Is reactive airways dysfunction syndrome a variant of occupational asthma?

Verification of chlorine exposure via LC-MS/MS analysis of base hydrolyzed chlorophenols from chlorotyrosine-protein adducts

Inhalation of chlorine gas, with subsequent hydrolysis in the airway and lungs to form hydrochloric acid (HCl) and hypochlorous acid (HOCl), can cause pulmonary edema (i.e., fluid build-up in the lungs), pulmonary inflammation (with or without infection), respiratory failure, and death. The HOCl produced from chlorine is known to react with tyrosine to form adducts via electrophilic aromatic substitution, resulting in 3-chlorotyrosine and 3,5-dichlorotyrosine adducts. While several analysis methods are available for determining these adducts, each method has significant disadvantages. Hence, a simple and sensitive ultra-high performance liquid chromatography-tandem mass spectroscopy (UHPLC-MS/MS) method was developed for the determination of chlorotyrosine adducts. The sample preparation involves base hydrolysis of isolated plasma proteins to form 2-chlorophenol (CP) from monochlorotyrosine adducts and 2,6-dichlorophenol (2,6-DCP), from dichlorotyrosine adducts, as markers of chlorine exposure. The chlorophenols are extracted with cyclohexane prior to UHPLC-MS/MS analysis. The method produced excellent sensitivity for 2,6-DCP with a limit of detection of 2.2 μg/kg, calibration curve linearity extending from 0.054-54 mg/kg (R2 ≥ 0.9997 and %RA > 94), and accuracy and precision of 100 ± 14 %, and <15 % relative standard deviation, respectively. The sensitivity of the method for 2-CP was relatively poor, so it was used only as a secondary marker for severe chlorine exposure. The method successfully detected elevated levels of 2,6-DCP from hypochlorite-spiked plasma protein and plasma protein isolated from chlorine-exposed rats.

Clinical Characteristics of Irritant-Induced Occupational Asthma

BACKGROUND

Work is a substantial contributing factor of adult-onset asthma. A subtype of occupational asthma (OA) is caused by irritant agents, but knowledge of the clinical outcomes of irritant-induced asthma (IIA) is incomplete.

OBJECTIVES

To evaluate whether the clinical picture of IIA differs from that of sensitizer-induced OA.

METHODS

This retrospective study analyzed acute and subacute IIA patients diagnosed in an occupational medicine clinic during 2004 to 2018. Sixty-nine patients fulfilled the inclusion criteria, and their characteristics were analyzed at the time of the diagnosis and 6 months later. The results were compared with those of 2 subgroups of sensitizer-induced OA: 69 high-molecular-weight (HMW) and 89 low-molecular-weight (LMW) agent-induced OA patients.

RESULTS

Six months after the diagnosis, 30% of the patients with IIA needed daily short-acting β-agonists (SABA), 68% were treated with Global Initiative for Asthma, 2020 report (GINA) step 4-5 medication, and 24% of the patients had asthma exacerbation after the first appointment. IIA depicted inferiority to LMW-induced OA in daily need for SABA (odds ratio [OR]: 3.80, 95% confidence interval [CI]: 1.38-10.46), treatment with GINA step 4-5 medication (OR: 2.22, 95% CI: 1.08-4.57), and exacerbation (OR: 3.85, 95% CI: 1.35-11.04). IIA showed poorer results than HMW-induced OA in the latter 2 of these features (OR: 2.49, 95% CI: 1.07-5.79 and OR: 6.29, 95% CI: 1.53-25.83, respectively).

CONCLUSIONS

Six months after the OA diagnosis, a significant proportion of the patients with IIA remain symptomatic and the majority of these patients use asthma medications extensively suggesting uncontrolled asthma. The short-term outcomes of IIA appear poorer than that of sensitizer-induced OA.

Reactive airways dysfunction syndrome following inhalation of hydrogen chloride vapor

Hydrogen chloride is available commercially as an anhydrous gas or an aqueous solution, hydrochloric acid. Exposure to this gas has been associated with the development of reactive airways dysfunction syndrome. However, there are few published reports. A 37-year-old woman developed progressive bronchospasm and acute respiratory failure after cleaning an enclosed space with an unknown concentration of hydrochloric acid gas from a cleaning substance. She had no prior history of asthma or atopy. Severe bronchospasm developed, leading to hypoxemia and diffuse interstitial infiltrates, necessitating orotracheal intubation and admission to the intensive care unit. Asthma-like symptoms such as cough, wheezing, and dyspnea; requiring bronchodilators, and repeated hospitalizations are persistent a year after the accident. Pulmonary function testing showed mild airflow obstruction.

Occupations and exposure events in acute and subacute irritant-induced asthma

Background

Exposures leading to irritant-induced asthma (IIA) are poorly documented.

Methods

We retrospectively screened the medical records of patients with IIA diagnosed in an occupational medicine clinic during 2000–2018. We classified the cases into acute (onset after single exposure) and subacute (onset after multiple exposures) IIA. We analysed in detail, occupations, causative agents and their air levels in the workplace, exposure events and the root causes of high exposure.

Results

Altogether 69 patients were diagnosed with IIA, 30 with acute and 39 with subacute IIA. The most common occupational groups were industrial operators (n=23, 33%), metal and machinery workers (n=16, 11%) and construction workers (n=12, 8%). Among industrial operators significantly more cases had subacute IIA than acute IIA (p=0.002). Forty cases (57%) were attributable to some type of corrosive acidic or alkaline chemical. Acute IIA followed accidents at work in different types of occupation, while subacute IIA was typical among industrial operators performing their normal work tasks under poor work hygiene conditions. The most common root cause was lack of information or false guidance in acute IIA (n=11, 36%) and neglect of workplace hygiene measures in subacute IIA (n=29, 74%).

Conclusions

Accidents are the main causes of acute IIA, whereas subacute IIA can develop in normal work in risk trades with poor work hygiene. Airborne strong acids or bases seem to be the most important causative agents of acute and subacute IIA. The different risk profiles of acute and subacute IIA should be considered in the prevention and identification of the cases.

Clinical Presentations and Outcomes of Industrial Chlorine Gas Exposure Incidence in Oman

OBJECTIVE

The main objective was to study different clinical presentations and outcomes of patients after acute industrial chlorine gas exposure in Oman with evaluation of overall incident management to help develop a chemical exposure incident protocol.

METHODS

This was a retrospective observational study of 15 patients exposed to chlorine gas after an accidental chlorine gas leak in a metal melting factory in Oman.

RESULTS

Six (40%) patients were admitted and nine (60%) patients were discharged from the emergency department (ED) after initial management. The important post-chlorine gas exposure clinical symptoms were eye irritation (66.6%), cough (73.3%), shortness of breath (40.0%), chest discomfort (66.6%), rhinorrhea (66.6%), dizziness (40.0%), vomiting (46.6%), sore throat (13.3%), and stridor (53.3%). Important signs included tachycardia (40.0%), tachypnea (40.0%), wheeze (20.0%), and use of accessory muscles for breathing (20.0%). Signs and symptoms of eye irritation, rhinorrhea, tachycardia, tachypnea, wheeze, and use of accessory muscles for breathing have shown significant correlation with outcome (admission) having P value of <.05.

CONCLUSION

In the presented acute chlorine gas exposure incidence, 15 exposed persons were brought to the ED, out of which six were admitted and nine were discharged after symptomatic treatment. Signs and symptoms of eye irritation, rhinorrhea, tachycardia, tachypnea, wheeze, and use of accessory muscles of breathing show significant relation with the outcome of admission.

Acute lung injury and persistent small airway disease in a rabbit model of chlorine inhalation

Chlorine is a pulmonary toxicant to which humans can be exposed through accidents or intentional releases. Acute effects of chlorine inhalation in humans and animal models have been well characterized, but less is known about persistent effects of acute, high-level chlorine exposures. In particular, animal models that reproduce the long-term effects suggested to occur in humans are lacking. Here, we report the development of a rabbit model in which both acute and persistent effects of chlorine inhalation can be assessed. Male New Zealand White rabbits were exposed to chlorine while the lungs were mechanically ventilated. After chlorine exposure, the rabbits were extubated and were allowed to survive for up to 24h after exposure to 800ppm chlorine for 4min to study acute effects or up to 7days after exposure to 400ppm for 8min to study longer term effects. Acute effects observed 6 or 24h after inhalation of 800ppm chlorine for 4min included hypoxemia, pulmonary edema, airway epithelial injury, inflammation, altered baseline lung mechanics, and airway hyperreactivity to inhaled methacholine. Seven days after recovery from inhalation of 400ppm chlorine for 8min, rabbits exhibited mild hypoxemia, increased area of pressure-volume loops, and airway hyperreactivity. Lung histology 7days after chlorine exposure revealed abnormalities in the small airways, including inflammation and sporadic bronchiolitis obliterans lesions. Immunostaining showed a paucity of club and ciliated cells in the epithelium at these sites. These results suggest that small airway disease may be an important component of persistent respiratory abnormalities that occur following acute chlorine exposure. This non-rodent chlorine exposure model should prove useful for studying persistent effects of acute chlorine exposure and for assessing efficacy of countermeasures for chlorine-induced lung injury.

Persistent effects of chlorine inhalation on respiratory health

Chlorine gas is a toxic respiratory irritant that is considered a chemical threat agent because of the potential for release in industrial accidents or terrorist attacks. Chlorine inhalation damages the respiratory tract, including the airways and distal lung, and can result in acute lung injury. Some individuals exposed to chlorine experience a full recovery from acute injury, whereas others develop persistent adverse effects, such as respiratory symptoms, inflammation, and lung-function decrements. In animal models, chlorine can produce persistent inflammation, remodeling, and obstruction in large or small airways, depending on species. Airways with pseudostratified epithelia are repaired efficiently, with surviving basal epithelial cells serving as progenitor cells that repopulate the complement of differentiated cell types. Distal airways lacking basal cells are repaired less efficiently, leading to chronic inflammation and fibrosis at these sites. Persistent chlorine-induced airway disease in humans is treated with asthma medication to relieve symptoms. However, such treatment does not ameliorate the underlying disease pathogenesis, so treatments that are more effective at preventing initial development of airway disease after irritant gas exposure and at reversing established disease are needed.

Abnormal epithelial structure and chronic lung inflammation after repair of chlorine-induced airway injury

Chlorine is a toxic gas used in a variety of industrial processes and is considered a chemical threat agent. High-level chlorine exposure causes acute lung injury, but the long-term effects of acute chlorine exposure are unclear. Here we characterized chronic pulmonary changes following acute chlorine exposure in mice. A/J mice were exposed to 240 parts per million-hour chlorine or sham-exposed to air. Chlorine inhalation caused sloughing of bronchial epithelium 1 day after chlorine exposure, which was repaired with restoration of a pseudostratified epithelium by day 7. The repaired epithelium contained an abnormal distribution of epithelial cells containing clusters of club or ciliated cells rather than the uniformly interspersed pattern of these cells in unexposed mice. Although the damaged epithelium in A/J mice was repaired rapidly, and minimal airway fibrosis was observed, chlorine-exposed mice developed pneumonitis characterized by infiltration of alveoli with neutrophils and prominent, large, foamy macrophages. Levels of CXCL1/KC, CXCL5/LPS-induced CXC chemokine, granulocyte colony-stimulating factor, and VEGF in bronchoalveolar (BAL) fluid from chlorine-exposed mice showed steadily increasing trends over time. BAL protein levels were increased on day 4 and remained elevated out to day 28. The number of bacteria cultured from lungs of chlorine-exposed mice 4 wk after exposure was not increased compared with sham-exposed mice, indicating that the observed pneumonitis was not driven by bacterial infection of the lung. The results indicate that acute chlorine exposure may cause chronic abnormalities in the lungs despite rapid repair of injured epithelium.

Acute health effects of accidental chlorine gas exposure

OBJECTIVES

This study was conducted to report the course of an accidental release of chlorine gas that occurred in a factory in Gumi-si, South Korea, on March 5, 2013. We describe the analysis results of 2 patients hospitalized because of chlorine-induced acute health problems, as well as the clinical features of 209 non-hospitalized patients.

METHODS

We analyzed the medical records of the 2 hospitalized patients admitted to the hospital, as well as the medical records and self-report questionnaires of 209 non-hospitalized patients completed during outpatient treatment.

RESULTS

Immediately after the exposure, the 2 hospitalized patients developed acute asthma-like symptoms such as cough and dyspnea, and showed restrictive and combined pattern ventilatory defects on the pulmonary function test. The case 1 showed asthma-like symptoms over six months and diurnal variability in peak expiratory flow rate was 56.7%. In case 2, his FEV1 after treatment (93%) increased by 25% compared to initial FEV1 (68%). Both cases were diagnosed as chlorine-induced reactive airways dysfunction syndrome (RADS) on the basis of these clinical features. The most frequent chief complaints of the 209 non-hospitalized patients were headache (22.7%), followed by eye irritation (18.2%), nausea (11.2%), and sore throat (10.8%), with asymptomatic patients accounting for 36.5%. The multiple-response analysis of individual symptom revealed headache (42.4%) to be the most frequent symptom, followed by eye irritation (30.5%), sore throat (30.0%), cough (29.6%), nausea (27.6%), and dizziness (27.3%).

CONCLUSIONS

The 2 patients hospitalized after exposure to chlorine gas at the leakage site showed a clinical course corresponding to RADS. All of the 209 non-hospitalized patients only complained of symptoms of the upper airways and mucous membrane irritation.

EAACI position paper: irritant-induced asthma

The term irritant-induced (occupational) asthma (IIA) has been used to denote various clinical forms of asthma related to irritant exposure at work. The causal relationship between irritant exposure(s) and the development of asthma can be substantiated by the temporal association between the onset of asthma symptoms and a single or multiple high-level exposure(s) to irritants, whereas this relationship can only be inferred from epidemiological data for workers chronically exposed to moderate levels of irritants. Accordingly, the following clinical phenotypes should be distinguished within the wide spectrum of irritant-related asthma: (i) definite IIA, that is acute-onset IIA characterized by the rapid onset of asthma within a few hours after a single exposure to very high levels of irritant substances; (ii) probable IIA, that is asthma that develops in workers with multiple symptomatic high-level exposures to irritants; and (iii) possible IIA, that is asthma occurring with a delayed-onset after chronic exposure to moderate levels of irritants. This document prepared by a panel of experts summarizes our current knowledge on the diagnostic approach, epidemiology, pathophysiology, and management of the various phenotypes of IIA.

The Immediate Pulmonary Disease Pattern following Exposure to High Concentrations of Chlorine Gas

Background. Classification of pulmonary disease into obstructive, restrictive, and mixed patterns is based on 2005 ATS/ERS guidelines and modified GOLD criteria by Mannino et al. (2003), but these guidelines are of limited use for simple spirometry in situations involving mass casualties. Aim. The purpose of this study was to apply these guidelines to patients who underwent simple spirometry following high concentration of chlorine gas inhalation after a train derailment in Graniteville, South Carolina. Methods. We retrospectively investigated lung functions in ten patients. In order to classify pulmonary disease pattern, we used 2005 ATS/ERS guidelines and modified GOLD criteria along with our own criteria developed using available simple spirometry data. Results. We found predominant restrictive pattern in our patients with both modified GOLD and our criteria, which is in contrast to other chlorine exposure studies where obstructive pattern was more common. When compared to modified GOLD and our criteria, 2005 ATS/ERS guidelines underestimated the frequency of restrictive disease. Conclusion. Diagnosis of pulmonary disease patterns is of importance after irritant gas inhalation. Acceptable criteria need to be developed to evaluate pulmonary disease through simple spirometry in events leading to mass casualty and patient surge in hospitals.

Elevated peripheral eosinophils are associated with new-onset and persistent wheeze and airflow obstruction in world trade center-exposed individuals

BACKGROUND

Exposure to World Trade Center (WTC) dust and fumes is associated with the onset of asthma-like respiratory symptoms in rescue and recovery workers and exposed community members. Eosinophilic inflammation with increased lung and peripheral eosinophils has been described in subpopulations with asthma. We hypothesized that persistent asthma-like symptoms in WTC-exposed individuals would be associated with systemic inflammation characterized by peripheral eosinophils.

METHODS

The WTC Environmental Health Center (WTC EHC) is a treatment program for local residents, local workers, and cleanup workers with presumed WTC-related symptoms. Patients undergo a standardized evaluation including questionnaires and complete blood count. Between September 2005 and March 2009, 2462 individuals enrolled in the program and were available for analysis. Individuals with preexisting respiratory symptoms or lung disease diagnoses prior to September 2001 and current or significant tobacco use were excluded,

RESULTS

One thousand five hundred and seventeen individuals met the inclusion criteria. Patients had a mean age of 47 years, were mostly female (51%), and had a diverse race/ethnicity. Respiratory symptoms that developed after WTC dust/fume exposure and remained persistent included dyspnea on exertion (68%), cough (57%), chest tightness (47%), and wheeze (33%). A larger percentage of patients with wheeze had elevated peripheral eosinophils compared with those without wheeze (21% vs. 13%, p < .0001). Individuals with elevated peripheral eosinophils were more likely to have airflow obstruction on spirometry (16% vs. 7%, p = .0003).

CONCLUSION

Peripheral eosinophils were associated with wheeze and airflow obstruction in a diverse WTC-exposed population. These data suggest that eosinophils may participate in lung inflammation in this population with symptoms consistent with WTC-related asthma.

Differential susceptibility of inbred mouse strains to chlorine-induced airway fibrosis

Chlorine is a reactive gas that is considered a chemical threat agent. Humans who develop acute lung injury from chlorine inhalation typically recover normal lung function; however, a subset can experience chronic airway disease. To examine pathological changes following chlorine-induced lung injury, mice were exposed to a single high dose of chlorine, and repair of the lung was analyzed at multiple times after exposure. In FVB/NJ mice, chlorine inhalation caused pronounced fibrosis of larger airways that developed by day 7 after exposure and was associated with airway hyperreactivity. In contrast, A/J mice had little or no airway fibrosis and had normal lung function at day 7. Unexposed FVB/NJ mice had less keratin 5 staining (basal cell marker) than A/J mice in large intrapulmonary airways where epithelial repair was poor and fibrosis developed after chlorine exposure. FVB/NJ mice had large areas devoid of epithelium on day 1 after exposure leading to fibroproliferative lesions on days 4 and 7. A/J mice had airways covered by squamous keratin 5-stained cells on day 1 that transitioned to a highly proliferative reparative epithelium by day 4 followed by the reappearance of ciliated and Clara cells by day 7. The data suggest that lack of basal cells in the large intrapulmonary airways and failure to effect epithelial repair at these sites are factors contributing to the development of airway fibrosis in FVB/NJ mice. The observed differences in susceptibility to chlorine-induced airway disease provide a model in which mechanisms and treatment of airway fibrosis can be investigated.

Definitions and classification of work-related asthma

The workplace can trigger or induce asthma and cause the onset of different types of work-related asthma (WRA). Based on current knowledge of clinical features, pathophysiologic mechanisms, and evidence supporting a causal relationship, the following conditions should be distinguished in the spectrum of WRA: (1) immunologic occupational asthma (OA), (2) nonimmunologic OA, (3) work-exacerbated asthma, and (4) variant syndromes, including eosinophilic bronchitis, potroom asthma, and asthmalike disorders caused by organic dusts. The rationale, issues, and controversies relating to this approach are critically reviewed to stimulate the development of a consensus on operational definitions of the various phenotypes of WRA.

Work-related asthma: a case-based approach to management

The management of work-related asthma has some differences from management of other asthma. Components of management include not only making as accurate a diagnosis as possible, identifying the causative agent or triggers at work, and managing the asthma with pharmacologic treatment as for other patients with asthma, but also advising on the appropriate work changes that may be needed, assisting the worker with appropriate compensation claims, and supporting protective measures for coworkers. This article discusses the approaches that may be taken for patients with different forms of work-related asthma.

Successful treatment of reactive airways dysfunction syndrome by high-dose vitamin D

Reactive airways dysfunction syndrome is a controversial and poorly understood condition produced by inhalational injury from gas, vapors, or fumes. The symptoms mimic asthma, but appear unresponsive to asthma treatments. If symptoms persist for more than 6 months, there is a risk that they can become chronic. For these cases, effective treatments are lacking and quality of life is poor. We describe the first use of high-dose vitamin D in a patient with this condition, who fulfilled the 1995 American College of Chest Physicians criteria for this syndrome. The patient we describe presented an extremely difficult management problem and was refractory to conventional treatments, but responded to high-dose oral vitamin D supplements.

Chlorine gas inhalation: human clinical evidence of toxicity and experience in animal models

Humans can come into contact with chlorine gas during short-term, high-level exposures due to traffic or rail accidents, spills, or other disasters. By contrast, workplace and public (swimming pools, etc.) exposures are more frequently long-term, low-level exposures, occasionally punctuated by unintentional transient increases. Acute exposures can result in symptoms of acute airway obstruction including wheezing, cough, chest tightness, and/or dyspnea. These findings are fairly nonspecific, and might be present after exposures to a number of inhaled chemical irritants. Clinical signs, including hypoxemia, wheezes, rales, and/or abnormal chest radiographs may be present. More severely affected individuals may suffer acute lung injury (ALI) and/or acute respiratory distress syndrome (ARDS). Up to 1% of exposed individuals die. Humidified oxygen and inhaled beta-adrenergic agents are appropriate therapies for victims with respiratory symptoms while assessments are underway. Inhaled bicarbonate and systemic or inhaled glucocorticoids also have been reported anecdotally to be beneficial. Chronic sequelae may include increased airways reactivity, which tends to diminish over time. Airways hyperreactivity may be more of a problem among those survivors that are older, have smoked, and/or have pre-existing chronic lung disease. Individuals suffering from irritant-induced asthma (IIA) due to workplace exposures to chlorine also tend to have similar characteristics, such as airways hyperresponsiveness to methacholine, and to be older and to have smoked. Other workplace studies, however, have indicated that workers exposed to chlorine dioxide/sulfur dioxide have tended to have increased risk for chronic bronchitis and/or recurrent wheezing attacks (one or more episodes) but not asthma, while those exposed to ozone have a greater incidence of asthma. Specific biomarkers for acute and chronic exposures to chlorine gas are currently lacking. Animal models for chlorine gas inhalation have demonstrated evidence of oxidative injury and inflammation. Early epithelial injury, airways hyperresponsiveness, and airway remodeling, likely diminishing over time, have been shown. As in humans, ALI/ARDS can occur, becoming more likely when the upper airways are bypassed. Inhalation models of chlorine toxicity provide unique opportunities for testing potential pharmacologic rescue agents.

Irritant vocal cord dysfunction and occupational bronchial asthma: differential diagnosis in a health care worker

OBJECTIVES

Vocal cord dysfunction (VCD) is an uncommon respiratory disease characterized by the paradoxical adduction of vocal cords during inspiration, that may mimic bronchial asthma. The pathogenesis of VCD has not been clearly defined but it is possible to recognize non-psychologic and psychologic causes. The majority of patients are female but, interestingly, a high incidence of VCD has been documented in health care workers. A misdiagnosis with asthma leads to hospitalisation, unnecessary use of systemic steroids with related adverse effects, and sometimes tracheostomy and intubation. In a subset of VCD patients, the disease can be attributed to occupational or environmental exposure to inhaled irritants.

MATERIALS AND METHODS

We report the case of a 45-year-old woman, working as a nurse, who complained of wheezing, cough, dyspnoea related to inhalation of irritating agents (isopropylic alcohol, formaldehyde, peracetic acid). She underwent chest radiography, pulmonary function assessment both in the presence and in the absence of symptoms, bronchial provocation with methacholine and bronchodilation test with salbutamol to recognize asthma's features, allergy evaluation by skin prick tests and patch tests and video-laryngoscopy.

RESULTS

VCD diagnosis was made on the basis of video-laryngoscopy, that visualized the paradoxical motion of the vocal cords during symptoms, in the absence of other pathologic processes.

CONCLUSIONS

This case fulfils the proposed criteria for the diagnosis of irritant VCD (IVCD). This is the first report of VCD onset following exposure to several irritants: formaldehyde, glutaraldehyde, sopropylic alcohol, peracetic acid-hydrogen peroxide mixture. These substances are used as cleaning and antiseptic agents in healthcare settings and some ones can also be found in many indoor environments. A correct diagnosis is important both to give the appropriate treatment and for medical legal implications.

Long-term pathologic consequences of acute irritant-induced asthma

BACKGROUND

Acute irritant-induced asthma (IrIa) or reactive airways dysfunction syndrome is caused by exposure to a high concentration of an agent. The long-term pathologic consequences of IrIa remain thus far unknown.

OBJECTIVE

The aim of our study was to investigate the chronic airway inflammation and remodeling that occur in association with IrIa.

METHODS

Ten subjects with a history of IrIa (mean interval of 10.9 years, minimum of 4 years, since the inhalational accident) underwent bronchoscopy followed by bronchoalveolar lavage and bronchial biopsies. Immunologic and morphologic data from patients with IrIa were compared with those of patients with mild to moderate asthma as well as healthy controls.

RESULTS

Bronchoalveolar lavage fluid analysis showed increased eosinophil and neutrophil counts in 30% and 60% of subjects with IrIa, respectively. In the supernatant of bronchoalveolar lavage, we found a significant increase in the majority of mediators compared with healthy subjects and a significant increase in eosinophilic cationic protein, IL-8, basic fibroblast growth factor, and matrix metalloproteinase 1 compared with control patients with asthma. Evaluation of basement membrane thickness (subepithelial fibrosis) demonstrated a significant increase in patients with IrIa compared with healthy subjects and subjects with asthma. Basement membrane thickness also significantly correlated with the PC(20) value. The epithelial cell detachment showed an elevated although not significant trend compared with subjects with asthma and control subjects. Immunocytochemical analysis demonstrated increases in the number of eosinophil cationic protein and TGF-beta1-positive cells compared with healthy controls.

CONCLUSION

This study provides evidence of a significant eosinophilic and neutrophilic inflammation as well as remodeling in IrIa many years after an inhalational accident.

Irreversible airway obstruction in asthma

Asthma is generally characterized by fully reversible airway obstruction. However, a significant proportion of asthma patients demonstrate an incomplete reversibility of airway obstruction (IRAO) despite optimal treatment and the absence of a significant smoking history. Such partially irreversible airway obstruction may be due to residual airway inflammation, particularly of the eosinophilic type, and structural changes. Risks factors for IRAO include reduced pulmonary function early in life, frequent exacerbations, smoking, continuing exposure to a sensitizing agent, and adult-onset asthma. IRAO is associated with increased disease severity and increased asthma-related morbidity and mortality. Optimal asthma control, including prevention of asthma exacerbations, smoking avoidance, and sufficient anti-inflammatory therapy, should be implemented in an effort to avoid an accelerated decline in lung function and the development or worsening of IRAO.

Long-term outcomes of acute irritant-induced asthma

RATIONALE

The long-term outcomes of acute irritant-induced asthma (IIA) are mostly unknown.

OBJECTIVES

To study the long-term outcomes of IIA.

METHODS

We reassessed 35 subjects who experienced IIA at a mean interval of 13.6 +/- 5.2 years.

MEASUREMENTS AND MAIN RESULTS

The causal agent was chlorine in 20 cases (57%). At diagnosis, the mean +/- SD FEV(1) was 74.5 +/- 19.5% predicted, and all subjects showed bronchial hyperresponsiveness. At reassessment, all subjects reported respiratory symptoms, and 24 (68%) were on inhaled steroids. There were no significant improvements in FEV(1) and FEV(1)/FVC values. Twenty-three subjects had a methacholine test, and only six subjects had normal levels of responsiveness. Of the remaining 12 subjects, six had improvement in FEV(1) after bronchodilator >or=10%. In samples of induced sputum obtained from 27 subjects, six had eosinophils >or=2%. Levels of inflammatory and remodeling mediators were higher than in control subjects but were no different from subjects with occupational asthma due to sensitization. Quality of life score was 4.4 +/- 1.5 on a 0 (worst) to 7 (best) scale. Twelve subjects had an abnormal depression score.

CONCLUSIONS

This study provides the first evidence of significant long-term impact of acute IIA on various outcomes.

Reactive Airways Dysfunction Syndrome in Housewives Due to a Bleach–Hydrochloric Acid Mixture

The sudden onset of asthmalike symptoms and persistence of airway reactivity following an acute exposure to an irritant gas or vapor has been termed reactive airways dysfunction syndrome (RADS). A mixture of sodium hypochlorite (bleach, 40%) and hydrochloric acid (18%) is commonly used as a household cleaning solution in our region. From this mixture, chlorine gas is produced, which can cause airway damage and ensuing RADS. Here we describe findings of patients with RADS due to this cleaning mixture, and determine factors associated with a favorable outcome. Data were collected retrospectively on 55 symptomatic patients presenting to our emergency department after inhalation exposure to a mixture of bleach and hydrochloric acid. Symptoms, past medical and smoking history, details of the exposure, initial peak expiratory flow rate (PEFR) and oxygenation, and acute reversibility of airways obstruction were documented. All patients met previously defined criteria for the diagnosis of RADS, but did not undergo methacholine challenge testing and bronchoalveolar lavage or histopathologic study. Fifty patients were followed over the course of 3 mo. The majority of exposures (64%) occurred in the bathroom or kitchen. Only 21 of 55 (38%) patients showed an improvement in PEFR of 15% or greater following two beta(2)-agonist inhalation treatments. In follow-up, 48 patients (87%) improved clinically and functionally (FEV(1)). Seven patients (13%) deteriorated, with ARDS developing in two, one of whom died from respiratory failure. Advanced age, initial low PEFR, exposure in a small enclosed area, use immediately after mixing, and prolonged short- and long-term exposures were associated with a poorer prognosis. This descriptive study is the largest case series in the literature of RADS developing after exposure to a bleach-hydrochloric acid mixture. The optimum acute treatment and long-term outcomes for patients with RADS due to this combination still need to be determined.

Time course of airway remodelling after an acute chlorine gas exposure in mice

Accidental chlorine (Cl2) gas inhalation is a common cause of acute airway injury. However, little is known about the kinetics of airway injury and repair after Cl2 exposure. We investigated the time course of airway epithelial damage and repair in mice after a single exposure to a high concentration of Cl2 gas. Mice were exposed to 800 ppm Cl2 gas for 5 minutes and studied from 12 hrs to 10 days post-exposure. The acute injury phase after Cl2 exposure (< or = 24 hrs post-exposure) was characterized by airway epithelial cell apoptosis (increased TUNEL staining) and sloughing, elevated protein in bronchoalveolar lavage fluid, and a modest increase in airway responses to methacholine. The repair phase after Cl2 exposure was characterized by increased airway epithelial cell proliferation, measured by immunoreactive proliferating cell nuclear antigen (PCNA), with maximal proliferation occurring 5 days after Cl2 exposure. At 10 days after Cl2 exposure the airway smooth muscle mass was increased relative to controls, suggestive of airway smooth muscle hyperplasia and there was evidence of airway fibrosis. No increase in goblet cells occurred at any time point. We conclude that a single exposure of mice to Cl2 gas causes acute changes in lung function, including pulmonary responsiveness to methacholine challenge, associated with airway damage, followed by subsequent repair and airway remodelling.

The effect of nebulized NaHCO3 treatment on "RADS" due to chlorine gas inhalation

Chlorine is one of the most common substances involved in toxic inhalation. As with all irritant gases, the airway injuries caused by chlorine gas may result in clinical manifestations similar to those of asthma. In this study, we investigated the effect of nebulized sodium bicarbonate (NSB) on the treatment and quality of life (QoL) of victims exposed to chlorine gas. Forty-four consecutive patients with reactive airways dysfunction syndrome (RADS) due to chlorine inhalation (40 females and 4 males, age range 17-56 yr) were included in this study. Patients were placed in control and treatment groups in a sequential odd-even fashion based on their order of presentation. Treatment of all patients included corticosteroids and nebulized short-acting beta2-agonists. Then the control group (n = 22) received nebulized placebo (NP), and the NSB group (n = 22) received NSB treatment (4 cm3 of 4.20% sodium bicarbonate solution). A quality of life (QoL) questionnaire and pulmonary function tests (PFTs) were performed before and after treatments in both groups. The most common symptoms were dyspnea (82%) and chest tightness (82%). Baseline characteristics of both groups were similar. Compared to the placebo group, the NSB group had significantly higher FEV1 values at 120 and 240 min (p < .05). Significantly more improvement in QoL questionnaire scores occurred in the NSB group compared to the NP group (p < .001). Thus, NSB is a clinically useful treatment, as tested by PFTs and QoL questionnaire, for patients with RADS caused by exposure to chlorine gas.

Vapor, dust, and smoke exposure in relation to adult-onset asthma and chronic respiratory symptoms: the Singapore Chinese Health Study

Occupational factors contribute to a significant fraction of respiratory disease and symptoms. The authors evaluated the role of occupational exposures in asthma, chronic bronchitis, and respiratory symptoms in the Singapore Chinese Health Study, a population-based cohort of adults aged 45-74 years at enrollment in 1993-1998. Information on occupations and occupational exposures was collected at enrollment for 52,325 subjects for whom respiratory outcomes were obtained via follow-up interviews in 1999-2004. Exposure to dusts from cotton, wood, metal, minerals, and/or asbestos was associated with nonchronic cough and/or phlegm (odds ratio (OR) = 1.19, 95% confidence interval (CI): 1.08, 1.30), chronic bronchitis (OR = 1.26, 95% CI: 1.01, 1.57), and adult-onset asthma (OR = 1.14, 95% CI: 1.00, 1.30). Cotton dust was the major contributor to respiratory symptoms. Vapor exposure from chemical solvents, dyes, cooling oils, paints, wood preservatives, and/or pesticides was associated with nonchronic cough or phlegm (OR = 1.14, 95% CI: 1.03, 1.27), chronic dry cough (OR = 1.55, 95% CI: 1.19, 2.01), and adult-onset asthma (OR = 1.34, 95% CI: 1.15, 1.56). Chemical solvents, cooling oils, and pesticides were the major contributors to respiratory symptoms. These data support the role of occupational exposures in the etiology of respiratory illness in a population-based cohort in Singapore with a low prevalence of atopic illness.

A 5-year follow-up of airway symptoms after nitrogen dioxide exposure in an indoor ice arena

The authors investigated whether exposure to high levels of nitrogen dioxide (NO2) in an indoor ice hockey arena might be associated with airway symptoms 5 yr later. A follow-up questionnaire was answered by 71 subjects who had experienced such an exposure, accompanied by acute respiratory illness, in Stockholm in 1994. The same questionnaire was answered by 40 reference subjects. The overall response rate for both groups was 71%. Information was obtained regarding various background factors, such as smoking and respiratory symptoms since 1994. For those who had stopped playing ice hockey during the follow-up period, the exposure to high NO2 levels appeared to be associated with an increase in upper airways symptoms (i.e., nasal blockage or rhinitis) (odds ratio = 3.1, 95% confidence interval = 1.1, 8.8), after adjustment for age, smoking, and family history of allergy. These data suggest that exposure to high NO2 levels in an indoor ice arena may be associated with increased airway symptoms several years later.

Occupational asthma

Substantial epidemiologic and clinical evidence indicates that agents inhaled at work can induce asthma. In industrialized countries, occupational factors have been implicated in 9 to 15% of all cases of adult asthma. Work-related asthma includes (1) immunologic occupational asthma (OA), characterized by a latency period before the onset of symptoms; (2) nonimmunologic OA, which occurs after single or multiple exposures to high concentrations of irritant materials; (3) work-aggravated asthma, which is preexisting or concurrent asthma exacerbated by workplace exposures; and (4) variant syndromes. Assessment of the work environment has improved, making it possible to measure concentrations of several high- and low-molecular-weight agents in the workplace. The identification of host factors, polymorphisms, and candidate genes associated with OA is in progress and may improve our understanding of mechanisms involved in OA. A reliable diagnosis of OA should be confirmed by objective testing early after its onset. Removal of the worker from exposure to the causal agent and treatment with inhaled glucocorticoids lead to a better outcome. Finally, strategies for preventing OA should be implemented and their cost-effectiveness examined.

Assessment of bronchial responsiveness following exposure to inhaled occupational and environmental agents

Inhalation of a range of agents can result in airway inflammation and/or irritation. This may result in occupational asthma or reactive airways dysfunction syndrome. Reactive airways dysfunction syndrome follows a single large exposure to a chemical agent but is now frequently embraced under the wider term of irritant-induced asthma, a term that also includes asthma due to persistent, lower dose irritant exposures. Bronchial hyperresponsiveness is a hallmark of both occupational asthma and reactive airways dysfunction syndrome, although some patients with occupational asthma may occasionally have typical clinical features without increased bronchial hyperresponsiveness. Following removal of the causal agent in occupational asthma, bronchial hyperresponsiveness generally returns towards normal over a 2-year period, although some individuals demonstrate increased bronchial hyperresponsiveness for longer. Measurement of specific bronchial hyperresponsiveness to the primary causal agent in occupational asthma is used diagnostically but not for assessing prognosis. Bronchial hyperresponsiveness to inhaled methacholine can be measured across individual workshifts to assess work-related change. It may also be measured at the end of a work period when exposure has occurred, and compared with values following a period away from work. There have been no direct, systematic comparisons of changes in methacholine responsiveness in the diagnosis of occupational asthma compared with the more frequently used serial peak flow measurements. Patients with reactive airways dysfunction syndrome classically exhibit non-specific bronchial hyperresponsiveness, which can be readily measured by evaluating responses to inhaled methacholine. Bronchial hyperresponsiveness in reactive airways dysfunction syndrome can persist for many years after initial exposure and serial changes can be used to assess recovery and subsequent disability over time.

Workplace irritant exposures: do they produce true occupational asthma?

OBJECTIVE

To describe the features of irritant-induced asthma and discuss the diagnosis in relation to differing workplace irritant exposures and symptomatic responses.

DATA SOURCES

A review of MEDLINE articles on this topic from January 1, 1985, through December 31, 2001 was performed.

STUDY SELECTION

The author selected relevant articles for inclusion in the review.

RESULTS

Many reports indicate that unintentional high-level respiratory irritant exposures can induce the new onset of asthma. Cases that meet strict criteria for a syndrome of irritant-induced asthma, termed reactive airways dysfunction syndrome, can be diagnosed with relative certainty. Several reports of irritant-induced asthma, especially prevalence studies, have relied on historical data or have otherwise modified the reactive airways dysfunction syndrome criteria for diagnosis (eg, expanding the definition to include the symptom onset several days after exposure). Such modifications, or inclusion of cases with incomplete documentation, likely increase diagnostic sensitivity but may reduce the certainty of diagnosis for individual cases. Expanding exposure criteria to moderate or long-term low-level irritant exposures causes difficulty in excluding transient irritant exacerbation of underlying asthma or coincidental onset of asthma during working life. Although recent population studies suggest a greater relative risk of asthma in occupations with expected low-to-moderate respiratory irritant exposures, currently no objective laboratory tests exist to exclude coincidental asthma in such patients.

CONCLUSIONS

Irritant-induced asthma can be produced by high-level unintentional respiratory irritant exposures at work or outside the workplace. Lower levels of exposure to respiratory irritants at work are more common, and additional studies are needed to determine the airway effects of such exposures.

Differential diagnosis of occupational asthma

Confidently establishing the diagnosis of occupational asthma (OA) is a complicated undertaking, because it requires that the patient's asthma symptoms are caused exclusively (or at least in large part) by occupational exposures. Asthma is a common disease, and the differential diagnosis of asthma is a frequently discussed subject that includes common and uncommon disorders. This article presents a broad characterization of OA, including the elements necessary to establish a diagnosis. Differential diagnosis also is discussed.

Occupational asthma

The workplace can be responsible for approximately one in 10 cases of adult-onset asthma. Two types of occupational asthma (OA) are distinguished by whether they arise after a latency period that is necessary for acquiring sensitization or as a result of acute exposure to irritant materials (irritant-induced asthma). The pathophysiology of OA with a latency period is similar to that of nonoccupational asthma, whereas the mechanism of irritant-induced asthma is still uncertain. HLA haplotypes and other genetic polymorphisms have been found to be associated with OA. According to various sources of data, the overall frequency of OA has remained stable in the last 10 years, although the frequency of causal agents vary. Registers of causal occupations and agents have been issued on Web sites (eg, www.asmanet.com ). Improved sampling methods have shown that the degree of exposure plays a key role in the onset of the disease, whereas prospective data collected in high-risk workplaces have also identified personal risk factors (eg, atopy, smoking, and rhinoconjunctivitis). A diagnosis of OA should no longer be based on a compatible history only but should be confirmed by means of objective testing. Once the diagnosis is confirmed, the worker should be removed from exposure, and satisfactory compensation programs should be offered, the most important being retraining programs with financial compensations because affected workers are generally young. The cost-effectiveness of prevention programs in high-risk workforces should be assessed.

Quality of life and capsaicin sensitivity in patients with sensory airway hyperreactivity

BACKGROUND

A group of patients with asthma-like symptoms and sensitivity to chemical irritants has shown an increased cough sensitivity to inhaled capsaicin compared to patients with asthma and to healthy controls. The condition is called sensory hyperreactivity (SHR), and the patients often feel that they are socially handicapped because of the risk of exposure to chemical irritants in daily life.

METHODS

Twenty-six patients with asthma-like symptoms after exposure to nonspecific irritating stimuli, but without IgE-mediated allergy or demonstrable bronchial obstruction, were selected for a study of the response to a capsaicin test and measurement of quality of life by a general health profile (the Nottingham Health Profile [NHP]). We also investigated whether there was a correlation between quality of life and sensitivity to capsaicin.

RESULTS

The patients demonstrated a dose-dependent response to the capsaicin provocation, with coughing and respiratory and other symptoms, that significantly differed from 12 healthy controls. The health profile showed that patients with SHR had a significantly reduced quality of life compared to reference values, and there was a significant correlation between the health profile and sensitivity to capsaicin.

CONCLUSIONS

Patients with asthma-like symptoms verified by the capsaicin inhalation test for sensory hyperreactivity have a poor quality of life. The correlation between quality of life and sensitivity to capsaicin objectively demonstrates the validity of this general health profile study.

Irritant-induced asthma: clinical and functional aspects

We report on three patients who experienced persistent asthma symptoms after repetitive irritant exposure which took place over a period from several days to months. Airway inflammation was assessed by induction of sputum and functional follow-up information was obtained from serial lung function tests. All patients had bronchial hyperresponsiveness to methacholine at the time of diagnosis. However, induced sputum samples did not show increased differential count of eosinophils. Treatment with inhaled corticosteroids was started in all of the patients and two of them were removed from work. In the two patients who left the workplace, methacholine inhalation test became negative when symptoms disappeared, whereas the patient who continued working had persistent asthma symptoms and a deterioration of bronchial hyperresponsiveness.

Mechanisms of occupational asthma

BACKGROUND

The pathogenesis and the pathologic alterations of occupational asthma are similar to those of nonoccupational asthma. Occupational asthma may therefore represent a useful model of "human asthma" to investigate mechanisms and pathophysiology of asthma in general. In an occupational setting the cause and onset of asthma may be easily identified, and the natural history may be examined in follow-up studies. The mechanisms involved in occupational asthma include genetic predisposition, immunologically mediated responses, as well as nonspecific airway inflammation. In particular, high molecular weight (eg, grain dust, flour) and some low molecular weight sensitizers (eg, acid anhydrides and platinum halide salts) have been shown to induce occupational asthma through an immunoglobulin E (IgE)-dependent mechanism, while cell-dependent immunologic mechanisms are likely to be more relevant for occupational asthma induced by other low molecular weight sensitizers (eg, toluene diisocyanate and plicatic acid contained in western red cedar). The pathology of the airway mucosa of occupational asthma is remarkably similar to the pathology of nonoccupational asthma, ie, characterized by infiltration and accumulation of eosinophils, mast cells, and activated lymphocytes along with subepithelial fibrosis. In this article, the most relevant mechanisms are discussed with particular reference to the similarities and discrepancies between occupational and nonoccupational asthma.

Reactive airways dysfunction syndrome (RADS): guidelines for diagnosis and treatment and insight into likely prognosis

Reactive airways dysfunction syndrome (RADS) is defined as the sudden onset of asthma following a high level exposure to a corrosive gas, vapor, or fume. This variant of occupational asthma continues to generate controversy regarding the criteria for its diagnosis. There is also some disagreement as to the likely prognosis with this disorder. Currently, the diagnosis requires the assumption of normal premorbid pulmonary physiology and absence of bronchial hyperreactivity. Criteria for the diagnosis of RADS are discussed with a proposal for both major and minor criteria to increase the confidence of an accurate diagnosis. The pathology of RADS involves a primarily lymphocytic inflammatory response with some evidence of subepithelial thickening and fibrosis. Most patients with this condition who survive the short-term exposure to a toxicant recover completely without significant clinical or physiologic sequelae. The issue of low-level RADs remains controversial and problematic as a tenable diagnosis, and will require further careful investigation to evaluate the premise that chronic, low-level toxicants are capable of leading to such a condition. More likely, most of the cases which have been reported represent preexisting asthma and/or expressions of an atopic predisposition.

Chronic rhinitis in workers at risk of reactive airways dysfunction syndrome due to exposure to chlorine

BACKGROUND

To assess the frequency of chronic upper airways symptoms and to relate the presence of these symptoms to accidental exposure to chlorine and changes in lower airways symptoms, airway function, and bronchial responsiveness in a cohort of workers at risk of sporadic occupational exposure to high concentrations of chlorine.

METHODS

Data were collected on symptom assessment, spirometry, and methacholine challenge tests from 211 workers seen twice at a 2 year interval (1992-4).

RESULTS

The proportion of workers reporting chronic rhinitis was 46.9% in 1992 and 42.2% in 1994. Chronic rhinitis reported in 1994 was significantly associated with acute exposure to chlorine (self reports, p = 0.02; first aid reports, p = 0.001). In a multivariate logistic regression analysis the presence of reported accidents at the first aid unit (one accident, odds ratio (OR) 3.1, 95% confidence interval (95% CI) 1.3 to 7.5; two or more accidents, OR 6.2, 1.1 to 35.8) and of personal atopy (OR 5.5, 2.2 to 10.8) were significant predictors of chronic rhinitis in 1994. Chronic lower airways symptoms were more frequent in 1994 among workers reporting chronic rhinitis on both assessments than in others (p = 0.03) and changes in bronchial responsiveness were more pronounced in those with persistent rhinitis (p = 0.09).

CONCLUSIONS

These results suggest that persistent nasal symptoms in workers at risk of reactive airways dysfunction syndrome could be a useful marker of lower respiratory tract abnormalities.

Asthma and chemical bronchitis in vanadium plant workers

BACKGROUND

Whether vanadium induces bronchial hyperresponsiveness and asthma in previously normal subjects is unresolved: the two reported series addressing this question both have shortcomings.

OBJECTIVE

To determine the cause of cough and breathlessness in vanadium plant workers after variable periods of exposure.

DESIGN

Case series of employees presenting with persistent symptoms over a 24-month study period.

PATIENTS AND METHODS

Forty of an estimated 1,440 patients were investigated by 1) blood count and serum IgE, 2) intracutaneous allergen skin tests, 3) spirometry, and 4) bronchoprovocation by histamine inhalation or exercise challenge. Exposure was assessed by measurement of 1) ambient V2O5, NH3 and SO2 over 7 days during the 24-month study period, 2) urine vanadium concentration at time of first presentation.

RESULTS

Twelve of 40 subjects had bronchial hyperreactivity (BHR), and these were compared to 12 age-matched companion subjects whose BHR was normal. In 10, BHR was diagnosed by histamine inhalation (PC20 0.25-1.82 mg/ml, nl > 8.0 mg/ml), and in six of these the abnormality was severe (PC20 < 0.5 mg/ml). A further two had BHR by exercise challenge (FEV1, 600 ml/30% and 770 ml/18% pre/post exercise). After removal from exposure, 9 of the 12 subjects returned for follow-up 5 to 23 months later. BHR was worse in one, still present although less severe in five, and was no longer found in one subject. Baseline spirometry measurements were normal in seven subjects and only mildly impaired in the remaining five of the 12 subjects with BHR.

CONCLUSION

This study provides strong supporting evidence that inhaled V2O5 induces BHR and asthma in subjects previously free of lung disease; the abnormality may persist for up to 23 months following exposure; routine spirometry will not detect affected subjects.

The spectrum of irritant-induced asthma: sudden and not-so-sudden onset and the role of allergy

A retrospective investigation of 86 asthmatic subjects defined clinical features of irritant-induced asthma and assessed the contributory role of an allergic predisposition. Three categories of asthma were evaluated: (1) occupational asthma due to a sensitizer (11 subjects, 13%); (2) irritant-induced asthma (54 persons, 63%); and (3) not occupational/environmental exposure-related asthma (21 subjects, 24%). Two distinct clinical presentations of irritant-induced asthma emerged: the first was sudden onset (29 subjects) and the second was not so sudden in onset (25 subjects). Sudden-onset, irritant-induced asthma was analogous to the reactive airways dysfunction syndrome. Clinical manifestations began immediately or within a few hours (always within 24 h) following an accidental, brief, and massive exposure. In contrast, for the not-so-sudden-onset asthma subjects, the causative irritant exposure was not brief, usually not massive, continued for > 24 h, and the initiation of asthma took longer to evolve. Eighty-eight percent of individuals with not-so-sudden irritant-induced asthma displayed an atopy/allergy status (p < 0.01). Some of the atopy/allergy subjects with presumed new-onset asthma were found to have suffered preexisting asthma that had been clinically quiescent for at least 1 year before the triggering exposure (16 persons). We conclude that preexisting allergic/atopy and/or preexisting asthma were significant contributors to the pathogenesis of not-so-sudden, irritant-induced asthma and emphasizes a critical interaction between environmental and host factors in the pathogenesis of asthma.

Bronchial subepithelial fibrosis correlates with airway responsiveness to methacholine

OBJECTIVES

To evaluate the relationships between airway subepithelial collagen deposition and epithelial desquamation with airflow obstruction and hyperresponsiveness in different types of asthma and other respiratory conditions such as chronic cough and allergic rhinitis.

DESIGN AND PARTICIPANTS

We compared the histopathologic features observed on bronchial biopsy specimens obtained from 80 subjects: 38 with different types of asthma, 19 with chronic cough, 13 with allergic rhinitis, and 10 normal control subjects. Each subject had a questionnaire on respiratory symptoms and medication needs, measurements of expiratory flows and methacholine responsiveness, allergy skin prick tests, and a bronchoscopy with bronchial biopsies. None of the subjects studied used bronchial anti-inflammatory agents.

RESULTS

Different degrees of bronchial subepithelial fibrosis were present in asthmatic subjects, the most intense being observed in occupational asthma; a subepithelial deposition of collagen was also found in subjects with allergic rhinitis, although it was less intense than in asthma and irregularly distributed under the basement membrane. On global analysis, we found a significant correlation between individual provocative concentration of methacholine inducing a 20% fall in FEV1 (PC20) and subepithelial fibrosis intensity (rs=-0.70, p<0.001). The degree of epithelial desquamation was correlated with that of subepithelial fibrosis (rs=0.36, p=0.02) in subjects with normal airway responsiveness, but it was not correlated with the PC20 (rs=0.10, p>0.05). Neither the degree of subepithelial fibrosis nor epithelial desquamation was correlated with the FEV1.

CONCLUSION

These results suggest that structural airway changes such as subepithelial collagen deposition may be significant determinants or markers of a process that results in airway hyperresponsiveness.

Occupational asthma

Occupational asthma is a common disorder that may be caused by several hundred agents and has a variety of pathogenetic mechanisms. Level of exposure is an important risk factor, and reduction of exposure is the only certain method of prevention. Atopy and smoking are further risk factors for IgE-mediated asthma but have not been found to increase risk in forms of the disorder that have other mechanisms. The key to diagnosis is a low threshold of suspicion; several investigative procedures can be used to confirm the diagnosis. Many patients suffer from continued asthma despite cessation of exposure; early diagnosis and early removal from exposure are the most important factors for improving the long-term outcome.