Hyperpnea-induced bronchoconstriction and urinary CC16 levels in athletes

Mechanisms and Biomarkers of Exercise-induced Bronchoconstriction: Current Insights and Future Directions

Exercise-induced bronchoconstriction (EIB) refers to temporary lower airway narrowing that occurs during or after vigorous physical exertion, with a high incidence in athletes and individuals with pre-existing asthma. The pathophysiology of EIB is not completely understood, but it is thought to involve a complex interplay among airway epithelial changes, immune responses, and environmental interactions. Phenotypic differences are apparent among those affected by EIB. This clinical review aims to summarize the complex mechanisms underlying EIB, explore the role of biomarkers in the diagnosis and management, and identify current gaps in knowledge to pave the way for future scientific discoveries.

Exercise-induced bronchoconstriction, allergy and sports in children

Exercise-induced bronchoconstriction (EIB) is characterized by the narrowing of airways during or after physical activity, leading to symptoms such as wheezing, coughing, and shortness of breath. Distinguishing between EIB and exercise-induced asthma (EIA) is essential, given their divergent therapeutic and prognostic considerations. EIB has been increasingly recognized as a significant concern in pediatric athletes. Moreover, studies indicate a noteworthy prevalence of EIB in children with atopic predispositions, unveiling a potential link between allergic sensitivities and exercise-induced respiratory symptoms, underpinned by an inflammatory reaction caused by mechanical, environmental, and genetic factors. Holistic management of EIB in children necessitates a correct diagnosis and a combination of pharmacological and non-pharmacological interventions. This review delves into the latest evidence concerning EIB in the pediatric population, exploring its associations with atopy and sports, and emphasizing the appropriate diagnostic and therapeutic approaches by highlighting various clinical scenarios.

The acute effects of endurance exercise on epithelial integrity of the airways in athletes and non-athletes: A systematic review and meta-analysis

INTRODUCTION

Acute endurance exercise may induce airway epithelium injury. However, the response of epithelial integrity markers of the airways including club cell secretory protein (CC16) and surfactant protein D (SP-D) to endurance exercise have not been systematically reviewed. Therefore, the aim of this systematic review and meta-analysis was to assess the acute effects of endurance exercise on markers of epithelial integrity of the airways (CC16, SP-D and the CC16/SP-D ratio) in athletes and non-athletes.

METHODS

A systematic search was performed utilizing PubMed/Medline, EMBASE, Web of Science, and hand searching bibliographies of retrieved articles through to September 2022. Based on the inclusion criteria, articles with available data about the acute effects of endurance exercise on serum or plasma concentrations of CC16, SP-D and CC16/SP-D ratio in athletes and non-athletes were included. Quality assessment of studies and statistical analysis were conducted via Review Manager 5.4 software.

RESULTS

The search resulted in 908 publications. Finally, thirteen articles were included in the review. Acute endurance exercise resulted in an increase in CC16 (P = 0.0006, n = 13) and CC16/SP-D ratio (P = 0.005, n = 2) whereas SP-D (P = 0.47, n = 3) did not change significantly. Subgroup analysis revealed that the type (P = 0.003), but not the duration of exercise (P = 0.77) or the environmental temperature (P = 0.06) affected the CC16 response to endurance exercise.

CONCLUSIONS

Acute endurance exercise increases CC16 and the CC16/SP-D ratio, as markers of epithelial integrity, but not SP-D in athletes and non-athletes.

Diagnostic approach to lower airway dysfunction in athletes: a systematic review and meta-analysis by a subgroup of the IOC consensus on 'acute respiratory illness in the athlete'

OBJECTIVES

To compare the performance of various diagnostic bronchoprovocation tests (BPT) in the assessment of lower airway dysfunction (LAD) in athletes and inform best clinical practice.

DESIGN

Systematic review with sensitivity and specificity meta-analyses.

DATA SOURCES

PubMed, EBSCOhost and Web of Science (1 January 1990-31 December 2021).

ELIGIBILITY CRITERIA

Original full-text studies, including athletes/physically active individuals (15-65 years) who underwent assessment for LAD by symptom-based questionnaires/history and/or direct and/or indirect BPTs.

RESULTS

In 26 studies containing data for quantitative meta-analyses on BPT diagnostic performance (n=2624 participants; 33% female); 22% had physician diagnosed asthma and 51% reported LAD symptoms. In athletes with symptoms of LAD, eucapnic voluntary hyperpnoea (EVH) and exercise challenge tests (ECTs) confirmed the diagnosis with a 46% sensitivity and 74% specificity, and 51% sensitivity and 84% specificity, respectively, while methacholine BPTs were 55% sensitive and 56% specific. If EVH was the reference standard, the presence of LAD symptoms was 78% sensitive and 45% specific for a positive EVH, while ECTs were 42% sensitive and 82% specific. If ECTs were the reference standard, the presence of LAD symptoms was 80% sensitive and 56% specific for a positive ECT, while EVH demonstrated 65% sensitivity and 65% specificity for a positive ECT.

CONCLUSION

In the assessment of LAD in athletes, EVH and field-based ECTs offer similar and moderate diagnostic test performance. In contrast, methacholine BPTs have lower overall test performance.

PROSPERO REGISTRATION NUMBER

CRD42020170915.

Cold air exposure at - 15 °C induces more airway symptoms and epithelial stress during heavy exercise than rest without aggravated airway constriction

PURPOSE

Exposure to cold air may harm the airways. It is unclear to what extent heavy exercise adds to the cold-induced effects on peripheral airways, airway epithelium, and systemic immunity among healthy individuals. We investigated acute effects of heavy exercise in sub-zero temperatures on the healthy airways.

METHODS

Twenty-nine healthy individuals underwent whole body exposures to cold air in an environmental chamber at - 15 °C for 50 min on two occasions; a 35-min exercise protocol consisting of a 5-min warm-up followed by 2 × 15 min of running at 85% of VO2max vs. 50 min at rest. Lung function was measured by impulse oscillometry (IOS) and spirometry before and immediately after exposures. CC16 in plasma and urine, and cytokines in plasma were measured before and 60 min after exposures. Symptoms were surveyed pre-, during and post-trials.

RESULTS

FEV1 decreased after rest (- 0.10 ± 0.03 L, p < 0.001) and after exercise (- 0.06 ± 0.02 L, p = 0.012), with no difference between trials. Exercise in - 15 °C induced greater increases in lung reactance (X5; p = 0.023), plasma CC16 (p < 0.001) as well as plasma IL-8 (p < 0.001), compared to rest. Exercise induced more intense symptoms from the lower airways, whereas rest gave rise to more general symptoms.

CONCLUSION

Heavy exercise during cold air exposure at - 15 °C induced signs of an airway constriction to a similar extent as rest in the same environment. However, biochemical signs of airway epithelial stress, cytokine responses, and symptoms from the lower airways were more pronounced after the exercise trial.

Is airway damage during physical exercise related to airway dehydration? Inputs from a computational model

In healthy subjects, at low minute ventilation (V̇e) during physical exercise, the water content and temperature of the airways are well regulated. However, with the increase in V̇e, the bronchial mucosa becomes dehydrated and epithelial damage occurs. Our goal was to demonstrate the correspondence between the ventilatory threshold inducing epithelial damage, measured experimentally, and the dehydration threshold, estimated numerically. In 16 healthy adults, we assessed epithelial damage before and following a 30-min continuous cycling exercise at 70% of maximal work rate, by measuring the variation pre- to postexercise of serum club cell protein (cc16/cr). Blood samples were collected at rest, just at the end of the standardized 10-min warm-up, and immediately, 30 min and 60 min postexercise. Mean V̇e during exercise was kept for analysis. Airway water and heat losses were estimated using a computational model adapted to the experimental conditions and were compared with a literature-based threshold of bronchial dehydration. Eleven participants exceeded the threshold for bronchial dehydration during exercise (group A) and five did not (group B). Compared with post warm-up, the increase in cc16/cr postexercise was significant (mean increase ± SE: 0.48 ± 0.08 ng·L-1 only in group A but not in group B (mean difference ± SE: 0.10 ± 0.04 ng·L-1). This corresponds to an increase of 101 ± 32% [range: 16%-367%] in group A (mean ± SE). Our findings suggest that the use of a computational model may be helpful to estimate an individual dehydration threshold of the airways that is associated with epithelial damage during physical exercise.NEW & NOTEWORTHY Using a computational model for heat and water transfers in the bronchi, we identified a threshold in ventilation during exercise above which airway dehydration is thought to occur. When this threshold was exceeded, epithelial damage was found. This threshold might therefore represent the ventilation upper limit during exercise in susceptible individuals. Our results might help to prevent maladaptation to chronic exercise such as exercise-induced bronchoconstriction or asthma.

The interaction effect of aerobic exercise and vitamin D supplementation on inflammatory factors, anti-inflammatory proteins, and lung function in male smokers: a randomized controlled trial

Background

This study aimed to investigate the interaction effect of aerobic exercise and vitamin D supplementation on inflammation (TNF-α, IL-6, CC16, SP-D, and CC16/SP-D ratio) and lung function (FEV₁, FVC, and FEV₁/FVC ratio) in male smokers.

Methods

After applying inclusion criteria, a total of 40 healthy male smokers were recruited in this study. The participants were randomly divided into four groups as follows: Aerobic Exercise + vitamin D Supplementation (AE + VitD, n = 10), Aerobic Exercise (AE, n = 10), vitamin D Supplementation (VitD, n = 10), and Control (C, n = 10). The participants in the AE + VitD and AE groups performed aerobic exercise training (running) up to 50% of the maximum heart rate, three times a week for four weeks. Participants in AE + VitD and VitD groups received 6000 IU/w vitamin D₃ for four weeks. The participants in control group did not receive any intervention. Serum tumor necrosis factor (TNF)-α, interleukin (IL)-6, Clara cell protein (CC16), surfactant protein (SP)-D, CC16/SP-D ratio, and lung function (FEV1, FVC, and FEV1/FVC ratio) were measured before and after four weeks of intervention.

Results

Serum levels of TNF-α, IL-6, and CC16 decreased significantly in AE + VitD, VitD, and AE groups after four weeks (P < 0.05). Serum SP-D level decreased significantly only in the AE + VitD group (P = 0.011). In addition, FEV1 and FVC increased significantly (P < 0.05) in AE + VitD and AE groups after four weeks of intervention. However, the interventions did not have a significant effect on CC16/SP-D ratio and FEV1/FVC ratio (P > 0.05). Furthermore, serum levels of 1,25-dihydroxyvitamin D increased significantly in AE + VitD and VitD groups (P < 0.05) after four weeks of intervention. However, except for TNF-α, between-group comparisons showed no significant differences in levels of IL-6, CC16, SP-D, CC16/SP-D ratio, FEV1, FVC, FEV1/FVC, and 1,25-dihydroxyvitamin D (P > 0.05).

Conclusions

The results of present study were that aerobic exercise combined with vitamin D supplementation can reduce serum inflammatory factors and anti-inflammatory proteins and improve lung function after four weeks of intervention. Further trials with larger sample size and longer duration are suggested to confirm these results.

Trial registration Retrospectively registered. IRCT20180513039637N4. Registration date: 2020/10/20. URL: https://www.irct.ir/search/result?query=IRCT20180513039637N4

An experimental exposure study revealing composite airway effects of physical exercise in a subzero environment

Exposure to a cold climate is associated with an increased morbidity and mortality, but the specific mechanisms are largely unknown. People with cardiopulmonary disease and winter endurance athletes are particularly vulnerable. This study aimed to map multiple domains of airway responses to exercise in subzero temperature in healthy individuals.

Thirty-one healthy subjects underwent whole-body exposures for 50 minutes on two occasions in an environmental chamber with intermittent moderate-intensity exercise in +10 °C and -10 °C. Lung function, plasma/urine CC16 , and symptoms were investigated before and after exposures.

Compared to baseline, exercise in -10 °C decreased FEV₁ (p=0.002), FEV₁/FVC (p<0.001), and increased R20Hz (p=0.016), with no differences between exposures. Reactance increased after +10 °C (p=0.005), which differed (p=0.042) from a blunted response after exercise in -10 °C. Plasma CC16 increased significantly within exposures, without differences between exposures. Exercise in -10 °C elicited more intense symptoms from the upper airways, compared to +10 °C. Symptoms from the lower airways were few and mild. 

Short-duration moderate-intensity exercise in -10 °C induces mild symptoms from the lower airways, no lung function decrements or enhanced leakage of biomarkers of airway epithelial injury, and no peripheral bronchodilatation, compared to exercise in +10 °C. 

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.

Continuous exercise induces airway epithelium damage while a matched-intensity and volume intermittent exercise does not

BACKGROUND

While continuous exercise (CE) induces greater ventilation ([Formula: see text]_E) when compared to intermittent exercise (IE), little is known of the consequences on airway damage. Our aim was to investigate markers of epithelial cell damage - i.e. serum levels of CC16 and of the CC16/SP-D ratio - during and following a bout of CE and IE of matched work.

METHODS

Sixteen healthy young adults performed a 30-min continuous (CE) and a 60-min intermittent exercise (IE; 1-min work: 1-min rest) on separate occasions in a random order. Intensity was set at 70% of their maximum work rate (WR_max). Heart rate (HR) and [Formula: see text]_E were measured throughout both tests. Blood samples were taken at rest, after the 10th min of the warm-up, at the end of both exercises, half way through IE (matched time but 50% work done for IE) as well as 30- and 60-min post-exercise. Lactate and CC16 and SP-D were determined.

RESULTS

Mean [Formula: see text]_E was higher for CE compared to IE (85 ± 17 l.min^- 1 vs 50 ± 8 l.min^- 1, respectively; P < 0.001). Serum-based markers of epithelial cell damage remained unchanged during IE. Interaction of test × time was observed for SP-D (P = 0.02), CC16 (μg.l^- 1) (P = 0.006) and CC16/SP-D ratio (P = 0.03). Maximum delta CC16/SP-D was significantly correlated with mean [Formula: see text]_E sustained (r = 0.83, P < 0.001) during CE but not during IE.

CONCLUSION

The 30-min CE performed at 70% WR_max induced mild airway damage, while a time- or work-matched IE did not. The extent of the damage during CE was associated with the higher ventilation rate.

The Role of Airway Inflammation and Bronchial Hyperresponsiveness in Athlete's Asthma

PURPOSE

Asthma is frequently reported in endurance athletes. The aim of the present study was to assess the long-term airway inflammatory response to endurance exercise in high-level athletes with and without asthma.

METHODS

In a cross-sectional design, 20 asthmatic athletes (10 swimmers and 10 cross-country skiers), 19 athletes without asthma (10 swimmers and 9 cross-country skiers), and 24 healthy nonathletes completed methacholine bronchial challenge, lung function tests, and sputum induction on two separate days. All athletes competed on a national or international level and exercised ≥10 h·wk. The nonathletes exercised ≤5 h·wk and reported no previous lung disease. Bronchial hyperresponsiveness (BHR) was defined as a methacholine provocation dose causing 20% decrease in the forced expiratory volume in 1 s of ≤8 μmol.

RESULTS

BHR was present in 13 asthmatic athletes (62%), 11 healthy athletes (58%), and 8 healthy nonathletes (32%), and the prevalence differed among groups (P = 0.005). Sputum inflammatory and epithelial cell counts did not differ between groups and were within the normal range. Median (25th to 75th percentiles) sputum interleukin-8 was elevated in both asthmatic (378.4 [167.0-1123.4]) and healthy (340.2 [175.5-892.4]) athletes as compared with healthy nonathletes (216.6 [129.5-314.0], P = 0.02). No correlations were found between provocation dose causing 20% decrease and sputum cell counts.

CONCLUSION

Independent of asthma diagnosis, a high occurrence of BHR and an increased sputum interleukin-8 were found in athletes as compared with nonathletes. Airway inflammation or epithelial damage was not related to BHR.

Mechanisms and Biomarkers of Exercise-Induced Bronchoconstriction

Exercise is a common trigger of bronchoconstriction. In recent years, there has been increased understanding of the pathophysiology of exercise-induced bronchoconstriction. Although evaporative water loss and thermal changes have been recognized stimuli for exercise-induced bronchoconstriction, accumulating evidence points toward a pivotal role for the airway epithelium in orchestrating the inflammatory response linked to exercise-induced bronchoconstriction. Overproduction of inflammatory mediators, underproduction of protective lipid mediators, and infiltration of the airways with eosinophils and mast cells are all established contributors to exercise-induced bronchoconstriction. Sensory nerve activation and release of neuropeptides maybe important in exercise-induced bronchoconstriction, but further research is warranted.

Mechanisms of exercise-induced bronchoconstriction in athletes: Current perspectives and future challenges

The evidence of exercise-induced bronchoconstriction (EIB) without asthma (EIBw_A ) occurring in athletes led to speculate about different endotypes inducing respiratory symptoms within athletes. Classical postulated mechanisms for bronchial obstruction in this population include the osmotic and the thermal hypotheses. More recently, the presence of epithelial injury and inflammation in the airways of athletes was demonstrated. In addition, neuronal activation has been suggested as a potential modulator of bronchoconstriction. Investigation of these emerging mechanisms is of major importance as EIB is a significant problem for both recreational and competitive athletes and is the most common chronic condition among Olympic athletes, with obvious implications for their competing performance, health and quality of life. Hereby, we summarize the latest achievements in this area and identify the current gaps of knowledge so that future research heads toward better defining the etiologic factors and mechanisms involved in development of EIB in elite athletes as well as essential aspects to ultimately propose preventive and therapeutic measures.

Club cell protein (CC16) in plasma, bronchial brushes, BAL and urine following an inhaled allergen challenge in allergic asthmatics

BACKGROUND

Club cell protein (CC16) is a pneumoprotein secreted by epithelial club cells. CC16 possesses anti-inflammatory properties and is a potential biomarker for airway epithelial damage. We studied the effect of inhaled allergen on pulmonary and systemic CC16 levels.

METHODS

Thirty-four subjects with allergic asthma underwent an inhaled allergen challenge. Bronchoscopy with bronchoalveolar lavage (BAL) and brushings was performed before and 24 h after the challenge. CC16 was quantified in BAL and CC16 positive cells and CC16 mRNA in bronchial brushings. CC16 was measured in plasma and urine before and repeatedly after the challenge. Thirty subjects performed a mannitol inhalation challenge prior to the allergen challenge.

RESULTS

Compared to baseline, CC16 in plasma was significantly increased in all subjects 0-1 h after the allergen challenge, while CC16 in BAL was only increased in subjects without a late allergic response. Levels of CC16 in plasma and in the alveolar fraction of BAL correlated significantly after the challenge. There was no increase in urinary levels of CC16 post-challenge. Mannitol responsiveness was greater in subjects with lower baseline levels of CC16 in plasma.

CONCLUSIONS

The increase in plasma CC16 following inhaled allergen supports the notion of CC16 as a biomarker of epithelial dysfunction.

Eucapnic Voluntary Hyperpnea: Gold Standard for Diagnosing Exercise-Induced Bronchoconstriction in Athletes?

In athletes, a secure diagnos is of exercise-induced bronchoconstriction (EIB) is dependent on objective testing. Evaluating spirometric indices of airflow before and following an exercise bout is intuitively the optimal means for the diagnosis; however, this approach is recognized as having several key limitations. Accordingly, alternative indirect bronchoprovocation tests have been recommended as surrogate means for obtaining a diagnosis of EIB. Of these tests, it is often argued that the eucapnic voluntary hyperpnea (EVH) challenge represents the ‘gold standard’. This article provides a state-of-the-art review of EVH, including an overview of the test methodology and its interpretation. We also address the performance of EVH against the other functional and clinical approaches commonly adopted for the diagnosis of EIB. The published evidence supports a key role for EVH in the diagnostic algorithm for EIB testing in athletes. However, its wide sensitivity and specificity and poor repeatability preclude EVH from being termed a ‘gold standard’ test for EIB.

Exercise-induced dehydration alters pulmonary function but does not modify airway responsiveness to dry air in athletes with mild asthma

This study is the first to investigate the effect of whole body dehydration on airway responsiveness. Our data suggest that the airway response to dry air hyperpnea in athletes with mild asthma and/or exercise-induced bronchoconstriction is not exacerbated in a state of mild dehydration. On the basis of recorded alterations in lung volumes, however, exercise-induced dehydration appears to compromise small airway function.

Local airway water loss is the main physiological trigger for exercise-induced bronchoconstriction (EIB). Our aim was to investigate the effects of whole body water loss on airway responsiveness and pulmonary function in athletes with mild asthma and/or EIB. Ten recreational athletes with a medical diagnosis of mild asthma and/or EIB completed a randomized, crossover study. Pulmonary function tests, including spirometry, whole body plethysmography, and diffusing capacity of the lung for carbon monoxide (Dl_CO), were conducted before and after three conditions: 1) 2 h of exercise in the heat with no fluid intake (dehydration), 2) 2 h of exercise with ad libitum fluid intake (control), and 3) a time-matched rest period (rest). Airway responsiveness was assessed 2 h postexercise/rest via eucapnic voluntary hyperpnea (EVH) to dry air. Exercise in the heat with no fluid intake induced a state of mild dehydration, with a body mass loss of 2.3 ± 0.8% (SD). After EVH, airway narrowing was not different between conditions: median (interquartile range) maximum fall in forced expiratory volume in 1 s was 13 (7–15)%, 11 (9–24)%, and 12 (7–20)% in dehydration, control, and rest conditions, respectively. Dehydration caused a significant reduction in forced vital capacity (300 ± 190 ml, P = 0.001) and concomitant increases in residual volume (260 ± 180 ml, P = 0.001) and functional residual capacity (260 ± 250 ml, P = 0.011), with no change in Dl_CO. Mild exercise-induced dehydration does not exaggerate airway responsiveness to dry air in athletes with mild asthma/EIB but may affect small airway function.

NEW & NOTEWORTHY This study is the first to investigate the effect of whole body dehydration on airway responsiveness. Our data suggest that the airway response to dry air hyperpnea in athletes with mild asthma and/or exercise-induced bronchoconstriction is not exacerbated in a state of mild dehydration. On the basis of alterations in lung volumes, however, exercise-induced dehydration appears to compromise small airway function.

Is Performance of a Modified Eucapnic Voluntary Hyperpnea Test in High Ventilation Athletes Reproducible?

Purpose

Exercise-induced bronchoconstriction (EIB) is common in “high ventilation” athletes, and the Eucapnic Voluntary Hyperpnea (EVH) airway provocation test is the standard EIB screen. Although the EVH test is widely used, the in-test performance in high ventilation athletes as well as the reproducibility of that performance has not been determined. Reproducibility of pre- and post-test spirometry and self-reported atopy/cough was also examined.

Methods

High ventilation athletes (competitive swimmers; n=11, 5 males) completed an atopy/cough questionnaire and EVH testing (operator controlled FiCO₂) on 2 consecutive days.

Results

Swimmers achieved 85%±9% and 87%±9% of target FEV1 volume on days 1 and 2, respectively, (P=0.45; ICC 0.57 [0.00-0.86]) resulting in a total ventilation of 687 vs 684 L [P=0.89, ICC 0.89 (0.65-0.97]) equating to 83%±8% and 84%±9% of predicted total volume (ICC 0.54 [0.00-0.85]) between days 1 and 2. FiCO₂ required to maintain eucapnic conditions was 2.5%. Pre-test FEV1 was less on day 2 (P=0.04; ICC >0.90). Day 1 to 2 post-test FEV1 was not different, and 4 swimmers were EIB positive (>10% fall in pre-post FEV1) on day 1 (3 on day 2).

Conclusions

EVH in-test performance is reproducible however required less FiCO₂ than standard protocol and the swimmers under-ventilated by 125 and 139 L/min for days 1 and 2, respectively. How this affects EIB diagnosis remains to be determined; however, our results indicate a post-test FEV1 fall of ≥20% may be recommended as the most consistent diagnostic criterion.

Self-reported Symptoms after Induced and Inhibited Bronchoconstriction in Athletes

Purpose

A change in the perception of respiratory symptoms after treatment with inhaled beta2 agonists is often used to aid diagnosis of exercise-induced bronchoconstriction (EIB). Our aim was to test the association between subjective ratings of respiratory symptoms and changes in airway caliber after induced and inhibited bronchoconstriction in athletes with EIB.

Methods

Eighty-five athletes with diagnosed or suspected EIB performed a eucapnic voluntary hyperpnea (EVH) challenge with dry air. Of the 45 athletes with hyperpnea-induced bronchoconstriction [i.e., post-EVH fall in forced expiratory volume in 1 s (FEV₁) ≥10%, EVH⁻], 36 were randomized in a double-blind, placebo-controlled, crossover study. Terbutaline (0.5 mg) or placebo was administered by inhalation 15 min before EVH. Spirometry (for FEV₁) was performed before and after EVH, and respiratory symptoms were recorded 15 min after EVH on visual analog scales.

Results

Terbutaline inhibited bronchoconstriction (i.e., maximal fall in FEV₁ <10% after EVH) in 83% of the EVH-positive athletes, with an average degree of bronchoprotection of 53% (95% confidence interval [CI], 45% to 62%). Terbutaline reduced group mean symptom scores (P < 0.01), but the degree of bronchoprotection did not correlate with individual differences in symptom scores between terbutaline and placebo. Of the 29 athletes who had less than 10% FEV₁ fall after EVH in the terbutaline condition, almost half (48%) rated at least one respiratory symptom higher under terbutaline, and more than one quarter (28%) had a higher total symptom score under terbutaline.

Conclusion

Self-reports of respiratory symptoms in conditions of induced and inhibited bronchoconstriction do not correlate with changes in airway caliber in athletes with EIB. Therefore, subjective ratings of respiratory symptoms after treatment with inhaled beta2 agonists should not be used as the sole diagnostic tool for EIB in athletes.

Air quality and temperature effects on exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) is exaggerated constriction of the airways usually soon after cessation of exercise. This is most often a response to airway dehydration in the presence of airway inflammation in a person with a responsive bronchial smooth muscle. Severity is related to water content of inspired air and level of ventilation achieved and sustained. Repetitive hyperpnea of dry air during training is associated with airway inflammatory changes and remodeling. A response during exercise that is related to pollution or allergen is considered EIB. Ozone and particulate matter are the most widespread pollutants of concern for the exercising population; chronic exposure can lead to new-onset asthma and EIB. Freshly generated emissions particulate matter less than 100 nm is most harmful. Evidence for acute and long-term effects from exercise while inhaling high levels of ozone and/or particulate matter exists. Much evidence supports a relationship between development of airway disorders and exercise in the chlorinated pool. Swimmers typically do not respond in the pool; however, a large percentage responds to a dry air exercise challenge. Studies support oxidative stress mediated pathology for pollutants and a more severe acute response occurs in the asthmatic. Winter sport athletes and swimmers have a higher prevalence of EIB, asthma and airway remodeling than other athletes and the general population. Because of fossil fuel powered ice resurfacers in ice rinks, ice rink athletes have shown high rates of EIB and asthma. For the athlete training in the urban environment, training during low traffic hours and in low traffic areas is suggested.

Exercise and asthma: an overview

The terms 'exercise-induced asthma' (EIA) and 'exercise-induced bronchoconstriction' (EIB) are often used interchangeably to describe symptoms of asthma such as cough, wheeze, or dyspnoea provoked by vigorous physical activity. In this review, we refer to EIB as the bronchoconstrictive response and to EIA when bronchoconstriction is associated with asthma symptoms. EIB is a common occurrence for most of the asthmatic patients, but it also affects more than 10% of otherwise healthy individuals as shown by epidemiological studies. EIA and EIB have a high prevalence also in elite athletes, especially within endurance type of sports, and an athlete's asthma phenotype has been described. However, the occurrence in elite athletes shows that EIA/EIB, if correctly managed, may not impair physical activity and top sports performance. The pathogenic mechanisms of EIA/EIB classically involve both osmolar and vascular changes in the airways in addition to cooling of the airways with parasympathetic stimulation. Airways inflammation plays a fundamental role in EIA/EIB. Diagnosis and pharmacological management must be carefully performed, with particular consideration of current anti-doping regulations, when caring for athletes. Based on the demonstration that the inhaled asthma drugs do not improve performance in healthy athletes, the doping regulations are presently much less strict than previously. Some sports are at a higher asthma risk than others, probably due to a high environmental exposure while performing the sport, with swimming and chlorine exposure during swimming as one example. It is considered very important for the asthmatic child and adolescent to master EIA/EIB to be able to participate in physical activity on an equal level with their peers, and a precise early diagnosis with optimal treatment follow-up is vital in this aspect. In addition, surprising recent preliminary evidences offer new perspectives for moderate exercise as a potential therapeutic tool for asthmatics.

Exercise and asthma: an overview

The terms 'exercise-induced asthma' (EIA) and 'exercise-induced bronchoconstriction' (EIB) are often used interchangeably to describe symptoms of asthma such as cough, wheeze, or dyspnoea provoked by vigorous physical activity. In this review, we refer to EIB as the bronchoconstrictive response and to EIA when bronchoconstriction is associated with asthma symptoms. EIB is a common occurrence for most of the asthmatic patients, but it also affects more than 10% of otherwise healthy individuals as shown by epidemiological studies. EIA and EIB have a high prevalence also in elite athletes, especially within endurance type of sports, and an athlete's asthma phenotype has been described. However, the occurrence in elite athletes shows that EIA/EIB, if correctly managed, may not impair physical activity and top sports performance. The pathogenic mechanisms of EIA/EIB classically involve both osmolar and vascular changes in the airways in addition to cooling of the airways with parasympathetic stimulation. Airways inflammation plays a fundamental role in EIA/EIB. Diagnosis and pharmacological management must be carefully performed, with particular consideration of current anti-doping regulations, when caring for athletes. Based on the demonstration that the inhaled asthma drugs do not improve performance in healthy athletes, the doping regulations are presently much less strict than previously. Some sports are at a higher asthma risk than others, probably due to a high environmental exposure while performing the sport, with swimming and chlorine exposure during swimming as one example. It is considered very important for the asthmatic child and adolescent to master EIA/EIB to be able to participate in physical activity on an equal level with their peers, and a precise early diagnosis with optimal treatment follow-up is vital in this aspect. In addition, surprising recent preliminary evidences offer new perspectives for moderate exercise as a potential therapeutic tool for asthmatics.

Exhaled breath temperature in elite swimmers: The effects of a training session in adolescents with or without asthma

BACKGROUND

Cooling of the airways and inflammation have been pointed as possible mechanisms for exercise-induced asthma (EIA). We aimed to investigate the effect of training and asthma on exhaled breath temperature (EBT) of elite swimmers.

METHODS

Elite swimmers annually screened (skin prick tests, spirometry before and after salbutamol inhalation, induced sputum cell counts, and methacholine bronchial challenge) at our department (n = 27) were invited to this prospective study. Swimmers who agreed to participate in the present study (n = 22, 10 with asthma) had axillary temperature and EBT measured (X-halo(®) ) before and after a swimming training session (aerobic/non-aerobic). Linear regression models were used to assess the effect of asthma and other possible explanatory variables (demographics, PD20 , baseline EBT, training intensity, axillary temperature, and the number of hours trained in that week) on EBT change.

RESULTS

EBT significantly increased after training independently of lung function, airway responsiveness, and inflammation in all swimmers (mean ± SD: 0.32 ± 0.57; p = 0.016). No differences were observed between asthmatic swimmers and others. A significant correlation was observed between baseline and post-exercise EBTs (r = 0.827, p < 0.001). Asthma was not a predictor of ΔEBT after adjusting for confounders; baseline EBT was the variable most strongly associated with ΔEBT, explaining by itself alone 46% of the outcome (r(2) = 0.464).

CONCLUSION

Although these are preliminary data, a relationship between airway's inflammation and respiratory heat loss during exercise could not be confirmed, suggesting that the increase in exhaled breath temperature is a physiologic rather than a pathological response to exercise.

Airway response to methacholine following eucapnic voluntary hyperpnea in athletes

Aim

To evaluate the changes in airway responsiveness to methacholine inhalation test (MIT) when performed after an eucapnic voluntary hyperpnea challenge (EVH) in athletes.

Methods

Two MIT preceded (visit 1) or not (visit 2) by an EVH, were performed in 28 athletes and 24 non-athletes. Twelve athletes and 13 non-athletes had airway hyperresponsiveness (AHR) to methacholine, and 11 athletes and 11 non-athletes had AHR to EVH (EVH+).

Results

The MIT PC₂₀ post-EVH was significantly lower compared to baseline MIT PC₂₀ by 1.3±0.7 doubling-concentrations in EVH+ athletes only (p<0.0001). No significant change was observed in EVH- athletes and EVH+/EVH- non-athletes. A significant correlation between the change in MIT PC₂₀ post-EVH and EVH+/EVH- status and athlete/nonathlete status was found (Adjusted R²=0.26 and p<0.001). Three (11%) athletes and one (4%) non-athlete had a change in the diagnosis of AHR when MIT was performed consecutively to EVH.

Conclusion

The responsiveness to methacholine was increased by a previous indirect challenge in EVH+ athletes only. The mechanisms for such increase remain to be determined. MIT and EVH should ideally be performed on separate occasions as there is a small but possible risk to obtain a false-positive response to methacholine when performed immediately after the EVH.

Trial Registration

ClinicalTrials.gov NCT00686491

Perception of bronchoconstriction following methacholine and eucapnic voluntary hyperpnea challenges in elite athletes

OBJECTIVE

Self-reported respiratory symptoms are poor predictors of exercise-induced bronchoconstriction (EIB) in athletes. The objective of this study was to determine whether athletes have an inadequate perception of bronchoconstriction.

METHODS

One hundred thirty athletes and 32 nonathletes completed a standardized questionnaire and underwent eucapnic voluntary hyperpnea (EVH) and methacholine inhalation test. Perception scores were quoted on a modified Borg scale before each spirometry measurement for cough, breathlessness, chest tightness, and wheezing. Perception slope values were also obtained by plotting the variation of perception scores before and after the challenges against the fall in FEV1 expressed as a percentage of the initial value [(perception scores after - before)/FEV1].

RESULTS

Up to 76% of athletes and 68% of nonathletes had a perception score of ≤0.5 at 20% fall in FEV1 following methacholine. Athletes with EIB/airway hyperresponsiveness (AHR) had lower perception slopes to methacholine than nonathletes with asthma for breathlessness only (P=.02). Among athletes, those with EIB/AHR had a greater perception slope to EVH for breathlessness and wheezing (P=.02). Female athletes had a higher perception slope for breathlessness after EVH and cough after methacholine compared with men (P<.05). The age of athletes correlated significantly with the perception slope to EVH for each symptom (P<.05).

CONCLUSIONS

Minimal differences in perception of bronchoconstriction-related symptoms between athletes and nonathletes were observed. Among athletes, the presence of EIB/AHR, older age, and female sex were associated with slightly higher perception scores.

Association of serum Clara cell protein CC16 with respiratory infections and immune response to respiratory pathogens in elite athletes

BACKGROUND

Respiratory epithelium integrity impairment caused by intensive exercise may lead to exercise-induced bronchoconstriction. Clara cell protein (CC16) has anti-inflammatory properties and its serum level reflects changes in epithelium integrity and airway inflammation. This study aimed to investigate serum CC16 in elite athletes and to seek associations of CC16 with asthma or allergy, respiratory tract infections (RTIs) and immune response to respiratory pathogens.

METHODS

The study was performed in 203 Olympic athletes. Control groups comprised 53 healthy subjects and 49 mild allergic asthmatics. Serum levels of CC16 and IgG against respiratory viruses and Mycoplasma pneumoniae were assessed. Allergy questionnaire for athletes was used to determine symptoms and exercise pattern. Current versions of ARIA and GINA guidelines were used when diagnosing allergic rhinitis and asthma, respectively.

RESULTS

Asthma was diagnosed in 13.3% athletes, of whom 55.6% had concomitant allergic rhinitis. Allergic rhinitis without asthma was diagnosed in 14.8% of athletes. Mean CC16 concentration was significantly lower in athletes versus healthy controls and mild asthmatics. Athletes reporting frequent RTIs had significantly lower serum CC16 and the risk of frequent RTIs was more than 2-fold higher in athletes with low serum CC16 (defined as equal to or less than 4.99 ng/ml). Athletes had significantly higher anti-adenovirus IgG than healthy controls while only non-atopic athletes had anti-parainfluenza virus IgG significantly lower than controls. In all athletes weak correlation of serum CC16 and anti-parainfluenza virus IgG was present (R = 0.20, p < 0.01). In atopic athletes a weak positive correlations of CC16 with IgG specific for respiratory syncytial virus (R = 0.29, p = 0.009), parainfluenza virus (R = 0.31, p = 0.01) and adenovirus (R = 0.27, p = 0.02) were seen as well.

CONCLUSIONS

Regular high-load exercise is associated with decrease in serum CC16 levels. Athletes with decreased CC16 are more susceptible to respiratory infections. Atopy may be an additional factor modifying susceptibility to infections in subjects performing regular high-load exercise.

Airway dysfunction in elite athletes--an occupational lung disease?

Airway dysfunction is prevalent in elite endurance athletes and when left untreated may impact upon both health and performance. There is now concern that the intensity of hyperpnoea necessitated by exercise at an elite level may be detrimental for an athlete's respiratory health. This article addresses the evidence of causality in this context with the aim of specifically addressing whether airway dysfunction in elite athletes should be classified as an occupational lung disease. The approach used highlights a number of concerns and facilitates recommendations to ensure airway health is maintained and optimized in this population. We conclude that elite athletes should receive the same considerations for their airway health as others with potential and relevant occupational exposures.

Urinary CC16 after challenge with dry air hyperpnoea and mannitol in recreational summer athletes

Airway epithelial injury is regarded as a key contributing factor to the pathogenesis of exercise-induced bronchoconstriction (EIB) in athletes. The concentration of the pneumoprotein club cell (Clara cell) CC16 in urine has been found to be a non-invasive marker for hyperpnoea-induced airway epithelial perturbation. Exercise-hyperpnoea induces mechanical, thermal and osmotic stress to the airways. We investigated whether osmotic stress alone causes airway epithelial perturbation in athletes with suspected EIB. Twenty-four recreational summer sports athletes who reported respiratory symptoms on exertion performed a standard eucapnic voluntary hyperpnoea test with dry air and a mannitol test (osmotic challenge) on separate days. Median urinary CC16 increased from 120 to 310 ρg μmol creatinine(-1) after dry air hyperpnoea (P = 0.002) and from 90 to 191 ρg μmol creatinine(-1) after mannitol (P = 0.021). There was no difference in urinary CC16 concentration between athletes who did or did not bronchoconstrict after dry air hyperpnoea or mannitol. We conclude that, in recreational summer sports athletes with respiratory symptoms, osmotic stress per se to the airway epithelium induces a rise in urinary excretion of CC16. This suggests that hyperosmolarity of the airway surface lining perturbs the airway epithelium in symptomatic athletes.

Effect of terbutaline on hyperpnoea-induced bronchoconstriction and urinary club cell protein 16 in athletes

Repeated injury of the airway epithelium caused by hyperpnoea of poorly conditioned air has been proposed as a key factor in the pathogenesis of exercise-induced bronchoconstriction (EIB) in athletes. In animals, the short-acting β2-agonist terbutaline has been shown to reduce dry airflow-induced bronchoconstriction and the associated shedding of airway epithelial cells. Our aim was to test the efficacy of inhaled terbutaline in attenuating hyperpnoea-induced bronchoconstriction and airway epithelial injury in athletes. Twenty-seven athletes with EIB participated in a randomized, double-blind, placebo-controlled, crossover study. Athletes completed an 8-min eucapnic voluntary hyperpnoea (EVH) test with dry air on two separate days 15 min after inhaling 0.5 mg terbutaline or a matching placebo. Forced expiratory volume in 1 s (FEV1) and urinary concentration of the club cell (Clara cell) protein 16 (CC16, a marker of airway epithelial perturbation) were measured before and up to 60 min after EVH. The maximum fall in FEV1 of 17 ± 8% (SD) on placebo was reduced to 8 ± 5% following terbutaline (P < 0.001). Terbutaline gave bronchoprotection (i.e., post-EVH FEV1 fall <10%) to 22 (81%) athletes. EVH caused an increase in urinary excretion of CC16 in both conditions (P < 0.001), and terbutaline significantly reduced this rise (pre- to postchallenge CC16 increase 416 ± 495 pg/μmol creatinine after placebo vs. 315 ± 523 pg/μmol creatinine after terbutaline, P = 0.016). These results suggest that the inhalation of a single therapeutic dose of terbutaline offers significant protection against hyperpnoea-induced bronchoconstriction and attenuates acute airway epithelial perturbation in athletes.

Increase of club cell (Clara) protein (CC16) in plasma and urine after exercise challenge in asthmatics and healthy controls, and correlations to exhaled breath temperature and exhaled nitric oxide

Exercise is known to affect the airway epithelium through dehydration, followed by a release of mediators, such as club cell (Clara) protein (CC16). The aim of this study was to follow the CC16 levels at repeated time points in plasma and urine after exercise in asthmatic subjects and controls, and to relate the findings to exhaled breath temperature (EBT) and exhaled nitric oxide (NO). Twenty-two asthmatics and 18 healthy subjects performed an exercise challenge test on a treadmill. Lung function, CC16 in plasma and urine, EBT and fractional exhaled NO were investigated before and repeatedly for 60 min after the exercise. The increase in CC16 concentration in plasma was seen already one minute after exercise (p < 0.001) and increased further after 20 (p = 0.009) until 60 min (p = 0.001). An increase in urinary levels of CC16 peaked after 30 min (p < 0.001), and declined after 60 min but were still higher than baseline (p = 0.002). There were no differences in plasma or urine CC16 levels between asthmatics and controls, but males had higher plasma levels compared to females (p < 0.001) at all time points. EBT peaked at 15 min (p < 0.001) and thereafter declined, and FENO50 (p < 0.0001), alveolar NO concentration (p = 0.049) and bronchial flux of NO (p = 0.0055) decreased after exercise. In conclusion, this study shows that CC16 in plasma increased during 60 min after exercise, not synchronized with CC16 levels in urine. CC16 levels in plasma correlated to EBT and exhaled NO, reflecting an overall epithelial involvement. There was no difference between asthmatics and healthy controls, showing a physiological rather than pathophysiological response.

The effect of nebulized salbutamol or isotonic saline on exercise-induced bronchoconstriction in elite skaters following a 1,500-meter race: study protocol for a randomized controlled trial

Background

Prevalence of exercise-induced bronchoconstriction (EIB) is high in elite athletes, especially after many years training in cold and dry air conditions. The primary treatment of EIB is inhaling a short-acting beta-2-agonist such as salbutamol. However, professional speed skaters also inhale nebulized isotonic saline or tap water before and after a race or intense training. The use of nebulized isotonic saline or tap water to prevent EIB has not been studied before, raising questions about safety and efficacy. The aim of this study is to analyze the acute effect of nebulized isotonic saline or salbutamol on EIB in elite speed skaters following a1,500-meter race.

Methods

This randomized controlled trial compares single dose treatment of 1 mg nebulized salbutamol in 4 mL of isotonic saline, or with 5 mL of isotonic saline. A minimum of 13 participants will be allocated in each treatment group. Participants should be between 18 and 35 years of age and able to skate 1,500 m in less than 2 min 10 s (women) or 2 min 05 s (men). Repeated measurements of spirometry, forced oscillation technique, and electromyography will be performed before and after an official 1,500-m race. Primary outcome of the study is the difference in fall in FEV₁ after exercise in the different treatment groups. The trial is currently enrolling participants.

Discussion

Elite athletes run the risk of pulmonary inflammation and remodeling as a consequence of their frequent exercise, and thus increased ventilation in cold and dry environments. Although inhalation of nebulized isotonic saline is commonplace, no study has ever investigated the safety or efficacy of this treatment.

Trial registration

This trial protocol was registered with the Dutch trial registration for clinical trials under number NTR3550

Marine lipid fraction PCSO-524 (lyprinol/omega XL) of the New Zealand green lipped mussel attenuates hyperpnea-induced bronchoconstriction in asthma

PURPOSE

Evaluate the effect of the marine lipid fraction of the New Zealand green-lipped mussel (Perna canaliculus) PCSO-524 (Lyprinol/Omega XL), rich in omega-3 fatty acids, on airway inflammation and the bronchoconstrictor response to eucapnic voluntary hyperpnea (EVH) in asthmatics.

METHODS

Twenty asthmatic subjects, with documented HIB, participated in a placebo controlled double-blind randomized crossover trial. Subjects entered the study on their usual diet and were then placed on 3 weeks of PCSO-524 or placebo supplementation, followed by a 2 week washout period, before crossing over to the alternative diet. Pre- and post-eucapnic voluntary hyperpnea (EVH) pulmonary function, fraction of exhaled nitric oxide (FENO), asthma symptom scores, medication use, exhaled breath condensate (EBC) pH, cysteinyl leukotrienes (cyst-LT), 8-isoprostane and urinary 9α, 11β-prostaglandin (PG)F2 and Clara (CC16) protein concentrations were assessed at the beginning of the trial and at the end of each treatment period.

RESULTS

The PCSO-524 diet significantly reduced (p < 0.05) the maximum fall in post-EVH FEV1 (-8.4 ± 3.2%) compared to usual (-19.3 ± 5.4%) and placebo diet (-22.5 ± 13.7%). Pre- and post- EVH EBC cyst-LT and 8-isoprostane, and urinary 9α, 11β-PGF2 and CC16 concentrations were significantly reduced (p < 0.05) on the PCSO-524 diet compared to the usual and placebo diet. EBC pH and asthma symptom scores were significantly improved (p < 0.05) and rescue medication use significantly reduced (p < 0.05) on the PCSO-524 diet compared to the usual and placebo diet.

CONCLUSION

PCSO-524 (Lyprinol)/Omega XL) may have beneficial effects in HIB and asthma by serving as a pro-resolving agonist and/or inflammatory antagonist.

Pathogenesis of exercise-induced bronchoconstriction

This article presents the various potential mechanisms responsible for the development of exercise-induced bronchoconstriction (EIB). Although the etiology of EIB is multifactorial, and the physiologic processes involved may vary between individuals (especially between those with and without asthma), drying of the small airways with an associated inflammatory response seems prerequisite for EIB. Dysregulated repair processes following exercise-induced airway epithelial injury may also serve as basis for EIB development/progression.

Where to from here for exercise-induced bronchoconstriction: the unanswered questions

The role of epithelial injury is an unanswered question in those with established asthma and in elite athletes who develop features of asthma and exercise-induced bronchorestriction (EIB) after years of training. The movement of water in response to changes in osmolarity is likely to be an important signal to the epithelium that may be central to the onset of EIB. It is generally accepted that the mast cell and its mediators play a major role in EIB and the presence of eosinophils is likely to enhance EIB severity.

Air quality and exercise-induced bronchoconstriction in elite athletes

A higher prevalence of airway hyperresponsiveness, airway remodeling, and asthma has been identified among athletes who compete and train in environmental conditions of cold dry air and/or high air pollution. Repeated long-duration exposure to cold/dry air at high minute ventilation rates can cause airway damage. Competition or training at venues close to busy roadways, or in indoor ice arenas or chlorinated swimming pools, harbors a risk for acute and chronic airway disorders from high pollutant exposure. This article discusses the effects of these harsh environments on the airways, and summarizes potential mechanisms and prevalence of airway disorders in elite athletes.

New insights into pathogenesis of exercise-induced bronchoconstriction

PURPOSE OF REVIEW

Exercise-induced bronchoconstriction (EIB) refers to acute airflow obstruction that is triggered by a period of physical exertion. Here we review recent findings about the epidemiology of EIB, immunopathology leading to EIB, and the latest understanding of the pathogenesis of EIB.

RECENT FINDINGS

Longitudinal studies demonstrated that airway hyper-responsiveness to exercise or cold air at an early age are among the strongest predictors of persistent asthma. Patients that are susceptible to EIB have epithelial disruption and increased levels of inflammatory eicosanoids such as cysteinyl leukotrienes (CysLT)s. The leukocytes implicated in production of eicosanoids in the airways include both a unique mast cell population as well as eosinophils. A secreted phospholipase A(2) (sPLA(2)) enzyme that serves as a regulator of CysLT formation is present in increased quantities in asthma. Transglutaminase 2 (TGM2) is expressed at increased levels in asthma and serves as a regulator of secreted phospholipase A(2) group X (sPLA(2)-X). Further, sPLA(2)-X acts on target cells such as eosinophils to initiate cellular eicosanoid synthesis.

SUMMARY

Recent studies have advanced our understanding of EIB as a syndrome that is caused by the increased production of inflammatory eicosanoids. The airway epithelium may be an important regulator of the production of inflammatory eicosanoids by leukocytes.

Effect of inspired air conditions on exercise-induced bronchoconstriction and urinary CC16 levels in athletes

Injury to the airway epithelium has been proposed as a key susceptibility factor for exercise-induced bronchoconstriction (EIB). Our goals were to establish whether airway epithelial cell injury occurs during EIB in athletes and whether inhalation of warm humid air inhibits this injury. Twenty-one young male athletes (10 with a history of EIB) performed two 8-min exercise tests near maximal aerobic capacity in cold dry (4°C, 37% relative humidity) and warm humid (25°C, 94% relative humidity) air on separate days. Postexercise changes in urinary CC16 were used as a biomarker of airway epithelial cell perturbation and injury. Bronchoconstriction occurred in eight athletes in the cold dry environment and was completely blocked by inhalation of warm humid air [maximal fall in forced expiratory volume in 1 s = 18.1 ± 2.1% (SD) in cold dry air and 1.7 ± 0.8% in warm humid air, P < 0.01]. Exercise caused an increase in urinary excretion of CC16 in all subjects ( P < 0.001), but this rise in CC16 was blunted following inhalation of warm humid air [median CC16 increase pre- to postchallenge = 1.91 and 0.35 ng/μmol in cold dry and warm humid air, respectively, in athletes with EIB ( P = 0.017) and 1.68 and 0.48 ng/μmol in cold dry and warm humid air, respectively, in athletes without EIB ( P = 0.002)]. The results indicate that exercise hyperpnea transiently disrupts the airway epithelium of all athletes (not only in those with EIB) and that inhalation of warm moist air limits airway epithelial cell perturbation and injury.