TRPV1 antagonists as potential antitussive agents

Advancing cough research: Methodological insights into cough challenge in guinea pig models using double chamber vs whole-body plethysmography

OBJECTIVE

This study compares two methods of citric acid-induced cough in guinea pigs in whole-body plethysmography (WBP) and double chamber plethysmography (DCP) to evaluate their efficacy.

METHODS

Sixteen specific pathogen-free (SPF) and sixteen conventionally-bred (CON) animals were exposed to 0.4 M citric acid aerosol. They underwent cough provocation using both DCP and WBP methods. The number of coughs and latency to the first cough were recorded and analysed using statistical methods to determine significant differences between the two techniques.

RESULTS

WBP resulted in significantly higher cough counts (WBP vs. DCP: 13±9 vs 2±3 for SPF; 14±8 vs 5±5 for CON; p<0.0001) and shorter latency (WBP vs. DCP: 59±6 s vs 159±14 s for SPF; 77±4 s vs 112±12 s for CON; p<0.0001) compared to DCP in both groups.

CONCLUSION

Methodological differences substantially impact cough responses. WBP provides a more reliable and physiologically relevant methodology for cough assessment, suggesting the need for standardized protocols in cough research to enhance translational relevance.

Coughing in Small Animal Patients

Cough is one of the most common complaints in human medicine. In veterinary medicine cough is equally frequent and plays a significant role in an owner's perception of their pet's quality of life. In human and veterinary medicine, therapy for chronic cough is often ineffective. The complexity of the cough pathway and species differences have made it difficult to develop an effective antitussive agent for veterinary patients. The few effective antitussive agents currently available are associated with significant adverse effects. Fortunately, several promising drugs currently being studied in human clinical trials may offer options for use of novel antitussive therapies in small animal patients. This article reviews current understanding about cough pathophysiology, diagnostic strategies used to uncover underlying etiology of cough, and examines available options for controlling cough, including novel antitussive therapies used in human medicine.

The Role of Transient Receptor Potential Vanilloid 1 in Common Diseases of the Digestive Tract and the Cardiovascular and Respiratory System

Transient receptor potential vanilloid subtype 1 (TRPV1), a member of the transient receptor potential vanilloid (TRPV) channel family, is a nonselective cation channel that is widely expressed in sensory nerve fibers and nonneuronal cells, including certain vascular endothelial cells and smooth muscle cells. The activation of TRPV1 may be involved in the regulation of various physiological functions, such as the release of inflammatory mediators in the body, gastrointestinal motility function, and temperature regulation. In recent years, a large number of studies have revealed that TRPV1 plays an important role in the physiological and pathological conditions of the digestive system, cardiovascular system, and respiratory system, but there is no systematic report on TRPV1. The objective of this review is to explain the function and effects of TRPV1 on specific diseases, such as irritable bowel syndrome, hypertension, and asthma, and to further investigate the intrinsic relationship between the expression and function of TRPV1 in those diseases to find new therapeutic targets for the cure of related diseases.

Inhibitors of phosphodiesterases in the treatment of cough

A group of 11 enzyme families of metalophosphohydrolases called phosphodiesterases (PDEs) is responsible for a hydrolysis of intracellular cAMP and cGMP. Xanthine derivatives (methylxanthines) inhibit PDEs without selective action on their single isoforms and lead to many pharmacological effects, e.g. bronchodilation, anti-inflammatory and immunomodulating effects, and thus they can modulate the cough reflex. Contrary, selective PDE inhibitors have been developed to inhibit PDE isoforms with different pharmacological effects based on their tissue expression. In this paper, effects of non-selective PDE inhibitors (e.g. theophylline) are discussed, with a description of other putative mechanisms in their effects on cough. Antitussive effects of selective inhibitors of several PDE isoforms are reviewed, focusing on PDE1, PDE3, PDE4, PDE5 and PDE7. The inhibition of PDEs suggests participation of bronchodilation, suppression of TRPV channels and anti-inflammatory action in cough suppression. Selective PDE3, PDE4 and PDE5 inhibitors have demonstrated the most significant cough suppressive effects, confirming their benefits in chronic inflammatory airway diseases associated with bronchoconstriction and cough.

TRPV1 Blocking Alleviates Airway Inflammation and Remodeling in a Chronic Asthma Murine Model

Purpose

Asthma is a chronic inflammatory airway disease characterized by airway hyperresponsiveness (AHR), inflammation, and remodeling. There is emerging interest in the involvement of the transient receptor potential vanilloid 1 (TRPV1) channel in the pathophysiology of asthma. This study examined whether TRPV1 antagonism alleviates asthma features in a murine model of chronic asthma.

Methods

BALB/c mice were sensitized to and challenged by ovalbumin to develop chronic asthma. Capsazepine (TRPV1 antagonist) or TRPV1 small interfering RNA (siRNA) was administered in the treatment group to evaluate the effect of TPV1 antagonism on AHR, airway inflammation, and remodeling.

Results

The mice displayed increased AHR, airway inflammation, and remodeling. Treatment with capsazepine or TRPV1 siRNA reduced AHR to methacholine and airway inflammation. Type 2 T helper (Th2) cytokines (interleukin [IL]-4, IL-5, and IL-13) were reduced and epithelial cell-derived cytokines (thymic stromal lymphopoietin [TSLP], IL-33, and IL-25), which regulate Th2 cytokine-associated inflammation, were also reduced. Airway remodeling characterized by goblet cell hyperplasia, increased α-smooth muscle action, and collagen deposition was also alleviated by both treatments.

Conclusions

Treatment directed at TRPV1 significantly alleviated AHR, airway inflammation, and remodeling in a chronic asthma murine model. The TRPV1 receptor can be a potential drug target for chronic bronchial asthma.

TRPing on the pore phenomenon: what do we know about transient receptor potential ion channel-related pore dilation up to now?

Ion channels allow for rapid ion diffusion through the plasma membrane. In some conditions, ion channels induce changes in the critical plasma membrane permeability that permit 900-Da solutes to enter cells. This process is known as the pore phenomenon. Some transient receptor potential (TRP) channel subtypes have been highlighted such as the P2X7 receptor, plasma membrane VDAC-1 channel, and pannexin hemichannels. The TRP ion channels are considered multimodal transducers that respond to several kinds of stimuli. In addition, many TRP channel subtypes are involved in physiological and pathophysiological processes such as inflammation, pain, and cancer. The TRPA1, TRPM8, and TRPV1-4 subtypes have been shown to promote large-molecular-weight solute uptake, including impermeable fluorescent dyes, QX-314 hydrophilic lidocaine derivative, gabapentin, and antineoplastic drugs. This review discusses the current knowledge of TRP-associated pores and encourages scientists to study their features and explore them as novel therapeutic tools.

TRPV1 modulators: Synthesis and in vitro evaluation of 1-heteroaryl piperidinecarboxamide and piperazinylurea derivatives

A series of new 1-heteroaryl piperidinecarboxamide and piperazinylurea derivatives was synthesized and evaluated as TRPV1 modulators in a Ca(2+) channel assay in HEK-293 cells overexpressing the human recombinant TRPV1 channel. Structural variations in the putative key portions of the molecules afforded several compounds endowed with agonist and/or antagonist/desensitizing activity at low micromolar concentration. As promising examples from this series, the piperidine-3-carboxamide derivative 31 exerts agonist/desensitizing activity at low micromolar concentration, while piperazinylurea derivatives 39 and 41 act as antagonists with sub-micromolar potency.

Preliminary study on pathogenesis of bronchial asthma in children

BACKGROUND

The etiology and pathogenesis of bronchial asthma remain unclear. This study is to investigate the risk factors related to bronchial asthma onset in children from genetics and immunology and preliminarily reveal the pathogenesis of bronchial asthma in children.

METHODS

Real-time quantitative PCR was adopted to detect the expression level of TRPV1 gene and mRNA and enzyme-linked immunosorbent assay method to the total immunoglobulin E level and levels of IL-4, IL-5, and IFN-γ in serum in peripheral venous blood for children in two groups. Logistic regression analysis was applied to analyze the most essential factors inducing bronchial asthma in children.

RESULTS

The mRNA level of TRPV1 in peripheral blood in the case group was higher than that in the control group (P < 0.01). The levels of IL-4, IL-5, and eosinophils in serum in the case group were markedly higher than those in the control group (P < 0.01), while IFN-γ level in the case group was lower than that in the control group (P < 0.01). The results of logistic regression analysis indicated that TRPV1 expression level, IL-4 level, and rs4790522 site mutation were the main risk factors inducing bronchial asthma in children.

CONCLUSION

The levels of TRPV1 gene expression and Th1/Th2 cytokines have a close relationship with asthma onset in children, which provides theoretical evidences for molecular targeted treatment in children with bronchial asthma.

In silico research to assist the investigation of carboxamide derivatives as potent TRPV1 antagonists

The transient receptor potential vanilloid type 1 (TRPV1), a non-selective cation channel, is known for its essential role in the pathogenesis of various pain conditions such as nerve damage induced hyperalgesia, diabetic neuropathy and cancer pain.

Recent additions in the treatment of cough

BACKGROUND

Worldwide, cough is regarded as a challenging clinical problem due to its frequency and often limited therapeutic options. Chronic cough that remains refractory to usual medical treatment causes significant quality of life impairment in people with this problem.

METHODS

We have examined current evidence on recent additions in the treatment of cough, specifically treatment of refractory chronic cough with speech pathology and gabapentin. Relevant randomised control trials, reviews and case reports were identified through a PubMed and SCOPUS search of English-language literature referring to these concepts over the last eight years.

SUMMARY

Of the one hundred and two articles comprising this review the majority investigated the role of the transient receptor potential (TRP) receptors TRP Vanilloid 1 (TRPV1) and TRPA1 in cough and the potential of TRP antagonists as effective anti-tussives. However, these have only been tested in the laboratory and therefore their clinical effectiveness is unknown. Behavioural treatments such as speech pathology have gained momentum and this was evident in the increasing number of articles investigating its positive effect on cough. Investigation on the effectiveness of neuromodulating medications in the treatment of cough have been supported primarily through case series reports and prospective reviews however; their use (particularly gabapentin) has been significantly advanced through recently conducted randomised controlled trials.

CONCLUSIONS

Recent additions in the treatment of chronic cough have been significant as they consider cough to have a unifying diagnosis of cough hypersensitivity with or without the presence of a neuropathic basis. Primarily, effective treatments for chronic cough target these areas and include behavioural treatment such as speech pathology and pharmaceutical treatment with neuromodulating medications such as gabapentin.

Linoleic acid metabolite drives severe asthma by causing airway epithelial injury

Airway epithelial injury is the hallmark of various respiratory diseases, but its mechanisms remain poorly understood. While 13-S-hydroxyoctadecadienoic acid (13-S-HODE) is produced in high concentration during mitochondrial degradation in reticulocytes little is known about its role in asthma pathogenesis. Here, we show that extracellular 13-S-HODE induces mitochondrial dysfunction and airway epithelial apoptosis. This is associated with features of severe airway obstruction, lung remodeling, increase in epithelial stress related proinflammatory cytokines and drastic airway neutrophilia in mouse. Further, 13-S-HODE induced features are attenuated by inhibiting Transient Receptor Potential Cation Channel, Vanilloid-type 1 (TRPV1) both in mouse model and human bronchial epithelial cells. These findings are relevant to human asthma, as 13-S-HODE levels are increased in human asthmatic airways. Blocking of 13-S-HODE activity or disruption of TRPV1 activity attenuated airway injury and asthma mimicking features in murine allergic airway inflammation. These findings indicate that 13-S-HODE induces mitochondrial dysfunction and airway epithelial injury.

TRPV1 inhibition attenuates IL-13 mediated asthma features in mice by reducing airway epithelial injury

Even though neurogenic axis is well known in asthma pathogenesis much attention had not been given on this aspect. Recent studies have reported the importance of TRP channels, calcium-permeable ion channels and key molecules in neurogenic axis, in asthma therapeutics. The role of TRPV1 channels has been underestimated in chronic respiratory diseases as TRPV1 knockout mice of C57BL/6 strains did not attenuate the features of these diseases. However, this could be due to strain differences in the distribution of airway capsaicin receptors. Here, we show that TRPV1 inhibition attenuates IL-13 induced asthma features by reducing airway epithelial injury in BALB/c mice. We found that IL-13 increased not only the lung TRPV1 levels but also TRPV1 expression in bronchial epithelia in BALB/c rather than in C57BL/6 mice. TRPV1 knockdown attenuated airway hyperresponsiveness, airway inflammation, goblet cell metaplasia and subepithelial fibrosis induced by IL-13 in BALB/c mice. Further, TRPV1 siRNA treatment reduced not only the cytosolic calpain and mitochondrial calpain 10 activities in the lung but also bronchial epithelial apoptosis indicating that TRPV1 siRNA might have corrected the intracellular and intramitochondrial calcium overload and its consequent apoptosis. Knockdown of IL-13 in allergen induced asthmatic mice reduced TRPV1, cytochrome c, and activities of calpain and caspase 3 in lung cytosol. Thus, these findings suggest that induction of TRPV1 with IL-13 in bronchial epithelia could lead to epithelial injury in in vivo condition. Since TRPV1 expression is correlated with human asthma severity, TRPV1 inhibition could be beneficial in attenuating airway epithelial injury and asthma features.

Mechanisms underlying the augmentation of phenylbiguanide and capsaicin induced cardiorespiratory reflexes by Mesobuthus tamulus venom

Phenylbiguanide (PBG) and capsaicin evoke cardiorespiratory reflexes utilizing two separate pathways. It is known that Indian Red Scorpion (Mesobuthus tumulus; MBT) venom augments PBG (5-HT(3)) responses but, the effect of MBT venom on capsaicin (TRPV1)-induced response is not known. Therefore, the present study was undertaken to ascertain whether MBT venom also augments the capsaicin-induced reflex responses involving mechanisms similar to PBG. Experiments were performed on anaesthetized adult rats. Blood pressure, respiratory excursions and ECG were recorded. At the end of each experiment pulmonary water content was determined. PBG (10 μg/kg) produced hypotension, bradycardia and apnoea-bradypnoea. Capsaicin (10 μg/kg) also produced hypotension, bradycardia and apnoea-bradypnoea. MBT venom (100 μg/kg) augmented PBG as well as capsaicin-induced responses and produced pulmonary oedema (increased pulmonary water content). Prostaglandin synthase inhibitor (indomethacin; 10 mg/kg) blocked the venom-induced augmentation of PBG and capsaicin reflexes. Kinin synthase inhibitor (aprotinin; 6000 KIU) and guanylate cyclase (GC) inhibitor (methylene blue; 5 mg/kg) blocked the venom-induced augmentation of PBG response but not the capsaicin response. However, pulmonary oedema was blocked by these antagonists. Phosphodiesterase V inhibitor (sildenafil; 100 μg/kg) augmented the PBG response but not the capsaicin response, though pulmonary oedema was seen in both the groups. The present results indicate that MBT venom also augments the capsaicin-induced responses. The augmentation of capsaicin response involves PGs and pulmonary oedema-independent mechanisms whereas, the augmentation of PBG response involves kinin mediated GC-cGMP pathway and pulmonary oedema-dependent mechanisms.

Involvement of nitric oxide (NO) in cough reflex sensitivity between non-sensitized and OVA-sensitized guinea pigs

Background

Exhaled nitric oxide (ENO) is elevated in bronchial asthma patients, and inhaled corticosteroid therapy lowers the elevated ENO levels in such patients. ENO appears to be an inflammatory marker, but its role in the pathophysiology of cough remains unclear. This study aimed to elucidate the relationship between NO and increased cough reflex sensitivity induced by allergic airway reactions.

Methods

Cough reflex sensitivity to inhaled capsaicin was observed under NO depletion caused by NO synthase (NOS) inhibitors in non-sensitized and ovalbumin (OVA)-sensitized guinea pigs. The bronchoalveolar lavage fluid (BALF) was analyzed in an NO depletion setting using the inducible NOS (iNOS) inhibitor ONO1714 in OVA-sensitized guinea pigs.

Results

NO depletion by the non-selective NOS inhibitor L-NAME suppressed cough reflex sensitivity in non-sensitized guinea pigs and OVA-induced increase in cough reflex sensitivity in sensitized guinea pigs; however, iNOS inhibition caused by ONO1714 partially suppressed the OVA-induced increase in cough reflex sensitivity, but not the normal cough response in non-sensitized guinea pigs. ONO1714 did not change BAL cell components in OVA-sensitized guinea pigs.

Conclusions

The results suggest that NO may be involved not only in the normal cough reflex circuit, but also in the OVA-induced increase in cough reflex sensitivity, possibly via a different mechanism of action. Further studies are needed to clarify the precise mechanism.

Pharmacologic therapy for cough

Cough is the commonest symptom for which patients seek medical care and yet effective, well-tolerated cough medicines remain a significant unmet clinical need. The development of anti-tussive agents has probably been restricted by a number of factors; our understanding of the specific mechanisms evoking cough in different diseases and how this differs from the role of cough as a protective reflex is limited. Also well-validated tools for the assessment of cough have been lacking. These issues have not encouraged investment by the pharmaceutical industry and there have been no new licensed treatments for cough in more than 50 years. This article will use a mechanism-based approach to discuss the clinical evidence for the anti-tussive activity of currently available agents.

TRPV1 as a cough sensor and its temperature-sensitive properties

In the respiratory tract, TRPV1, a non-selective cation channel and a polymodal transducer, is expressed primarily in non-myelinated sensory nerves. A significant role of TRPV1 in eliciting the cough reflex has been extensively documented. Inhalation of capsaicin aerosol, a selective agonist of TRPV1, consistently and reproducibly evoked coughs in a dose-dependent manner in both healthy humans and in patients with airway inflammatory diseases. A number of endogenous inflammatory mediators known to upregulate the TRPV1 sensitivity, such as prostaglandin E(2) and bradykinin, also enhanced the cough sensitivity. Furthermore, a substantial increase of TRPV1-immunoreactive nerve profiles was found in the bronchial tissue of patients with chronic cough. In addition to the cough reflex, activation of TRPV1-expressing sensory nerves in the airways is also known to elicit reflex bronchoconstriction and mucus secretion mediated through cholinergic pathways. One of the physiological stimuli known to activate TRPV1 receptor directly is high temperature. Recent studies have demonstrated that increasing temperature within the normal physiological range significantly elevated the baseline activity and sensitivity of isolated rat vagal pulmonary sensory neurons, and the sensitizing effect of hyperthermia appeared to be mediated selectively through the TRPV1 channel. This temperature-sensitive property of TRPV1 may play an important role in regulating the physiological function of the TRPV1-expressing airway sensory nerves and the sensitivity of their reflex responses, such as cough and reflex bronchoconstriction.

Rhinogenic laryngitis, cough, and the unified airway

Over the past 10 years, there has been increasing recognition of the interaction between the upper and lower airways in patients with a variety of infectious and inflammatory illnesses, including allergic rhinitis, rhinosinusitis, and asthma. Epidemiologic and mechanistic links have been proposed to demonstrate these relationships and to offer possible etiologic explanations to account for these observations. Among patients with upper respiratory illnesses, cough can be seen as a common symptom, both from the direct influences of upper airway inflammation, which incite reflex changes and bronchospasm, and from the exacerbation of associated pulmonary processes, such as asthma. Despite this increasing awareness of interaction between the upper and lower airways, the influence of both upstream and downstream respiratory inflammatory processes on laryngeal pathophysiology has not been extensively studied. Research suggests, however, that both direct stimulatory effects on the larynx and secondary effects of mucus production and mucus trafficking can create a range of laryngeal symptoms, including cough. This review discusses the interaction of the upper and lower airway in respiratory disease, and focuses on the effect of these respiratory processes on laryngeal inflammation, function, and symptoms.

Unexplained cough in the adult

Unexplained cough is a diagnosis of exclusion that should not be made until a thorough validated diagnostic evaluation is performed, specific and appropriate validated treatments have been tried and failed, and uncommon causes have been ruled out. When chronic cough remains troublesome after the initial work up, determine that a protocol has been used that has been shown to lead to successful results. If such a protocol has been used, next consider whether or not pitfalls in management have been avoided. If they have been, the frequency of truly unexplained chronic cough usually should not exceed 10%. While patients with truly unexplained coughs have an overly sensitive cough reflex, the mere presence of an overly sensitive cough reflex does not by itself explain why they do not get better, because most patients with chronic cough, even those who respond to treatment and get better, have demonstrable heightened cough sensitivity. Management options include referral to a cough clinic with interdisciplinary expertise, speech therapy, and self-limited trials of drugs, preferentially with those shown to be effective in randomized, double-blind placebo-controlled trials in patients with unexplained chronic cough.

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.

Spiro-piperidine azetidinones as potent TRPV1 antagonists

A series of spiro-piperidine azetidinone were synthesized and evaluated as potential TRPV1 antagonists. An important issue of plasma stability was investigated and resolved. Further focused SAR study lead to the discovery of a potent antagonist with good oral pharmacokinetic profile in rat.

The pharmacological challenge to tame the transient receptor potential vanilloid-1 (TRPV1) nocisensor

The transient receptor potential vanilloid-1 (TRPV1) cation channel is a receptor that is activated by heat (>42 degrees C), acidosis (pH<6) and a variety of chemicals among which capsaicin is the best known. With these properties, TRPV1 has emerged as a polymodal nocisensor of nociceptive afferent neurones, although some non-neuronal cells and neurones in the brain also express TRPV1. The activity of TRPV1 is controlled by a multitude of regulatory mechanisms that either cause sensitization or desensitization of the channel. As many proalgesic pathways converge on TRPV1 and this nocisensor is upregulated and sensitized by inflammation and injury, TRPV1 is thought to be a central transducer of hyperalgesia and a prime target for the pharmacological control of pain. As a consequence, TRPV1 agonists causing defunctionalization of sensory neurones and a large number of TRPV1 blockers have been developed, some of which are in clinical trials. A major drawback of many TRPV1 antagonists is their potential to cause hyperthermia, and their long-term use may carry further risks because TRPV1 has important physiological functions in the peripheral and central nervous system. The challenge, therefore, is to pharmacologically differentiate between the physiological and pathological implications of TRPV1. There are several possibilities to focus therapy specifically on those TRPV1 channels that contribute to disease processes. These approaches include (i) site-specific TRPV1 antagonists, (ii) modality-specific TRPV1 antagonists, (iii) uncompetitive TRPV1 (open channel) blockers, (iv) drugs interfering with TRPV1 sensitization, (v) drugs interfering with intracellular trafficking of TRPV1 and (vi) TRPV1 agonists for local administration.

TRPA1 is a major oxidant sensor in murine airway sensory neurons

Sensory neurons in the airways are finely tuned to respond to reactive chemicals threatening airway function and integrity. Nasal trigeminal nerve endings are particularly sensitive to oxidants formed in polluted air and during oxidative stress as well as to chlorine, which is frequently released in industrial and domestic accidents. Oxidant activation of airway neurons induces respiratory depression, nasal obstruction, sneezing, cough, and pain. While normally protective, chemosensory airway reflexes can provoke severe complications in patients affected by inflammatory airway conditions like rhinitis and asthma. Here, we showed that both hypochlorite, the oxidizing mediator of chlorine, and hydrogen peroxide, a reactive oxygen species, activated Ca(2+) influx and membrane currents in an oxidant-sensitive subpopulation of chemosensory neurons. These responses were absent in neurons from mice lacking TRPA1, an ion channel of the transient receptor potential (TRP) gene family. TRPA1 channels were strongly activated by hypochlorite and hydrogen peroxide in primary sensory neurons and heterologous cells. In tests of respiratory function, Trpa1(-/-) mice displayed profound deficiencies in hypochlorite- and hydrogen peroxide-induced respiratory depression as well as decreased oxidant-induced pain behavior. Our results indicate that TRPA1 is an oxidant sensor in sensory neurons, initiating neuronal excitation and subsequent physiological responses in vitro and in vivo.

Cough, basic science, and the clinician

Cough is a major cause of disability and distress worldwide. In June 2007, the First American Cough Conference was held in New York City and covered a spectrum of topics of interest to the basic scientist as well as the clinician. The conference was organized by Dr. Peter Dicpinigaitis and its proceedings are published in the February Supplement of LUNG. This supplement consists of a series of articles that provide a valuable overview of recent advances in our understanding of mechanism, etiology, and treatment of cough and constitute an adjunct to the guidelines recently published by the American College of Chest Physicians, the British Thorax Society, the European Respiratory Society, and the Japanese Respiratory Society.