Late asthmatic response in exercise-induced asthma

Cold air-induced late-phase bronchoconstriction in horses

REASON FOR PERFORMING STUDY

Inspired air is warmed to body temperature and fully humidified by the upper airway mucosa under normal resting conditions. This conditioning process may not be completed by the upper airways during conditions of increased minute ventilation or when the inspired air is unusually cold, resulting in cooling and desiccation of lower respiratory surfaces. Excess heat and water loss from intrapulmonary airways is believed to be the provocative stimulus for exercise-induced bronchoconstriction (occurring immediately after exercise) and associated late phase airway obstruction (occurring a few hours after exercise).

HYPOTHESIS

Exercise while breathing cold air results in airway obstruction in horses.

METHODS

Eight healthy horses performed a 15 min submaximal exercise challenge in a random crossover design. Independent variable was inspired air temperature during the challenge (25 or -5 degrees C). The dependent variables were total respiratory impedance, resistance, and reactance at 5, 24 and 48 h post exercise challenge, expressed as a percentage of the prechallenge baseline.

RESULTS

No significant effect of inspired air temperature was found on any respiratory mechanical parameter 5 h after exercise challenge. However, cold inspired air was associated with higher respiratory impedance and resistance 48 h after the exercise challenges.

CONCLUSIONS

These findings support the hypothesis that submaximal exercise while breathing subfreezing air can adversely affect respiratory mechanical properties in normal horses. However, the timecourse for development of abnormal respiratory mechanical properties is longer than that reported in other mammals.

CLINICAL RELEVANCE

Exercise in cold weather may be a common cause of lower airway disease in horses.

The role of endothelium-derived mediators in exercise-induced bronchoconstriction

BACKGROUND

Exercise-induced bronchoconstriction (EIB) is a highly prevalent condition whose pathogenesis and effect on airways remain unclear. The aim of the study was to evaluate the changes in endothelial-derived mediators following intensive exercise in asthmatic patients.

METHODS

The study was conducted in a group of 25 asthmatic patients (15 with EIB, 10 without EIB) and 8 healthy volunteers. Changes induced by intensive exercise in the plasma concentrations of endothelin-1 (ET-1), thrombomodulin and soluble E-selectin were determined. Moreover, the possible correlations of these measurements with the results of baseline lung function, bronchial hyperreactivity (BHR), exhaled nitric oxide (F(ENO)), baseline eosinophil cationic protein, peripheral blood eosinophilia and total IgE were investigated.

RESULTS

In the group of asthmatics with EIB, statistically significantly higher baseline concentrations of ET-1 and soluble E-selectin compared with asthmatics with negative exercise test results were revealed. In this group of patients, ET-1, thrombomodulin and soluble E-selectin concentrations significantly increased after exercise. Baseline concentrations of ET-1 as well as an increase in soluble E-selectin concentrations 60 min after exercise showed a statistically significant correlation with baseline eosinophil cationic protein, F(ENO) and BHR. The increase in plasma concentrations of ET-1 15 min after exercise and soluble E-selectin 60 min after exercise showed a statistically significant correlation with the increase in F(ENO) and BHR to histamine 24 h after exercise.

CONCLUSIONS

We suggest that during EIB changes in the function of pulmonary endothelium occur and these changes may influence inflammation of the airway and remodeling in asthmatic patients.

Asthma associated with exercise

Exercise is a potent stimulus to asthma. The diagnosis is not always straightforward, and health care providers should have a high index of suspicion. Treatment usually controls exercise-induced asthma but usually requires therapy tailored for each individual patient.

Review of exercise-induced asthma

PURPOSE

The purpose of this manuscript is to review the recent literature on exercise-induced asthma (EIA) and summarize the pathogenesis, diagnosis, and treatment of this condition.

METHOD

A review of the English language medical literature was performed to obtain articles on EIA.

RESULTS

The pathophysiology of EIA is not fully understood, but there are two theories: 1) the hyperosmolar theory and 2) the airway rewarming theory. In addition, there have been data to show that airway inflammation is present in some elite athletes, especially in cold weather sports. The diagnosis of EIA is usually straightforward in most patients, but a number of patients may have atypical symptoms and may be more difficult to diagnose. They may well need exercise testing or eucapnic voluntary ventilation testing. Most people respond to treatment with an inhaled beta agonist and or cromolyn before exercise, but some patients will also need other medications, including daily medications such as inhaled steroids. When treatment does not control the problem, then further diagnostic evaluation should be done to rule out conditions other than EIA, such as vocal cord dysfunction or cardiac or pulmonary problems.

CONCLUSIONS

EIA is a condition that may occur in schoolchildren in gym class and also in Olympic athletes. The diagnosis and treatment is usually fairly straightforward, but at times it may be challenging. However, all patients should be followed to make sure that the correct diagnosis is made and to make sure that treatment is effective.

Exercise-induced bronchoconstriction in children: montelukast attenuates the immediate-phase and late-phase responses

BACKGROUND

Montelukast, a leukotriene receptor antagonist, attenuates exercise-induced bronchoconstriction. We and others have shown that there is a late-phase response 3 to 8 hours after exercise in a subset of asthmatic patients.

OBJECTIVE

We sought to evaluate the protective effect of montelukast on immediate-phase and late-phase responses after exercise challenges.

METHODS

Twenty-two atopic asthmatic children aged 7 to 16 years with reproducible exercise-induced bronchoconstriction (minimum of 15% decrease of FEV(1) from baseline) were enrolled in this placebo-controlled crossover study. Exercise challenges were performed while breathing cold dry air, and FEV(1) measurements were taken up to 480 minutes after exercise. Patients underwent exercise challenges on a screening day and 1 week after placebo treatment. Subsequently, after a week with no treatment, pulmonary function was assessed after breathing dry cold air (control day). Finally, an exercise challenge was carried out after a week of treatment with montelukast.

RESULTS

Reproducible late-phase reactions occurred in 5 of 22 patients, which correlated with the extent of the immediate response (P <.05). After 1 week of treatment with montelukast, a significant decrease of immediate responses was observed. Montelukast treatment compared with placebo was associated with a lower mean maximum decrease of FEV(1) (mean +/- SEM: 17.3% +/- 2.4% and 35.1% +/- 2.6%, respectively), decrease of the area above the curve (267.8% +/- 42.7%/min and 868.0% +/- 103.8%/min, respectively), and shorter time for recovery (6.9 +/- 1.1 minutes and 30.9 +/- 4.0 minutes, respectively; P <.05). Treatment with montelukast also abolished late-phase responses.

CONCLUSION

Once daily treatment with oral montelukast attenuated the immediate-phase response and abolished the late-phase response induced by means of exercise challenge in asthmatic children.

Mast-cell stabilising agents to prevent exercise-induced bronchoconstriction

BACKGROUND

Exercise-induced bronchoconstriction (or asthma) following strenuous physical exertion is common and can cause sub-optimal performance, symptoms such as cough, dyspnea, wheeze, chest tightness, and can lead people to avoid physical activity. Management focuses on prevention with pre-exercise treatment using various pharmacologic agents. Mast cell stabilizing agents are effective in attenuating exercise-induced bronchoconstriction but their effectiveness compared to bronchodilator agents is unclear.

OBJECTIVES

To quantitatively compare the effects of inhaling a single dose of either mast cell stabiliser - nedocromil sodium or sodium cromoglycate - to a single dose of short acting beta-agonists or anti-cholinergic agents - atropine or ipratropium bromide - prior to a strenuous exercise challenge in participants with asthma who are at least 6 years of age and suffer from reproducible exercise-induced bronchoconstriction. The review also compares the effects between a short acting beta-agonist alone to a combination of a short acting beta-agonist + mast cell stabiliser.

SEARCH STRATEGY

We searched the Cochrane Airways Group ASTHMA and WHEEZ* trials register, Cochrane CENTRAL, Current Contents, review articles, textbooks and reference lists of articles. We also contacted the drug manufacturer and primary authors for additional citations.

SELECTION CRITERIA

Randomised trials comparing a single prophylactic dose of a mast cell stabiliser to a short acting beta-agonist, anti-cholinergic agent, or a short acting beta-agonist alone to a combination of short acting beta-agonist plus a mast cell stabiliser to prevent exercise-induced bronchoconstriction in asthmatics over six years old. The exercise challenge had to conform to acceptable standards and pulmonary function (PFT) reported as percent decrease from baseline of FEV1 or peak flow. Complete protection (maximum % fall PFT <15% post-exercise) and clinical protection (50% improvement over placebo effect) measures were included.

DATA COLLECTION AND ANALYSIS

Trial inclusion and quality assessments were conducted independently by two reviewers using standardised forms. A second reviewer confirmed data extraction and calculations. Attempts were made to contact study authors. The pooled estimate involving continuous pulmonary function measures are reported as a weighted mean difference (WMD), dichotomous data as an odds ratio (OR), both with 95% confidence intervals (95%CI) using a random effects model. Heterogeneity tests for pooled results were performed.

MAIN RESULTS

Twenty-four trials (518 participants) conducted in 13 countries between 1976 and 1998 were included. All drugs were effective at attenuating the exercise-induced bronchoconstriction response but to varying degrees even within the same individual. Compared to anti-cholinergic agents, mast cell stabilisers were somewhat more effective at attenuating bronchoconstriction. On average the maximum fall on MCS was reduced to 7.1% compared to 13.8% on AC ( WMD = 6.7%; 95% CI: 3.3 to 10.0), provided more individuals with complete protection (73% vs 56%; OR = 2.2; 95% CI: 1.3 to 3.7) and clinical protection (73% vs 52%; OR = 2.7; 95% CI: 1.1 to 6.4). There were no subgroup differences based on age, severity, or study quality, and no adverse effects were reported for either agent group. When compared to short acting beta-agonists mast cell stabilisers were not as effective at preventing deterioration. On average the maximum fall on MCS was 11.2% compared to 4.3% on beta agonists ( WMD = 6.8%; 95% CI: 4.5 to 9.2). MCS provided fewer individuals with complete protection (66% vs 85%; OR = 0.3; 95% CI: 0.2 to 0.5) or clinical protection (55% vs 77%; OR = 0.4; 95% CI: 0.2 to 0.8). There were no significant subgroup differences based on age, severity, drug, delivery, or study quality. A non-significant difference in side effects was demonstrated with 11% of short acting beta-agonist patients experiencing side effects compared to 3% of those receiving mast cell stabilisers (OR = 0.2; 95% CI: 0.0 to 8.2). Combining masta-agonist patients experiencing side effects compared to 3% of those receiving mast cell stabilisers (OR = 0.2; 95% CI: 0.0 to 8.2). Combining mast cell stabilisers with a short acting beta-agonist did not produce significant advantages to pulmonary function over short acting beta-agonists alone. On average the maximum fall on SABA only was reduced to 5.3% compared to 3.5% on the combination ( WMD = 1.8%; 95% CI: -1.1 to 4.6). Beta-agonists alone provided fewer individuals with complete protection (68% vs 80%; OR = 0.5; 95% CI: 0.2 to 1.4) or clinical protection (70% vs 86%; OR=0.4; 95% CI: 0.1 to 1.2) but the difference did not reach significance (p=0.17). There were no subgroup differences.

REVIEWER'S CONCLUSIONS

In a population of stable asthmatics short acting beta-agonists, mast cell stabilisers, or anticholinergics will provide a significant protective effect against exercise-induced bronchoconstriction with few adverse effects. On average, SABAs resulted in more effective attenuation than mast cell stabilisers, while mast cell stabilisers were more effective than anti-cholinergic agents. Combining SABA and mast cell stabilisers may be appropriate in selected cases. The variability in the individual degree of response to these drugs in multi arm trials suggests clinicians and patients work together to identify the most effective prophylactic therapy.

Airway cooling and mucosal injury during cold weather exercise

In human subjects that exercise strenuously in cold weather, there is evidence that hyperventilation with cold air leads to peripheral airway cooling, desiccation and mucosal injury. Our hypothesis was that hyperventilation with cold air can result in penetration of unconditioned air (air that is not completely warmed and humidified) into the peripheral airways of exercising horses, resulting in peripheral airway mucosal injury. To test this hypothesis, a thermister-tipped catheter was inserted through the midcervical trachea and advanced into a sublobar bronchus in three horses that cantered on a treadmill at 6.6 m/s while breathing cold (5 degrees C) air. The mean (+/- s.e.) intra-airway temperature during cantering was 33.3 +/- 0.4 degrees C, a value comparable to the bronchial lumen temperatures measured in man during maximal exercise while breathing subfreezing dry air. In a second experiment, 6 fit Thoroughbred racehorses with satisfactory performance were used to determine whether strenuous exercise in cold conditions can produce airway injury. Horses were assigned to Exercise (E) or Control (C) groups in a random crossover design. Samples of bronchoalveolar lavage fluid (BALF) in the E treatment were recovered within 30 min of galloping exercise in 4 degrees C, 100% relative humidity (E), while in C BALF samples were obtained when the horses had not performed any exercise for at least 48 h prior. Ciliated epithelial cells in BALF were higher in E than in the C treatment. Similar results have been found in human athletes and laboratory animal models of cold weather exercise. These results support the hypothesis that, similar to man, horses that exercise in cold weather experience peripheral airway mucosal injury due to the penetration of unconditioned air. Furthermore, these results suggest that airway cooling and desiccation may be a factor in airway inflammation commonly found in equine athletes.

Modeling the acute- and late-phase responses to peripheral airway cooling and desiccation

Acute bronchoconstriction after isocapnic hyperpnea can be produced in most asthmatic individuals. However, the existence of a late-phase response is less certain. We used a canine model of isocapnic hyperpnea to test the hypothesis that this discrepancy is due to differences in the challenge threshold for the responses. Acute-phase and late-phase bronchoconstriction was measured in nine dogs after peripheral airway exposure to unconditioned air. Additionally, bronchoalveolar lavage fluid (BALF) was obtained during the late-phase response. The acute-phase response was a polynomial function with a decreasing slope at higher challenges, whereas the late-phase response suggested that a minimum threshold of challenge severity was needed to produce late-phase bronchoconstriction. BALF leukocyte and eicosanoid concentrations had linear relationships with challenge severity. Our data support the hypothesis that acute- and late-phase posthyperpnea responses have different dose-response relationships, a fact that may explain the frequent lack of a late-phase response. However, our data suggest that mild inflammation can be induced with relatively lower challenge severity.

Heparin inhibits hyperventilation-induced late-phase hyperreactivity in dogs

Inhalation of heparin attenuates hyperventilation-induced bronchoconstriction in humans and dogs. The purpose of this study was to determine whether heparin inhibits the late-phase response to hyperventilation, which is characterized by increased peripheral airway resistance (RP), eicosanoid mediator production, neutrophilic/ eosinophilic inflammation, and airway hyperreactivity (AHR) at 5 h after dry air challenge (DAC). Fiberoptic bronchoscopy was used to record RP and airway reactivity (DeltaRP) to aerosol and intravenous histamine before and 5 h after DAC. Bronchoalveolar lavage fluid (BALF) cells and eicosanoid mediators were also measured approximately 5 h after DAC. DAC of vehicle-treated bronchi resulted in late-phase airway obstruction (approximately 120% increase over baseline RP), inflammation, increased BALF concentrations of leukotriene (LT) C(4), LTD(4), and LTE(4) and prostaglandin (PG)D(2), and AHR. Pretreatment with aerosolized heparin attenuated late-phase airway obstruction by approximately 50%, inhibited eosinophil infiltration, reduced BALF concentrations of LTC(4), LTD(4), and LTE(4) and PGD(2), and abolished AHR. We conclude that heparin inhibits hyperventilation-induced late-phase changes in peripheral airway function, and does so in part via the inhibition of eosinophil migration and eicosanoid mediator production and release.

Eicosanoids modulate hyperpnea-induced late phase airway obstruction and hyperreactivity in dogs

A canine model of exercise-induced asthma was used to test the hypothesis that the development of a late phase response to hyperventilation depends on the acute production of pro-inflammatory mediators. Peripheral airway resistance, reactivity to hypocapnia and aerosol histamine, and bronchoalveolar lavage fluid (BALF) cell and eicosanoid content were measured in dogs approximately 5 h after dry air challenge (DAC). DAC resulted in late phase obstruction, hyperreactivity to histamine, and neutrophilic inflammation. Both cyclooxygenase and lipoxygenase inhibitors administered in separate experiments attenuated the late phase airway obstruction and hyperreactivity to histamine. Neither drug affected the late phase inflammation nor the concentrations of eicosanoids in the BALF obtained 5 h after DAC. This study confirms that hyperventilation of peripheral airways with unconditioned air causes late phase neutrophilia, airway obstruction, and hyperreactivity. The late phase changes in airway mechanics are related to the hyperventilation-induced release of both prostaglandins and leukotrienes, and appear to be independent of the late phase infiltration of inflammatory cells.

Hypertonic saline aerosol increases airway reactivity in the canine lung periphery

Hyperventilation with dry air increases airway surface fluid (ASF) osmolality and causes acute mucosal injury, leukocyte infiltration, and delayed airway obstruction and hyperreactivity in canine peripheral airways. The purpose of this study was to determine whether ASF hypertonicity per se can account for these hyperventilation-associated effects. We first measured ASF osmolality before and after normal (NSC) and hypertonic (HSC) saline aerosol challenges to document the magnitude of hypertonicity produced by these stimuli. We then measured canine peripheral airway resistance and reactivity to hypocapnia and aerosolized histamine before and after NSC and HSC. Cells and eicosanoid mediators recovered in bronchoalveolar lavage fluid at 5 and 24 h after NSC and HSC were examined. We found that HSC but not NSC caused acute ASF hyperosmolality, increased mediator release, and delayed airway hyperreactivity in the absence of mucosal injury and leukocyte infiltration. These observations suggest that ASF hyperosmolality contributes to the development of the late-phase response to hyperventilation and further suggest that hyperventilation-induced mucosal injury independently initiates leukocyte infiltration and late-phase airway obstruction.