Reduced pH and chloride levels in exhaled breath condensate of patients with chronic cough

Chloride ions in health and disease

Chloride is a key anion involved in cellular physiology by regulating its homeostasis and rheostatic processes. Changes in cellular Cl- concentration result in differential regulation of cellular functions such as transcription and translation, post-translation modifications, cell cycle and proliferation, cell volume, and pH levels. In intracellular compartments, Cl- modulates the function of lysosomes, mitochondria, endosomes, phagosomes, the nucleus, and the endoplasmic reticulum. In extracellular fluid (ECF), Cl- is present in blood/plasma and interstitial fluid compartments. A reduction in Cl- levels in ECF can result in cell volume contraction. Cl- is the key physiological anion and is a principal compensatory ion for the movement of the major cations such as Na+, K+, and Ca2+. Over the past 25 years, we have increased our understanding of cellular signaling mediated by Cl-, which has helped in understanding the molecular and metabolic changes observed in pathologies with altered Cl- levels. Here, we review the concentration of Cl- in various organs and cellular compartments, ion channels responsible for its transportation, and recent information on its physiological roles.

Hypertonic Aerosols Hydrate Airways Longer and Reduce Acidification Risk with Nonpermeating Cation and Permeating Anion Salts

Background: Hyperosmolar aerosols appear to promote or suppress upper airway dysfunction caused by dehydration in a composition-dependent manner. We sought to explore this composition dependence experimentally, in an interventional human clinical study, and theoretically, by numerical analysis of upper airway ion and water transport. Methods: In a double-blinded, placebo-controlled clinical study, phonation threshold pressure (PTP) was measured prenasal and postnasal inhalation of hypertonic aerosols of NaCl, KCl, CaCl2, and MgCl2 in seven human subjects. Numerical analysis of water and solute exchanges in the upper airways following deposition of these same aerosols was performed using a mathematical model previously described in the literature. Results: PTP decreased by 9%-22% relative to baseline (p < 0.05) for all salts within the first 30 minutes postadministration, indicating effective laryngeal hydration. Only MgCl2 reduced PTP beyond 90 minutes (21% below baseline at 2 hours postadministration). By numerical analysis, we determined that, while airway water volume up to 15 minutes postdeposition is dictated by osmolarity, after 30 minutes, divalent cation salts, such as MgCl2, better retain airway surface liquid (ASL) volume by slow paracellular clearance of the divalent cation. Fall of CFTR chloride flux with rise in ASL height, a promoter of airway acidification, appears to be a signature of permeating cation (NaCl) and nonpermeating anion (mannitol) aerosol deposition. For hypertonic aerosols that lack permeating cation and include permeating anion (CaCl2 and MgCl2), this acid-trigger signature does not exist. Conclusions: Nonpermeating cation and permeating anion hypertonic aerosols appear to hydrate upper airways longer and, rather than provoke, may reduce laryngeal dysfunction such as cough and bronchoconstriction.

Mucus Transpiration as the Basis for Chronic Cough and Cough Hypersensitivity

Chronic cough is characterized by a state of cough hypersensitivity. We analyze the process of transpiration, by which water appears to evaporate from laryngeal and tracheal mucus as from the surface of a leaf, as a potential cause of cough hypersensitivity. In this process, osmotic pressure differences form across mucus, pulling water toward the air, and preventing mucus dehydration. Recent research suggests that these osmotic differences grow on encounter with dry and dirty air, amplifying pressure on upper airway epithelia and initiating a cascade of biophysical events that potentially elevate levels of ATP, promote inflammation and acidity, threaten water condensation, and diminish mucus water permeability. Among consequences of this inflammatory cascade is tendency to cough. Studies of isotonic, hypotonic, and hypertonic aerosols targeted to the upper airways give insights to the nature of mucus transpiration and its relationship to a water layer that forms by condensation in the upper airways on exhalation. They also suggest that, while hypertonic NaCl and mannitol may provoke cough and bronchoconstriction, hypertonic salts with permeating anions and non-permeating cations may relieve these same upper respiratory dysfunctions. Understanding of mucus transpiration and its role in cough hypersensitivity can lead to new treatment modalities for chronic cough and other airway dysfunctions promoted by the breathing of dry and dirty air.

Cystic Fibrosis and the Cells of the Airway Epithelium: What Are Ionocytes and What Do They Do?

Cystic fibrosis (CF) is caused by defects in an anion channel, the cystic fibrosis transmembrane conductance regulator (CFTR). Recently, a new airway epithelial cell type has been discovered and dubbed the pulmonary ionocyte. Unexpectedly, these ionocytes express higher levels of CFTR than any other airway epithelial cell type. However, ionocytes are not the sole CFTR-expressing airway epithelial cells, and CF-associated disease genes are in fact expressed in multiple airway epithelial cell types. The experimental depletion of ionocytes perturbs epithelial physiology in the mouse trachea, but the role of these rare cells in the pathogenesis of human CF remains mysterious. Ionocytes have been described in diverse tissues(kidney and inner ear) and species (frog and fish). We draw on these prior studies to suggest potential roles of airway ionocytes in health and disease. A complete understanding of ionocytes in the mammalian airway will ultimately depend on cell type-specific genetic manipulation.

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

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

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.

Exhaled Breath Condensate: Pilot Study of the Method and Initial Experience in Healthy Subjects

Analysis of Exhaled breath condensate (EBC) is a re-discovered approach to monitoring the course of the disease and reduce invasive methods of patient investigation. However, the major disadvantage and shortcoming of the EBC is lack of reliable and reproducible standardization of the method. Despite many articles published on EBC, until now there is no clear consensus on whether the analysis of EBC can provide a clue to diagnosis of the diseases. The purpose of this paper is to investigate our own method, to search for possible standardization and to obtain our own initial experience. Thirty healthy volunteers provided the EBC, in which we monitored the density, pH, protein, chloride and urea concentration. Our results show that EBC pH is influenced by smoking, and urea concentrations are affected by the gender of subjects. Age of subjects does not play a role. The smallest coefficient of variation between individual volunteers is for density determination. Current limitations of EBC measurements are the low concentration of many biomarkers. Standardization needs to be specific for each individual biomarker, with focusing on optimal condensate collection. EBC analysis has a potential become diagnostic test, not only for lung diseases.

Small and large airway reactions to osmotic stimuli in asthma and chronic idiopathic cough

BACKGROUND

Chronic cough is a common symptom and related to several pulmonary, airway and heart diseases. When all likely medical explanations for the coughing are excluded, there remains a large group of patients with chronic coughing, which is mostly a cough reflex easily triggered by environmental irritants and noxious stimuli. The main aim of this study was to improve the diagnostic ability to differentiate chronic idiopathic cough (CIC) from asthma.

METHODS

Twenty-three patients with CIC, 16 patients with mild asthma and 21 control participants were included. The study consisted of three randomised bronchial provocations with osmotic stimuli: mannitol, eucapnic dry air and hypertonic saline. At each provocation lung function was assessed by spirometry and impulse oscillometry (IOS).

RESULTS

In a comparison of the groups, while the FEV₁ measurements did not differ, the CIC group had increased airway resistance and reactance after provocation with hypertonic saline compared to the control subjects. After mannitol provocation the patients with asthma had significantly increased airway resistance compared to the controls and from eucapnic dry air provocations these patients had a significant reduction in spirometry values and increased airway resistance compared to both the patients with CIC and the controls.

CONCLUSION

The asthma group reacted in a predictable way with impaired lung function from osmotic provocations, whereas the patients with CIC demonstrated peripheral airway changes from hypertonic saline, also known to be a noxious stimulus. The IOS method uncovers differences between patients with CIC and control participants that contribute to our ability to provide a correct diagnosis.

Living near a Major Road in Beijing: Association with Lower Lung Function, Airway Acidification, and Chronic Cough

Background:

The effects of near-road pollution on lung function in China have not been well studied. We aimed to investigate the effects of long-term exposure to traffic-related air pollution on lung function, airway inflammation, and respiratory symptoms.

Methods:

We enrolled 1003 residents aged 57.96 ± 8.99 years living in the Shichahai Community in Beijing. Distances between home addresses and the nearest major roads were measured to calculate home-road distance. We used the distance categories 1, 2, and 3, representing <100 m, 100–200 m, and >200 m, respectively, as the dose indicator for traffic-related air pollution exposure. Lung function, exhaled breath condensate (EBC) pH, and interleukin 6 levels were measured. As a follow-up, 398 participants had a second lung function assessment about 3 years later, and lung function decline was also examined as an outcome. We used regression analysis to assess the impacts of home-road distance on lung function and respiratory symptoms. As the EBC biomarker data were not normally distributed, we performed correlation analysis between home-road distance categories and EBC biomarkers.

Results:

Participants living a shorter distance from major roads had lower percentage of predicted value of forced expiratory volume in 1 s (FEV1% −1.54, 95% confidence interval [CI]: −0.20 to −2.89). The odds ratio for chronic cough was 2.54 (95% CI: 1.57–4.10) for category 1 and 1.97 (95% CI: 1.16–3.37) for category 2, compared with category 3. EBC pH was positively correlated with road distance (rank correlation coefficient of Spearman [r_s] = 0.176, P < 0.001).

Conclusions:

Long-term exposure to traffic-related air pollution in people who live near major roads in Beijing is associated with lower lung function, airway acidification, and a higher prevalence of chronic cough. EBC pH is a potential useful biomarker for evaluating air pollution exposure.

Cough associated with gastro-oesophageal reflux disease (GORD): Japanese experience

Differences in the aetiology as well as patient background of chronic cough have been recognised among US, UK, and Japan. One of the marked differences has been the prevalence of gastro-oesophageal reflux disease (GORD), which has been one of the top three causes in Western countries. It was indeed uncommon or rare in Japan, but, with the increasing prevalence of GOR itself, chronic cough associated with GORD seems to have become more common. In this article, cough associated with GORD will be reviewed based on literature and our Japanese experience. Further, potentially broader relevance of GORD in chronic cough will also be mentioned, highlighting the potential importance of dysmotiliy/non-acid reflux.

Evidence for neuropathic processes in chronic cough

Chronic cough is a very common symptom for which patients seek medical attention but can often be difficult to manage, because associated causes may remain elusive and treatment of any associated causes does not always provide adequate relief. Current antitussives have limited efficacy and undesirable side-effects. Patients with chronic cough typically describe sensory symptoms suggestive of upper airway and laryngeal neural dysfunction. They often report cough triggered by low-level physical and chemical stimuli supporting the recently emerging concept of 'cough hypersensitivity syndrome'. Chronic cough is a neuropathic condition that could be secondary to sensory nerve damage caused by inflammatory, infective and allergic factors. Mechanisms underlying peripheral and central augmentation of the afferent cough pathways have been identified. Successful treatment of chronic cough with agents used for treating neuropathic pain, such as gabapentin and amitriptyline, would also support this concept. Further research of neuropathic cough may lead to the discovery of more effective antitussives in the future.

Exhaled Breath Condensate pH in Lung Cancer, the Impact of Clinical Factors

PURPOSE

Lung cancer may be associated with airway acidification due to enhanced airway inflammation and oxidative stress. Exhaled breath condensate (EBC) pH is a non-invasive indicator of airway acidity; however, it is still unclear how EBC pH changes in lung cancer. The aim of the study was to investigate EBC pH in lung cancer together with clinical variables.

METHODS

Thirty-five patients with lung cancer and 37 control subjects (21 patients with stable COPD and 16 non-COPD smokers) were enrolled. EBC was collected for pH, which was determined with the argon-purging method, compared among the groups and correlated with clinical variables of patients with lung cancer.

RESULTS

No difference was found in EBC pH between patients with lung cancer and control subjects. However, endobronchial tumour localisation, squamous-cell carcinoma subtype and gastro-oesophageal reflux were associated with low EBC pH values. No relationship was observed between EBC pH and the presence of COPD, lung function variables or smoking history.

CONCLUSIONS

Although, EBC pH is unchanged in lung cancer, lower EBC pH values are associated with distinct phenotypes. Our findings could facilitate further research on airway acidity in lung cancer.

Exhaled Breath Condensate: Technical and Diagnostic Aspects

Purpose. The aim of this study was to evaluate the 30-year progress of research on exhaled breath condensate in a disease-based approach. Methods. We searched PubMed/Medline, ScienceDirect, and Google Scholar using the following keywords: exhaled breath condensate (EBC), biomarkers, pH, asthma, gastroesophageal reflux (GERD), smoking, COPD, lung cancer, NSCLC, mechanical ventilation, cystic fibrosis, pulmonary arterial hypertension (PAH), idiopathic pulmonary fibrosis, interstitial lung diseases, obstructive sleep apnea (OSA), and drugs. Results. We found 12600 related articles in total in Google Scholar, 1807 in ScienceDirect, and 1081 in PubMed/Medline, published from 1980 to October 2014. 228 original investigation and review articles were eligible. Conclusions. There is rapidly increasing number of innovative articles, covering all the areas of modern respiratory medicine and expanding EBC potential clinical applications to other fields of internal medicine. However, the majority of published papers represent the results of small-scale studies and thus current knowledge must be further evaluated in large cohorts. In regard to the potential clinical use of EBC-analysis, several limitations must be pointed out, including poor reproducibility of biomarkers and absence of large surveys towards determination of reference-normal values. In conclusion, contemporary EBC-analysis is an intriguing achievement, but still in early stage when it comes to its application in clinical practice.

Measurement of eNO with portable analyser might improve the management of persistent cough at primary care practice in Japan

BACKGROUND AND AIMS

There are some controversial reports that investigated the usefulness of exhaled nitric oxide (eNO) to predict the efficacy of inhaled corticosteroids (ICS) in chronic cough patients. Therefore, we retrospectively analysed the usefulness of eNO measurement with portable analyser to predict the requirement of ICS therapy in persistent cough (defined as lasting for 3 weeks or more) patients in Japan and investigated whether it might improve the management of persistent cough at primary care practice.

METHODS

We retrospectively reviewed the clinical records of adult patients who had been referred to our hospital for persistent cough from 1 June 2009 to 30 April 2011.

RESULTS

Forty-two patients had the requirement of ICS (group S) and 35 patients had no requirement of ICS (group N). Forty-three per cent of the patients who required ICS had not received ICS, and 29% of the patients who did not required ICS had received ICS. In the steroid-naive patients without current smoking, mean eNO level was significantly higher in group S [60.6 ± 14.1 parts per billion (ppb) vs 22.2 ± 2.3 ppb, P = 0.001] and the sensitivity and the specificity of eNO for predicting the requirement of ICS were 78.6% and 80.0%, respectively. The rate of the patients who received inappropriate treatment about ICS tended to be reduced from 41% to 21% if the eNO was used to predict the requirement of ICS with cut-off value of eNO 26.5 ppb (P = 0.118).

CONCLUSION

Measurement of eNO could be one of the management tools for persistent cough at primary care practice.

Approach to chronic cough: the neuropathic basis for cough hypersensitivity syndrome

Chronic cough is a common symptom that can be difficult to manage because associated causes may remain elusive and treatment of any associated cause may not provide relief. Current antitussives have limited efficacy and undesirable side-effects. Patients with chronic cough describe sensory symptoms suggestive of upper airway and laryngeal neural dysfunction, and report cough triggered by low-level physical and chemical stimuli supporting the concept of cough reflex hypersensitivity. Mechanisms underlying peripheral and central augmentation of the afferent cough pathways have been identified. Chronic cough is a neuropathic condition that could be secondary to sensory nerve damage caused by inflammatory, infective and allergic factors. Recent success in the treatment of chronic cough with agents used for treating neuropathic pain such as gabapentin and amitryptiline would also support this concept. Research into neuropathic cough may lead to the discovery of more effective antitussives.

Exhaled breath condensate pH does not discriminate asymptomatic gastroesophageal reflux or the response to lansoprazole treatment in children with poorly controlled asthma

BACKGROUND

Although exhaled breath condensate (EBC) pH has been identified as an "emerging" biomarker of interest for asthma clinical trials, the clinical determinants of EBC pH remain poorly understood. Other studies have associated acid reflux-induced respiratory symptoms, for example, cough, with transient acidification of EBC.

OBJECTIVE

We sought to determine the clinical and physiologic correlates of EBC acidification in a highly characterized sample of children with poorly controlled asthma. We hypothesized that (1) children with asymptomatic gastroesophageal reflux determined by 24-hour esophageal pH monitoring would have a lower EBC pH than children without gastroesophageal reflux, (2) treatment with lansoprazole would alter EBC pH in those children, and (3) EBC acidification would be associated with increased asthma symptoms, poorer asthma control and quality of life, and increased formation of breath nitrogen oxides (NOx).

METHODS

A total of 110 children, age range 6 to 17 years, with poor asthma control and esophageal pH data enrolled in the Study of Acid Reflux in Children with Asthma (NCT00442013) were included. Children submitted EBC samples for pH and NOx measurement at randomization and at study weeks 8, 16, and 24.

RESULTS

Serial EBC pH measurements failed to distinguish asymptomatic gastroesophageal reflux and was not associated with breath NOx formation. EBC pH also did not discriminate asthma characteristics such as medication and health care utilization, pulmonary function, and asthma control and quality of life both at baseline and across the study period.

CONCLUSION

Despite the relative ease of EBC collection, EBC pH as a biomarker does not provide useful information of children with asthma who were enrolled in asthma clinical trials.

Exhaled breath condensate--from an analytical point of view

Over the past three decades, the goal of many researchers is analysis of exhaled breath condensate (EBC) as noninvasively obtained sample. A total quality in laboratory diagnostic processes in EBC analysis was investigated: pre-analytical (formation, collection, storage of EBC), analytical (sensitivity of applied methods, standardization) and post-analytical (interpretation of results) phases. EBC analysis is still used as a research tool. Limitations referred to pre-analytical, analytical, and post-analytical phases of EBC analysis are numerous, e.g. low concentrations of EBC constituents, single-analyte methods lack in sensitivity, and multi-analyte has not been fully explored, and reference values are not established. When all, pre-analytical, analytical and post-analytical requirements are met, EBC biomarkers as well as biomarker patterns can be selected and EBC analysis can hopefully be used in clinical practice, in both, the diagnosis and in the longitudinal follow-up of patients, resulting in better outcome of disease.

Cough variant and cough-predominant asthma are major causes of persistent cough: a multicenter study in Japan

OBJECTIVE

Persistent cough is a frequent cause of doctor and hospital visits, and its incidence may be increasing. However, diagnosis of the cause of cough remains difficult. Because different causes of cough have different treatments, accurate diagnosis of the cause of cough is critical. To gain a better understanding of the causes of cough in Japan, we performed a multicenter epidemiological study of Japanese patients.

METHODS

The study involved seven institutions in five different areas of Japan, and was conducted over 1 year from March 2009. Patients aged ≥16 years attending the participating centers for the first time complaining of cough persisting for ≥3 weeks were eligible. Patients with chest X-ray abnormalities responsible for cough, fever or blood-stained sputum were excluded, while those with wheeze or shortness of breath were included. Frequency and severity of cough were assessed using questionnaires, and laboratory tests were performed to enable differential diagnoses.

RESULTS

Among the 313 patients evaluated, mean duration of cough symptoms was 192.1 ± 558.4 days. Cough variant asthma (CVA) was the most common cause of prolonged/chronic cough (42.2%), followed by cough-predominant asthma (CPA) (28.4%), atopic cough (7.3%) and chronic obstructive pulmonary disease (6.7%). Patients with an unclear diagnosis were treated with tulobuterol, a transdermal β2-agonist preparation, for 1-2 weeks. Transdermal tulobuterol improved assessments of cough in patients with CVA or CPA, enabling rapid diagnosis of these diseases.

CONCLUSIONS

These findings show that CVA and CPA are the main causes of cough persisting for ≥3 weeks.

Biomarkers for gastroesophageal reflux in respiratory diseases

Gastroesophageal reflux (GER) is commonly associated with respiratory symptoms, either through a vagal bronchoconstrictive reflex or through microaspiration of gastric contents. No diagnostic test is available, however, to diagnose when respiratory illnesses are caused by GER and when not, but research in this field has been moving forward. Various biomarkers in different types of biosamples have been studied in this context. The aim of this review is to summarize the present knowledge in this field. GER patients with respiratory diseases seem to have a different biochemical profile from similar patients without GER. Inflammatory biomarkers differ in asthmatics based on GER status, tachykinins are elevated in patients with GER-related cough, and bile acids are elevated in lung transplant patients with GER. However, studies on these biomarkers are often limited by their small size, methods of analysis, and case selections. The two pathogenesis mechanisms are associated with different respiratory illnesses and biochemical profiles. A reliable test to identify GER-induced respiratory disorders needs to be developed. Bronchoalveolar lavage is too invasive to be of use in most patients. Exhaled breath condensate samples need further evaluation and standardization. The newly developed particles in exhaled air measurements remain to be studied further.

The role of exhaled nitric oxide and exhaled breath condensates in evaluating airway inflammation in asthma

BACKGROUND

Airway inflammation is central to the development and progression of asthma. Monitoring airway inflammation can be invasive and technically difficult, making its use limited in clinical practice. Several advances have been made in non-invasive techniques to monitor and measure inflammation from the airways.

OBJECTIVE

To examine the suitability of exhaled nitric oxide and exhaled breath condensates as diagnostic tools in asthma.

METHOD

The current literature regarding the use of exhaled nitric oxide and exhaled breath condensate to assess and manage asthma was reviewed.

CONCLUSION

Exhaled nitric oxide is a clinically useful marker of eosinophilic airway inflammation in asthma. Although showing promise, significant validation and investigation are required before exhaled breath condensate could be utilized in clinical practice.

Safety of an alkalinizing buffer designed for inhaled medications in humans

BACKGROUND

Airway acidification plays a role in disorders of the pulmonary tract. We hypothesized that the inhalation of alkalinized glycine buffer would measurably alkalinize the airways without compromising lung function or causing adverse events. We evaluated the safety of an inhaled alkaline glycine buffer in both healthy subjects and in subjects with stable obstructive airway disease.

METHODS

This work includes 2 open-label safety studies. The healthy controls were part of a phase 1 safety study of multiple inhalations of low-dose alkaline glycine buffer; nebulized saline was used as a comparator in 8 of the healthy controls. Subsequently, a phase 2 study in subjects with stable obstructive airway disease was completed using a single nebulized higher-dose strategy of the alkaline inhalation. We studied 20 non-smoking adults (10 healthy controls and 10 subjects with obstructive airway disease), both at baseline and after inhalation of alkaline buffer. We used spirometry and vital signs as markers of clinical safety. We used changes in fraction of exhaled nitric oxide (NO) and exhaled breath condensate (EBC) pH as surrogate markers of airway pH modification.

RESULTS

Alkaline glycine inhalation was tolerated by all subjects in both studies, with no adverse effects on spirometric parameters or vital signs. Airway alkalinization was confirmed by a median increase in EBC pH of 0.235 pH units (IQR 0.56-0.03, P = .03) in subjects after inhalation of the higher-dose alkaline buffer (2.5 mL of 100 mmol/L glycine).

CONCLUSIONS

Alkalinization of airway lining fluid is accomplished with inhalation of alkaline glycine buffer and causes no adverse effects on pulmonary function or vital signs.

Exhaled breath condensate pH in mechanically ventilated patients

OBJECTIVES

In this prospective clinical trial we aimed to answer if spontaneous exhaled breath condensate (EBC) in the trap of the expiratory arm of the ventilator could replace EBC collected by coolant chamber standardized with Argon as an inert gas. Second, if EBC pH could predict ventilator associated pneumonia (VAP) and mortality.

PATIENTS

We included 34 critically ill patients (males = 26), aged = 54.85 ± 19.86 (mean ± SD) yrs, that required mechanical ventilation due to non-pulmonary direct cause (APACHE II score = 23.58 ± 14.7; PaO(2)/FiO(2) = 240.00 ± 98.29).

SETTING

ICU with 9 beds from a regional teaching hospital.

INTERVENTION AND RESULTS

The patients were followed up until development of VAP, successful weaning or death. There were significant differences between mean EBC pH from the 4 procedures with the exception of spontaneous EBC de-aerated with Argon (n = 79; 6.74 ± 0.28) and coolant chamber deaerated with Argon (n = 79; 6.70 ± 0.36; p = NS by Tukey's Multiple Comparison Test). However, none of the procedures were extrapolated between each other according to Bland & Altman method. The mean EBC pH from the trap without Argon was 6.50 ± 0.28. From the total of 34 patients, 22 survived and were discharged and 12 patients died in the ICU.

CONCLUSION

Spontaneous EBC pH could not be extrapolated to EBC pH from coolant chamber and it did not change in subjects who dead, neither subject with VAP in comparison with baseline data. The lack of other biomarker in EBC and the lack of a control group determinate the need for further studies in this setting.

Exhaled breath condensate pH is influenced by respiratory droplet dilution

Several studies support that airway acid stress plays a role in the pathophysiology of asthma. Exhaled breath condensate pH (EBC pH) was suggested as a surrogate marker of airway acidification. The dilution of airway lining fluid (ALF) acids and bases by alveolar water may influence condensate pH, but it has not been studied yet. The aim of our study was to investigate the relationship between EBC pH and ALF dilution in EBC samples obtained from asthmatic and healthy subjects. EBC was collected from 55 asthmatic and 57 healthy subjects for pH and conductivity measurements. Fractional exhaled nitric oxide (FE(NO)) and lung function tests were also performed in asthmatic patients. EBC pH was determined after 10 min of argon deareation and the dilution was estimated by the measurement of conductivity in vacuum-treated samples. There was no difference either in EBC pH or dilution between the two groups. However, a significant relationship was found between EBC pH and dilution in both groups (p < 0.05, r = -0.35 and r = -0.29, asthmatic and healthy groups, respectively). Our results suggest important methodological aspect indicating that EBC pH is affected by respiratory droplet dilution, and this effect should be taken into consideration when interpreting EBC pH data.

Exhaled breath condensate pH in patients with cystic fibrosis

OBJECTIVE AND DESIGN

Exhaled breath condensate (EBC) pH has been proposed as a useful, non-invasive marker of airway inflammation in pulmonary diseases. In this study we tested whether cystic fibrosis (CF) is associated with acidification of EBC, when pH is assessed by the CO(2) gas standardization method.

METHODS

EBC was collected using two different devices (EcoScreen and R-Tube) in 46 stable CF patients during routine clinical visits and in 28 healthy controls.

RESULTS

Mean EBC pH in CF patients and in healthy controls was similar (EcoScreen: CF patients: 6.38 ± 0.03 versus controls: 6.39 ± 0.03, p = 0.699; R-tube: CF patients: 5.94 ± 0.04 versus controls: 6.02 ± 0.03, p = 0.159). Inflammatory cell counts in spontaneously expectorated sputum obtained in a subset of patients (n = 20) showed no correlation with pH values. EBC samples collected with the R-tube were more acidic than those collected with the EcoScreen device (p < 0.001).

CONCLUSIONS

Our data suggest that EBC pH does not discriminate between healthy controls and those with CF disease indicating that the clinical applicability of EBC pH measurements for assessing airway inflammation in CF is limited.

Chronic cough and OSA: a new association?

Chronic cough is defined as cough lasting more than 2 months. Common causes for chronic cough in nonsmokers with normal chest radiographs and pulmonary functions include gastroesophageal reflux disease (GERD), cough-variant asthma (CVA), and upper airway cough syndrome (UACS). Current guidelines recommend diagnosing the etiology of chronic cough based upon the results of therapy for suspected GERD, CVA, and UACS. Despite following current recommendations for diagnosis and treatment, the cause for a significant proportion of chronic cough remains unexplained.Recent reports indicate the resolution of chronic cough following treatment of concomitantly diagnosed obstructive sleep apnea (OSA). Whether this represents a co-occurrence of two commonly prevalent disorders or a pathophysiologic relationship between OSA and cough remains unknown. This review offers insights into a pathophysiologic link between OSA and the commonly purported etiologies for cough, namely, GERD, UACS, and CVA. In addition, evidence for a relationship between airway inflammation that can trigger or perpetuate cough and OSA is discussed. This review explores mechanisms by which nocturnal continuous positive airway therapy resolves cough by improving underlying airway inflammation secondary to OSA and impacts upon GERD, CVA, and UACS.

Calcium and magnesium in exhaled breath condensate of children with endogenous and exogenous airway acidification

BACKGROUND AND AIMS

Regulation of pH in the airways is of physiological importance. As acidification of the airways causes bronchoconstriction, the aim of the present study was to find out whether there is any difference in calcium and magnesium in exhaled breath condensate (EBC) of children with uncontrolled asthma (i.e., with endogenous acidification) and children with gastroesophageal reflux disease, GERD (i.e., with exogenous acidification).

MATERIAL AND METHODS

A total of 142 children were included in the study: children with uncontrolled asthma (N = 51), children with GERD (N = 61), and healthy controls (N = 30). In addition, according to the pH cut-off value children with asthma and GERD were divided into two subgroups, that is, patients with pH ≤ 6.93 (subgroup A) and patients with pH > 6.93 (subgroup B).

RESULTS

The mean EBC pH was significantly lower in children with asthma than in children with GERD (6.791 ± 0.374 vs. 7.002 ± 0.361, p = .006). Concentration [median and interquartile range-M (IQR)] of total magnesium, but not calcium, was lower in both asthmatic [(10 (10-40) μmol/L, p = .016)] and GERD children [(20 (10-40) μmol/L, p = .012)] in comparison with controls (47 ± 27 μmol/L). There was no statistically significant difference in EBC calcium and magnesium concentrations between asthmatic and GERD children. In asthmatic children a positive correlation was confirmed between forced expiratory volume in the first second (FEV1) and magnesium in EBC (r = 0.307; p = .030), and negative correlation was found between FEV1 and calcium/magnesium ratio (r = -0.290; p = .047). In addition, positive correlation was confirmed between fractional concentration of exhaled NO and calcium/magnesium ratio (r = 0.360; p = .018). In GERD patients a negative correlation (r = -0.404; p = .003) was found between magnesium and pH values. Concentration of calcium was higher in the GERD subgroup A children [(50 (30-90) μmol/L)] than in the subgroup B children [(30 (20-45) μmol/L, p = .031)]. In addition, concentration of magnesium was higher in the GERD subgroup A children [(30 (20-70) μmol/L)] than in the subgroup B children [(10 (10-20) μmol/L, p < .001)].

CONCLUSION

The present study indicates that decreased total magnesium concentration may be found in EBCs, irrespective of whether the acidification is the result of endogenous pathomechanisms or reflux-induced mechanisms. In children with GERD, EBC pH-metry should be performed after acute coughing episode. Future research is needed to investigate the mechanisms of onset and dynamics of these changes.

SCIENTIFIC SIGNIFICANCE

Lower concentration of magnesium may indicate its role in bronchoconstiction.

Exhaled breath marker in asthma patients with gastroesophageal reflux disease

Prevention of acid is important in gastroesophageal reflex disease (GERD)-related asthma therapy. Proton pump inhibitors (PPI) and H₂-receptor blockers have been reported as useful therapies for improving asthma symptoms. GERD prevalence is high in asthma; however, methods for validating GERD existence based on questionnaire, endoscopic examination and 24h-pH monitoring do not directly determine GERD influence on the airway. Exhaled breath condensate analysis is a novel and non-invasive tool for assessing information directly from the airway. Breath collected by cooling can be applied to pH, 8-isoprostane and cytokine analysis in patients with GERD-related asthma, and the pH and 8-isoprostane levels have been shown to reflect the effects of PPI therapy in these patients. Although the analysis of cooled breath has not yet been established in a clinical setting, this method is expected to provide a novel tool for monitoring airway acidification associated with GERD.

Exhaled breath condensate pH in lung transplant recipients with bronchiolitis obliterans syndrome

BACKGROUND

Assessment of exhaled breath condensate (EBC) pH is a promising method for investigating airway pathology. However, inaccurate measurement techniques may bias pH readings. In this longitudinal study, we tested whether development of bronchiolitis obliterans syndrome (BOS) in lung transplant recipients is associated with acidification of EBC.

METHODS

EBC was collected in 15 patients with BOS and 16 stable BOS-free patients during routine clinical visits. From nine BOS patients, samples were collected before and after the onset of BOS, as well. Twenty healthy nontransplant subjects served as controls. EBC pH was measured by the carbon dioxide gas standardization method.

RESULTS

EBC pH in patients with and without BOS and controls was similar (BOS group: 6.40±0.04, BOS-free group: 6.45±0.03; controls: 6.39±0.02; P>0.05). In patients who developed BOS during the follow-up, EBC pH before and after the onset of BOS was comparable (pre-BOS: 6.41±0.04 vs. post-BOS: 6.41±0.04; P>0.05). Coefficient of variation for repeated pH measurements in controls and subjects with and without BOS was 2.3%±0.3%, 2.0%±0.3%, and 1.7%±0.2%, respectively (P>0.05). Similarly, the limits of agreement for between-visit variability determined by the Bland-Altman test were comparable among the study groups.

CONCLUSIONS

These data suggest that assessment of EBC pH is of limited value for the diagnosis of BOS.

The effect of different periods of argon deaeration on exhaled breath condensate pH

BACKGROUND

Exhaled breath condensate (EBC) pH has been considered as a biomarker of airway inflammation in asthma. However, little information is available on the duration of argon deaeration required to achieve a stable pH in EBC samples.

OBJECTIVE

To identify differences in EBC pH after argon deaeration for 2, 4, and 8 min.

METHODS

EBC pH was determined in EBC samples from 48 subjects with allergic rhinitis (11 asthmatics) and 14 healthy volunteers without deaeration and after argon deaeration for 2, 4, and 8 min.

RESULTS

The mean (95% CI) pH values obtained from samples analyzed after 4 min [7.66 (7.52-7.80)] and 8 min [7.70 (7.55-7.85)] of argon deaeration were significantly less acidic (p < .001) than those identified after 2 min of deaeration [7.53 (7.40-7.66)]; differences between pH values at 4 and 8 min were not significant. Furthermore, changes in EBC pH of nondeaerated samples after 4 and 8 min of deaeration were significantly greater than those after 2 min, the mean difference being 0.11 (95% CI, 0.02-0.20, p < .05) and 0.13 (95% CI, 0.04-0.22, p < .01), respectively; differences between changes at 4 and 8 min were not significant.

CONCLUSIONS

Stabilization of EBC pH is achieved after argon deaeration for 4 min. Therefore, this deaeration period may be recommended instead of the 7-8 min used in several studies.

Evaluation of exhaled breath condensate pH as a biomarker for COPD

INTRODUCTION

We assessed the utility of EBC pH as a biomarker in COPD in a large cohort of well-characterised individuals with COPD and control subjects from the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE) study. We also determined short term reproducibility and the response of EBC to oral prednisolone.

METHODS

EBC was collected with R-Tubes(TM), using techniques for sampling and measurement that have been shown to be reproducible.

RESULTS

EBC pH was lower in COPD (n = 676, 7.29 ± SD 0.60) and in smoking controls (n = 31, 7.18 ± 0.85), compared with non-smoking controls (n = 50, 7.59 ± 0.44, p = 0.0008 and 0.0033 respectively), but was not different between COPD and smoking controls. There was no relationship between EBC pH and disease severity, as assessed by the percent predicted FEV(1), nor with airway inflammation as assessed by sputum leukocyte counts. Treatment with 20 mg.day-1 prednisolone for 4 weeks did not change EBC pH.

CONCLUSION

EBC pH is lower in COPD than in healthy control non-smokers, but does not differentiate COPD from smokers without COPD, relate to disease severity or to airway inflammation, and does not respond to corticosteroids. EBC pH therefore does not appear to be a useful biomarker in COPD.

Cough and Asthma

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

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

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

Levels of Exhaled Breath Condensate pH and Fractional Exhaled Nitric Oxide in Retired Coal Miners

Inhaled inorganic dusts, such as coal, can cause inflammation and fibrosis in the lungs, known as pneumoconiosis. Diagnosis of pneumoconiosis depends on morphological changes by radiological findings and functional change by pulmonary function test (PFT) . Unfortunately, current diagnostic findings are limited only to lung fibrosis, which is usually irreversibly progressive. Therefore, it is important that research on potential and prospective biomarkers for pneumoconiosis should be conducted prior to initiation of irreversible radiological or functional changes in the lungs. Analytical techniques using exhaled breath condensate (EBC) or exhaled gas are non-invasive methods for detection of various respiratory diseases. The objective of this study is to investigate the relationship between inflammatory biomarkers, such as EBC pH or fractional exhaled nitric oxide (FENO) , and pneumoconiosis among 120 retired coal miners (41 controls and 79 pneumoconiosis patients) . Levels of EBC pH and FENO did not show a statistically significant difference between the pneumoconiosis patient group and pneumoconiosis patients with small opacity classified by International Labor Organization (ILO) classification. The mean concentration of FENO in the low percentage FEV1 (< 80%) was lower than that in the high percentage (80% ≤) (p = 0.023) . The mean concentration of FENO in current smokers was lower than that in non smokers (never or past smokers) (p = 0.027) . Although there was no statistical significance, the levels of FENO in smokers tended to decrease, compared with non smokers, regardless of pneumoconiosis. In conclusion, there was no significant relationship between the level of EBC pH or FENO and radiological findings or PFT. The effects between exhaled biomarkers and pneumoconiosis progression, such as decreasing PFT and exacerbation of radiological findings, should be monitored.

Assessment of exhaled breath condensate pH in exacerbations of asthma and chronic obstructive pulmonary disease: A longitudinal study

RATIONALE

Exhaled breath condensate pH has been proposed as a noninvasive marker of airway inflammation. However, due to standardization difficulties in pH measurement techniques, different pH readings were obtained in previous studies.

OBJECTIVES

In this longitudinal study we assessed condensate pH in patients with an exacerbation of asthma or chronic obstructive airway disease using the very precise carbon dioxide standardization method that negates the effect of this gas on condensate acidity.

METHODS

Condensate pH, fractional exhaled nitric oxide, lung function, and blood gases were measured in 20 nonsmoking patients with asthma and 21 smoking and 17 ex-smoking patients with chronic obstructive airway disease first at hospital admission due to an acute exacerbation of the disease and again at discharge after treatment. Condensate pH was also assessed in 18 smoking and 18 nonsmoking healthy control subjects.

MEASUREMENTS AND MAIN RESULTS

In patients with asthma, condensate pH was significantly decreased at the time of exacerbation compared with nonsmoking control subjects and increased with treatment. In patients with chronic obstructive airway disease, condensate pH remained unchanged during exacerbation, both in smokers and ex-smokers. Nevertheless, condensates collected from smokers were more acidic than those of ex-smokers. A similar difference was observed between smoker and nonsmoker healthy control subjects. No correlations were found between condensate pH and fractional exhaled nitric oxide or lung function variables measured either at admission or discharge.

CONCLUSIONS

Our data suggest that exacerbation of asthma, but not chronic obstructive airway disease, is associated with acidification of breath condensate.

The paradoxical role of the transient receptor potential vanilloid 1 receptor in inflammation

The transient potential receptor vanilloid 1 (TRPV1) receptor is a non-selective cation channel that is chemically activated by capsaicin, the pungent component of hot peppers. In addition, endogenous compounds, in particular the endogenous cannabinoid receptor activator, anandamide, have been demonstrated to activate TRPV1 in vivo. TRPV1 receptors are also activated by temperatures within the noxious range (>43 degrees C) and low pH (<pH 6.0). TRPV1 receptors are predominantly expressed in primary afferent fibres which are peptidergic sensory neurones, such as the thinly myelinated A-delta and unmyelinated C-fibres. TRPV1 receptors have also been demonstrated to be present in non-neuronal cells. Historically, TRPV1 has been considered as a pro-inflammatory receptor due to its key role in several conditions, including neuropathic pain, joint inflammation and inflammatory bowel disease, amongst others. However, the purpose of this review is to underline the emerging new evidence which demonstrate paradoxical, protective functions for this unique receptor in vivo. For example, in experimentally induced sepsis, TRPV1 null mice demonstrated elevated levels of pathological markers in comparison to wild-type mice. In addition to the pro-inflammatory and protective roles of TRPV1 in pathophysiological states, TRPV1 has also been shown to have important functions under normal physiological conditions, for example in urinary bladder function, thermoregulation and neurogenesis. The emerging functions of TRPV1 highlight the necessity for further research in light of increasing reports of potential TRPV1 antagonists undergoing pre-clinical experimentations.

Magnesium and calcium in exhaled breath condensate of children with asthma and gastroesophageal reflux disease

BACKGROUND

Magnesium and calcium physiologic functions are closely related. Magnesium is primarily an intracellular cation, the action of which also involves maintenance of cellular ionic balance, while influencing calcium homeostasis by blocking calcium channels. The aim of this study was to compare the concentrations of magnesium and calcium in exhaled breath condensate (EBC) of children with asthma and gastroesophageal reflux disease (GERD).

SUBJECTS AND METHODS

EBC was collected from 66 children aged 7-14 years (23 children with acute asthma, 17 children with GERD, and 26 healthy children). Determination of magnesium and calcium concentrations was preceded by optimization and validation for low concentrations.

RESULTS

No difference was recorded for either magnesium or calcium concentration between study groups. However, the magnesium to calcium ratio was statistically significantly lower in both GERD and asthma children as compared with control group.

CONCLUSION

Study results showed the magnesium to calcium ratio to be a statistically significantly better indicator of certain pathologic changes than absolute concentration of either ion.

Exhaled breath condensate hydrogen peroxide and pH for the assessment of lower airway inflammation in the horse

Measurement of hydrogen peroxide (H(2)O(2)) concentration and pH in exhaled breath condensate (EBC) is useful for detection and monitoring of asthma in humans. In contrast, limited information on the use of these parameters for the investigation of lower airway inflammation (LAI) is available for horses. Aims of the current study were to investigate the intra- and inter-day variations of EBC H(2)O(2) concentration and pH in horses and establish any relationship(s) with LAI. Both intra- and inter-day variability of EBC H(2)O(2) concentration were large, while those of pH were small. No significant difference in the intra-day or inter-day H(2)O(2) concentrations or pH measurements were found in control or LAI horses, except for inter-day H(2)O(2) concentration in horses with LAI (p=0.019). There was no significant difference in EBC pH or H(2)O(2) concentration between control and LAI horses, however a trend for a reduced pH in horses with LAI was observed.

Breathtaking TRP channels: TRPA1 and TRPV1 in airway chemosensation and reflex control

New studies have revealed an essential role for TRPA1, a sensory neuronal TRP ion channel, in airway chemosensation and inflammation. TRPA1 is activated by chlorine, reactive oxygen species, and noxious constituents of smoke and smog, initiating irritation and airway reflex responses. Together with TRPV1, the capsaicin receptor, TRPA1 may contribute to chemical hypersensitivity, chronic cough, and airway inflammation in asthma, COPD, and reactive airway dysfunction syndrome.

Eosinophilic airway disorders associated with chronic cough

Chronic cough is a major clinical problem. The causes of chronic cough can be categorized into eosinophilic and noneosinophilic disorders, the former being comprised of asthma, cough variant asthma (CVA), atopic cough (AC) and non-asthmatic eosinophilic bronchitis (NAEB). Cough is one of the major symptoms of asthma. Cough in asthma can be classified into three categories; 1) CVA: asthma presenting solely with coughing, 2) cough-predominant asthma: asthma predominantly presenting with coughing but also with dyspnea and/or wheezing, and 3) cough remaining after treatment with inhaled corticosteroid (ICS) and beta2-agonists in patients with classical asthma, despite control of other symptoms. There may be two subtypes in the last category; one is cough responsive to anti-mediator drugs such as leukotriene receptor antagonists and histamine H1 receptor antagonists, and the other is cough due to co-morbid conditions such as gastroesophageal reflux. CVA is one of the commonest causes of chronic isolated cough. It shares a number of pathophysiological features with classical asthma with wheezing such as atopy, airway hyperresponsiveness (AHR), eosinophilic airway inflammation and various features of airway remodeling. One third of adult patients may develop wheezing and progress to classical asthma. As established in classical asthma, ICS is considered the first-line treatment, which improves cough and may also reduce the risk of progression to classical asthma. AC proposed by Fujimura et al. presents with bronchodilator-resistant dry cough associated with an atopic constitution. It involves eosinophilic tracheobronchitis and cough hypersensitivity and responds to ICS treatment, while lacking in AHR and variable airflow obstruction. These features are shared by non-asthmatic eosinophilic bronchitis (NAEB). However, atopic cough does not involve bronchoalveolar eosinophilia, has no evidence of airway remodeling, and rarely progresses to classical asthma, unlike CVA and NAEB. Histamine H1 antagonists are effective in atopic cough, but their efficacy in NAEB is unknown. AHR of NAEB may improve with ICS within the normal range. Taken together, NAEB significantly overlaps with atopic cough, but might also include milder cases of CVA with very modest AHR. The similarity and difference of these related entities presenting with chronic cough and characterized by airway eosinophilia will be discussed.

Is TRPV1 a useful target in respiratory diseases?

This review focuses on the transient receptor potential vanilloid 1 (TRPV1). TRPV1 is a non-selective cation channel predominantly expressed in the cell membranes of sensory afferent fibers, which are activated multi-modally. In the mammalian respiratory system, immunohistochemical and electrophysiological studies have revealed heterogeneous localizations of TRPV1 channels in the airways and their presence in pleural afferents. TRPV1 channels in afferents are not only involved with sensory inputs, but also release several neuropeptides upon stimulation. These processes trigger pathophysiological effects (e.g. reflex bronchoconstriction, hypersecretion, cough, etc.) that cause various symptoms of airway diseases. Recent studies have identified several endogenous and exogenous substances that can activate TRPV1 in the lung. Because of its key role in initiating inflammatory processes, TRPV1 receptor antagonists have been proposed as therapeutic candidates. Therefore, a critical update of recent therapeutic results is also given in this review.

Normative values for exhaled breath condensate pH and its relationship to exhaled nitric oxide in healthy African Americans

BACKGROUND

Exhaled breath condensate (EBC) pH and exhaled nitric oxide (FeNO) have been proposed as markers of asthma severity. EBC pH values below 6.5 have been associated with asthma exacerbations. Protonation of airway nitrite occurs at low pH and may contribute to FeNO.

OBJECTIVE

To establish normative EBC pH values and to determine the contribution of EBC pH to FeNO in healthy African Americans.

METHODS

Two hundred seventy healthy African American subjects without asthma between 18 and 40 years old were evaluated. Subjects had simultaneous measurement of EBC pH, EBC nitrite, nitrate, and FeNO.

RESULTS

The median EBC pH was 8.14 (interquartile range, 7.83-8.28). Of subjects, 11.9% had an EBC pH < or = 6.5. In subjects with EBC pH values below 6.5, there was an inverse correlation between EBC pH and FeNO (r(2) = 0.158; P = .0245; n = 32). In the entire cohort, there was a direct correlation between EBC pH and EBC nitrite (r(2) = 0.163; P < .0001), but there was no correlation between EBC nitrite and FeNO. In multivariate analyses, EBC pH and nitrite did not contribute significantly to FeNO variation while controlling for other confounders of FeNO.

CONCLUSION

There was an increased prevalence (11.9%) of low EBC pH (less than 6.5) in healthy African American subjects compared with white subjects (<5%). EBC pH and nitrite were directly correlated, but there was no correlation between EBC nitrite and FeNO. FeNO correlated with EBC pH at pH values less than 6.5 in univariate but not multivariate analyses. This suggests that EBC pH and nitrite are not significant determinants of FeNO in healthy subjects.

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.