Perception of airway narrowing in a general population sample

Research progress on the pathogenesis of chest tightness variant asthma characterized by chest tightness

Chest tightness variant asthma (CTVA) is an atypical form of asthma with chest tightness as the sole or predominant symptom. The underlying receptors for chest tightness are bronchial C-fibers or rapidly adapting receptors. The nerve impulses are transmitted via the vagus nerve and processed in different regions of the cerebral cortex. Chest tightness is associated with sensory perception, and CTVA patients may have heightened ability to detect subtle changes in lung function, but such sensory perception is unrelated to respiratory muscle activity, lung hyperinflation, or mechanical loading of the respiratory system. Airway inflammation, pulmonary ventilation dysfunction (especially involving small airways), and airway hyperresponsiveness may underlie the sensation of chest tightness. CTVA patients are prone to comorbid anxiety and depression, which share similar central nervous system processing pathways with dyspnea, suggesting a possible neurological basis for the development of CTVA. This article examines the recognition and mechanisms of chest tightness, and explores the pathogenesis of CTVA, focusing on its association with airway inflammation, ventilation dysfunction, airway hyperresponsiveness, and psychosocial factors.

Different cutoff values of methacholine bronchial provocation test depending on age in children with asthma

BACKGROUND

Bronchial hyperresponsiveness (BHR) is a fundamental pathophysiological characteristic of asthma. Although several factors such as airway caliber can affect BHR, no study has established age-dependent cutoff values of BHR to methacholine for the diagnosis of asthma in children. We investigated the cutoff values of the methacholine challenge test (MCT) in the diagnosis of asthma according to age.

METHODS

A total of 2383 individuals aged from 6 to 15 years old were included in this study. MCTs using the five-breath technique were performed in 350 children with suspected asthma based on symptoms by pediatric allergists and in 2033 healthy children from a general population-based cohort. We determined the provocative concentration of methacholine producing a 20% decrease in forced expiratory volume in 1 second from baseline (PC₂₀). A modified Korean version of the International Study of Asthma and Allergies in Childhood questionnaire was used to distinguish asthmatics and healthy subjects. Receiver-operator characteristic curve analysis was used to assess the cutoff value of PC₂₀ for the diagnosis of asthma.

RESULTS

Cutoff values of methacholine PC₂₀, which provided the best combination of diagnostic sensitivity and specificity, showed an increasing pattern with age: 5.8, 9.1, 11.8, 12.6, 14.9, 21.7, 23.3, 21.1, 21.1, and 24.6 mg/mL at ages 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 years, respectively.

CONCLUSION

The application of different cutoff values of methacholine PC₂₀ depending on age might be a practical modification for the diagnosis of asthma in children and adolescents with asthmatic symptoms.

Symptom evaluation during the methacholine test: Does it add to the interpretation of the test results based on the PC20FEV1?

PURPOSE

Conventionally, symptoms occurring during the methacholine test are not taken into account when interpreting the test results. We examined whether the evaluation of methacholine-induced symptoms (MIS) added to the test interpretation based on the PC20FEV1 by assessing their prevalence, their similarity with symptoms justifying referral and their relationship with airway responsiveness.

METHODS

Eighty-two patients with suspected asthma completed a questionnaire of symptoms and underwent bronchial challenge with methacholine. Based on MIS and airway responsiveness (responders = PC20FEV1 < 8 mg/mL), subjects were classified as asymptomatic non-responders (ANRs), asymptomatic responders (ARs), symptomatic non-responders (SNRs) and symptomatic responders (SRs). Airway responsiveness for all subjects, including non-responders (ie, fall in FEV1 < 20%), was assessed by the methacholine concentration response-slope (MCRS) obtained using all points of the curve.

RESULTS

ARs (n = 6) were poor-perceivers of bronchoconstriction. SNRs (n = 16) did not differ from SRs (n = 34) in any clinical parameter, including the proportion of subjects (∼80%) whose methacholine test reproduced symptoms justifying referral. In turn, SNRs differed significantly from ANRs (n = 26) by having lower baseline FEV1 (P = .005), more physician-diagnosed asthma (P < .001), more use of respiratory medication (P = .032), and relatively greater responsiveness as manifested by a steeper MCRS (P < .001).

CONCLUSIONS

The occurrence of asthma-like symptoms during the methacholine test was associated with milder airway hyperresponsiveness that would go unnoticed by the PC20FEV1. This finding suggests that SNRs should not be merely classified as having normal responsiveness, as currently recommended, but further assessed for airway inflammation. Our results helped planning a longitudinal study to investigate the prognostic validity of this approach.

Asthma symptoms and airway narrowing in children growing up in an urban versus rural environment

The development of asthma and allergy appears to be the result of gene-environment interaction. Potential environmental risk factors such as outdoor and indoor air pollution, infections, allergen exposure, diet, and lifestyle patterns may trigger respiratory symptoms and compromise lung function in children. Specific features of urban and rural lifestyle may constitute distinct risk factors but may also coexist within certain socioeconomic levels. Children of rural environments are at lower risk for asthma and aeroallergen sensitization. The protective effect has been associated with close contact with large animals, but the genetic factor also plays a contributory role. Children with prolonged exposure to urban environment are at increased risk of reduced lung function and those that reside in polluted areas exhibit slower lung growth. It is possible that polluted urban environment per se facilitates subclinical small airway disease. Evidence to date supports a strong relation between residential area as a potential risk factor for childhood asthma symptoms and airway obstruction and a western type of socioeconomic development.

Different effects of sensitization to mites and pollens on asthma symptoms and spirometric indices in children: a population-based cohort study

BACKGROUND

We have previously shown that long-term exposure of children to a highly polluted urban compared with a rural environment is associated with subclinical airway narrowing and increased prevalence of atopy.

OBJECTIVE

To test the hypothesis that sensitization to indoor perennial, compared with seasonal, aeroallergens has distinct effects on asthma symptoms and/or spirometric indices.

METHODS

We evaluated the respiratory health of 478 and 342 children aged 8 to 10 years living in an urban and a rural area, respectively, during a period of 8 years. Children were evaluated by parental questionnaire in 3 phases, 1995 to 1996 (phase 1), 1999 to 2000 (phase 2), and 2003 to 2004 (phase 3), and by spirometry and skin prick testing to 9 common local aeroallergens in phases 1 and 2.

RESULTS

Sensitization to pollens was associated with current wheezing in phase 1 of the study (odds ratio [OR], 3.36; 95% confidence interval [CI], 1.71 to 6.62; P < .001) but not with spirometric indices. Sensitization to mites was negatively associated with forced expiratory volume in 1 second (95% CI, -7.26 to -0.90; P = .01) and forced expiratory flow at 50% of forced vital capacity (95% CI, -10.80 to -1.33; P = .01) in study phase 1 but not in phase 2.

CONCLUSIONS

Our results indicate that sensitization to mites is associated with insidious involvement of large and small airways, whereas sensitization to pollens is associated with childhood wheezing at the age of 8 to 10 years. Subsequent loss of these associations implies that risk factors other than allergy influence airway disease at a later age.

Breath-holding test in subjects with near-fatal asthma. A new index for dyspnea perception

RATIONALE

Identification of asthmatic subjects with low perception of dyspnea (POD) that are at higher risk of hospitalization, near-fatal and fatal asthma could improve their management.

OBJECTIVE

Create a simple procedure that facilitate the recognition of low POD.

METHODS

We enrolled near fatal asthma (NFA) subjects and a wide spectrum of non-NFA subjects. Each subject was asked to stop breathing at end-expiration. Dyspnea was assesssed by a modified Borg scale. To design the new index, we combined the Borg score at the end of the voluntary breath-holding maneuver with the airway limitation. The equation was as follows: FEV(1)/FVC%/(breath-holding time in seconds/final Borg score minus basal Borg score).

RESULTS

Eleven NFA subjects (4 females) aged 21-73yr and 55 non-NFA (14 severe, 18 moderate and 23 mild asthmatic subjects) completed the study. The threshold value of the index that could predict POD is <12. The mean (+/-sd) of the new index perception was significantly lower in NFA group (n=11; 5.21+/-3.59; vs. n=55; 13.67+/-11.08; P=0.006). This threshold value had 100% sensitivity and it best discriminated between mild and NFA groups. The negative likelihood ratio (when the index > or = 12) was zero. A result > or = 12 represented an almost null probability of poor POD.

CONCLUSION

The breath-holding test is simple and rapid. Its negative likelihood ratio was zero. Accordingly, a test result of 12 or greater might exclude the probability of poor perception of dyspnea in subjects with stable asthma.

Prevalence of respiratory symptoms in an athlete population

This study aimed to look at the prevalence and type of respiratory symptoms experienced by athletes and to assess the possible influence on the perception of symptoms of training duration and environment. A group of 698 athletes (107 with diagnosed or self-reported asthma) filled out a questionnaire on their respiratory condition. They exercised either in cold air (n = 176), dry air (n = 384), humid air (n = 95) or mixed dry and humid air (n = 43). Past exercise-related symptoms reported by athletes were breathlessness (48.7%), phlegm production (22.8%), wheezing (15.6%), cough (15.2%), and chest tightness (7.4%). Only 25% of asthmatic athletes reported having current exercise-induced symptoms of breathlessness, 21.7%, wheezing and 17.4%, chest tightness; current exercise-induced symptoms of breathlessness, wheezing or chest tightness were also reported, respectively, in 38.9%, 3.6% and 2.7% of athletes without a diagnosis of asthma. The perception of exercise-induced symptoms was not influenced by the duration of training or environment. In conclusion, (1) a minority of asthmatic athletes report troublesome respiratory symptoms with exercise, (2) breathlessness is not more frequently reported in asthmatic athletes than in those without such diagnosis while cough and wheezing are more common in asthmatic subjects and (3) the prevalence of respiratory symptoms is independent of training environment and duration of training.

Discriminant analysis in allergic rhinitis and asthma: methacholine dose-response slope allows a good differentiation between mild asthma and rhinitis

Asthma and rhinitis frequently coexist in allergic patients, but nasal symptoms may predominate, leading to asthma underdiagnosis and undertreatment. Discriminant analysis obtains the best differentiation between groups using one or one set of variables. Our aim was to identify the laboratory test [allergen exposure, total and specific serum IgE, lung function, blood eosinophils and, bronchial response and sensitivity to methacholine (Mth) and allergen] or combination of them that allowed the best differentiation between mild asthma and allergic rhinitis. A cross-sectional analysis was performed in 86 Dermatophogoides pteronyssinus allergic rhinitis patients, who were classified according to clinical data as rhinitis plus mild asthma (n = 62) or "pure" rhinitis (n = 24). Bronchial symptoms had been exhaustively evaluated during a 2-years pre-inclusion period. Patients underwent skin tests and bronchial challenge with Mth and allergen. The exposure to D. pteronyssinus allergen (Der pl) was quantified in dust samples. Dose-response curves with Mth [until the FEV1 fell by 40% or the maximal dose (200 mg/ml) was inhaled] were attained. We developed multiple models of discriminant analysis in order to evaluate the capacity of the above variables to differentiate groups. Asthma patients had higher total and specific IgE levels and a greater sensitivity (PD20 values) and response [dose-response slope (DRS)] to both Mth and allergen. The model entering these variables was the one that correctly classified more patients (79.2%). The discriminative power of the model that only included Mth-DRS values was similar to the above (78.8%). Bronchial response to Mth is quantitatively different in allergic rhinitis patients who display mild asthma symptoms when compared to those that only report rhinitis, suggesting a distinct bronchial intrinsic behavior. The utilization of complete dose-response curves with Mth allows a good separation between mild asthma and "pure" rhinitis patients and might be useful in the diagnosis of mild asthma. Whether the early detection and treatment of these patients prevents the development of symptomatic asthma needs further evaluation.

Sputum eosinophilia and maximal airway narrowing in Dermatophagoides pteronyssinus allergic rhinitis patients: only rhinitis or rhinitis plus mild asthma?

STUDY OBJECTIVE

To study the existence of bronchial disease among rhinitis patients. To evaluate the laboratory test or set of tests (ie, symptoms, exposure, and sensitization to the allergen, and the provocative dose of methacholine [Mth] causing a 20% fall in FEV(1) [PD(20)] and the maximal response plateau [MRP] to Mth) that best identifies a case of mild asthma.

DESIGN

Cross-sectional analysis in 52 Dermatophagoides pteronyssinus-monosensitized patients who were consulting a physician for perennial rhinitis.

SETTING

Allergy Department, Hospital Doctor Negrín, Las Palmas, Grand Canary Island, Spain.

INTERVENTIONS AND MEASUREMENTS

Patients filled out a standardized asthma symptom questionnaire, and underwent sputum induction and Mth challenge in which 40% falls in FEV(1) were attained. Dose-response curves were expressed in terms of both PD(20) values and the level of the MRP. D pteronyssinus allergen exposure was assessed in dust samples from patients' beds.

RESULTS

No difference between patients who positively responded to the questionnaire and those who did not was observed. Mth-PD(20) values were not detected in 13% of the patients reporting bronchial symptoms, and an MRP was not identified in 59% of the subjects who did not respond positively. A higher degree of allergen sensitization (ascertained from skin test results, and total and specific serum IgE levels) and higher degree of sputum eosinophilia were detected in subjects in whom an MRP had not been identified. The presence of sputum eosinophilia provided the best differentiation between those patients who presented with an MRP and those who did not.

CONCLUSION

The individual perception of bronchial symptoms is highly variable among perennial allergic rhinitis patients. The lack of a maximal airway-narrowing plateau is related to the presence of sputum eosinophilia, which might be useful in the detection of patients susceptible to anti-inflammatory therapy. Prospective studies evaluating whether these patients are more likely to develop symptomatic asthma in the future and if the early anti-inflammatory treatment prevents its development are needed.

Má percepção da limitação aos fluxos aéreos em pacientes com asma moderada a grave

Introdução: Este estudo avaliou a percepção da obstrução das vias aéreas em pacientes ambulatoriais com asma moderada a grave e a capacidade da ausculta torácica em identificar a limitação aos fluxos aéreos. Métodos: Trinta e três pacientes foram avaliados em sete visitas semanais usando escores de sintomas por meio de escala visual analógica de sintomas (EVAS, 0-100mm), índice clínico de hiper-reatividade brônquica (1-10), a classificação clínica de gravidade da asma (GINA, 1-4) e um escore de ausculta torácica (EAT, 0-5), espirometria e pico de fluxo expiratório (PFE), que foram correlacionados por meio do coeficiente de Spearman. Os pacientes foram classificados como percebedores (--1 <FONT FACE=Symbol>£ </FONT>r < 0) e não percebedores (0 <= r <= 1) através das correlações entre a EVAS para dispnéia e o VEF1. A correlação entre a ausculta e a obstrução brônquica foi considerada acurada quando um r <= --0,5 (EAT vs. VEF1) era observado. Resultados: Dezessete asmáticos (51,5%) não perceberam acuradamente o grau de obstrução das vias aéreas (não-percebedores). Nenhuma característica clínica pôde distinguir os grupos. Apenas 39,4% das correlações individuais entre EAT e VEF1 indicaram discriminação acurada pela ausculta. Asma grave não foi associada com ausculta não-acurada ou com má percepção neste estudo. Conclusão: Uma proporção significativa desta amostra de asmáticos não percebeu acuradamente a obstrução das vias aéreas. Além disso, o exame torácico mostrou ser um marcador inadequado da limitação aos fluxos aéreos em asmáticos moderados a graves, estáveis e ambulatoriais.

Effect of current exposure to Der p 1 on asthma symptoms, airway inflammation, and bronchial hyperresponsiveness in mite-allergic asthmatics

The existence of a dose-response relationship between indoor allergen exposure and sensitization has been widely described, but the effect of allergen exposure on asthma activity (symptoms, bronchial hyperresponsiveness [BHR], and inflammation) is not clear. Our aim was to determine the existence of an association among current exposure to mite allergens and symptoms, BHR, and airway inflammation assessed in blood and sputum from asthmatic patients sensitized to Dermatophagoides pteronyssinus. We selected 31 mild and recently diagnosed (12-24 months) asthma patients sensitized to D. pteronyssinus. Allergenic exposure (Der p 1, Der 2) was assessed by a commercial assay based on monoclonal antibodies (mAb), carried out on the dust samples collected from patients' beds in a standardized way. Patients completed an asthma symptom questionnaire and underwent skin tests, methacholine bronchial challenge, and sputum induction. Sputum cell profile was analyzed and eosinophil cationic protein (ECP), tryptase, albumin, and interleukin(IL)-5 levels were quantified in sputum supernatant. Total eosinophil numbers and ECP levels were measured in blood samples. Most patients were exposed to Der p 1 levels under 2 microg/g of dust. Der p 1 exposure was higher among the subjects with positive sputum tryptase detection (P = 0.020). Der p 1 levels showed a trend toward correlation with asthma symptoms (P = 0.066, r = 0.36) and correlated with sputum tryptase levels (P = 0.032, r = 0.42). No relationship between BHR, eosinophilic inflammation, and allergenic exposure was found. Our results suggest that asthma symptoms and lung mast-cell activation are at least partially dependent on current allergen exposure. The lack of correlation between mite exposure, eosinophilic inflammation, and BHR supports the role of other factors that enhance the immunologic response initiated by allergen, increasing the activity of asthma.