Humidity influences exercise capacity in subjects with exercise-induced bronchoconstriction (EIB)

Association of temperature and absolute humidity with incidence of exercise-induced bronchoconstriction in children

AIM

Exercise test outdoors is widely used to diagnose asthma in children, but it is unclear how much outdoor air factors affect the results.

METHODS

We analysed 321 outdoor exercise challenge tests with spirometry in children 6-16 years conducted due to suspicion of asthma or for assessing the effect of medication on asthma. We studied the association of FEV1 decrease and incidence of exercise-induced bronchoconstriction (EIB) with temperature, relative humidity (RH) and absolute humidity (AH).

RESULTS

Asthma was diagnosed in 57% of the subjects. AH ≥5 g/m3, but not RH or temperature, was associated with the EIB incidence (p = 0.035). In multivariable logistic regression, AH ≥5 g/m3 was negatively associated (OR = 0.51, 95% CI [0.28─0.92], p = 0.026) while obstruction before exercise (OR = 2.11, 95% CI [1.16─3.86], p = 0.015) and IgE-mediated sensitisation were positively associated with EIB (OR = 2.24, 95% CI [1.11─4.51], p = 0.025). AH (r = -0.12, p = 0.028) and temperature (r = -0.13, p = 0.023) correlated with decrease in FEV1. In multivariable linear regression, only AH was associated with FEV1 decrease (coefficient = -0.044, 95% CI [-0.085 to -0.004], p = 0.033).

CONCLUSION

AH of outdoor air associates with occurrence and severity of EIB in outdoor exercise tests in children. Care should be taken when interpreting negative outdoor exercise test results if AH of air is high.

Nonlinear effects of humidex on risk of outpatient visit for allergic conjunctivitis among children and adolescents in Shanghai, China: A time series analysis

Background

Various epidemiological studies have focused on the adverse health outcomes of meteorological factors. However, there has been little research on the impact of humidex on allergic conjunctivitis, especially in child and adolescent populations. We aimed to explore the impact of humidex, a comprehensive index of relative humidity and temperature, on child and adolescent allergic conjunctivitis admissions.

Methods

Outpatient visit data for allergic conjunctivitis, meteorological factors and air pollutants in Shanghai for the 2017-2022 period were retrieved. For the purpose of analysing the nonlinear connection and lag impact between humidex and admissions for paediatric and adolescent allergic conjunctivitis, the distributed lag nonlinear model (DLNM) was fitted.

Results

A total of 147 090 cases were included in our cohort. We found a significantly nonlinear effect on humidex and allergic conjunctivitis. In the single-day lag pattern, the relative risks (RR) of allergic conjunctivitis were significant at lag 0 (RR = 1.08, 95% confidence interval (CI) = 1.05-1.11) to lag 2 (RR = 1.01, 95% CI = 1.00-1.01), lag 5 (RR = 1.01, 95% CI = 1.00-1.01) to lag 9 (RR = 1.01, 95% CI = 1.00-1.01), and lag 14 (RR = 1.02, 95% CI: 1.01-1.03). In the cumulative-lag day pattern, the RR of allergic conjunctivitis were significant at lag 0-0 (RR = 1.08, 95% CI = 1.05-1.11) to lag 0-14 (RR = 1.21, 95% CI = 1.13-1.28). We found that boys, children aged 7-17 years, and children in the warm season were more vulnerable to humidex. In addition, the highest attributable fraction (AF) and attributable number (AN) of humidex are at lag 0-14 (AF = 0.17, AN = 25 026).

Conclusions

Humidex exposure markedly increased the risk of allergic conjunctivitis, especially in highly high humidex. Appropriate public health management is needed for disease management and early intervention.

Exercise-induced laryngeal obstruction (EILO) in athletes: a narrative review by a subgroup of the IOC Consensus on 'acute respiratory illness in the athlete'

Exercise-induced laryngeal obstruction (EILO) is caused by paradoxical inspiratory adduction of laryngeal structures during exercise. EILO is an important cause of upper airway dysfunction in young individuals and athletes, can impair exercise performance and mimic lower airway dysfunction, such as asthma and/or exercise-induced bronchoconstriction. Over the past two decades, there has been considerable progress in the recognition and assessment of EILO in sports medicine. EILO is a highly prevalent cause of unexplained dyspnoea and wheeze in athletes. The preferred diagnostic approach is continuous visualisation of the larynx (via laryngoscopy) during high-intensity exercise. Recent data suggest that EILO consists of different subtypes, possibly caused via different mechanisms. Several therapeutic interventions for EILO are now in widespread use, but to date, no randomised clinical trials have been performed to assess their efficacy or inform robust management strategies. The aim of this review is to provide a state-of-the-art overview of EILO and guidance for clinicians evaluating and treating suspected cases of EILO in athletes. Specifically, this review examines the pathophysiology of EILO, outlines a diagnostic approach and presents current therapeutic algorithms. The key unmet needs and future priorities for research in this area are also covered.

Changes in pulmonary function after long-duration adventure racing in adolescent athletes

The present study investigated the acute effects of a mixed-modality, long-duration adventure race on pulmonary function in adolescent athletes. Twenty male adolescents aged 14 to 17 years volunteered to participate in a wilderness adventure race of 68.5-km. Expiratory function was evaluated before, immediately after, and 24 h after race completion. Measurements included forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and peak expiratory flow (PEF). Maximal inspiratory and expiratory mouth static pressures (MIP and MEP, respectively) were also measured using a portable hand-held mouth pressure meter across the same time points. The mean completion time of the race was 05:38 ± 00:20 hours. A significant post-race decrease in FVC was observed immediately after the race (-5.2%, p = 0.01). However, no significant changes were observed for FEV1, PEF and the FEV1/FVC and FEV1/PEF ratios. In addition, estimates of respiratory muscle strength (MIP and MEP) were unaffected by the race. The long-duration adventure race induced no marked reduction in expiratory pulmonary function and this response was associated with no apparent respiratory muscle fatigue. Therefore, the pulmonary system of trained adolescent athletes was sufficiently robust to sustain the mixed-modality, long-duration adventure race of ∽5-6 h.

Impact of climate variability on exercise-induced bronchospasm in adolescents living in a semi-arid region

OBJECTIVE

To examine the impact of climate variability on the occurrence of exercise-induced bronchospasm in the rainy and dry seasons of a Brazilian semi-arid region.

METHODS

This sample comprised 82 adolescents aged 15 to 18 years, who were submitted to exercise-induced bronchospasm assessment on a treadmill and outdoors, during the rainy and the dry season. Anthropometric variables, sexual maturity and forced expiratory volume in the first second were analyzed. Air temperature and humidity, decline in forced expiratory volume in the first second (%) and frequency of bronchospasm were compared between seasons using the independent Student's t test, the Wilcoxon and McNemar tests, respectively. The level of significance was set at p<0.05.

RESULTS

The mean age was 15.65±0.82 years. Air temperature, air humidity and decline in forced expiratory volume in the first second (%) differed between seasons, with higher air temperature and humidity in the rainy season (29.6ºC±0.1 and 70.8%±0.6 versus 28.5ºC±0.2 and 48.5%±0.6; p<0.05). The decline in forced expiratory volume in the first second (%) was greater in the dry season (9.43%±9.97 versus 12.94%±15.65; p<0.05). The frequency of bronchospasm did not differ between seasons.

CONCLUSION

The dry season had a negative impact on forced expiratory volume in the first second in adolescents, with greater decrease detected during this period. Findings of this study suggested bronchospasm tends to be more severe under low humidity conditions.

Validity and reproducibility of VO2 max testing in a respiration chamber

The aim of this study was to investigate whether VO₂max can be accurately measured in a respiration chamber. Thirty participants aged 23.4 ± 3.9 years with a wide range in VO₂max were included. Participants performed four incremental cycle ergometer tests (VO₂max) with a minimum of 5 days between tests. These tests consisted of one familiarization test with face mask, followed by two VO₂max tests in the respiration chamber and one test with face mask in randomized order. Oxygen consumption and CO₂ production were measured continuously using Omnical (Maastricht University, the Netherlands) gas analysis system. The mean VO₂max was 3634 ± 766 ml, which resulted in mean VO₂max per lean body mass of 60.8 ± 8.0 ml/kg. Repeated respiration chamber tests showed a high concordance, and no significant differences were detected between tests (Lin's concordance correlation coefficient (Rc) = 0.99; ∆70 ± 302 ml/min; p = .38). There was high concordance between the mean VO₂max from both respiration chamber tests and the mean face mask tests, and no significant difference (Rc = 0.99; ∆41 ± 173 ml/min; p = .22) was observed. The Bland‐Altman plots showed no proportional bias between different tests. In conclusion, the respiration chamber has been found to be a valid and reproducible method for measuring VO₂max. New research opportunities are possible in the respiration chamber, such as maximal exercise testing during 24‐hour measurements.

Humidity prevents the exercise-induced formation of hydrogen peroxide and nitrite in exhaled breath condensate in recreational cyclists

PURPOSE

The aerobic exercise affects the respiratory redox-state. The influence of different relative humidity (RH) levels on the formation of respiratory reactive chemical species associated with redox-state altered by exercise has been poorly explored. Our aim was to evaluate the effect of two different RH conditions (40% vs. 90%) on the concentration of hydrogen peroxide and nitrite in exhaled breath condensate ([H₂O₂]_EBC and [NO₂^-]_EBC) and spirometry parameters in recreational cyclists.

METHODS

Sixteen men and women (12/4) (mean age ± SD: 23.5 ± 2.2 years) completed 60-min of cycling at 166.3 ± 26.9 watts (70% of maximum load of [Formula: see text]-max. test, 49.3 ± 7.6 mL·min^-1·kg^-1) at random 40%-RH and 90%-RH conditions separated by 7 days. The two-way RM-ANOVA test was applied to compare [H₂O₂]_EBC, [NO₂^-]_EBC, [NO₂^-]_EBC/[NO₂^-]_Plasma at rest and 80-min post-exercise (80-post); and spirometry parameters at rest, 20-post and 80-post.

RESULTS

The interaction of factors (humidity × time) was significant in [H₂O₂]_EBC, [NO₂^-]_EBC, [NO₂^-]_EBC/[NO₂^-]_Plasma (p = 0.005, p = 0.030, p = 0.043, respectively). At 40%-RH conditions, the same parameters were higher in 80-post than at rest (p < 0.001, p = 0.001, p = 0.014, respectively). At the same time, the [H₂O₂]_EBC and [NO₂^-]_EBC/[NO₂^-]_Plasma were higher in 40%-RH than 90%-RH (p = 0.010, p < 0.001, respectively). The interaction was significant in FEV₁ (p = 0.013) and FEF_25-75% (p = 0.023), but not in FEV₁/FVC (p = 0.362). At 80-post, the changes are kept in 90%-RH (p < 0.001), diminishing in 40%-RH being similar to rest.

CONCLUSION

In recreational cyclists, 90%-RH prevents the increase of hydrogen peroxide and nitrite in exhaled breath condensate samples observed at 40%-RH and prolonging the bronchodilation until 80-post cycling exercise.

Cardiopulmonary exercise testing in patients with asthma: What is its clinical value?

Asthma is one of the most common respiratory disorders, characterized by fully or largely reversible airflow limitation. Asthma symptoms can be triggered or magnified during exertion, while physical activity limitation is often present among asthmatic patients. Cardiopulmonary exercise testing (CPET) is a dynamic, non-invasive technique which provides a thorough assessment of exercise physiology, involving the integrative assessment of cardiopulmonary, neuromuscular and metabolic responses during exercise. This review summarizes current evidence regarding the utility of CPET in the diagnostic work-up, functional evaluation and therapeutic intervention among patients with asthma, highlighting its potential role for thorough patient assessment and physician clinical desicion-making.

Diagnosis of Exercise-induced Bronchoconstriction in Swimmers: Context Matters

Swimmers have a high prevalence of exercise-induced bronchoconstriction (EIB), which may be associated with repeated exposure to chlorinated pool water. The eucapnic voluntary hyperpnea (EVH) test is used to diagnose EIB; however, it fails to replicate the environmental conditions experienced by swimmers. The relationship between the composition of the EVH inspired gas and the development of EIB from swim exercise remains unclear.

PURPOSE

This study aimed to compare the bronchoconstrictive effect of a chlorinated inspirate EVH test and swim test to a laboratory-based EVH test in swimmers.

METHODS

Fifteen collegiate swimmers (n = 5 male, n = 10 female; 21 ± 2 yr) completed 3 d of testing in pseudorandom order; a standard EVH test (EVHL), a pool air EVH test (EVHCl), and a swimming test (Swim). Spirometry was measured at baseline, and 3, 5, 10, 15, and 20 min after each test.

RESULTS

EVHL elicited a forced expired volume in 1 s (FEV1) fall index of -9.7% ± 6.4% compared with -6.6% ± 9.2% and -3.0% ± 7.5% after EVHCl and Swim, respectively (P < 0.05). Using Bland-Altman analysis, we found good agreement between EVHL and EVHCl (bias = -2.8, r = 0.79; P < 0.05) with poor agreement between EVHL and Swim (bias = -6.7, r = 0.20) and between EVHCl and Swim (bias = -3.9, r = 0.50; both P < 0.05). Forced expired flow between 25% and 75% lung volume and peak expired flow were significantly reduced by the EVHL compared with the EVHCl and Swim tests (P < 0.05).

CONCLUSIONS

EVHL elicits a greater forced expired volume in 1-s fall index compared with EVHCl and Swim. The unique aquatic environment of swimmers potentially protects against bronchoconstriction and should be considered in the determination of EIB.

Recommendations for 24-Hour Movement Behaviours in Adults with Asthma: A Review of Current Guidelines

Background: Many countries have clinical practice guidelines (CPG) for asthma that serve as an important resource for healthcare professionals and inform the development of policies and practices relevant to asthma care. The purpose of this scoping review was to search for CPGs related to asthma to determine what recommendations related to the 24-h movement behaviours are provided. Methods: We searched for the most recent CPGs published by a national authoritative body from 195 countries. Guidelines were reviewed for all movement behaviours; that is, physical activity, sedentary behaviour, and sleep. Results: In total, 82 documents were searched for eligibility and 19 were included in our review. Of these, only 10 CPGs provided information on physical activity; none provided recommendations consistent with the FITT principle, while seven recommended activity levels similar to the general population. None of the guidelines included information on sedentary behaviour. Nine guidelines included information on sleep: recommendations mostly focused on changes to medication to reduce disruptions in sleep. Conclusions: It is recommended that future work be conducted to create comprehensive movement behaviour guidelines accompanied with relevant precautions and strategies to ensure that adults with asthma are able to safely and effectively engage in movement behaviours throughout the day.

Impacts of exposure to humidex on the risk of childhood asthma hospitalizations in Hefei, China: Effect modification by gender and age

BACKGROUND

With global climate change, there is growing concern about the effects of temperature changes on childhood asthma. However, current research only focuses on the effects of temperature, while ignoring the adverse effects of humidity on children.

OBJECTIVES

Our study aimed to quantify the impact of humidex on childhood asthma hospitalizations, which combined temperature and humidity, and further to assess how the effect is modified by individual-factors, such as age and gender.

METHODS

Poisson generalized linear models combined with distributed lag nonlinear models were used to estimate the association between daily childhood asthma hospitalizations and humidex from 2013 to 2016. Air pollutions (CO, O_3, and NO₂) and wind velocity were modelled simultaneously using DLNM, as well as day of week, seasonality and long-term trend.

RESULTS

Low humidex was associated with an increased risk of admissions for asthma in children. The adverse effect appeared on the 4th day, with the RR of 1.045 (95%CI: 1.007-1.084) and lasted until the 7th day (RR: 1.045, 95%CI: 1.006-1.085). Compared with the male, there was an immediate effect on female exposed to low humidex. And the female seems to be more sensitive to low humidex. Besides, the significant effects of humidex on children asthma were detected in the children with preschool and school-age, whereas not for the subgroup of infants. And the school-age children are most sensitive to low humidex.

CONCLUSIONS

Low humidex was associated with the increased risk of admissions for childhood asthma in Hefei. Children suffering from asthma should avoid exposure to the low humidex environment, especially in female and school-age children. In addition, the index of humidex was more significant for disease prevention and public health than the average temperature. These findings may provide epidemiology evidence for formulating precaution guidelines to reduce the risk of childhood asthma hospitalizations.

Pharmacologic Strategies for Exercise-Induced Bronchospasm with a Focus on Athletes

Exercise-induced bronchoconstriction (EIB) is the transient narrowing of the airways during and after exercise that occurs in response to increased ventilation in susceptible individuals. It occurs across the age spectrum in patients with underlying asthma and can occur in athletes without baseline asthma. The inflammatory mechanisms underlying EIB in patients without asthma may be distinct from those underlying EIB in patients with asthma. This review summarizes mechanistic and clinical data that can guide the choice of chronic and acute pharmacologic therapies targeting control of EIB. Relevant regulations from the World Anti-Doping Agency are also discussed.

Exercise-Induced Bronchoconstriction and the Air We Breathe

An association between airway dysfunction and airborne pollutant inhalation exists. Volatilized airborne fluorocarbons in ski wax rooms, particulate matter, and trichloromines in indoor environments are suspect to high prevalence of exercise-induced bronchoconstriction and new-onset asthma in athletes competing in cross-country skiing, ice rink sports, and swimming. Ozone is implicated in acute decreases in lung function and the development of new-onset asthma from exposure during exercise. Mechanisms and genetic links are proposed for pollution-related new-onset asthma. Oxidative stress from airborne pollutant inhalation is a common thread to progression of airway damage. Key pollutants and mechanisms for each are discussed.

Respiratory Function and Symptoms Post Cold Air Exercise in Female High and Low Ventilation Sport Athletes

Purpose

Cold weather exercise is common in many regions of the world; however, it is unclear whether respiratory function and symptom worsen progressively with colder air temperatures. Furthermore, it is unclear whether high-ventilation sport background exacerbates dysfunction and symptoms.

Methods

Seventeen active females (measure of the maximum volume of oxygen [VO_2max]: 49.6±6.6 mL·kg^-1·min^-1) completed on different days in random order 5 blinded running trials at 0℃, -5℃, -10℃, -15℃, and -20℃ (humidity 40%) in an environmental chamber. Distance, heart rate, and rating of perceived exertion (RPE) were measured within each trial; forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), forced expiratory flow at 25%-75% (FEF_25-75), and forced expiratory flow at 50% (FEF₅₀) were measured pre- and post-test (3, 6, 10, 15, and 20 minutes). Respiratory symptoms and global effort were measured post-test spirometry.

Results

Mean decreases were found in FEV1 (4%-5% at 0℃, -5℃, -10℃, and -15℃; 7% at -20℃). FEF_25-75 and FEF₅₀ decreased 7% and 11% at -15℃ and -20℃, respectively. Post-exertion spirometry results were decreased most at 3 to 6 minutes, recovering back to baseline at 20 minutes. Respiratory symptoms and global effort significantly increased at -15℃ and -20℃ with decreased heart rate. High-ventilation sports decreased function more than low-ventilation participants but had fewer symptoms.

Conclusions

These results indicate that intense exercise at cold air temperatures up to -20℃ is achievable; however, greater effort along with transient acute bronchoconstriction and symptoms of cough after exercising in temperatures colder than -15℃ are likely. It is recommended that individuals cover their mouth and reduce exercise intensity to ameliorate the effects of cold weather exercise.

Exercise-induced bronchospasm in a hot and dry region: study of asthmatic, rhinitistic and asymptomatic adolescents

BACKGROUND

Exercise-induced bronchospasm (EIB) is the bronchial narrowing that occurs after intense exercise in a significant number of asthmatics and in some non-asthmatics. This study aims to evaluate the occurrence of EIB in adolescents with asthma, rhinitis and respiratory asymptomatics in a hot and dry climate.

RESEARCH DESIGN AND METHODS

This is a cross-sectional study based on an epidemiological study that evaluated the prevalence of asthma in schoolchildren in a semi-arid zone of Brazil. The EIB was defined as a reduction in forced expiratory volume in first second (FEV₁) greater than 10%.

RESULTS

A total of 114 individuals participated in the study (36.8% male), of whom 54 were asymptomatic, 30 asthmatic and 30 with rhinitis. Asthmatics presented a higher proportion of EIB in comparison to rhinitis and asymptomatics (46.7% vs. 13.3% and 7.4%, p = 0.001) and none of the individuals had severe EIB (ΔFEV₁ ≥ 50%).

CONCLUSIONS

A large proportion of the asthmatics selected from the community for the clinical study had EIB. Among participants with rhinitis, EIB was found in slightly more than 10%, while in the asymptomatics the frequency was slightly more than 5%. This study presents an important aspect in individuals living in hot and dry climates.

Exercise inducible laryngeal obstruction: diagnostics and management

Obstruction of the central airways is an important cause of exercise-induced inspiratory symptoms (EIIS) in young and otherwise healthy individuals. This is a large, heterogeneous and vastly understudied group of patients. The symptoms are too often confused with those of asthma. Laryngoscopy performed as symptoms evolve during increasing exercise is pivotal, since the larynx plays an important role in symptomatology for the majority. Abnormalities vary between patients, and laryngoscopic findings are important for correct treatment and handling. The simplistic view that all EIIS is due to vocal cord dysfunction [VCD] still hampers science and patient management. Causal mechanisms are poorly understood. Most treatment options are based on weak evidence, but most patients seem to benefit from individualised information and guidance. The place of surgery has not been settled, but supraglottoplasty may cure well-defined severe cases. A systematic clinical approach, more and better research and randomised controlled treatment trials are of utmost importance in this field of respiratory medicine.

Monitoring asthma in childhood: lung function, bronchial responsiveness and inflammation

This review focuses on the methods available for measuring reversible airways obstruction, bronchial hyperresponsiveness (BHR) and inflammation as hallmarks of asthma, and their role in monitoring children with asthma. Persistent bronchial obstruction may occur in asymptomatic children and is considered a risk factor for severe asthma episodes and is associated with poor asthma outcome. Annual measurement of forced expiratory volume in 1 s using office based spirometry is considered useful. Other lung function measurements including the assessment of BHR may be reserved for children with possible exercise limitations, poor symptom perception and those not responding to their current treatment or with atypical asthma symptoms, and performed on a higher specialty level. To date, for most methods of measuring lung function there are no proper randomised controlled or large longitudinal studies available to establish their role in asthma management in children. Noninvasive biomarkers for monitoring inflammation in children are available, for example the measurement of exhaled nitric oxide fraction, and the assessment of induced sputum cytology or inflammatory mediators in the exhaled breath condensate. However, their role and usefulness in routine clinical practice to monitor and guide therapy remains unclear, and therefore, their use should be reserved for selected cases.

Larynx during exercise: the unexplored bottleneck of the airways

Exercise-induced shortness of breath is not uncommon in otherwise healthy young people. Based on the presenting symptoms alone, it is challenging to distinguish exercise-induced asthma (EIA) from exercise-induced obstruction of central airways, sometimes leading to diagnostic errors and inadequate treatment. Central airway obstruction usually presents with exercise-induced inspiratory symptoms (EIIS) during ongoing exercise. EIIS tends to peak towards the end of an exercise session or immediately after its completion, contradicting symptoms of EIA typically peaking 3-15 min after the exercise has stopped. EIIS is usually associated with some form of laryngeal obstruction. Transnasal flexible laryngoscopy performed continuously throughout an incremental exercise test from rest to exhaustion or to intolerable symptoms is usually diagnostic, and also provides information that is important for further handling and treatment. Reflecting the complex anatomy and functional features of the larynx, exercise-induced laryngeal obstruction (EILO) appears to be a heterogeneous condition. Contradicting previous beliefs, recent literature suggests that laryngeal adduction in a majority of cases starts in supraglottic structures and that vocal cord adduction (VCD) most often occurs as a secondary phenomenon. However, EILO is poorly understood and more and better research is needed to unravel causal mechanisms. The evidence base for treatment of EILO is weak. Speech therapy, psychotherapy, biofeedback, muscle training, anticholinergic aerosols have all been applied, as has laser supraglottoplasty. Randomized controlled trials with well-defined and verifiable inclusion and success criteria are required to establish evidence-based treatment schemes.

The impact of exercise-induced bronchoconstriction on athletic performance: a systematic review

BACKGROUND

Exercise-induced bronchoconstriction (EIB) describes the phenomenon of transient airway narrowing in association with physical activity. Although it may seem likely that EIB would have a detrimental impact on athletic performance, this has yet to be established.

OBJECTIVES

The aim of this review is to provide a systematic appraisal of the current status of knowledge regarding EIB and exercise performance and to highlight potential mechanisms by which performance may be compromised by EIB.

DATA SOURCES AND STUDY SELECTION

PubMed/Medline and EBSCO databases were searched up to May 2014 using the search parameter: [('exercise' OR 'athlete') AND ('asthma' OR 'bronchoconstriction' OR 'hypersensitivity') AND 'performance']. This search string returned 243 citations. After systematically reviewing all of the abstracts, 101 duplicate papers were removed, with 132 papers excluded for not including an exercise performance outcome measure.

RESULTS

The remaining ten studies that met the initial criteria were included in this review; six evaluated the performance of physically active individuals with asthma and/or EIB while four assessed the effects of medication on performance in a comparable population.

CONCLUSION

The evidence concludes that whilst it is reasonable to suspect that EIB does impact athletic performance, there is currently insufficient evidence to provide a definitive answer.

Anti-leukotriene agents compared to inhaled corticosteroids in the management of recurrent and/or chronic asthma in adults and children

BACKGROUND

Anti-leukotrienes (5-lipoxygenase inhibitors and leukotriene receptors antagonists) serve as alternative monotherapy to inhaled corticosteroids (ICS) in the management of recurrent and/or chronic asthma in adults and children.

OBJECTIVES

To determine the safety and efficacy of anti-leukotrienes compared to inhaled corticosteroids as monotherapy in adults and children with asthma and to provide better insight into the influence of patient and treatment characteristics on the magnitude of effects.

SEARCH METHODS

We searched MEDLINE (1966 to Dec 2010), EMBASE (1980 to Dec 2010), CINAHL (1982 to Dec 2010), the Cochrane Airways Group trials register, and the Cochrane Central Register of Controlled Trials (Dec 2010), abstract books, and reference lists of review articles and trials. We contacted colleagues and the international headquarters of anti-leukotrienes producers.

SELECTION CRITERIA

We included randomised trials that compared anti-leukotrienes with inhaled corticosteroids as monotherapy for a minimum period of four weeks in patients with asthma aged two years and older.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the methodological quality of trials and extracted data. The primary outcome was the number of patients with at least one exacerbation requiring systemic corticosteroids. Secondary outcomes included patients with at least one exacerbation requiring hospital admission, lung function tests, indices of chronic asthma control, adverse effects, withdrawal rates and biological inflammatory markers.

MAIN RESULTS

Sixty-five trials met the inclusion criteria for this review. Fifty-six trials (19 paediatric trials) contributed data (representing total of 10,005 adults and 3,333 children); 21 trials were of high methodological quality; 44 were published in full-text. All trials pertained to patients with mild or moderate persistent asthma. Trial durations varied from four to 52 weeks. The median dose of inhaled corticosteroids was quite homogeneous at 200 µg/day of microfine hydrofluoroalkane-propelled beclomethasone or equivalent (HFA-BDP eq). Patients treated with anti-leukotrienes were more likely to suffer an exacerbation requiring systemic corticosteroids (N = 6077 participants; risk ratio (RR) 1.51, 95% confidence interval (CI) 1.17, 1.96). For every 28 (95% CI 15 to 82) patients treated with anti-leukotrienes instead of inhaled corticosteroids, there was one additional patient with an exacerbation requiring rescue systemic corticosteroids. The magnitude of effect was significantly greater in patients with moderate compared with those with mild airway obstruction (RR 2.03, 95% CI 1.41, 2.91 versus RR 1.25, 95% CI 0.97, 1.61), but was not significantly influenced by age group (children representing 23% of the weight versus adults), anti-leukotriene used, duration of intervention, methodological quality, and funding source. Significant group differences favouring inhaled corticosteroids were noted in most secondary outcomes including patients with at least one exacerbation requiring hospital admission (N = 2715 participants; RR 3.33; 95% CI 1.02 to 10.94), the change from baseline FEV(1) (N = 7128 participants; mean group difference (MD) 110 mL, 95% CI 140 to 80) as well as other lung function parameters, asthma symptoms, nocturnal awakenings, rescue medication use, symptom-free days, the quality of life, parents' and physicians' satisfaction. Anti-leukotriene therapy was associated with increased risk of withdrawals due to poor asthma control (N = 7669 participants; RR 2.56; 95% CI 2.01 to 3.27). For every thirty one (95% CI 22 to 47) patients treated with anti-leukotrienes instead of inhaled corticosteroids, there was one additional withdrawal due to poor control. Risk of side effects was not significantly different between both groups.

AUTHORS' CONCLUSIONS

As monotherapy, inhaled corticosteroids display superior efficacy to anti-leukotrienes in adults and children with persistent asthma; the superiority is particularly marked in patients with moderate airway obstruction. On the basis of efficacy, the results support the current guidelines' recommendation that inhaled corticosteroids remain the preferred monotherapy. 

Exercise-related quality of life in subjects with asthma: a systematic review

OBJECTIVE

The purpose of this review was to analyze, based on a review of the current literature, the effects of physical activity on the quality of life (QoL) of subjects with asthma.

METHODS

The authors conducted a search of randomized controlled trials (RCTs) between January 2000 and August 2010 in a group of major databases of health sciences (Academic Search Complete, Directory of Open Access Journals, Elsevier--Science Direct, Highwire Press, PubMed, Scielo Global, Scirus, Scopus, SpringerLink, Taylor & Francis, and Wiley Interscience) with the keywords asthma, QoL, physical activity, exercise, training, and program in all possible combinations. Citations and references of each study selected were also examined.

RESULTS

Of the 1075 studies identified, only 11 were included. Five of these studies were performed in children between the ages of 7 and 15 and the remaining studies were performed on adults. Intervention programs were divided into aerobic training programs and breathing exercises programs. All aerobic training programs showed improvements in QoL, demonstrating a positive influence of aerobic training on asthma.

CONCLUSIONS

There is a noticeable trend in the benefit of aerobic training programs in the QoL for individuals with asthma. The breathing exercises programs were few and heterogeneous, making it difficult to reach a positive conclusion on whether it could be recommended for the improvement of QoL in this pathology. There is a great need for more RCTs with methodological rigor.

The relationships between weather-related factors and daily outdoor physical activity counts on an urban greenway

The purpose of this study was to examine relationships between weather and outdoor physical activity (PA). An online weather source was used to obtain daily max temperature [DMT], precipitation, and wind speed. An infra-red trail counter provided data on daily trail use along a greenway, over a 2-year period. Multiple regression analysis was used to examine associations between PA and weather, while controlling for day of the week and month of the year. The overall regression model explained 77.0% of the variance in daily PA (p < 0.001). DMT (b = 10.5), max temp-squared (b = -4.0), precipitation (b = -70.0), and max wind speed (b = 1.9) contributed significantly.

CONCLUSION

Aggregated daily data can detect relationships between weather and outdoor PA.

Lifestyle and the Respiratory Health of Children

This article offers a review of the potential influences of personal lifestyle on respiratory health in children, looking at both healthy individuals and those with respiratory disorders. As with many aspects of health, regular physical activity, an appropriate diet, and avoidance of obesity and cigarette smoke all contribute to optimal development of the healthy child. An active lifestyle is associated with greater static and dynamic lung volumes, greater efficiency of the ventilatory process, and an optimization of breathing patterns. The risk of upper respiratory infections is also reduced in those maintaining a moderate level of physical activity. Maternal smoking during pregnancy, as well as active and passive smoking, all have an adverse influence on lung function in the child, the largest effects being on dynamic lung volumes. The risk of developing asthma seems reduced in children who maintain a normal body mass and are physically active. A program of graded physical activity is of therapeutic value in a number of established respiratory conditions, including asthma, cystic fibrosis, and ventilatory impairment from neuromuscular disorders. Exercise carries a slight risk of fatalities from asthma and anaphylactic reactions. In designing an optimal physical activity program, it is also important to guard against the hazards of deep oronasal breathing, including the precipitation of bronchospasm by the inhalation of cold, dry air and pollens; an increased exposure to atmospheric pollutants (reducing and oxidant smog, fine and ultra-fine particulates, and carbon monoxide); and possible long-term dangers from chlorine derivatives in the atmosphere of indoor swimming pools.

Physical Activity in Childhood Asthma: Friend or Foe?

Physical activity has been considered as a double-edged sword for children with asthma. Children with asthma are recommended to participate in physical activities like their healthy nonasthmatic peers because regular physical activity positively affects psychological functioning, quality of life, morbidity, and aerobic fitness in children with asthma. However, uncontrolled asthma with ongoing exercise-induced bronchoconstriction may limit participation in sports, free play, and daily living. Observations also suggest that high-intensity exercise performed in cold air, seasonal allergens, pollutants, or respiratory virus infections may increase the risk for asthma in the highly active child. In contrast, a sedentary lifestyle has been highlighted as the explanation for the increased prevalence of asthma in the past decades. However, there is no consensus on whether a low level of physical activity increases the severity or risk of asthma. Use of asthma medications and good asthma control can make the conditions favorable for a physically active lifestyle and influence physical activity level and the level of aerobic fitness.

Effect of acute cold exposure on lung perfusion and tracheal smooth muscle contraction in rabbit

Acute exposure to cold temperature can affect the respiratory system of those exposed to extreme weather and induces asthma in asthmatic patients. However, the effect on lung perfusion and the pulmonary circulation was not addressed in any previous study. The present study investigates the effects of acute cold exposure on tracheal smooth muscle and lung perfusion. New Zealand White rabbits were used in these experiments. For in vitro experiments, isolated tracheal segments were suspended in organ baths containing Krebs' solution for isometric tension recording. Tissue response to cooling from 37 to 4°C was examined. For in vivo experiments, the rabbits were kept in a cold room (4°C) for 1 h. Lung perfusion scintigraphy was performed at the end of this period. Each rabbit was injected with 74 MBq (2 mCi) technetium-99m macroaggregated ((99m)Tc MAA). Perfusion studies were done by using Gamma camera equipped with a low-energy, high-resolution, parallel-hole collimator interfaced with a computer. Static images were acquired 5 min after administration of the radiotracer. Cooling induced a rapid and reproducible contraction in the tracheal smooth muscle. Rabbits exposed to cold temperature had lesser lung perfusion than controls using radionuclide perfusion study. Our results highlight the response of tracheal muscle and pulmonary circulation to cold exposure. These results indicate that cooling induced contraction of the trachea and decreased pulmonary circulation and lung perfusion. This summation of acute cooling for tracheal smooth muscle and pulmonary circulation seems to be the reason for the severe cooling-induced contraction.

Changes in weather and the effects on pediatric asthma exacerbations

BACKGROUND

Pediatric asthma exacerbations may correlate with changes in weather, yet this relationship is not well defined.

OBJECTIVE

To determine the effects of fluctuations in climatic factors (temperature, humidity, and barometric pressure) on pediatric asthma exacerbations.

METHODS

A retrospective study was performed at 1 large urban hospital during a 2-year period (January 1, 2004, to December 31, 2005). Children presenting to the emergency department (ED) for an asthma exacerbation were included. Data on climactic factors, pollutants, and aeroallergens were collected daily. The relationship of daily (intraday) or between-day (interday) changes in climactic factors and asthma ED visits was evaluated using time series analysis, controlling for seasonality, air pollution, and aeroallergen exposure. The effects of climactic factors were evaluated on the day of admission (T=0) and up to 5 days before admission (T-5 through T-1).

RESULTS

There were 25,401 asthma ED visits. A 10% intraday increase in humidity on day T-1 or day T-2 was associated with approximately 1 additional ED visit for asthma (P < .001 and P = .01, respectively). Interday changes in humidity from day T - 3 to T-2 were also associated with more ED visits (P < .001). Interday changes in temperature from T-1 to T = 0 increased ED visits, with a 10 degrees F increase being associated with 1.8 additional visits (P = .006). No association was found with changes in barometric pressure.

CONCLUSION

Fluctuations in humidity and temperature, but not barometric pressure, appear to influence ED visits for pediatric asthma. The additional ED visits occur 1 to 2 days after the fluctuation.

An imbalance in C/EBPs and increased mitochondrial activity in asthmatic airway smooth muscle cells: novel targets in asthma therapy?

The asthma prevalence was increasing over the past two decades worldwide. Allergic asthma, caused by inhaled allergens of different origin or by food, is mediated by inflammatory mechanisms. The action of non-allergic asthma, induced by cold air, humidity, temperature or exercise, is not well understood. Asthma affects up to 15% of the population and is treated with anti-inflammatory and muscle relaxing drugs which allow symptom control. Asthma was first defined as a malfunction of the airway smooth muscle, later as an imbalanced immune response of the lung. Recent studies placed the airway smooth muscle again into the focus. Here we summarize the molecular biological basis of the deregulated function of the human airway smooth muscle cell as a cause or important contributor to the pathology of asthma. In the asthmatic human airway smooth muscle cells, there is: (i) a deregulation of cell differentiation due to low levels of maturation-regulating transcription factors such as CCAAT/enhancer binding proteins and peroxisome proliferator-activated receptors, thereby reducing the cells threshold to proliferate and to secrete pro-inflammatory cytokines under certain conditions; (ii) a higher basal energy turnover that is due to increased number and activity of mitochondria; and (iii) a modified feedback mechanism between cells and the extracellular matrix they are embedded in. All these cellular pathologies are linked to each other and to the innate immune response of the lung, but the sequence of events is unclear and needs further investigation. However, these findings may present the basis for the development of novel curative asthma drugs.

Asthma and the elite athlete: summary of the International Olympic Committee's consensus conference, Lausanne, Switzerland, January 22-24, 2008

Respiratory symptoms cannot be relied on to make a diagnosis of asthma and/or airways hyperresponsiveness (AHR) in elite athletes. For this reason, the diagnosis should be confirmed with bronchial provocation tests. Asthma management in elite athletes should follow established treatment guidelines (eg, Global Initiative for Asthma) and should include education, an individually tailored treatment plan, minimization of aggravating environmental factors, and appropriate drug therapy that must meet the requirements of the World Anti-Doping Agency. Asthma control can usually be achieved with inhaled corticosteroids and inhaled beta(2)-agonists to minimize exercise-induced bronchoconstriction and to treat intermittent symptoms. The rapid development of tachyphylaxis to beta(2)-agonists after regular daily use poses a dilemma for athletes. Long-term intense endurance training, particularly in unfavorable environmental conditions, appears to be associated with an increased risk of developing asthma and AHR in elite athletes. Globally, the prevalence of asthma, exercise-induced bronchoconstriction, and AHR in Olympic athletes reflects the known prevalence of asthma symptoms in each country. The policy of requiring Olympic athletes to demonstrate the presence of asthma, exercise-induced bronchoconstriction, or AHR to be approved to inhale beta(2)-agonists will continue.

Exercise and other indirect challenges to demonstrate asthma or exercise-induced bronchoconstriction in athletes

The prevalence of exercise-induced bronchoconstriction is reported to be high among recreational and elite athletes, yet diagnosis is often symptom-based. Indirect challenges such as the laboratory exercise challenge provide objective criteria for proper diagnosis and treatment. However, a standardized protocol using appropriate exercise intensity, duration, and dry air inhalation is often not implemented, and thus a false-negative test may result. This article reviews and describes the symptom-based diagnosis, the exercise challenge, and other indirect challenges such as eucapnic voluntary hyperpnea, hypertonic saline inhalation, and inhaled powdered mannitol as methods to diagnose and evaluate exercise-induced bronchoconstriction. Advantages and disadvantages of each diagnostic procedure are presented.

Exercise capacity and exercise-induced bronchoconstriction (EIB) in a cold environment

INTRODUCTION

Exercise in a cold environment has been reported to increase exercise-induced bronchoconstriction (EIB). However, the effect of a cold environment upon exercise capacity in subjects with EIB has, to our knowledge, not been previously reported.

PURPOSE

Primary: To examine the influence of changing environmental temperature upon exercise capacity measured by peak oxygen uptake (VO(2 peak)), peak ventilation (VE(peak)) and peak running speed in subjects with diagnosed EIB. Secondary: To assess the influence of changing environmental temperature upon EIB.

METHODS

Twenty subjects (10-45 years old, male/female: 13/7) with EIB underwent exercise testing by running on a treadmill in a climate chamber under standardised, regular conditions, 20.2 degrees C (+/-1.1) and 40.0% (+/-3.3) relative humidity [mean(+/-SD)], and in a standardised cold environment, -18.0 degrees C (+/-1.4) and 39.2% (+/-3.8) relative humidity in random order on separate days. Oxygen uptake (VO(2)), minute ventilation (V E), respiratory exchange ratio (RER), heart rate (HR) and running speed were measured during exercise. Lung function (flow volume loops) was measured before and 1, 3, 6, 10 and 15 min after exercise and 15 min after inhalation of salbutamol.

RESULTS

VO(2 peak) decreased 6.5%, from 47.9 (45.0, 50.8) to 44.8 ml kg(-1)min(-1) (41.2, 48.4) [mean (95% confidence intervals)] (p=0.004) in the cold environment. Also running speed was significantly lower in the cold environment (p=0.02). No differences were found for VE(peak), RER(peak) or HR(peak). The post-exercise reduction in forced expiratory volume in 1s (FEV(1)) (DeltaFEV(1)) increased significantly from 24% (19,29) to 31% (24,38), respectively (p=0.04) after exercise in the cold environment. No correlation was found between reduction in VO(2 peak) and the increased maximum fall in FEV(1) in the cold environment.

CONCLUSION

Exercise capacity (VO(2 peak) and peak running speed) was markedly reduced during exercise in a cold environment whereas EIB increased in subjects suffering from EIB.