Perception of airway narrowing during reduction of inhaled corticosteroids and asthma exacerbation

Symptoms and perception of airway obstruction in asthmatic patients: Clinical implications for use of reliever medications

BACKGROUND

Asthma causes the unpleasant sensation of breathlessness (dyspnea) caused by airway obstruction. Patients with poor perception of airway obstruction are at risk of delay in seeking medical attention and undertreatment, which can lead to avoidable deaths. Conversely, those with heightened perception are at risk of overtreatment and iatrogenic adverse effects with reliever medications, anxiety, and unnecessary use of health care resources.

OBJECTIVE

We sought to review evidence about symptom misperception in asthmatic patients and how to identify and manage affected patients, particularly with regard to reliever medications.

METHODS

We conducted a systematic literature search for studies of perception of airway function in asthmatic patients. We searched the OVID (Medline and Medline [R] in process [PubMed]), Embase, and Adisearch/Odyssey databases, restricting our search to human studies published in English from 1990-2018, with no restrictions on age, sex, or racial origin.

RESULTS

We found that both underperception and overperception assessed during induced bronchoconstriction or bronchodilation or during changes in airway resistance were common across all age groups and that aging, disease severity, smoking, sex, ethnicity, psychologic factors, and medication are all associated with differences in perception. Importantly, airway inflammation was associated with impaired perception and a history of severe or near-fatal asthma. We also identified knowledge gaps, such as whether an individual patient's perception varies over time and the influence perception has on patients' use of reliever medication.

CONCLUSION

We found that abnormal perception of airway obstruction has important clinical implications for the management of patients with asthma.

Exertional Dyspnea in Childhood: Is There an Iceberg Beneath the Apex?

This essay expounds on fundamental, quantitative elements of the exercise ventilation in children, which was the subject of the Tom Rowland Lecture given at the NASPEM 2018 Conference. Our knowledge about how much ventilation rises during aerobic exercise is reasonably solid; our understanding of its governance is a work in progress, but our grasp of dyspnea and ventilatory limitation in children (if it occurs) remains embryonic. This manuscript summarizes ventilatory mechanics during dynamic exercise, then proceeds to outline our current understanding of mechanisms of dyspnea, particularly during exercise (exertional dyspnea). Most research in this field has been done in adults, and the vast majority of these studies in patients with chronic obstructive pulmonary disease. To what extent conclusions drawn from this literature apply to children and adolescents-both healthy and those with cardiopulmonary disease-will be discussed. The few, recent, pertinent, pediatric studies will be reviewed in an attempt to provide an empirical basis for proposing a hypothetical model to study exertional dyspnea in youth. Just as somatic growth will have consequences for ventilatory and exercise capacity, so too will neural developmental plasticity and experience affect perception of dyspnea. Our path to understand how these evolving inputs and influences summate during a child's life will be Columbus' India.

The efficacy and safety of mannitol challenge in a workplace setting for assessing asthma prevalence

OBJECTIVE

There is no standard definition of asthma for epidemiological purposes; most surveys use symptoms and bronchial hyperresponsiveness. Few studies tested mannitol challenge test (MCT) in occupational settings. We sought to determine efficacy and safety of MCT in detecting subjects with asthma symptoms in the workplace.

METHODS

In this cross-sectional study we recruited 908 workers in 2 universities; they underwent a respiratory questionnaire, spirometry, skin prick tests, and MCT.

RESULTS

Eight hundred and eleven subjects completed the study; 11.1% had a positive MCT; 8.14% had asthma. MCT had low sensitivity (35.4-61.9%) but high specificity (90.2-94.9%) to detect symptomatic individuals. The most prevalent symptom was wheezing in the last 12 months. Twenty-four of those with a positive MCT (26.7%) had no positive replies to the questions on asthma symptoms. Among subjects with a positive MCT, 71.9% achieved 95% of baseline FEV₁ after 15 minutes of salbutamol recovery treatment. Nine subjects (1.1%) had adverse events that prevented the test from being completed.

CONCLUSIONS

MCT has high specificity but low sensitivity to detect symptomatic subjects in the workplace. It may detect subjects with hyperresponsiveness but no symptoms, who could be at risk of developing airway diseases. The test is safe and well tolerated.

Mechanisms, measurement and management of exertional dyspnoea in asthma: Number 5 in the Series "Exertional dyspnoea" Edited by Pierantonio Laveneziana and Piergiuseppe Agostoni

Asthma is a heterogeneous condition, with dyspnoea during exercise affecting individuals to a variable degree. This narrative review explores the mechanisms and measurement of exertional dyspnoea in asthma and summarises the available evidence for the efficacy of various interventions on exertional dyspnoea. Studies on the mechanisms of dyspnoea in asthma have largely utilised direct bronchoprovocation challenges, rather than exercise, which may invoke different physiological mechanisms. Thus, the description of dyspnoea during methacholine challenge can differ from what is experienced during daily activities, including exercise. Dyspnoea perception during exercise is influenced by many interacting variables, such as asthma severity and phenotype, bronchoconstriction, dynamic hyperinflation, respiratory drive and psychological factors. In addition to the intensity of dyspnoea, the qualitative description of dyspnoea may give important clues as to the underlying mechanism and may be an important endpoint for future interventional studies. There is currently little evidence demonstrating whether pharmacological or non-pharmacological interventions specifically improve exertional dyspnoea, which is an important area for future research.

Reality and understanding of asthma control

The aim of this study was to describe the level and perception of control in severe asthma in Trinidad after the introduction of revised guidelines for asthma management. Adult asthmatics (N = 329) at Trinidad's chest clinics were cross-sectionally examined for guideline-defined disease control. Patients' mean (SD) age was 54.36 (14.9) years, with body mass index = 28.54 (7.4) kg/meter(2), and females were proportionally more (246, 74.74%). Measured (45.29%) and perceived (18.96%) uncontrolled disease were poorly concordant (κ statistic = 0.197). Co-morbidity (≥2 conditions) correlated with uncontrolled disease in 55.80% of patients (Spearman correlation p = 0.03). Absolute peak expiratory flow was higher (p < 0.001) in controlled and/or partially controlled disease than in uncontrolled asthma. Routine work limitation, night-time disturbances, work absenteeism, exacerbations, rescue inhalation and perceived control correlated with uncontrolled asthma (p < 0.001). Few patients self-monitored lung function (9.73%) or kept an asthma diary (6.69%), but 65.1% believed they had to live with their symptoms. The asthma burden was at least one hospitalization (53.80%) and emergency department visit (66.36%) in the past year, cough (74.49%), dyspnoea (84.50%), wheezing (80.55%) and chest tightness (66.87%). After the revised guidelines, uncontrolled asthma and related morbidity remain suboptimal, with disagreeing actual and perceived control. Efforts to transform guidelines into patient care with realistic interpretation of control are recommended.

Perception of bronchoconstriction: a complementary disease marker in children with asthma

INTRODUCTION

Asthma guidelines use symptoms as the most important aspect of asthma control. Symptom perception varies widely between individuals. Over-perception as well as underperception of bronchoconstriction could have a negative effect on asthma management. We hypothesized that perception of bronchoconstriction in childhood asthma is not related to common measures of disease control. For that reason, we examined the clinical determinants of the perception of bronchoconstriction and the repeatability of perception measurements.

PATIENTS AND METHODS

In school-age children with moderately severe atopic asthma, we measured the perception of bronchoconstriction (decrease in forced expiratory volume in 1 second (FEV(1)) during methacholine bronchoprovocation challenges. The perception of bronchoconstriction was assessed as the slope of the relation between FEV(1) and Borg score, and as the Borg score at a 20% decrease in FEV(1) from baseline during the provocation test (PS(20)). Data from subjects who had a 20% or more decrease in FEV(1) (n = 112) were used for the analysis. Fifty-four children repeated the test after 3 months. Symptoms, use of rescue medication, and peak expiratory flows were scored in diaries during the 2 weeks before testing.

RESULTS

Symptom perception was significantly better in children without (PD(20) > 1570 μg, n = 28) than in children with airway hyperresponsiveness (PD(20) ≤ 1570 μg, n = 112), slope 0.22 versus 0.13 respectively (p < .001). Borg scores correlated with PD(20) (p = .01), baseline FEV(1) (only for slope, p = .04), and use of rescue beta agonist (p = .01), but not with other aspects of asthma control. Repeatability of Borg scores was good (slope: R = 0.59, PS(20): R = 0.52).

CONCLUSION

Poorer symptom perception in asthmatic children correlated with hyperresponsiveness, and was associated with lower baseline FEV(1) and less use of rescue bronchodilators. This suggests that the measurement of symptom perception should be taken into account in individual management plans for children with asthma.

Comparison between two methods of asthma control evaluation based on individual perception

OBJECTIVE

To compare the subjective perception of asthma control reported by the patient with that measured by the score obtained on the Asthma Control Questionnaire 6-item version (ACQ-6) in patients with severe asthma and to determine whether asthma control is associated with the number of emergency room visits in the previous month.

METHODS

This was a cross-sectional study involving 528 patients treated at the Bahia State Asthma and Allergic Rhinitis Control Program Central Referral Clinic between August of 2008 and March of 2010, in the city of Salvador, Brazil. The patients completed the ACQ-6 and answered a specific additional question in order to evaluate their own perception of asthma control in the previous week.

RESULTS

We evaluated 423 patients who met the inclusion criteria. The sample was predominantly female (81.3%), and 64.3% had an income lower than two times the national minimum wage. The mean age was 49.85 ± 13.71 years, and the duration of asthma symptoms was 32.11 ± 16.35 years. The patients had been regularly treated via the program for 36.65 ± 18.10 months. Based on the subjective perception of asthma control, only 8% of the patients considered their asthma to be uncontrolled, whereas 38.8% had an ACQ-6 score > 1.5, which indicates poor control. The kappa statistic revealed poor concordance between the two methods. There was a direct association between uncontrolled asthma and the number of emergency room visits in the previous month (p < 0.001).

CONCLUSIONS

In this sample of patients, the subjective perception of asthma control differed from that measured by the ACQ-6 score, and the patients overestimated their own level of asthma control, which puts them at risk of being undertreated.

Difference in time-course of improvement in asthma control measures between budesonide and budesonide/formoterol

Combinations of inhaled corticosteroids (ICS) and inhaled long-acting beta(2)-agonists (LABA) have become widely used for the initiation of maintenance treatment for asthma. However, it has not been fully elucidated whether ICS/LABA alters the time-course of different control outcome measures in steroid-naive patients with asthma compared to the treatment with ICS alone. We compared the time-response in Asthma Control Questionnaire (ACQ), forced expiratory volume in 1 s (FEV1), exhaled nitric oxide fraction (FE(NO)), and airway responsiveness to methacholine (PD(200)) between budesonide (BUD) and budesonide/formoterol (BUD/FM). BUD/FM therapy significantly improved the ACQ score at week 2 and week 4 (p < 0.01 and p < 0.05), and increased FEV1 and the methacholine threshold at week 8 and week 24 (all p < 0.05) compared to BUD alone. A logistic function model showed that the BUD/FM combination significantly improved ACQ, FEV1, FE(NO) and PD(200) at a faster rate than BUD over 24 weeks (p < 0.001 for ACQ, FEV1, PD(200), and p < 0.05 for FE(NO), z-test). A significant variance in the time-response was also found in the outcomes of the two treatment groups (FE(NO) and ACQ > FEV1 and PD(200), p < 0.001, z-test). The present study provides evidence that ICS/LABA combination therapy results in a more rapid improvement in asthma symptoms, lung function, and airway inflammation compared to ICS monotherapy in steroid-naive patients with asthma.

Adrenal suppression: A practical guide to the screening and management of this under-recognized complication of inhaled corticosteroid therapy

Inhaled corticosteroids (ICSs) are the most effective anti-inflammatory agents available for the treatment of asthma and represent the mainstay of therapy for most patients with the disease. Although these medications are considered safe at low-to-moderate doses, safety concerns with prolonged use of high ICS doses remain; among these concerns is the risk of adrenal suppression (AS). AS is a condition characterized by the inability to produce adequate amounts of the glucocorticoid, cortisol, which is critical during periods of physiological stress. It is a proven, yet under-recognized, complication of most forms of glucocorticoid therapy that can persist for up to 1 year after cessation of corticosteroid treatment. If left unnoticed, AS can lead to significant morbidity and even mortality. More than 60 recent cases of AS have been described in the literature and almost all cases have involved children being treated with ≥500 μg/day of fluticasone.

The risk for AS can be minimized through increased awareness and early recognition of at-risk patients, regular patient follow-up to ensure that the lowest effective ICS doses are being utilized to control asthma symptoms, and by choosing an ICS medication with minimal adrenal effects. Screening for AS should be considered in any child with symptoms of AS, children using high ICS doses, or those with a history of prolonged oral corticosteroid use. Cases of AS should be managed in consultation with a pediatric endocrinologist whenever possible. In patients with proven AS, stress steroid dosing during times of illness or surgery is needed to simulate the protective endogenous elevations in cortisol levels that occur with physiological stress.

This article provides an overview of current literature on AS as well as practical recommendations for the prevention, screening and management of this serious complication of ICS therapy.

[Adult asthma exacerbations in questions]

In this article a French working party critically review the international literature to revise the definition, pathophysiology, treatment and cost of exacerbations of adult asthma. The various guidelines do not always provide a consistent definition of exacerbations of asthma. An exacerbation can be defined as deterioration of clinical and/or functional parameters lasting more than 24 hours, without return to baseline, requiring a change of treatment. No single clinical or functional criterion can be used as an early marker of an exacerbation. Innate and acquired immune mechanisms, modified by contact with infectious, irritant or allergenic agents, participate in the pathogenesis of exacerbations, which are accompanied by bronchial inflammation. In 2010, mortality is related to progression of exacerbations, often occurring before the patient seeks medical attention. The objective of treatment is to control asthma and prevent exacerbations. However, many factors can trigger exacerbations and often cannot be controlled. The efficacy of inhaled corticosteroids has been demonstrated on reduction of the number of exacerbations and the number of asthma-related deaths. This treatment is cost-effective, especially in terms of reduction of exacerbations.

Perception of dyspnea during acetylcholine-induced bronchoconstriction in asthmatic children

BACKGROUND

Few studies have examined the relationship between dyspnea perception and bronchial hyperresponsiveness (BHR) in asthmatic children.

OBJECTIVE

To test the hypothesis that severe BHR is associated with poor perception of the severity of airway obstruction.

METHODS

One hundred one asthmatic children (mean [SD] age, 11.1 [2.3] years) were evaluated using acetylcholine chloride (Ach) challenge. The BHR was assessed as the provocative concentration of Ach causing a 20% decrease in forced expiratory volume in 1 second (FEV1) (PC20). Perception of dyspnea was scored using a modified Borg scale after each dose of Ach and bronchodilator. The dyspnea threshold was defined as the point at which the Borg scale score became higher than 0. We evaluated the dyspnea perception score at a 20% decrease in FEV1 relative to baseline (PS20) and after bronchodilator administration (PS(BD)).

RESULTS

The mean (SD) PS20 and PS(BD) were significantly lower in the severe vs the mild BHR group (PS20: 2.1 [1.9] vs 4.2 [2.4], P < .001; PS(BD): 0.5 [1.0] vs 1.0 [1.3], P = .048). The mean (SD) % decrease in FEV1 at the dyspnea threshold was significantly greater in the severe vs the mild BHR group (14.1% [11%] vs 5.4% [11%], P < .001). The PS20 was correlated positively with the PC20 (r2 = 0.25, P < .001), and the decrease in FEV1 at the dyspnea threshold was correlated negatively with the PC20 (r2 = 0.18, P < .001).

CONCLUSIONS

Moderate to severe asthmatic children with severe BHR perceive dyspnea only after the stage of mild bronchoconstriction has passed. This relative insensitivity to dyspnea in asthmatic children with severe BHR may lead to undertreatment of asthma.

Relation between inflammation and symptoms in asthma

Asthma symptoms are the main reason for healthcare utilization and are a fundamental parameter for the evaluation of asthma control. Currently, asthma is defined as a chronic inflammatory disease. A French expert group studied the association between inflammation and asthma symptoms by carrying out a critical review of the international literature. Uncontrolled asthmatics have an increased number of polynuclear eosinophils in the induced sputum and an increased production of exhaled NO. Control by anti-inflammatory treatment is accompanied by a reduction in bronchial eosinophilia and exhaled NO. Asthma symptoms are the result of complex mechanisms and many factors modify their perception. Experimental data suggest that there is a relationship between the perception of symptoms and eosinophilic inflammation and that inhaled corticoid therapy improves this perception. Although they are still not applicable in routine practice, follow-up strategies based on the evaluation of inflammation are thought to be more effective in reducing exacerbations than those usually recommended based on symptoms and sequential analysis of respiratory function. Inhaled corticosteroid therapy is the reference disease-modifying therapy for persistent asthma. Recent studies demonstrated that adjustment of anti-inflammatory treatment based on symptoms is an effective strategy to prevent exacerbations and reduce the total number of doses of inhaled corticosteroids.

[The relationship between inflammation and symptoms in asthma]

In asthma, symptoms are the main reason for recourse to healthcare and are a fundamental parameter for the evaluation of asthma control. Currently, asthma is defined as a chronic inflammatory disease. Uncontrolled asthmatics have an increased number of eosinophils in induced sputum and an increased production of exhaled NO. Control by anti-inflammatory treatment is accompanied by a reduction in bronchial eosinophilia and exhaled NO. Asthma symptoms are the result of complex mechanisms and many factors modify their perception. Experimental data suggests that there is a relationship between the perception of symptoms and eosinophilic inflammation, and that inhaled corticoid therapy improves this perception. Although they are still not applicable in routine practice, follow-up strategies based on the evaluation of inflammation are thought to be more effective in reducing exacerbations than those usually recommended based on retrospective evaluation of symptoms and sequential analysis of respiratory function. Inhaled corticosteroid therapy is the reference maintenance therapy for persistent asthma and adjustment of anti-inflammatory treatment based on symptoms is an effective strategy to prevent exacerbations and reduce the total dose of inhaled corticosteroids. A French expert group has undertaken a study of the association between inflammation and asthma symptoms by carrying out a critical review of the international literature.

Asthma symptoms do not predict spirometry

BACKGROUND

Asthma is a disease characterized by variable airflow obstruction, but the measurement of airflow is often omitted in the process of diagnosis and management of the disease.

OBJECTIVES

Features of asthma severity and control were examined to determine the extent to which objective measurements, including forced expiratory volume in 1 s and forced expiratory volume in 1 s/forced vital capacity, correlated with other manifestations of the disease.

METHODS

Subjects were a consecutive sample of patients with asthma attending a university-based asthma clinic. All subjects underwent routine assessment using a standard questionnaire and spirometry.

RESULTS

A total of 500 subjects were included in the present study, and their assessment showed that neither symptoms nor history could predict or be predicted by their measurements of lung function.

CONCLUSION

Routine measurement of lung function should be performed on subjects with asthma if normal or near-normal lung function is a desired component of asthma control.

Diagnostic tests for asthma in firefighters

BACKGROUND

Subjects with asthma do not meet medical requirements for professions such as firefighting.

OBJECTIVE

To prospectively determine the diagnostic value of respiratory symptoms and various tests used in the assessment of asthma in a cohort of firefighters.

METHODS

A questionnaire, spirometry, direct and indirect airway challenge tests, exhaled nitric oxide, and skin-prick tests were administered prospectively to 101 of 107 firefighters employed in Basel, Switzerland. Asthma was defined as the combination of respiratory symptoms with airway hyperresponsiveness.

RESULTS

Six of 101 firefighters (6%) had physician-diagnosed asthma, which could be confirmed in 4 firefighters. In contrast, asthma was diagnosed in 14% (14 of 101 firefighters). Wheezing was the most sensitive symptom for the diagnosis of asthma (sensitivity, 78%; specificity, 93%). Other respiratory symptoms showed a higher specificity than wheezing but a markedly lower sensitivity. Bronchial airway challenge with mannitol was the most sensitive (92%) and specific (97%) diagnostic test for asthma. Using a cutoff point of 47 parts per billion, nitric oxide had a similar specificity (96%) but lower sensitivity (42%) compared to the direct (methacholine) and indirect (mannitol) airway challenge tests.

CONCLUSION

Asthma was considerably underdiagnosed in firefighters. The combination of a structured symptom questionnaire with a bronchial challenge test allows to identify patients with asthma and should routinely be used in the assessment of active firefighters and may be of help when evaluating candidates for this profession.

Perception of airway obstruction and airway inflammation in asthma: a review

Dyspnea has a multifactorial nature and the exact mechanism that causes breathlessness in asthma is not fully understood. There is compelling evidence that factors other than merely mechanical ones take part in the pathophysiology of breathlessness. Some recent reports attribute airway inflammation, which may contribute to the unexplained variability in the perception of dyspnea associated with bronchoconstriction. Eosinophil airway inflammation has been proposed as a determinant of breathlessness via mechanisms affecting either the mechanical pathways that control breathlessness or the afferent nerves involved in perception of dyspnea. In this review, data on the interrelation between inflammation and dyspnea sensation and the impact of treatment on dyspnea sensation are discussed. We conclude that regardless of whether mechanical or chemical inflammatory factors are involved, much variability in dyspnea scores remains unexplained.

The influence of corticosteroids on the perception of dyspnea in asthma

Corticosteroids are effective anti-inflammatory medications that are recommended for the control of persistent asthma. Little, however, is known about their influence on the perception of dyspnea, which, in turn, is important to the successful self-management of asthma. This paper provides a synopsis of available studies examining the impact of corticosteroids on the sensitivity to perceive dyspnea and presents possible mechanisms underlying this relationship. The results of these investigations are conflicting with some studies showing improved perception and other studies showing worsened perception of dyspnea after corticosteroid treatment. Thus, firm conclusions cannot be derived from the currently available data. Implications for future research, which is required to increase our understanding of potential influences of corticosteroids on the perception of dyspnea, are provided.

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.

Perception of dyspnea during exacerbation and histamine-related bronchoconstriction in patients with asthma

BACKGROUND

Numerous studies have been performed concerning the perception of dyspnea during changes in airway caliber provoked in the laboratory setting, but studies of asthma exacerbation are scarce.

OBJECTIVE

To investigate whether the perception of dyspnea during histamine-induced bronchoconstriction might be used to identify patients with asthma who sense dyspnea poorly during exacerbation.

METHODS

The perception of dyspnea in 50 patients (45 female, 5 male) with asthma was evaluated at admission with exacerbation and during a stable period. Perceived intensity of dyspnea was estimated using a modified Borg scale. The perception of dyspnea in the stable period 4 to 6 weeks after exacerbation was measured with the histamine challenge test. Perception parameters were defined as the change in Borg score divided by the change in forced expiratory volume in 1 second (FEV1) as a percentage of the baseline FEV1 (deltaBorg/deltaFEV1) and as the Borg score at 20% decrease (PS20Histamine) or increase (PS20Exacerbation) in FEV1.

RESULTS

The perception of dyspnea during asthma exacerbation was unrelated to the perception of dyspnea during histamine-induced bronchoconstriction (for deltaBorg/deltaFEV1, beta = .08, P = .50; for PS20, beta = -.11, P = .40). The kappa value for the agreement of poor perceivers at exacerbation and during the stable period was -0.21 (P = .10). However, the intensity of dyspnea caused by histamine-induced bronchoconstriction was lower than that caused by asthma exacerbation (PS20: 1.6 +/- 1.1 vs 2.8 +/- 2.5, respectively, P = .004; deltaBorg/deltaFEV1: 0.08 +/- 0.05 vs 0.21 +/- 0.28, respectively, P = .001).

CONCLUSION

The perception of dyspnea during asthma exacerbation is not correlated with the perception of dyspnea during histamine-induced bronchoconstriction. Therefore, the perception of dyspnea during histamine-induced bronchoconstriction cannot be used to identify the asthmatic patients who perceive dyspnea poorly.

Evaluation of severity of bronchial asthma through an exercise bronchial challenge

Optimum treatment of bronchial asthma requires accurate diagnosis and severity classification. We studied the use of an exercise bronchial challenge in the asthmatic patient as a diagnostic tool. An exercise bronchial challenge test was carried out in 431 asthmatic children and 114 children without a history of asthma in a moderate-altitude environment (2,230 m above sea level/7,314 feet above sea level). Values of peak expiratory flow (baseline and maximum fall) were analyzed through time in each asthma severity group (intermittent, mild persistent, moderate persistent, severe persistent, and nonasthmatic controls). There was a significant difference among responses of asthma severity groups for almost all variables. No difference was found between nonasthmatic and intermittent groups who had similar behavior, except in bronchodilator response. An exercise bronchial challenge helps classify a patient according to asthma severity; it is easy to reproduce and does not require expensive equipment. It allows diagnosing and classifying asthma severity easily and supplementing the clinical evaluation. Based on our results, we propose a fall of PEF >or= 11% as new cutoff point for making a diagnosis of persistent bronchial asthma. A fall of 11-25% indicates mild persistent asthma; from 25-50%, moderate persistent asthma; and a bigger fall, severe persistent asthma.