Background: Exercise-induced bronchoconstriction (EIB) describes acute airway narrowing that occurs as a result of exercise. EIB occurs in a substantial proportion of patients with asthma, but may also occur in individuals without known asthma.Methods: To provide clinicians with practical guidance, a multidisciplinary panel of stakeholders was convened to review the pathogenesis of EIB and to develop evidence-based guidelines for the diagnosis and treatment of EIB. The evidence was appraised and recommendations were formulated using the Grading of Recommendations, Assessment, Development, and Evaluation approach.Results: Recommendations for the treatment of EIB were developed. The quality of evidence supporting the recommendations was variable, ranging from low to high. A strong recommendation was made for using a short-acting β2-agonist before exercise in all patients with EIB. For patients who continue to have symptoms of EIB despite the administration of a short-acting β2-agonist before exercise, stron...

/pdf/an-official-american-thoracic-society-clinical-practice-2ev9b7wn92.pdf

An official American Thoracic Society clinical practice guideline: exercise-induced bronchoconstriction.

Exercise-induced asthma is a condition in which vigorous physical activity triggers acute airway narrowing in people with heightened airway reactivity. A more accurate description would be exercise-induced bronchospasm. Long usage, however, has left the former term firmly fixed in the lexicon. To emphasize the underlying pathogenesis, the term “thermally induced asthma” has been proposed1. Exercise-induced asthma is not an isolated disorder or a specific disease. Exercise is but one of many stimuli that result in a limitation of airflow. It is not uncommon for physical exertion to be the first precipitant of asthma. With time, however, others may emerge. . . .

Exercise-Induced Asthma

To determine if postexercise thermal events play a role in exercise-induced asthma (EIA), nine normal and eight asthmatic subjects on three occasions exercised while they inhaled frigid air. During the recovery period, either cold air, air at room temperature and humidity, or air at body conditions was administered in a random fashion. On a fourth occasion, body-condition air was given during exercise. Pulmonary mechanics were measured before and after each challenge. No changes in mechanics developed when air at body conditions was inhaled during exercise, however, increasing the heat content of the air during recovery produced progressively greater obstruction in both groups. On a separate occasion, seven asthmatics hyperventilated frigid air and either recovered spontaneously or had their ventilation slowly reduced. Controlling ventilation markedly attenuated the obstructive response. These data demonstrate that the severity of EIA is dependent not only on airway cooling but also upon the rapidity and magnitude of airway rewarming postchallenge.

/pdf/postexertional-airway-rewarming-and-thermally-induced-asthma-5bt1495wj9.pdf

Postexertional airway rewarming and thermally induced asthma. New insights into pathophysiology and possible pathogenesis.

Chief Editors: John M. Weiler, MD, MBA, President, CompleWare Corporation, Professor Emeritus, University of Iowa, Iowa City, Iowa; Sandra D. Anderson, PhD, DSc, Clinical Professor, Sydney Medical School, Royal Prince Alfred Hospital, Department of Respiratory and Sleep Medicine, Camperdown NSW 2050, Australia; Christopher Randolph, MD, Clinical Professor of Pediatrics, Yale Affiliated Programs, Waterbury Hospital, Center for Allergy, Asthma and Immunology, Waterbury, Connecticut

/pdf/pathogenesis-prevalence-diagnosis-and-management-of-exercise-15cs5qxwl5.pdf

Pathogenesis, prevalence, diagnosis, and management of exercise-induced bronchoconstriction: a practice parameter

ObjectivesRecent studies have explored the potential for swimming pool disinfection by-products (DBPs), which are respiratory irritants, to cause asthma in young children. Here we describe the stat...

Childhood Asthma and Environmental Exposures at Swimming Pools: State of the Science and Research Recommendations

Among factors which possibly influence the responses of asthmatic children to exercise, climate has received little attention. This study was performed to determine whether the level of air humidity is a factor to be considered. Twenty asthmatic (extrinsic perennial) girls and boys, 6 to 14 yr of age, with unverified history of exercise-induced asthma (EIA) took part. They rested and exercised in a climatic chamber in dry (25% relative humidity) and humid (90%) sessions at 25 degrees to 26 degrees C. One to three weeks separated the sessions, the order of which was counterbalanced. No changes in pulmonary functions (FVC, FEV 1.0, MMEF, MBC) were found following a sitting period of 60 min in either climate. Five and ten minutes following the treadmill run, however, bronchoconstriction was distinctly more pronounced in the dry than in the humid climate. Exercise heart rate and the subjective rating of effort were not affected by climate. It was concluded that, under the above experimental conditions, EIA is more likely in dry air than in humid air, possibly due to heat loss at the airway mucosa caused by evaporation. High humidity of inspired air could be the reason why EIA is less prevalent in swimming, as compared with other modes of exercise.

https://www.jacionline.org/article/0091-6749(77)90119-1/pdf

Effects of dry and humid climates on exercise-induced asthma in children and preadolescents.

Thirteen children each exercised for 6 min by running on a treadmill and by tethered swimming, breathing air at room temperature and either 8% or 99% relative humidity continuously. Ventilation, gas exchange and heart rate were closely matched in all four tests in each child, with a mean oxygen consumption of 32.3 +/- 1.7 ml x min-1 x kg-1. The post-exercise fall in FEV1 expressed as a percentage of the baseline FEV1 (delta FEV1) was significantly greater after running compared with swimming breathing either humid or dry air. The delta FEV1 was also related to respiratory heat loss (RHL) calculated from measurements of inspired and expired gas temperature and humidity. At a standardised RHL, the difference between running and swimming was highly significant [delta FEV1 (%) +/- SE = 39 +/- 5 and 28 +/- 4 respectively, p less than 0.01]. These experiments suggest that the type of exercise influences the severity of exercise-induced asthma even under conditions of the same metabolic stress and respiratory heat loss.

Differences between swimming and running as stimuli for exercise-induced asthma.

Recent studies have shown the relevance of air humidity to the provocation of bronchoconstriction by running. The present study was undertaken to ascertain whether the humid air breathed during swimming could explain the protective effect of swimming on the asthmatic. Nine asthmatic children 9–15 years old swam while inspiring dry (25–35% R. H.) or humid (80–90% R. H.) air administered in a random order, a week separating the two sessions. The exercise challenge was an 8-min tethered swim at a metabolic rate (\(\dot V\)O2) of 29 ml·kg−1·min−1, minute ventilation (VE) of 34 L·min−1, and a heart rate (HR) of 161 beats·min−1. Ambient air and water temperature were 28±2‡ C and 27±2‡ C, respectively. Pulmonary functions were tested pre and post swimming. Exercise VE, VO2 and HR were similar under the two conditions. No reduction in any of the pulmonary functions (FVC, FEV1.0, MMEFR, MBC) was found after 5 and 10 minutes following the swimming exercise in either of the conditions. In contrast, a treadmill run of similar metabolic and ventilatory intensity induced bronchoconstriction when room air was dried to 25–30% R. H. It is suggested that, unlike running, swimming is of low asthmogenicity even when inspired air is dried to 25–30% at neutral temperatures.

Ittai Neuman

Papers

Effects of dry and humid climates on exercise-induced asthma in children and preadolescents.

Differences between swimming and running as stimuli for exercise-induced asthma.

Breathing dry or humid air and exercise-induced asthma during swimming.