Comparison of the bronchial response to running and cycling in asthma using an improved definition of the response to work

Exercise-induced bronchoconstriction in adults with asthma--comparison between running and cycling and between cycling at different air conditions

The bronchial response to cycling and running was compared in six adult asthmatic persons. The effects of different air conditions during cycling regarding the induction of bronchoconstriction was studied. The exercise consisted of 6 minutes' work at an intensity of 80-85% of maximal heart rate. Heart rate, oxygen consumption and ventilation were measured to check that the exercise level was the same in all tests. Peak expiratory flow (PEF) was used to test for bronchoconstriction. Bicycling and treadmill running were performed under indoor conditions and bicycling while breathing cold, dry air (-18 degrees C) and room-tempered humid air (60% RH), respectively. No difference in bronchoconstriction was found between cycling and running under indoor conditions. However, bicycling exercise with inhalation of cold dry air provoked more bronchoconstriction than when inhalating humid air (PEF reductions of 19.4+/-6% and 6.1+/-2%, respectively). No differences were found between the exercise modes in heart rate, oxygen consumption, ventilation per minute, respiratory rate, carbon dioxide elimination or subjective ratings of perceived exertion and breathlessness. It is concluded that it is not the type of exercise, but the ventilation demand and humidity of the inspired air that are the main determinants of the occurrence and degree of bronchoconstriction.

Exercise and the asthmatic

Physical exercise is not hazardous to asthmatics. Some asthmatics may benefit from physical training, and almost all asthmatics can perform any kind of physical exercise. Free running was earlier thought to induce more asthma than swimming, for example; however, when ventilation is identical during running and swimming, the exercise-induced asthma will also be the same. Hyperventilation alone is as good as physical exercise to induce exercise-induced asthma. If the physical exercise provokes an asthmatic attack, this is most often easily reversed by inhaled beta 2-agonists. Pretreatment of exercise-induced asthma is most efficient by inhaled beta 2-agonist; orally dosed beta 2-agonist is not as efficient as inhaled beta 2-agonist in the pretreatment of exercise-induced asthma. Inhaled sodium cromoglycate diminishes exercise-induced asthma, and the effect seems to be better in children than in adults. Inhaled steroids have no immediate effect on exercise-induced asthma, but long term treatment with steroids diminishes exercise-induced asthma. The pathogenesis of exercise-induced asthma remains obscure. If the water content is low in the inhaled air, e.g. in cold air, the changes in ventilatory capacity following exercise. will be greater than when the exercise is performed while inhaling hot air with high humidity. Almost all asthmatics present changes in the ventilatory capacity following exercise. Seasonal changes in exercise-induced asthma are only present in asthmatics with seasonal allergies, e.g. pollen allergy. No diurnal variation is found in exercise-induced asthma. Asthmatics can do any form of physical exercise. Almost all asthmatics can prevent major changes in ventilatory capacity by pretreatment of exercise-induced asthma or be treated for exercise-induced asthma during the physical activity so that they will not suffer from asthma while performing physical exercise. Asthmatics who have been successfully treated for exercise-induced asthma can do physical exercise at the same level as non-asthmatics. Asthmatic children in particular should be encouraged to perform any sport they like, as the physiological and psychological effects may be beneficial to them. It is concluded that almost all asthmatics have exercise-induced asthma, and that physical training may be beneficial. Exercise-induced asthma is best treated and pretreated by inhalation of beta 2-agonists.

Plasma cyclic nucleotide levels in exercise-induced asthma

It is known that sympatho-adrenal control of airways is increased in asthma since beta blockade can cause severe bronchoconstriction in asthmatic individuals. It has not been established whether an altered catecholamine response to exercise plays any part in the production of the common symptom of exercise-induced asthma (EIA). We have investigated this indirectly by measuring arterial plasma cyclic nucleotide levels in 10 subjects with EIA and five normal subjects. Cyclic AMP, which in this context reflects beta stimulation, rose significantly by 25.4% in the normal subjects during exercise, while there was no significant change during or after exercise (less than 5%) in the asthmatic subjects. Cyclic GMP rose significantly after exercise in the asthmatic subjects. Six normal subjects repeated the protocol before and after inhalation of salbutamol aerosol, 1600 microgram daily for 18 days. This did not reduce the cAMP response to exercise, and we conclude that the diminished cAMP response of the asthmatic subjects was not caused by their medication. The results may indicate either impaired catecholamine production or endogenous beta receptor hyporesponsiveness in some asthmatic subjects and this may contribute to the development of EIA.

Hyperventilation or exercise to induce asthma?

Bronchoconstriction was induced in asthmatic patients by means of isocapnic hyperventilation with dry air. Responses both within a day and between days did not differ significantly and corresponded closely with those observed after exercise. The mean fall in forced expiratory volume in one second (FEV1) observed with both techniques was equivalent to 36%. Isocapnic hyperventilation with dry air, as used in this study, was a potent stimulus and provoked a reproducible response. The method was physically less demanding than exercise and was more acceptable to patients.

Effect of an inhaled antihistamine on exercise-induced asthma

The ability of the H1 receptor antagonist clemastine to prevent exercise-induced asthma (EIA) has been studied in 10 adult asthmatic subjects. Exercise was performed for eight minutes on a cycle ergometer on two occasions on each of two days. The first test each day was without premedication and the second was preceded by inhalation of 0.05% clemastine or saline placebo given single blind in random order. Ventilatory function was assessed by serial measurements of peak expiratory flow rate (PEFR) and forced expiratory volume in one second (FEV1). All four tests for each patient were closely matched in terms of oxygen uptake and total ventilation which were monitored throughout exercise. The response to exercise after clemastine or placebo has been compared both directly and in terms of the degree of protection afforded against EIA compared with the initial test on the same day. Clemastine was significantly better than placebo for both PEFR and FEV1. All 10 subjects had less EIA after clemastine, which suggests an important role for histamine in its production. Other mechanisms may also be involved to a variable degree in different individuals.

Cholinergic blockade in the prevention of exercise-induced asthma

The contribution of vagal mechanisms to exercise-induced asthma has been studied in 10 adult asthmatic patients using the anticholinergic drug ipratropium bromide. Exercise tests were performed for eight minutes on a cycle ergometer and each individual's tests were standardised by matching oxygen uptake. Two tests were done on each of three study days, the first being without previous medication, and the second preceded by inhalation of ipratropium bromide, 0.1, or 1 mg or saline placebo given 90 minutes beforehand. The mean falls in FEV1 and PEFR after the initial tests were very similar on the three study days. The mean falls in FEV1 after the second test were 22.3%, 19.5%, and 12.5% with placebo, 0.1 mg, and 1 mg ipratropium bromide respectively. Only the higher dose was significantly better than placebo. The results were also analysed using a protection index to compare the first and second tests each day and 1 mg ipratropium bromide was significantly better than both 0.1 mg and placebo. Similar results were obtained using PEFR. Equal bronchodilatation was produced by the two doses of drug. We conclude that conventional doses of anticholinergic drugs are not effective in preventing exercise-induced asthma, while large doses may do so in the same group of subjects.

The effects of pharmacological treatment on pulmonary function in children with exercise-induced asthma

The effects of two therapeutic regimens were investigated in eleven boys and eight girls (8--13 years) with a history of exercise-induced asthma (EIA), who reacted with subjective signs of EIA and a decrease in FEV1.0 exceeding 10% after an exercise test. A test program (TP) including complete spirometry, bicycle ergometer and treadmill exercise tests preceded and followed by dynamic spirometry at one and five min after exercise, was performed before and after each treatment period. In 12 patients with sporadic medication before the trials, continuous peroral treatment with a combination of a beta 2-stimulating drug and a xanthine derivative for three weeks did not significantly improve TP data. In 13 children (six from the above group) who were already on continuous treatment as above, addition of disodium cromoglycate (DSCG) inhalations for 3--4 weeks improved the response to acute administration of a beta-receptor stimulatory aerosol but did not influence EIA. Seven of the children continued their DSCG treatment for one year. Minor improvement of EIA provoked by cycling but not by treadmill was seen after this. The ventilatory effort in relation to working intensity was lowered. No significant differences were found between treadmill running and cycling in provoking asthma.

Running, walking, and hyperventilation causing asthma in children

To examine further the relation between type of exercise, workload, ventilation, and exercise-induced asthma, we compared treadmill walking with treadmill running and treadmill running with isocapnic hyperventilation in separate studies in children and adolescents. Inspired air conditions were identical during each pair of tests. Walking and running with similar minute ventilation and oxygen consumption were followed by similar falls in peak expiratory flow rate as were running and hyperventilation with similar minute ventilation and end-tidal carbon dioxide tension. This study supports the concept that hyperventilation is a central mechanism in exercise-induced asthma.

Effects of oral H1 and H2 receptor antagonists in asthma

1 There is evidence that H2 receptors are present in the lung, both on bronchial smooth muscle and mast cells. In animal studies, stimulation of H2 receptors causes a diminution, and conversely H2 receptor blockade can increase, smooth muscle contraction and mediator release. 2 The effects of H2 receptor blockade in ten patients with asthma has been studied using oral cimetidine in a dose of 1 g daily for 1 week. Treatment was compared with placebo and the H1 receptor antagonist chlorpheniramine. 3 There was no alteration in the severity of naturally-occurring or exercise-induced asthma with cimetidine or chlorpheniramine. 4 H2 receptor blockade with oral cimetidine in conventional doses is without ill effect in asthma. The use of larger parenteral doses is discussed.

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

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.