444 SA MEDIESE TYDSKRIF 3 September 1977
The Effect of Exercise in the Asthmatic Child - its Clinical
C. H. VAN NIEKERK
SUMMARY asthmatic child is typical.'" During the early stage of
exercise, bronchodilatation occurs. This is followed by
Appropriate exercise will provoke an attack of broncho-
marked bronchoconstriction which reaches its maximum
spasm in virtually all asthmatic children. Exercise-induced
3 - 5 minutes after stopping the exercise. The broncho-
asthma can effectively be prevented by pre-exercise treat-
constriction then reverses spontaneously and is usually
ment with sympathomimetic drugs or sodium cromogly-
completely absent 20 - 30 minutes after exercise. In adults
cate, and there is no reason why an asthmatic should not
bronchoconstriction comes on slightly later than in children.
participate in sporting activities. Running at a steady pace
Reversal of the process takes longer and may require
for 6 - 8 minutes (submaximal effort) is the most asthma-
an aerosol-inhalant bronchodilator for full recovery.'" The
genic exercise, whereas swimming is the least athma-
clinical presentation is that of an acute attack of broncho-
spasm with wheezing and rhonchi on auscultation, and
dyspnoea which occasionally results in respiratory distress
S. Afr. med. J., 52, 444 (1977).
For many years it has been recognized that exercise may The degree of bronchoconstriction is most commonly
affect sufferers from asthma. It is also known that different measured with simple lung function tes'ing apparatus.
types of exercise engaged in by asthmatics produce differ- The most useful measurements indicating changes in the
ent responses. These observations received little attention airway calibre are the peak expiratory flow rate (PEFR)
until 1962 when Jones et al."" reported the effect of and the forced expiratory volume in 1 second (FEV,).
exercise in asthmatic children. They noted that exercise PEFR is usually measured on a Wright flowmeter and
over a short period (l - 2 minutes) resulted in broncho- FEV, on a Vitallograph, both of which are simple to
dilatation; if the period of exercise was prolonged operate. They will yield as many positive results as
(8 - 12 minutes), marked bronchoconstriction resulted. This sophisticated body plethysmographic tests.'·
led to a renewed interest in exercise-induced asthma and The degree of bronchoconstriction which develops as a
many studies have since been published on the sub- result of exercise challenge is expressed as the percentage
ject. It was highlighted in competitive athletics at the fall in PEFR or FEV, from pre-exercise resting values.
1972 Munich Olympic Games when the gold-medal winner The formulae used are those of Silverman and Ander-
of the 400-metre free-style swimming event, an asthmatic, son :311
pre·exercise PEFR - postexercise PEFR
was disqualified for taking ephedrine." percentage fall = X 100
Controlled trials have clarified many of the uncertainties
about exercise-induced asthma. However, the mechanisms hi2hest overall PEFR - lowest overall PEFR
by which exercise provokes bronchoconstriction remain lability index calculated =
predicted normal PEFR at rest
Bronchoconstriction brought on by exercise can be This highest PEFR is measured after two puffs of
distressing and severely incapacitating for the active child salbutamol aerosol, followed by 1 minute of exercise.
who suffers from asthma. Although it may equally occur This is a slight modification of the J ones lability index,"
in adult asthmatics, it is often unnoticed and not as which measures FEV, instead of PEFR.
troublesome because most individuals lead a sedentary
life and only a small proportion are involved in active EFFECT OF THE TYPE, SEVERITY AND
sporting activities. DURATION OF EXEROSE
The response to exercise in the asthmatic child is closely
RESPONSE TO EXERCISE IN AN related to its form. From clinical experience it is well
ASTHMATIC CHILD known that some forms of exercise or some sports are bad
The response to an appropriate exercise stimulus in an for the asthmatic, while others have hardly any effect. The
effect of the type, severity and duration of exercise in
Allergy Clinic, Red Cross War Memorial Children's Hospital causing bronchoconstriction has been clarified with different
and Department of Paediatrics and Child Health, Institute standardized types of exercise.','3,".3',..
of Child Health, University of Cape Town The most potent stimulus causing exercise-induced asth-
C. H. VAN NIEKERK, F.e.p. (S.A.), D.C.H. (S.A.) ma has been found to be free-range running, and the least
Date received: 11 May 1977. potent, swimming or walking. The mean percentage fall in
3 September 1977 SA MEDICAL JOUR AL 445
PEFR from resting pre-exercise values for different types cise.-,l. ,:n.'" The mean percentage drop in PEFR in 548
of exercise is 47% for free-range running (in the open, or normal 12-year-old schoolchildren after 6 minute' free
in a corridor), 33% for treadmill running, and 25% for running was 2,5%, with the results distributed ym-
cycling; walking, swimming and canoeing cause a fall of metrically around the mean.' The upper limit for the per-
13 - 15%, which is just above the normal range. w,,,,,,, To centage fall in PEFR (mean 2 SD) was defined as 10%
eliminate the effect of different workloads, the subjects in 19 normal children.'"
were exercised continuously at a steady level for 6 minutes
at similar D,-consumption and heart rates:'" EFFECT OF EXERCISE IN CIDLDREN WITH
In one trial, children were exercised at a constant work- OTHER PULMO ARY DISORDERS
load on a treadmill." The effect of the duration of exer-
cise was assessed by determining the percentage fall in The response to exercise in patients suffering from other
PEFR after 1, 2, 4, 6, 8, 12 and 16 minutes. When lung conditions has also been studied. These include
the period of exercise was short (1 - 2 minutes) broncho- children with wheezy bronchitis, ex-wheezers, ex-a thma-
dilatation resulted, but when it was longer, the PEFR tics, their relatives and patients suffering from cy tic
fell - the greatest percentage fall occurred after 6 - 8 fibrosis.
minutes of exercise. Strangely enough, further prolongation An increased bronchial lability has been found in
of exercise, up to 16 minutes, often resulted in lesser de- children who suffered from wheezy bronchitis in infancy.:n
grees of bronchoconstriction than in the intermediate 6 - 8 This increased bronchial lability was also demonstrated
minute period, some patients showing no bronchocon- in adults who had had asthma as children, but who had
striction whatever after having run for 16 minutes. been symptom-free for a long time." These interesting
By changing the severity, i.e. the workload, a difference findings were further employed in studies involving the
in response to exercise is also found. The maximum bron- relatives of children who suffered from wheezy bronchitis
choconstriction results from running at a speed repre- and asthma.""" An increased bronchial lability was found
senting about 70% of the maximum aerobic power of in the first-degree relatives of wheezy babies and a thmatic
the subject, which should raise the heart rate in children children as compared with control group. This was also
to about 170 - 180 beats per minute."" found in the entirely healthy relatives. In all the groups
The asthmatic child responds to an appropriate exer- studied, the increased bronchial lability consisted of bron-
cise stimulus with a marked, and often precipitous, drop chodilation rather than bronchoconstriction. In no ca e
in PEFR or FEY" with values between 20% and 50% was the fall from resting values more than 10%. A
of the pre-exercise levels.'" marked postexercise fall is found only in the asthmatic.
The importance of these findings may be far-reaching.
WHAT IS EXERCISE-INDUCED ASTHMA? Bronchial lability could be used as a genetic marker in
identifying the asthmatic child and in clarifying the in-
In defining exercise-induced asthma, criteria ranging from heritance of asthma.
wheezing only after exercise" to a drop of 25·% or more In a study of children suffering from cystic fibrosis,
in FEY] from resting values" have been suggested. A they were shown to have an increased bronchial lability
drop of 10% in PEFR from resting values has been sug- after exercise." Bronchodilatation was the main cause of
gested as the upper limit of normal (mean + 2 SD).' The the total bronchial lability in these children and broncho-
child with exercise-induced asthma, however, has a marked constriction was mild. In another study, groups of patients
drop in PEFR and FEY]. Therefore, exercise-induced suffering from cystic fibrosis or primary tuberculosis, as
asthma is more generally regarded as a percentage drop well as normal controls, were indistinguishable from one
of 15% or more in PEFR or FEV, from resting pre- another as regards the drop in FEV, after exercise."
exercise values.-·'-·" Cystic fibrosis is not associated with bronchoconstriction
Bronchoconstriction provoked by exercise is unique and after exercise.
occurs in the asthmatic child only. It is so constant that Although abnormal bronchial lability has been seen in
failure to demonstrate it should lead to reconsideration patients with other conditions, the response of mild
of either the technique of the test used, or of the diag- bronchial dilatation during exercise and severe broncho-
nosis of asthma.'" This view is supported by Godfrey," constriction after exercise ha been found only in asthma-
who calls it 'the hallmark of the asthmatic child'. tics.
The form of exercise most likely to bring on an attack
of asthma is free-range· running at a steady, moderate EFFECT OF DRUGS IN
pace (submaximal effort) for 6 - 8 minutes. The maximum EXERCISE-INDUCED ASTHMA
bronchoconstriction occurs 3 - 5 minutes after the exercise
is completed and is measured as a drop of 15'~~ or more A brief attack of bronchospasm provoked by exercise
in PEFR or FEV,. provides an excellent model for studying the effects of
various drugs on asthmatic persons. Standardized con-
RESPONSE TO EXERCISE IN THE NORMAL trolled trials have been carried out to evaluate the efficacy
CHILD of different drugs in preventing asthma induced by exer-
cise. In 1963 Jones et al.'" noted that isoprenaline pre-
Jn contrast to the asthmatic, the normal child shows very vented postexercise bronchoconstriction when administered
little change in bronchial calibre as a result of exer- up to 5 minutes before the start of exercise. They also
446 S MEDIESE TYDSKRIF 3 September 1977
found that adrenaline gave a similar response if adminis- CLINICAL IMPLICATIO S
tered 2 minutes before exercise. Atropine was found to
be relatively ineffective. Exercise·induced asthma i an almost universal finding
in the asthmatic child. Asthmatic children may deny its
Virtually all cases of exercise-induced asthma can be presence, but this only reflects their own voluntary re-
prevented by any of the generally available ympatho- striction of those forms of exercise which will induce
mimetic bronchodilator drugs. while the ,B,-adrenergic bronchospasm.
inhalant aerosol, such a albutamol and feneterol, have Exercise-induced asthma is found in the asthmatic child
been shown to be highly effective.'·""·" The oral pre- only and is a useful, diagnostic non-invasive way of dis-
parations of the e drugs are less effective than the aero- tinguishing the asthmatic from the non-asthmatic child.
sols, and the effect may be time-related.' Xanthine Failure to provoke bronchoconstriction after appropriate
derivates (aminophylline and theophylline), if given be- exercise should lead to serious questioning of the diag-
fore exercise, will prevent exercise-induced asthma in nosis of asthma. The Wright spirometer for measuring
75°~ of case. Varying re ults have been found with PEFR is simple and easy to use. PEFR is a reliable in-
atropine, which was sometimes effective and sometimes dex for detecting exercise-induced asthma.
non-effective. It would seem that atropine will offer This condition is troublesome, especially in the active
protection only against exercise-induced asthma in about child uffering from asthma, and may incapacitate such
a third of cases.···'" Antihistamines have been shown to be a child severely.
ineffective. 33 It is prevented by pre-exercise treatment with sympa-
Although sodium cromoglycate produces no direct bron- thomimetic drugs, the ,B,-adrenergic inhalant aerosols being
chodilator response, it has proved very effective in pre- the most effective. These drugs, when given after exercise,
venting exercise-induced asthma if given before exercise, rapidly relieve exercise-induced asthma.
but not if given immediately afterwards."·"·311 Its efficacy The condition is also effectively prevented by pre-
in inhibiting exercise-induced asthma is a little greater exercise inhalation of sodium cromoglycate. It should
than that of the xanthines, but not as great as that of the be used shortly before the onset of exercise, in view of its
sympathomimetic drugs. The protective effect of sodium short protective action.
cromoglycate against exercise-induced asthma is of rather Owing to the varying duration of action of the different
short duration - the mean 50% protection time is 30 drugs, daily maintenance doses of either sympatho-
minutes, although some degree of protection lasts for up mimetic drugs or sodium cromoglycate will not necessarily
to 6 hours." Corticosteroids, although very effective in the protect the asthmatic child from developing broncho-
management of some cases of clinical asthma, have little constriction on exercise.
effect in preventing exercise-induced asthma and offer Some types of exercise are more liable to provoke
almo t no protection at all."·" exercise-induced asthma than others. Running for 6 - 8
The bronchoconstriction which occurs in exercise·in- minutes at a steady pace is the most asthmagenic. Short
duced asthma has been shown to be in the larger air- bursts of running cause bronchodilatation and prolonged
ways."'''' The efficacy of sympathomimetic drugs in re- running may result in diminished bronchoconstriction,
lieving the bronchial obstruction indicates that there has Le. running through the bronchoconstriction. Swimming
been bronchial smooth muscle contraction. The protective and walking are least likely to produce asthma.
effect of sodium cromoglycate suggests that there may be Steroids offer no effective protection against exercise-
mediator release during, or shortly after stopping, the induced asthma.
exercise that eau ed bronchoconstriction. Various factors There is no reason why asthma alone should debar a
have been put forward as the triggering mechanism of child from sporting activities.
exercise-induced bronchoconstriction, including hyperven- If the asthmatic child wishes to participate in sports
tilation, hypoxaemia, hypocapnia and acidosis.··l5· 33 ,33.36 The which involve steady running, pre-exercise treatment with
evidence in support of these hypotheses has often been a ,B,-adrenergic drug (aerosol or oral) or sodium cromo-
based on poorly controlled and isolated unusual cases of glycate will offer effective protection.
exercise-induced asthma. In properly controlled studies, If the use of drugs before exercise is unacceptable, then
where 0, consumption, minute ventilation, heart rate and other activities, e.g. swimming, which is the least asthma-
duration of work were kept constant, no single factor genic, or short-distance running, should be encouraged.
could be incriminated, and the triggering mechanism re- If the resting PEFR or FEV, values are well below
sponsible for exercise-induced bronchoconstriction is still the predicted normal for height, the child should not be
unknown.""" subjected to the kind of exercise which may bring on
bronchospasm, because a further fall in the PEFR can
The severity of exercise-induced asthma as indicated by cause acute respiratory embarrassment.
a percentage fall from pre-exercise resting levels in PEFR
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The 2-Deoxy-n-Glucose-Neutral Red Test and Vagotomy
An Experimental Study
L. C. J. VAN RENSBURG
SUMMARY 2-Deoxy-D-glucose (2-DG) is a powerful stimulus of
vagal gastric secretion and has been employed both ex-
The 2-deoxy-D-glucose - neutral red test proved to be
perimentally and clinically for some time.'-· eutral red
successful in assessing completeness of vagotomy in th~
(NR), a basic dye, will appear in the lumen of the stomach
baboon both intra- and postoperatively. There were no
after intravenous injection. The use of a combination of
deleterious side-effects and we found that both products
2-DG and NR has proved to be a reliable test for the
could be sterilized adequately. So far we have used this
completene s of vagotomy.'" However, it has not been
test on 5 patients in the immediate postoperative phase; generally accepted, for there are uggestions that 2-DG
in 1 patient, on whom thE:. surgeon thought he had done is a liver toxin, that it could cause cardiac irregularity
an incomplete parietal cell vagotomy, the test was found and that it cannot be adequately sterilized. The aim of
to be positive within a week of the operation. the present study was to test its effectiveness and possible
side-effects in the baboon. Jt might be added that very
S. Air. med. l., 52, 447 (1977). little work has been published on its use in association
with highly selective vagotomy.
Department of Surgery, Tygerberg Hospital and University
of SteHenbosch, ParowvalJei, CP MATERIALS AND METHODS
L. C. J. VAN RENSBURG, ~1.MED. (SURC.), F.C.S. (S.A.), F.R.e.S.
(Present addres : 828 Medipark, Foreshore, Cape Town) Chacma baboon (Papio ursinus ursinus) with an average
Date received: 21 October 1976. weight of 15 kg were u ed in this tudy. A ample of