fundoplication.

OBJECTIVES

To evaluate the efficacy of GORD treatment on chronic cough in children and adults with GORD and prolonged cough that is not related to an underlying respiratory disease, i.e. non-specific chronic cough.

SEARCH STRATEGY

We searched the Cochrane Airways Group Specialised Register, the Cochrane Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, review articles and reference lists of relevant articles. The date of last search was 8 April 2010.

SELECTION CRITERIA

All randomised controlled trials (RCTs) on GORD treatment for cough in children and adults without primary lung disease.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. We contacted study authors for further information.

MAIN RESULTS

We included 19 studies (six paediatric, 13 adults). None of the paediatric studies could be combined for meta-analysis. A single RCT in infants found that PPI (compared to placebo) was not efficacious for cough outcomes (favouring placebo OR 1.61; 95% CI 0.57 to 4.55) but those on PPI had significantly increased adverse events (OR 5.56; 95% CI 1.18 to 26.25) (number needed to treat for harm in four weeks was 11 (95% CI 3 to 232)). In adults, analysis of H(2) antagonist, motility agents and conservative treatment for GORD was not possible (lack of data) and there were no controlled studies of fundoplication. We analysed nine adult studies comparing PPI (two to three months) to placebo for various outcomes in the meta-analysis. Using intention-to-treat, pooled data from studies resulted in no significant difference between treatment and placebo in total resolution of cough (OR 0.46; 95% CI 0.19 to 1.15). Pooled data revealed no overall significant improvement in cough outcomes (end of trial or change in cough scores). We only found significant differences in sensitivity analyses. We found a significant improvement in change of cough scores at end of intervention (two to three months) in those receiving PPI (standardised mean difference -0.41; 95% CI -0.75 to -0.07) using generic inverse variance analysis on cross-over trials. Two studies reported improvement in cough after five days to two weeks of treatment.

AUTHORS' CONCLUSIONS

PPI is not efficacious for cough associated with GORD symptoms in very young children (including infants) and should not be used for cough outcomes. There is insufficient data in older children to draw any valid conclusions. In adults, there is insufficient evidence to conclude definitely that GORD treatment with PPI is universally beneficial for cough associated with GORD. Clinicians should be cognisant of the period (natural resolution with time) and placebo effect in studies that utilise cough as an outcome measure. Future paediatric and adult studies should be double-blind, randomised controlled and parallel-design, using treatments for at least two months, with validated subjective and objective cough outcomes and include ascertainment of time to respond as well as assessment of acid and/or non-acid reflux.

Relevance of GERD in lung transplant patients

Lung transplantation has become a valuable treatment for end-stage pulmonary disorders in an attempt to improve quality of life and extend survival. Development of chronic rejection, also known as bronchiolitis obliterans syndrome (BOS), is responsible for the vast majority of deaths after lung transplantation. Up to 50% of lung transplant patients develop BOS within the first 5 years after transplantation. A high prevalence of gastroesophageal reflux and aspiration of gastric components has been described after lung transplantation. Reflux and aspiration have been implicated in the development of BOS and antireflux surgery has been proposed; however, the causal relationship with BOS and the impact of reflux in lung transplantation survival needs to be further elucidated.

[Boundaries of the lung - Relationship to the gastrointestinal system]

The relation between the respiratory and gastrointestinal systems has been long recognized and depends on various anatomical, physiological and pathological mechanisms. The certain recognition of some interactions, such as the relation between asthma and gastroesophageal reflux, is more or less intuitive to the pulmonogist, whereas other areas of confluence are more easily missed, such as the relation between airway disorders and inflammatory bowel disease. The purpose of this article is to review the interaction between the lung and the gastrointestinal systems, as far as anatomy, physiology, pathology, clinical manifestations and therapeutical options go.

Role of ATP in the ROS-mediated laryngeal airway hyperreactivity induced by laryngeal acid-pepsin insult in anesthetized rats

The pathogenetic mechanisms of laryngeal airway hyperreactivity (LAH) in patients with extraesophageal reflux are unclear. We recently reported that a laryngeal acid-pepsin insult produces LAH that is mediated through sensitization of the capsaicin-sensitive laryngeal afferent fibers by reactive oxygen species (ROS) in rats. Since ROS may promote the release of ATP from cells, we hypothesized that activation of P2X purinoceptors by ATP subsequent to an increase in ROS induces LAH in an inflamed larynx that has been insulted by acid-pepsin or H(2)O(2) (a major type of ROS). The larynxes of 208 anesthetized rats were functionally isolated while the animals breathed spontaneously. Ammonia vapor was delivered into the larynx to measure laryngeal reflex reactivity. Laryngeal insult with acid-pepsin or H(2)O(2) produced LAH with similar characteristics. The H(2)O(2)-induced LAH was prevented by laryngeal pretreatment with dimethylthiourea (a hydroxyl radical scavenger), suggesting a critical role for ROS. The LAH induced by both insults were completely prevented by ATP scavengers (a combination of apyrase and adenosine deaminase) or a P2X receptor antagonist (iso-pyridoxalphosphate-6-azophenyl-2',5'-disulfonate). Laryngeal application of a P2X receptor agonist (alpha,beta-methylene-ATP) also produced LAH. An insult with either acid-pepsin or H(2)O(2) similarly promoted an increase in the levels of ATP, lipid peroxidation, and inflammation in the larynx. Our findings suggest that laryngeal insult with acid-pepsin or H(2)O(2) induces inflammation and produces excess ROS in the rat's larynx. The latter may in turn promote the release of ATP to activate P2X receptors, resulting in sensitization of capsaicin-sensitive laryngeal afferent fibers and LAH.

Gastroesophageal scintigraphy in the evaluation of adult patients with chronic cough due to gastroesophageal reflux disease

OBJECTIVE

The aim of this study was to evaluate the findings of gastroesophageal scintigraphy (GES) with late lung imaging in adult patients with chronic cough due to gastroesophageal reflux disease and a group of healthy participants.

METHODS

Fifty-five patients with chronic cough with reflux symptoms, and a control group of 12 healthy participants were examined. All patients had reflux esophagitis documented by upper gastrointestinal endoscopy and histology. All participants underwent laryngoscopic examination and GES. The correlation between gastroesophageal reflux and several related variables was evaluated.

RESULTS

Overall, 51 patients (92.7%) had positive GES findings for pathologic reflux; 19 (37.2%) of these patients had proximal reflux; and the remaining 32 (62.7%) had distal reflux. The frequency, duration, and percentage volume of gastric content of reflux episodes were significantly greater in patients with proximal reflux than in patients with distal reflux (P<0.0001). No statistically significant differences were seen between proximal reflux and distal reflux patients in terms of pulmonary function parameters, duration of cough, and reflux symptoms scores. However, severe grade (B and C) of esophagitis and the posterior laryngitis were more common in the patients with proximal reflux. Late lung imaging demonstrated evidence of pulmonary aspiration in only three of 51 (6%) patients.

CONCLUSION

Our study suggests that GES with late lung imaging objectively showed the presence of pathologic distal and/or proximal reflux, but rarely pulmonary aspiration, in the majority of chronic cough patients with gastroesophageal reflux disease. As the chronic cough patients with proximal reflux have more severe reflux characteristics, this examination may be effective in screening and following up these patients.

Cough and gastroesophageal reflux: insights from animal models

Chronic cough in gastroesophageal reflux disease (GERD) has been attributed to irritation of the esophagus and/or upper airways by reflux of gastric content. Animal models have provided insight into both of these putative mechanisms. In patients with chronic cough and GERD, stimuli associated with reflex in the esophagus sensitize the cough reflex. This sensitization can be reproduced in the guinea pig and is most likely mediated by the esophageal afferent nerve fibers carried by the vagus nerves. Studies in animals have identified several subtypes of vagal esophageal C-fibers that may subserve this function. The putative nociceptive vagal C-fibers in the guinea pig esophagus are stimulated by acid and express the TRPV1 and TRPA1 receptors that confer responsiveness to disparate noxious stimuli. Acute and/or chronic irritation of the upper airways by reflux may contribute to cough by stimulation and/or sensitization of the airway afferent nerves. Studies in animals have identified airway nerves that likely initiate cough due to aspirated reflux; have characterized their pharmacology; and have provided insight into changes of their sensitivity. Studies in animal models have also described the neurophysiology of reflexes that protect the airways from reflux. In conclusion, animal models provide mechanistic insight into the modulation of cough from the esophagus and the pharmacology of neural pathways mediating cough in GERD.

Mechanisms of the cough associated with rhinosinusitis

The diseases of the nose and paranasal sinuses (rhinosinusitis) often in combination with asthma and gastroesophageal reflux are common causes of chronic cough in patients with normal chest radiograph. The relationships between rhinosinusitis and cough are incompletely understood. We investigated modulation of the cough reflex by the inputs from the nose. We demonstrate that the cough reflex is sensitized by the intranasal administration of sensory nerve activators in animal models and in humans. Cough reflex is also sensitized in the guinea pig model of allergic nasal inflammation and in patients with allergic rhinitis. In patients with allergic rhinitis the cough sensitization is augmented during the allergen season. We conclude that the cough reflex can be sensitized from the nose. Our data indicate that this sensitization is mediated by nasal sensory nerves. We speculate that by inducing the cough reflex sensitization rhinosinusitis contributes to chronic cough. If combined with environmental or endogenous cough triggers, the cough reflex sensitization is predicted to cause excessive coughing. The potential endogenous cough triggers may be associated with rhinosinusitis (postnasal drip, aspiration of nasal secrets) or secondary to a coexistent disease such as asthma or gastroesophageal reflux.

Clinical cough II: therapeutic treatments and management of chronic cough

Chronic cough is a common and frequently disruptive symptom which can be difficult to treat with currently available medicines. Asthma/eosinophilic airway disease and gastro-oesophageal reflux disease are most commonly associated with chronic cough but it may also trouble patients with chronic obstructive pulmonary disease, pulmonary fibrosis and lung cancer. Over the last three decades there have been a number of key advances in the clinical approach to cough and a number of international guidelines on the management of cough have been developed. Despite the undoubted benefit of such initiatives, more effective treatments for cough are urgently needed. The precise pathophysiological mechanisms of chronic cough are unknown but central to the process is sensitization (upregulation) of the cough reflex. One well-recognized clinical consequence of this hypersensitive state is bouts of coughing triggered by apparently trivial provocation such as scents and odours and changes in air temperature. The main objective of new treatments for cough would be to identify ways to downregulate this heightened cough reflex but yet preserve its crucial role in protecting the airway. The combined efforts of clinicians, scientists and the pharmaceutical industry offer most hope for such a treatment breakthrough. The aim of this chapter is to provide some rationale for the current treatment recommendations and to offer some reflections on the management of patients with chronic cough.

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.

Review article: respiratory manifestations of gastro-oesophageal reflux disease

BACKGROUND

Respiratory manifestations represent one of the most prevalent and difficult-to-manage extra-oesophageal syndromes of gastro-oesophageal reflux disease.

AIMS

To review the epidemiology, pathophysiological mechanisms and therapeutic outcomes of reflux-related respiratory disorders.

METHODS

Search of the literature published in English using PubMed database.

RESULTS

There is a discrepancy between the high prevalence of reflux in asthmatics and the limited efficacy of antireflux therapies. Asthma per se may cause reflux. Patients with difficult-to-treat asthma and/or nocturnal symptoms should be screened for reflux. Reflux can induce chronic cough through different mechanisms including micro-aspiration and both local and central reflexes. Cough and reflux may precipitate each other. A meta-analysis found no significant difference between placebo and proton pump inhibitors in the resolution of cough. Encouraging results have been reported, following antireflux surgery in patients selected on the basis of pH-impedance monitoring. Attention has been drawn to obstructive sleep apnoea syndrome.

CONCLUSIONS

The role of gastro-oesophageal reflux disease in the pathogenesis of miscellaneous respiratory disorders has been discussed for decades and established in asthma and cough. However, no major therapeutic advances have been reported recently. Future trials should concentrate on patient selection and the control of efficacy using recently developed technologies, such as pH-impedance monitoring.

Acidification of the oesophagus acutely increases the cough sensitivity in patients with gastro-oesophageal reflux and chronic cough

Gastro-oesophageal reflux disease (GORD) is one of the most common causes of chronic cough; however, the mechanisms by which GOR initiates coughing are incompletely understood. We address the hypothesis that acidification of oesophagus acutely increases the cough reflex sensitivity in patients with GORD and chronic cough. Nine patients with GORD with chronic cough and 16 patients with GORD without cough were recruited. In a randomized double blind study, saline and acid (HCl, 0.1 mol L(-1)) were separately infused into oesophagus via naso-oesophageal catheter. Cough reflex sensitivity to inhaled capsaicin was determined immediately after completion of each infusion. Infusion of acid into oesophagus increased capsaicin cough reflex sensitivity in patients with GORD and chronic cough. In contrast, acid had no effect on the cough sensitivity in patients with GORD without cough. In a separate study, acid infusion into oesophagus did not affect the cough sensitivity in 18 healthy subjects. We conclude that acid in the oesophagus acutely increases the cough reflex sensitivity to capsaicin in patients with GORD and chronic cough. This phenomenon may contribute to the pathogenesis of cough due to GORD.

Therapy Insight: treatment of gastroesophageal reflux in adults with chronic cough

Gastroesophageal reflux (GER) is the second most common cause of chronic cough in immunocompetent patients who are nonsmokers, not on angiotensin-converting-enzyme inhibitors and have normal chest radiographs. Identification of GER in chronic cough patients can be difficult; most patients with GER-related cough have no esophageal symptoms and no esophageal test is adequate to make this diagnosis. Post-hoc analysis of four prospective intervention trials has identified a clinical patient profile that can predict the presence of GER-related cough 91% of the time. Clinical practice guidelines from the American College of Chest Physicians and the British Thoracic Society recommend initiating an initial empiric GER therapy trial, with esophageal testing being reserved for nonresponders. The empiric trial should include conservative measures and PPIs twice daily for 3 months. Selected patients who have dysphagia might benefit from the addition of a prokinetic agent. Esophageal manometry and pH testing with impedance monitoring (if available) should be performed in nonresponders while they are on therapy. It can take more than 50 days for cough to respond to medical GER therapy. Surgical fundoplication might be helpful in very carefully selected patients. Careful evaluation and treatment resolves cough in approximately 80% of patients with GER-related cough.

Cough reflex sensitivity after elective Caesarean section under spinal anaesthesia and after vaginal delivery

BACKGROUND

In pregnancy, airway oedema and heartburn may increase cough sensitivity, whereas spinal anaesthesia (SA) with local anaesthetics and opiates may decrease it. Decreased cough sensitivity increases the risk for pneumonia or retained secretions. The aim of this study was to determine whether cough sensitivity is increased in pregnant patients and if it is decreased after planned Caesarean section (CS) under SA.

METHODS

Twenty-seven non-pregnant volunteers, 27 patients after vaginal delivery (VD group), and 28 patients after CS under SA (CS group) were studied. For SA, hyperbaric bupivacaine 8-12 mg, sufentanil 5 microg, and morphine 100 microg was given. Increasing concentrations of nebulized citric acid were delivered until eliciting cough. The concentration eliciting one (C1) and two coughs (C2) were recorded and log transformed for analysis (log C1 and log C2).

RESULTS

Median (inter-quartile) log C1 was 1.3 (0.6) mg ml(-1) in the VD group, 1.6 (0.6) mg ml(-1) in the non-pregnant group (P < 0.01 vs VD group), and 2.2 (0.7) mg ml(-1) in the CS group (P < 0.0001 and P < 0.01 vs VD and non-pregnant groups, respectively). Similar results were observed with log C2. In CS group, log C1 and log C2 remained increased up to 4 h after SA.

CONCLUSIONS

Cough sensitivity was increased after VD but decreased for up to 4 h after SA.

Omeprazole reduces the response to capsaicin but not to methacholine in asthmatic patients with proximal reflux

OBJECTIVE

To study the relationships between airway responsiveness to methacholine and capsaicin, proximal or distal reflux and the effects of short-term acid inhibition.

MATERIAL AND METHODS

Twenty-nine asthmatics, not taking steroids regularly, underwent respiratory symptom measurements, 24-h dual-probe pH monitoring, and challenges with methacholine and capsaicin. Challenges and symptom measurements were repeated after 12 days' omeprazole treatment (20 mg b.i.d.). The results (median and range) were expressed as PD20 methacholine (mg) and PD5 capsaicin (dose causing five coughs, nmol).

RESULTS

Seventeen patients presented pathological reflux in the distal esophagus, and 17 in the proximal esophagus. At baseline no correlation was found between PD20 or PD5 and reflux. Treatment with omeprazole did not change bronchial responsiveness to methacholine (basal: 0.16 mg, 0.02-1.27; omeprazole: 0.15 mg, 0.02-1.60); omeprazole decreased the tussive response to capsaicin (basal: 0.08 nmol, 0.08-2.46; omeprazole: 0.61 nmol, 0.08-9.84, p<0.001) only in patients with pathological reflux. The decrease was positively correlated with proximal acid exposure (r2=0.70, p<0.001). Omeprazole reduced asthma symptoms in patients with proximal reflux, cough in those with proximal or distal reflux.

CONCLUSIONS

In asthmatics, inhibition of gastric acid secretion does not influence bronchial hyperresponsiveness but decreases tussive sensitivity and this effect is related to proximal reflux.

Gastro-oesophageal reflux treatment for prolonged non-specific cough in children and adults

BACKGROUND

Cough is a very common symptom presenting to medical practitioners. Gastroesophageal reflux disease (GORD) is said to be the causative factor in up to 41% of adults with chronic cough. However cough and GORD are common ailments and their co-existence by chance is high. Also cough can induce reflux episodes. Treatment for GORD includes conservative measures (diet manipulation), pharmaceutical therapy (motility or prokinetic agents, H(2) antagonist and proton pump inhibitors (PPI)) and fundoplication.

OBJECTIVES

To evaluate the efficacy of GORD treatment on chronic cough in children and adults with GORD and prolonged cough that is not related to an underlying respiratory disease i.e. non-specific chronic cough.

SEARCH STRATEGY

The Cochrane Register of Controlled Trials (CENTRAL), the Cochrane Airways Group Specialised Register Collaboration and Cochrane Airways Group, MEDLINE and EMBASE databases, review articles and reference lists of relevant articles were searched. The date of last search was 7th April 2006.

SELECTION CRITERIA

All randomised controlled trials on GORD treatment for cough in children and adults without primary lung disease.

DATA COLLECTION AND ANALYSIS

Results of searches were reviewed against pre-determined criteria for inclusion. Two independent reviewers selected, extracted and assessed data for inclusion. Authors were contacted for further information. Data was analysed as "intention to treat" as well as "treatment received". Paediatric and adults data were considered separately. Sensitivity analyses were performed.

MAIN RESULTS

Thirteen studies (3 paediatric, 10 adults) were included. Data from six were available for analysis. None of the paediatric studies could be included in meta-analysis. In adults, analysis on use of H(2) antagonist, motility agents and conservative treatment for GORD were not possible (from lack of data) and there were no controlled studies on fundoplication as an intervention. Six adult studies comparing PPI (2-3 months) to placebo were analysed for various outcomes in the meta-analysis. Enrolment of subjects for two studies were primarily from medical clinics and another 4 studies were otolaryngology clinic patients or patients with laryngitis. Using "intention to treat", pooled data from 4 studies resulted in no significant difference between treatment and placebo in total resolution of cough, Odds Ratio 0.46 (95% CI 0.19 to 1.15). Pooled data revealed no overall significant improvement in cough outcomes (end of trial or change in cough scores). Significant differences were only found in sensitivity analyses. A significant improvement in change of cough scores was found in end of intervention (2-3 months) in those receiving PPI with a standardised mean difference of -0.41 (95%CI -0.75, -0.07) using GIV analysis on cross over trials. Two studies reported improvement in cough after 5 days to 2 weeks of treatment.

AUTHORS' CONCLUSIONS

There is insufficient evidence to definitely conclude that GORD treatment with PPI is universally beneficial for cough associated with GORD in adults. The beneficial effect was only seen in sub-analysis and its effect was small. The optimal duration of such a trial of therapy to evaluate response could not be ascertained in the meta-analysis although two RCTs reported significant change by 2 weeks of therapy. Clinicians should be cognisant of a period (natural resolution with time) and placebo effect in studies that utilise cough as an outcome measure. Data in children are inconclusive. Future paediatric and adult studies are needed whereby studies should be double blind, randomised controlled, parallel design, using treatments for at least two months, with validated subjective and objective cough outcomes and include ascertainment of time to respond as well as assessment of acid and/or non acid reflux whilst on therapy.

Neural and hydroxyl radical mechanisms underlying laryngeal airway hyperreactivity induced by laryngeal acid-pepsin insult in anesthetized rats

Laryngopharyngeal or gastroesophageal reflux is associated with laryngeal airway hyperreactivity (LAH), but neither the cause-effect relationship nor the underlying mechanism has been elucidated. Here we established a rat model with enhanced laryngeal reflex reactivity induced by laryngeal acid-pepsin insult and investigated the neural and hydroxyl radical (*OH) mechanisms involved. The laryngeal segments of 103 anesthetized rats were functionally isolated while animals breathed spontaneously. Ammonia vapor was delivered into the laryngeal segment to measure laryngeal reflex reactivity. We found that the laryngeal pH 5-pepsin treatment doubled the reflex apneic response to ammonia, whereas laryngeal pH 7.4-pepsin, pH 2-pepsin, and pH 5-denatured pepsin treatment had no effect. Histological examination revealed limited laryngeal inflammation and epithelial damage after pH 5-pepsin treatment and more severe damage after pH 2-pepsin treatment. In rats that had received the laryngeal pH 5-pepsin treatment, the apneic response to ammonia was abolished by either denervation or perineural capsaicin treatment (PCT; a procedure that selectively blocks capsaicin-sensitive afferent fibers) of the superior laryngeal nerves, but was unaffected by perineural sham treatment. LAH was prevented by laryngeal application of either dimethylthiourea (DMTU; a *OH scavenger) or deferoxamine (DEF; an antioxidant for *OH), but was unaltered by the DMTU vehicle or iron-saturated DEF (ineffective DEF). LAH reappeared after recovery from PCT, DMTU, or DEF treatment. We conclude that 1) laryngeal insult by pepsin at a weakly acidic pH, but not at acidic pH, can produce LAH; and 2) LAH is probably mediated through sensitization of the capsaicin-sensitive laryngeal afferent fibers by a *OH mechanism.

The effects of nasal histamine challenge on cough reflex in healthy volunteers

The aim of the study was to investigate the effects of nasal histamine on the intensity of cough reflex and the effects of intensified nasal breathing following the nasal histamine challenge on cough sensitivity (CS) in humans. 20 volunteers (mean age 23, nonsmokers, no history of nasal or respiratory system diseases and atopy) were recruited to the study. Baseline CS was determined in all subjects. 2 days later the subjects (n = 20) were challenged with nasal histamine (8 mg/ml, 0.1 ml) and the number of coughs was determined after four consecutive single-breath inhalations of capsaicin C2 concentration during the period of the most intensive nasal symptoms (sneezing, itching of the nose). The same capsaicin C2 challenge was performed after nasal saline challenge two days later. One week later CS was determined after nasal histamine challenge with subsequent 10 min of intensified breathing (5-6 sniff-like aspirations to total lung capacity per minute) through the nose and mouth in randomized order in ten volunteers, and with a two-day interval between the challenges. The same manoeuvres after intranasal saline challenge were performed in volunteers of the control group (n = 10). The number of coughs after nasal histamine was significantly higher than that after intranasal saline challenge (8(6-10) vs 5(3-7); p = 0.038(. CS was not significantly different between the baseline challenge and challenges after nasal histamine followed by the intensified nasal and mouth breathing ((2.21 (1.8-2.62) vs 2.04 (1.57-2.51) vs 2.05 (1.6-2.5) log(10) of capsaicin concentration in mumol.l(-1); p = 0.09).

CONCLUSIONS

During the period of maximum nasal symptoms after nasal histamine challenge the cough response to inhaled capsaicin was enhanced. Capsaicin cough sensitivity measured after a 10-min. intensified nasal breathing after nasal histamine challenge, compared to a previous measurement of CS, remain unchanged.

Cough and Aspiration of Food and Liquids Due to Oral-Pharyngeal Dysphagia

BACKGROUND

Cough may be an indicator of aspiration due to oral-pharyngeal dysphagia.

METHODS

Relevant literature was identified by searching the Communication Sciences and Disorders Dome, the Cumulative Index to Nursing and Allied Health Literature, the Educational Resource Information Center, Health & Psychosocial Instruments, the American Psychological Association, and the National Library of Medicine databases from 1965 to 2004 using the terms "deglutition," "aspiration," and "cough."

RESULTS

Aspiration was observed on radiologic evaluation in over one third of acute stroke patients and in >40% of patients undergoing cervical spine surgery. Cough while eating may indicate aspiration, but aspiration may be clinically silent. Subjective patient and caregiver reports of cough while eating are useful in identifying patients who are at risk for aspiration. Objective measures of voluntary cough and tussigenic challenges to inhaled irritants are under investigation to determine their capacity to predict the risk for aspiration and subsequent pneumonia. The treatment of dysphagic patients by a multidisciplinary team, including early evaluation by a speech-language pathologist, is associated with improved outcomes. Effective clinical interventions such as the use of compensatory swallowing strategies and the alteration of food consistencies can be based on the results of instrumental swallowing studies. The efficacy of swallowing exercises and electrical muscle stimulation is under study. Surgical interventions may be considered in selected patients, but studies proving efficacy are generally lacking.

CONCLUSIONS

Patients who are at risk for aspiration can be identified, and appropriate interventions can reduce its associated morbidity.

Chronic Cough Due to Gastroesophageal Reflux Disease

OBJECTIVES

To critically review and summarize the literature on cough and gastroesophageal reflux disease (GERD), and to make evidence-based recommendations regarding the diagnosis and treatment of chronic cough due to GERD.

DESIGN/METHODOLOGY

Ovid MEDLINE literature review (through March 2004) for all studies published in the English language and selected articles published in other languages such as French since 1963 using the medical subject heading terms "cough," "gastroesophageal reflux," and "gastroesophageal reflux disease."

RESULTS

GERD, singly or in combination with other conditions, is one of the most common causes of chronic cough. In patients with normal chest radiographic findings, GERD most likely causes cough by stimulation of an esophageal-bronchial reflex. When GERD causes cough, there may be no GI symptoms up to 75% of the time. While 24-h esophageal pH monitoring is the most sensitive and specific test in linking GERD and cough in a cause-effect relationship, it has its limitations. In addition, there is no general agreement on how to best interpret the test, and it cannot detect non-acid reflux events. Therefore, when patients fit the clinical profile that has a high likelihood of predicting that GERD is the cause of cough, antireflux medical therapy should be empirically instituted. While some patients improve with minimal medical therapy, others require more intensive regimens. When empiric treatment fails, it cannot be assumed that GERD has been ruled out as a cause of chronic cough. Rather, an objective investigation for GERD is then recommended because the empiric therapy may not have been intensive enough or medical therapy may have failed. Surgery may be efficacious when intensive medical therapy has failed in selected patients who have undergone an extensive objective GERD evaluation.

CONCLUSIONS

Accurately diagnosing and successfully treating chronic cough due to GERD can be a major challenge.

Citric acid cough threshold in patients with gastroesophageal reflux disease rises after laparoscopic fundoplication

BACKGROUND

It has been reported that antireflux surgery can diminish chronic cough due to gastroesophageal reflux disease (GERD) that is resistant to pharmacologic therapy. The aim of this study was the assessment of citric acid cough threshold (CACT) in patients with chronic cough due to GERD before and 3 months after laparoscopic Toupet fundoplication.

METHODS

Thirty subjects (20 women and 10 men; median age, 45.3 years) with chronic cough due to GERD and 15 healthy volunteers underwent cough challenge with doubling concentrations of citric acid. Twenty subjects with GERD, a group of 14 women and 6 men (mean age, 45.5 years), underwent the same protocol 3 months after laparoscopic fundoplication. Daytime and nighttime cough score questionnaires (verbal category descriptive score) were completed in all groups.

RESULTS

The geometric mean of CACT was significantly lower in GERD patients (9.62 mg/mL) than in healthy volunteers (50.8 mg/mL, p < 0.001). The results of cough score measurement significantly improved within 2 weeks after laparoscopic surgery. In 13 weeks of postoperative follow-up, cough disappeared or was greatly improved in 14 of the 20 patients (70%); in 3 other patients, cough resolved partially. In three patients. there was no improvement in cough. Cough challenge after surgery revealed a significant increase in mean cough threshold, from 8.28 to 19.03 mg/mL (p < 0.05).

CONCLUSIONS

The results suggest that GERD influences CACT, which was significantly lower in GERD patients compared to healthy subjects. A significant correlation was found between subjective and objective measurements of cough in GERD patients. We found laparoscopic fundoplication to be objectively beneficial in GERD-induced chronic cough, as it reduced the CACT.

Airway inflammation and cough sensitivity in cough-variant asthma

BACKGROUND

Mechanisms underlying cough and bronchoconstriction in patients with cough-variant asthma (CVA) are not well established. Differences in location or degree of activation of eosinophils and allergic cytokines have been suggested as the likely causes. To address this issue, we have carried out a comparative study of airway inflammatory markers between patients with CVA and classic asthma (CA). The relationship between these markers with airway hyperresponsiveness (AHR) and cough sensitivity has also been studied.

METHODS

Twenty-seven non-smokers and steroid-naive patients with CVA (12) and CA (15) were examined. Capsaicin challenge, histamine bronchoprovocation test, nitric oxide levels in exhaled air and sputum induction were performed in all of them. Differential cell sputum recount and supernatant concentrations of eosinophil granule-derived cationic proteins (ECP), interleukin (IL)5, IL8 and tumour necrosis factor (TNF)-alpha were also measured.

RESULTS

There were no significant differences in either the inflammatory pattern of soluble markers or differential cell counts between CA and CVA. Histamine PC20 was correlated with IL-5 in CVA, whereas it was associated with sputum eosinophilia in CA. Cough sensitivity (log C5) and histamine PC20 were inversely related in CA.

CONCLUSIONS

Although the pattern of inflammatory sputum markers in patients with asthma and cough-variant asthma is similar, its relation with bronchial hyperreactivity and cough sensitivity is different in each group.

Inhaled corticosteroids for non-specific chronic cough in children

BACKGROUND

Cough in isolation of other clinical features is known as non-specific cough, which has been defined as non-productive cough in the absence of identifiable respiratory disease or any known aetiology. In children with non-specific cough the possibility of asthma being the underlying disorder is often raised (so called cough variant asthma). The proponents of cough variant asthma suggest a therapeutic trial of medications usually used to treat asthma.

OBJECTIVES

To determine the efficacy of inhaled corticosteroids in non-specific cough in children over the age of two years.

SEARCH STRATEGY

Searches were conducted on Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. Searches were current as of March 2004.

SELECTION CRITERIA

All randomised (randomised and quasi-randomised) controlled clinical trials in which an inhaled corticosteroid (beclomethasone (BDP), fluticasone (FP), triamcinalone (TAA) or any other corticosteroid) were given for cough in children over two years of age were included. Two review authors independently assessed articles for inclusion and methodological quality.

DATA COLLECTION AND ANALYSIS

Data from trials was extracted by both review authors and entered into the Cochrane Collaboration software program RevMan Analyses 1.0.2.

MAIN RESULTS

Two trials met the inclusion criteria (123 participants). One compared inhaled beclomethasone dipropionate (400 micrograms per day) with placebo and the other compared fluticasone propionate (2 mg per day for 3 days followed by 1 mg per day for 11 days) with placebo. Both studies used metered dose inhalers via a spacer. With the lower dose of inhaled corticosteroid there was no significant difference between the beclomethasone and placebo groups. With the higher dose there was a significant improvement in nocturnal cough frequency after two weeks in children presenting with persistent nocturnal cough. However, a significant but smaller improvement was also seen with placebo.

AUTHORS' CONCLUSIONS

In one study beclomethasone dipropionate (400 micrograms per day) was no different from placebo in reducing the frequency of cough measured objectively or scored subjectively. There might be a small improvement with very high-dose inhaled corticosteroid but the clinical impact of this is unlikely to beneficial.

Safety of capsaicin cough challenge testing

BACKGROUND

Capsaicin, the pungent extract of red peppers, has achieved widespread use in clinical research because it induces cough in a dose-dependent and reproducible manner. Although > 2 decades of experience has led investigators to consider capsaicin cough challenge testing a safe diagnostic modality, this issue has not been specifically addressed in the literature.

STUDY OBJECTIVES

To review the published experience with capsaicin inhalation challenge testing in terms of safety.

DESIGN

Literature review and personal communication with study authors.

SETTING

Academic medical center.

RESULTS

One hundred twenty-two published studies since 1984 described 4,833 subjects (4,374 adults, 459 children) undergoing capsaicin cough challenge, with no serious adverse events reported. Subjects included healthy volunteers as well as patients with asthma, COPD, pathologic cough, and other respiratory conditions. Minor complaints described in a small fraction of studies consisted mainly of transient throat irritation. Personal communication with the authors of > 90% of the studies confirmed an absence of any serious adverse events. Furthermore, these investigators have performed thousands of additional capsaicin challenge studies not reported in the literature, also without any associated serious adverse events.

CONCLUSIONS

A review of the 20-year clinical experience has failed to uncover a single serious adverse event associated with capsaicin cough challenge testing in humans. Given the need for better antitussive therapies, capsaicin represents a vital component of future scientific inquiry in the field of cough.

Inhaled beta2-agonists for treating non-specific chronic cough in children

BACKGROUND

The pathophysiology of so called 'cough variant asthma' has not received a great deal of research interest and opinion lies divided as to whether it is really asthma or not. The proponents of cough variant asthma suggest a therapeutic trial of medications usually used to treat asthma

OBJECTIVES

To determine the effectiveness of inhaled ss2 agonists in non-specific chronic cough in children over the age of 2 years.

SEARCH STRATEGY

The Cochrane Airways Group database (including MEDLINE, EMBASE and CINAHL) and the Cochrane Controlled Trials Register (CCRT) were searched. Additional searching included hand searching of medical journals through the Cochrane Collaboration, references, references of references listed in primary sources and personal communication with authors. In addition "Grey literature" including theses, internal reports, non-peer reviewed journals were sought.

SELECTION CRITERIA

All randomised (randomised and quasi-randomised) controlled clinical trials in which inhaled ss2 agonists were given for chronic cough in children over 2 years of age were included. Two reviewers independently assessed articles for inclusion and methodological quality.

DATA COLLECTION AND ANALYSIS

Data for trials of salbutamol versus placebo were extracted by both reviewers and entered into the Cochrane Collaboration software program Review Manager, version 4.2

MAIN RESULTS

In children presenting with isolated chronic cough there was no significant difference between salbutamol treated group and placebo group.

AUTHORS' CONCLUSIONS

Salbutamol was no different from placebo in reducing the frequency of cough measured objectively or scored subjectively.

Gastro-oesophageal reflux treatment for prolonged non-specific cough in children and adults

BACKGROUND

Cough is a very common symptom presenting to medical practitioners. Gastroesophageal reflux disease (GORD) is said to be the causative factor in up to 41% of adults with chronic cough. However cough and GORD are common ailments and their co-existence by chance is high. Also cough can induce reflux episodes. Treatment for GORD includes conservative measures (diet manipulation), pharmaceutical therapy (motility or prokinetic agents, H(2) antagonist and proton pump inhibitors (PPI)) and fundoplication.

OBJECTIVES

To evaluate the efficacy of GORD treatment on chronic cough in children and adults with GORD and prolonged cough that is not related to an underlying respiratory disease i.e. non-specific chronic cough.

SEARCH STRATEGY

The Cochrane Register of Controlled Trials (CENTRAL), the Cochrane Airways Group Specialised Register Collaboration and Cochrane Airways Group, MEDLINE and EMBASE databases, review articles and reference lists of relevant articles were searched. The date of last search was 4th April 2004.

SELECTION CRITERIA

All randomised controlled trials on GORD treatment for cough in children and adults without primary lung disease.

DATA COLLECTION AND ANALYSIS

Results of searches were reviewed against pre-determined criteria for inclusion. Two independent reviewers selected, extracted and assessed data for inclusion. Authors were contacted for further information. Data was analysed as "intention to treat" as well as "treatment received". Paediatric and adults data were considered separately. Sensitivity analyses were performed.

MAIN RESULTS

11 studies (3 paediatric, 8 adults; 383 participants) were included. None of the paediatric studies could be included in meta-analysis. In adults, analysis on use of H(2) antagonist, motility agents and conservative treatment for GORD were not possible (from lack of data) and there were no controlled studies on fundoplication as an intervention. Five adult studies comparing PPI (2-3 months) to placebo were analysed for various outcomes in the meta-analysis. Enrollment of subjects for two studies were primarily from medical clinics and another three studies were otolaryngeal clinic patients. Using "intention to treat", pooled data from three studies resulted in no significant difference between treatment and placebo in total resolution of cough. Pooled data revealed no significant improvement in cough outcomes (end of trial or change in cough scores). Significant differences were only found in sensitivity analysis. A significant improvement in change of cough scores was found in end of intervention (2-3 months) in those receiving PPI with a standardised mean difference of -0.41 (95%CI -0.75, -0.07) using GIV analysis on cross over trials. Two studies reported improvement in cough after 5 days to 2 weeks of treatment. Significant heterogeneity was found between studies using omeprazole and other PPIs.

AUTHORS' CONCLUSIONS

There is insufficient evidence to definitely conclude that GORD treatment with PPI is beneficial for cough associated with GORD in adults. The beneficial effect was only seen in sub-analysis and its effect was small. The optimal duration of such a trial of therapy to evaluate response could not be ascertained in the meta-analysis although two RCTs reported significant change by two weeks of therapy. Clinicians should be cognisant of a period (natural resolution with time) and placebo effect in studies that utilise cough as an outcome measure. Data in children are inconclusive. Future paediatric and adult studies are needed whereby studies should be double blind, randomised controlled, parallel design, using treatments for at least two months, with validated subjective and objective cough outcomes and include ascertainment of time to respond as well as assessment of acid and/or non acid reflux whilst on therapy.

Plasticity of vagal afferent fibres mediating cough

Increased sensitivity of cough pathways has been demonstrated in numerous studies. The underlying mechanisms of this sensitization are largely unknown; however, a burgeoning body of evidence suggests that vagal primary afferent neurones that innervate the airways are likely to be involved. This plasticity includes changes in anatomy, neurochemistry and function. PGE2 is an example of an inflammatory mediator that increases responsiveness to tussive stimuli. Electrophysiological studies of neurone cell bodies isolated from afferent ganglia have revealed that prostanoids modulate the function of a variety of distinct ion channels including those that carry TTX-insensitive voltage-gated sodium currents, slow post-spike hyperpolarizations and a hyperpolarization-activated cation current. Mediator-induced modulation of the function of various voltage-gated currents operating at the peripheral terminals of airway afferent neurons would probably influence input from the airways into the central nervous system and contribute to the urge to cough and increased responsiveness to tussive stimuli.

Cough . 6: Which investigations are most useful in the diagnosis of chronic cough?

There is no consensus as to the best diagnostic strategy for chronic cough. Many protocols combine empirical trials of treatment with laboratory investigations. More precise diagnostic tools and improved therapeutic options are required. Until then, the management of chronic cough will remain a clinical challenge.

Does laparoscopic fundoplication provide long-term control of gastroesophageal reflux related cough?

BACKGROUND

Of patients with chronic cough, 21% have GERD. Up to half of these patients may not respond adequately to medical, but the long-term results of antireflux surgery for cough is unknown.

METHODS

A total of 905 patients (209 with respiratory symptoms, mainly cough) underwent laparoscopic Nissen fundoplication. Preoperatively patients underwent esophageal motility studies, 24-h pH monitoring, and symptom evaluation using a validated scale. Of eligible patients, 81% were followed at 6 months, 73% at 2 years, and 60% at 5 years.

RESULTS

Before surgery, 83% of respiratory patients (RP) and 51% of nonrespiratory patients (NRP) had cough. RP had higher cough scores ( p < 0.0001), but improvement in cough compared to baseline was similar in the RP and NRP ( p = 0.1105 at 6 months, 0.4206 at 2 years, and 0.1348 at 5 years). Cough improved in 83% at 6 months, 74% at 2 years, and 71% at 5 years.

CONCLUSIONS

Laparoscopic Nissen fundoplication is successful in the long-term control of GERD-related cough, even in patients who fail medical therapy.

The association of gastroesophageal reflux disease with asthma and chronic cough in the adult

Gastroesophageal reflux disease (GERD) is a common condition which is particularly prevalent in patients with asthma and chronic cough. Physiologic changes caused by asthma and chronic cough promote acid reflux. GERD is also considered by many investigators as a factor contributing to airway inflammation. An etiological relationship between GERD and asthma/chronic cough and vice versa has been supported by a large number of experimental and clinical findings and refuted by others. Although further controlled studies are needed to clarify this relationship, GERD and asthma/chronic cough appear to be linked to each other. The association of GERD with asthma and chronic cough involves nerve reflexes, cytokines, inflammatory and neuroendocrine cells and, in some patients, tracheal aspiration of refluxing gastric fluids. GERD may present with typical symptoms but can also be asymptomatic. Sensitive methods for diagnosing GERD are available, which include esophageal pH monitoring, acid provocative tests, modified barium swallow and endoscopy. Consideration of the association of GERD with asthma and chronic cough is of practical value in the management of chronic cough or asthma resistant to treatment. Treatment of GERD in patients with asthma has been consistently shown to improve respiratory symptoms but not necessarily pulmonary function tests. Surgical treatment can be a useful and cost-effective approach in selected patients with asthma and GERD.

Extraesophageal manifestations of GERD

The association between gastroesophageal reflux disease (GERD) and extraesophageal disease is often referred to as extraesophageal reflux (EER). This article reviews EER, discussing epidemiology, pathogenesis, diagnosis, and treatment with a focus on the most studied and convincing EER disorders-asthma, cough, and laryngitis. Although EER comprises a heterogeneous group of disorders, some general characterizations can be made, as follows. First, although GERD's association with extraesophageal diseases is well-established, definitive evidence of causation has been more elusive, rendering epidemiological data scarce. Secondly, regarding the pathogenesis of EER, 2 basic models have been proposed: direct injury to extraesophageal tissue by acid and pepsin exposure or injury mediated through an esophageal reflex mechanism. Third, because heartburn and regurgitation are often absent in patients with EER, GERD may not be suspected. Even when GERD is suspected, the diagnosis may be difficult to confirm. Although endoscopy and barium esophagram remain important tools for detecting esophageal complications, they may fail to establish the presence of GERD. Even when GERD is diagnosed by endoscopy or barium esophagram, causation between GERD and extraesophageal symptoms cannot be determined. Esophageal pH is the most sensitive tool for detecting GERD, and it plays an important role in EER. However, even pH testing cannot establish GERD's causative relationship to extraesophageal symptoms. In this regard, effective treatment of GERD resulting in significant improvement or remission of the extraesophageal symptoms provides the best evidence for GERD's pathogenic role. Finally, EER generally requires more prolonged and aggressive antisecretory therapy than typical GERD requires.

Cough sensitivity in atopic dermatitis

The aim of study was to investigate the cough sensitivity (C2) to capsaicin (CAPS) in patients with atopic dermatitis without clinical respiratory symptoms. Cough sensitivity (C2) is defined as the lowest CAPS concentration, which evokes two or more coughs. Forty eight dermatological patients (21 M, 27 F; mean age 44 yr) and 24 healthy volunteers (14 M, 10 F; mean age 37 yr) inhaled deep breath (2 l) of CAPS aerosol in doubled concentrations (from 0.02 to 200 micromol/l) (Pari Provokationstest I, PARI WERK; mass median diameter 1.2 microm). Cough sensitivity (C2) expressed as geometric mean (95% CI) of CAPS concentration was 0.13 micromol/l (0.06-0.31) in 26 patients with atopic dermatitis (10 M, 16 F; mean age 41 yr), 5.51 micromol/l (1.33-22.90) in 22 patients with psoriasis (11 M, 11 F; mean age 46 yr) and 4.29 micromol/l (2.54-7.26) in 24 controls. There is significant difference of cough sensitivity (C2) between patients with atopic dermatitis and healthy volunteers (p<0.001) and also between patients with atopic dermatitis and psoriasis (p<0.001). Cough sensitivity (C2) in atopic dermatitis patients without clinical respiratory symptoms is significantly increased. In patients with psoriasis cough sensitivity (C2) is not significantly changed.

A study of the cough reflex in idiopathic pulmonary fibrosis

Little is known about the pathogenesis of cough in idiopathic pulmonary fibrosis (IPF). We hypothesized that abnormalities of respiratory tract tachykinin-containing sensory nerves may be implicated. We studied cough response to capsaicin, substance P (SP), and bradykinin in 10 healthy control subjects and 10 patients with IPF. Six patients were tested before and after steroid therapy. Induced sputum cell counts and neurotrophic factor levels were also measured in 13 patients and 13 control subjects. The results show that cough sensitivity to capsaicin was greater in patients (p < 0.01). Neither SP nor bradykinin induced cough in normal subjects. SP and bradykinin induced cough in 7/10 patients (p < 0.002) and 2/10 patients (not significant) with IPF, respectively. Prednisolone caused a reduction in cough sensitivity to capsaicin (p < 0.05) and SP (p < 0.05) in all six patients treated. There were significantly more neutrophils (p = 0.001) and higher levels of nerve growth factor (p < 0.01) and brain-derived neurotrophic factor (p < 0.01) in patient's sputa. These findings suggest functional upregulation of lung sensory neurones in IPF. The cough response to inhaled SP in most patients may reflect disrupted respiratory epithelium. The response to corticosteroids demonstrates that the cough is amenable to therapy.

Enhanced cough response to hyperpnea with cold air challenge in chronic cough patients showing increased cough sensitivity to inhaled capsaicin

BACKGROUND

Although many chronic cough patients have complained of an induced cough by cold air contact, the clinical relevance of cold air to inducing a cough and the diagnostic value of a hyperpnea with cold air (HCA) challenge to detect a hyperreactive cough reflex have not yet been investigated.

METHODS

Recordings of cough counts after a 2-min HCA challenge were performed in 49 chronic cough patients and 15 healthy controls. Capsaicin cough provocation tests, which determine the threshold concentration of capsaicin that induces five or more consecutive coughs (C5), were also administered.

RESULTS

After comparing the results from the capsaicin cough provocation tests of the patients and the controls, the chronic cough patients were divided into two groups: an increased cough sensitivity (ICS) group (n = 28) (C5 < 32 micromol/l) and a normal cough sensitivity (NCS) group (n = 21) (C5 >or= 32 micromol/l). The median value of induced cough counts after a HCA challenge was 11 coughs in patients with ICS and was a significantly enhanced cough response compared to that of the patients with NCS and healthy controls (four coughs, respectively).

CONCLUSIONS

A simple cough provocation test using a HCA challenge may be useful for detecting ICS. It also suggests that hyperreactive cough reflexes may be one of the mechanisms of inducing chronic cough.

Cough reflex testing with inhaled capsaicin in the study of chronic cough

OBJECTIVES

To assess the utility of capsaicin test in the differential diagnosis of non-productive causes of chronic cough and to examine the effects of treatment on this reflex.

PARTICIPANTS

86 healthy volunteers and 101 patients with chronic cough: asthma (n: 54) gastroesophageal reflux (n: 35) and post-nasal drip syndrome (n: 12).

DESIGN

Prospective intervention trial. Spirometry, bronchoprovocation test with histamine (PC20), and cough challenge with ascending concentrations of capsaicin (0.49-500 microM) were initially performed in all subjects. Patients were treated for 3 months according to the origin of the cough. Concentrations that elicited two (C2) and five or more coughs (C5) were determined before and after treatment.

RESULTS

In healthy subjects, cough sensitivity to capsaicin was not influenced by gender or smoking status; however, women with chronic cough were more sensitive to cough challenge than men. C2 and C5 were significantly lower in patients with asthma or gastroesophageal reflux than in post-nasal drip syndrome. No significant correlation was observed between the capsaicin cough threshold and PC20. Cough sensitivity did not improve significantly in most patients with asthma or gastroesophageal reflux despite adequate medical treatment during 3 months. Discriminative value of capsaicin test to differentiate healthy subjects from patients with asthma or reflux was poor.

CONCLUSIONS

Cough sensitivity to inhaled capsaicin is a safe and reproducible tool in the study of chronic cough. However, its usefulness for the management and differential diagnosis is limited.

Diagnosis and treatment of chronic cough due to gastro-esophageal reflux disease and postnasal drip syndrome

Gastro-esophageal reflux disease (GERD) and postnasal drip syndrome (PNDS) are common causes of chronic cough. In patients with normal chest radiographs, GERD most likely causes cough by an esophageal-bronchial reflex. When GERD causes cough, there may be no gastrointestinal symptoms up to 75% of the time. While 24-h esophageal pH monitoring is the most sensitive and specific test in linking GERD and cough in a cause and effect relationship, it has its limitations. There is no general agreement on how to best interpret the test and it cannot detect non-acid reflux events. While some patients improve with minimal medical therapy, others require intensive regimens. Surgery may be efficacious when intensive medical therapy has failed. Because there are no pathognomonic findings of PNDS, the diagnosis is inferential and is based upon a combination of clinical findings, the results of ancillary testing, and the response to specific therapy. Specific therapy depends upon the rhinosinus disease(s) causing the PND. A common error in managing PNDSs is to assume that all H(1)-antagonists are equally efficacious. The second-generation, relatively non-sedating H(1)-antagonists have been found to be less effective than the first-generation agents in treating cough due to non-histamine-mediated PNDSs.

Effects of esophageal acid perfusion on cough responsiveness in patients with bronchial asthma

STUDY OBJECTIVES

The effect of gastroesophageal reflux (GER) on cough responsiveness in patients with bronchial asthma has yet to be studied in significant detail. The purpose of this study was to assess the effect of distal esophageal acid perfusion on cough responsiveness in patients with bronchial asthma.

PATIENTS AND INTERVENTIONS

In seven patients with mild persistent bronchial asthma (mean +/- SD age, 57.7 +/- 3.7 years; four women and three men), esophageal pH was monitored by a pH meter and cough responsiveness was evaluated by single-breath aerosol inhalation of capsaicin with increasing dosage from 0.30 to 9.84 nmol. Simultaneously, esophageal perfusion was performed through an esophageal tube filled with either saline solution or 0.1 N hydrochloric acid (HCl), the order of which was selected at random, in 1-week intervals. Results were expressed as the lowest concentration of capsaicin eliciting three coughs (PD3). Spirometry was also performed during esophageal pH monitoring.

RESULTS

A significant decrease in the geometric mean of log PD3 was observed during distal esophageal HCl perfusion (0.45 +/- 0.04 nmol) compared with that of the saline solution perfusion (0.04 +/- 0.06 nmol) [p < 0.01]. However, no significant changes were observed either in FVC, FEV1, or peak expiratory flow during the periods of the saline solution or HCl perfusion.

CONCLUSION

The present data demonstrate that an increase in cough responsiveness may be induced when HCl stimulates the distal portion of esophagus in patients with bronchial asthma, suggesting that the GER would be one of the important factors that influence asthmatic status.

Characterization of increased cough sensitivity after antigen challenge in guinea pigs

Increased sensitivity of cough reflex is a fundamental feature of bronchodilator resistant non-productive cough associated with eosinophilic tracheobronchitis. Our hypothesis is that cough sensitivity is increased by airway allergic reaction characterized by airway eosinophilic inflammation. The aim of this study was to elucidate the hypothesis and clarify the characteristics of the increased cough sensitivity. Number of coughs elicited by inhalation of increasing concentrations of capsaicin (10-8, 10-6 and 10-4 M) was counted 24 h after an aerosolized antigen or saline in actively sensitized or non-sensitized (naive) conscious guinea pigs and then bronchoalveolar lavage was performed. The cough response was also measured 1 day before and 1, 2, 3, 5 and 7 days after an aerosolized antigen challenge in sensitized or naive animals. In addition, effect of procaterol (0.1 mg/kg), atropine (1 or 10 mg/kg), phosphoramidon (2.5 mg/kg) given intraperitoneally 30 min before the capsaicin challenge or capsaicin desensitization on the cough response was examined. Furthermore, the thromboxane A2 (TXA2) receptor antagonist S-1452 in a dose of 0.01 or 0.1 mg/kg or vehicle (saline) was given intraperitoneally at 24 and 1 h before the measurement of cough response. Number of coughs caused by capsaicin was extremely increased 24 h after an antigen challenge in sensitized guinea pigs compared with a saline or an antigen challenge in naive animals or a saline challenge in sensitized animals. The increased cough response disappeared at 3-7 days after the antigen challenge. Eosinophils in bronchoalveolar lavage fluid obtained after the measurement of capsaicin-induced coughs, which was performed 24 h after the antigen challenge, were significantly increased in sensitized guinea pigs. The eosinophil count was significantly correlated to the number of capsaicin-induced coughs. Procaterol or atropine did not alter the antigen-induced increase of cough sensitivity, whereas atropine did reduce the cough response in naive animals. Phosphoramidon increased the number of capsaicin-induced coughs in naive guinea pigs but not in sensitized and antigen-challenged animals. Capsaicin desensitization decreased the cough response in both antigen-challenged sensitized guinea pigs and naive animals. S-1452 reduced the antigen-induced increase of cough response in sensitized guinea pigs, but not in naive animals. Airway allergy accompanied with airway eosinophilia induces transient increase in cough sensitivity, which is not mediated by bronchoconstriction. The increased cough sensitivity may result in part from inactivation of neutral endopeptidase and TXA2, one of the inflammatory mediators.

The cough reflex and its relation to gastroesophageal reflux

Each cough involves a complex reflex arc beginning with the stimulation of sensory nerves that function as cough receptors. There is evidence, primarily clinical, that the sensory limb of the reflex exists in and outside of the lower respiratory tract. Although myelinated, rapidly adapting pulmonary stretch receptors (RARs), also known as irritant receptors, are the most likely type of sensory nerve that stimulates the cough center in the brain, afferent C-fibers and slowly adapting pulmonary stretch receptors (SARs) also may modulate cough. RARS, C-fibers, and SARs have been identified in the distal esophageal mucosa; however, studies have not been performed to determine whether they can participate in the cough reflex. Although gastroesophageal reflux disease can potentially stimulate the afferent limb of the cough reflex by irritating the upper respiratory tract without aspiration and by irritating the lower respiratory tract by micro- or macroaspiration, there is evidence that strongly suggests that reflux commonly provokes cough by stimulating an esophageal-bronchial reflex. Theoretically, the pathways of this reflex may be modeled in a variety of ways, and these are speculated upon in this article. The predominant role of acid in triggering cough by means of this reflex is unclear because of conflicting results from provocative challenge studies. It is interesting to speculate that a distal esophageal-bronchial reflex evolved as an early warning defense so that coughing could be started, just in case the refluxate were to reach the inlet of the lower respiratory tract. That is, thinking teleologically, it is possible that an esophageal-bronchial reflex evolved as one of several mechanisms designed to protect the lungs from aspiration of gastric contents.

Gastroesophageal reflux and asthma: are they related?

The relationship between asthma and gastroesophageal reflux (GER) is controversial. This paper reviews the evidence for an association between them, the effect of asthma on GER, and the effects of GER and antireflux therapy on asthma. The association between the two conditions seems firm but studies of the effects of GER on asthma and asthma on GER are contradictory. Critical review suggests that GER affects asthma symptoms but not pulmonary function. Antireflux therapy improves asthma symptoms and reduces medication requirements but does not improve pulmonary function. The paradox of GER causing asthma symptoms but not changing pulmonary function may be explained by its increasing minute ventilation rather than triggering bronchospasm.