Summary
950
EXERCISE
AND
ASTHMA
C. Warren Blerman, M.D., and WIllIam E. PIerson, M.D.
Asthma is the most frequent chronic respiratory illness of childhood. It is the number one cause of school absenteeism and forces afflicted youngsters to miss a total of 9 million school days annually. Athma and other respiratory allergies such as hay fever and perennial allergic rhinitis account for near-ly one third of all chronic conditions in children Un-den 17 years of age.
Among many of these young people, broncho-smasm induced by exercise is a physical handicap which is frequently overlooked by the child’s par-ents, physician, teachers and often by the child him-self. This condition may have lasting physical and psychological effects, for the individual with exer-cise bronchospasm may avoid sports and other physi-cal activities. This can result in poor physical condi-tion and poor self-image, which is reinforced by ridi-cule from peers, teachers, and physical education in-structors.
Exercise-induced asthma (EIA) or exercise-induced bronchospasm (EIB) as it has been variously termed has been mentioned from time to time in medical writings since the third century AD. Only during the past decade, however, has it been studied in a systematic fashion as to incidence, physiological changes, and pharmacological therapy. Few of these studies, however, are readily available to pediatni-cians.
This symposium has been organized to compile ex-isting knowledge concerning exercise and asthma for physicians caring for allergic children and ado-lescents as a guide to early recognition since ef-fective therapy is available for EIB. Thus, the physi-cian’s goal should be pharmacologic prevention rather than physical restriction, so that the child can participate in normal activities with his peers with the resulting physical and emotional benefits.
IDENTIFICATION
OF
THE
PATIENT
“AT
RISK”
There appears to be a definite relationship between bronchial lability and the allergic state. EIB is the characteristic form that this lability takes in the asth-matic. Bronchoconstniction following exercise re-sulting in at least a 15% fall in lung function occurs most frequently in children and adolescents who have active asthma. More than 70% of asthmatics have significant bronchospasm following exercise
and some believe that all asthmatic children can de-velop this reaction. Forty percent of patients with only allergic rhinitis may also have significant post-exercise bronchospasm, though generally it is less severe than in those with asthma. Children who have had wheezing with respiratory infections in infancy have a high incidence (58%) of bronchial lability and EIB in later childhood and adolescence. Thirty-eight percent of their immediate relatives are aJ#{128}osusceptible, suggesting that there is a common genetic basis for bronchial lability. Individuals with intrinsic asthma (asthma which is unrelated to demonstrable respiratory allergy by history on by skin test) have a lower incidence than those with extrinsic (allergic) asthma.
The degree or severity of EIB may vary from time to time. EIB may be increased by colds on other viral infections on exposure to airborne allergens or even to cold air. A positive or negative history of EIB is not a reliable prediction of its presence. Diagnosis can be documented only by testing the subject with an exercise tolerance test in which pulmonary func-tion is measured before and after exercise.
PHYSIOLOGIC
CHANGES
OCCURRING
IN
EIB
Even brief exercise periods (less than three mm-utes) frequently induce bronchoconstriction in asth-matic children. If the period is extended to five mm-utes on longer (optimal exercise period is six to eight minutes) and the exercise is strenuous enough to induce a pulse rate of 170 to 180 beats per minute, mild bronchodilation is followed by bronchoconstric-tion five to ten minutes later. This bronchoconstnic-tion may resolve spontaneously in 15 minutes on may persist for more than 30 minutes after exercise. Oc-casionally it requires bronchodilator therapy. During bronchoconstriction the following pulmonary physio-logical changes occur:
1. Decrease in forced expiratory volume at one second (FEy,).
2. Decrease in peak expiratory flow rate (PEFR). 3, Decrease in forced expiratory flow at 25#{176}kto 75% of vital capacity (FEF 25%-75%
)
or mid-maxi-mal expiratory flow (MMEF).4. Increase in airway resistance (Raw) and decrease in specific airway conductance (SGaw).
5. Decrease in forced vital capacity (FVC).
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SUPPLEMENT
951
TABLE I
SUGGESTED DRUG DOSAGES FOR EIB
Drug Dosage Route of
Administration
Time of Administration Prior to Exercise
Accepted for International
Competition
Theophylline 4 mg/kg Orally I hr Yes
Dyphylline 15 mg/kg Orally I hr Yes
Theophylline-ephednine combinations
/2 tablet
(5 to 10 yr) I tablet (10+ yr)
Orally I hr No
Metaproterenol 20 mg (12+ yr) Orally I hr No
Terbutaline 5 mg (12+ yr) Orally No
Cromolyn sodium 20 mg Inhalation I to 15 mm Yes
6. Increase in functional residual capacity (FRC). The most sensitive parameters to measure are SGaw and FEF 25%-50% on MMEF followed by FEV, and PEFR. The least sensitive is the FVC. While a fall in arterial carbon dioxide tensions and oxygen tensions can be detected following exercise, the ma-jon alteration appears in the alveolar-arterial oxygen difference, suggesting that perfusion-ventilation ab-narmalities existing prior to exercise are accentuated after exercise in those individuals who develop EIB.
PULMONARY
FUNCTION
TESTING
The type of pulmonary function test which should be utilized in children and adolescents in testing for EIB will depend to a large degree on the type of exercise used as a challenge, on the age of the child, and an the equipment available. Far clinical screen-ing, a recording spirometer from which the FEV, may be determined or a Wright Peak flaw meter from which a PEFR may be obtained will suffice. Bath of these measurements are easily performed, but re-quire more subject cooperation than other prace-dunes. Specific airway conductance or flow-volume curves are less effort-dependent, but require much more sophisticated equipment and are technically more difficult to perform. One measurement which can be calculated from a recording spirameter, FEF 25%-75% is relatively less effort-dependent and better reflects smaller airway function. It is useful with cycloengometer exercise, but is frequently map-propniate for free running or treadmill exercise, which induce greater bronchaspasm of large air-ways. Pulmonary function tests should be per-formed prior to exercise challenge and repeatedly after exercise for a long enough interval to identify abnormalities (at least at five-minute intervals for a minimal period of 15 minutes.
The mast commonly employed systems to test far the presence of EIB are (1) free running, (2) treadmill, and (3) cycloergometer. Several others, in-cluding rowing ergometer and swimming, have been used, but nearly all reported investigation has been based on one of the three major systems noted above.
Each system generally calls for an exercise period
of five to eight minutes that is strenuous enough to accelerate the pulse rate to 170 beats per minute or mare, or induce mare than 80% of maximal oxygen consumption. This time period is critical, as exercise of lesser or greater duration may not uncover the true
magnitude of EIB.
Free-range running is clinically the most impor-tant and the most practical of all tests. It simulates the type of exercise children and young adults mast frequently undertake, and it is readily carried an any-where. It also is the most “asthmagenic” of all tests, and does not require expensive or laboratory-based instrumentation. Thus it provides the ideal system far practical, inexpensive, and readily performed
clinical screening for EIB.
The treadmill is the next most productive method far inducing EIB, and has been widely used by in-vestigatars for evaluation of various drugs and their respective effects upon EIB. It can be regulated for each patient by changing the work load, and its speed and slope can be altered to increase patient compliance while still maintaining an adequate work load.
The cycloergometer is the least asthmagenic of the three systems. It has the advantage that it is very acceptable to children and adolescents, and even very young patients readily comply by “riding the bicycle.” The work load may be satisfactorily in-creased during exercise to induce an appropriate heart rate.
TREATMENT
Many different agents have been evaluated for their effectiveness in alleviating EIB. They include (1) -adrenergic agonists, (2) methyl xanthines, (3) cramolyn sodium, and (4) others (xanthones, aerosol steroids, chalinergic agents).
Beta-adrenergic agonists, including epinephnine, isoproterenol, metaproterenal, and terbutaline, signi-ficantly decrease post-exercise branchospasm. They can be administered by aerosol (immediately before exercise); the latter two are administered orally (30 to 60 minutes prior to exercise). Oral formulations are preferred since pressurized aerosols, though
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952
EXERCISE
AND
ASTHMA
fective in a laboratory setting, are more likely to be overused than are oral forms. Because of a high abuse potential, pressurized inhalers should be em-played only when they can be monitored by an adult.
The methyl x anthines (theophyllmne, dyphyllmne) in adequate dosage are also effective in decreasing past-exercise bronchospasm 30 to 60 minutes after oral administration. Combinations of ephedrine and theophyllmne have additive effects in diminishing EIB when administered one hour prior to exercise.
Cramalyn sodium diminishes EIB in many subjects if inhaled I to 15 minutes prior to exercise. This drug is usually well tolerated and easily administered and is an accepted drug for use in international athletic competition. The usual dose of one 20-mg capsule has been effective in Olympic athletes. It is useful for patients who can not tolerate theophylline or ephedrine, and may provide additional benefit to pa-tients who are already receiving full therapeutic do-sages of theophylline for their asthma or may require bronchadilators shortly after exercise.
Finally, several new drugs are being evaluated and include xanthones (an oral compound similar in acti-vity to cromolyn sodium) and aerosol carticosteroids. The xanthones appear promising, but will require mare extensive testing before any recommendation for their use can be made. The aerosol steroids like oral or parenteral steroids have not been strikingly effective in relieving post-exercise bronchospasm, and also carry the potential hazards of corticosteroid administration.
IMPLICATIONS
FOR
PATIENT
MANAGEMENT
Many asthmatic children and adolescents avoid sports participation whenever possible because the occurrence of EIB prevents them from competing on equal terms with their normal peers. For such chil-dren swimming is an optimal sport and recreational exercise, since swimming provokes less EIB than comparable exercise by running or cycling. Regular swimming results in improved posture, physique,
and muscle tone and enhanced aerobic fitness. Other athletic activities such as track, soccer, on basketball are very liable to provoke EIB, though some asthmatics have been able to excel in these sports with appropriate pharmacologic manage-ment. A period of “warm-up” appears helpful to such athletes. Asthmatics should be permitted and en-couraged to participate in an integrated physical education program containing a wide range of physi-cal activities and should also be permitted to select their own personal preferences for sports and exen-cise.
It is thus the physician’s obligation:
(1) Ta recognize the handicap imposed by EIB in patients at risk (those with allergic rhinitis or asthma or a history of wheezing with colds) by conducting (a) a simple exercise tolerance test to screen for this problem by employing a stairwell, a sidewalk, or a treadmill and asking the patient to nun fan five to eight minutes, and (b) carrying out pulmonary (air-way) function tests pre-exencise and post-exercise at five-minute intervals for 20 minutes, employing a timed vital capacity spirometen or Wright peak flow meter. A fall of 15% or more in lung function after exercise indicates significant EIB.
(2.) To advise his patient with EIB concerning ap-propniate therapy, including (a) use of theophyllmne or $2-bronchodilaton drugs 30 to 60 minutes prior to exercise and/on inhalation of comolyn sodium 1 to 15 minutes before exercise and (b) the importance of carrying out and participating in regular exercise periods.
(3) To take a more active role in restructuring health policies toward asthmatics in school by foster-ing understanding on the part of school personnel and parents of the nature and limitations of the con-dition.
The recognition and appropriate treatment of EIA are important steps in the rehabilitation of children and adolescents so as to minimize their handicaps and facilitate normal physical, social, and nec-reational activity.
