CONTACT: BECKY SOGLIN
2130 Medical Laboratories
Iowa City IA 52242
(319) 335-6660; fax (319) 335-9917
Release: July 7, 1999
UI study shows exercise-induced hyperventilation may
be misdiagnosed as asthma
IOWA CITY, Iowa Almost 10 percent of all children
have asthma, characterized by wheezing, coughing and shortness of breath.
However, University of Iowa Health Care researchers have found that, in some
cases, adolescents diagnosed with exercise-induced asthma may not have asthma
at all but exercise-induced hyperventilation. The findings were published
in the June issue of the Annals of Allergy, Asthma, & Immunology.
"Asthma is clearly the most common cause of exercise-induced
shortness of breath and needs to be appropriately treated," said lead
investigator Miles M. Weinberger, M.D., UI professor of pediatrics and director
of the UI pediatric pulmonary and allergy division. "But the bottom line
is its not the only cause of labored breathing during exercise. Our
study showed that some children who were initially diagnosed with asthma were
in fact hyperventilating when they exerted themselves."
An increased breathing rate during heavy exercise
normally helps lower carbon dioxide levels to compensate for lactic acid buildup
in the blood. With hyperventilation, deep breathing excessively lowers carbon
dioxide levels. In contrast, people with asthma have inflamed airways that
prevent air from traveling in and out of the lungs freely, causing the labored
What the study suggests, Weinberger said, is that
children with exercise-induced hyperventilation will not benefit from medication
and should stop using the bronchodilator inhalers or other asthma medications
prescribed to them when it was thought they had asthma.
Weinberger and Abdel-Hai Hammo, M.D., a former UI
resident in pediatrics now at Brown University in Providence, R.I., examined
32 patients, eight girls and 24 boys ages 8 to 18, diagnosed with exercise-induced
asthma. The children had a history of shortness of breath or chest tightness
while exercising. However, careful questioning did not reveal a typical history
of asthma. Additionally, in some children the use of conventional asthma treatment
with an inhaler did not alleviate symptoms.
The adolescents took treadmill running tests while
sophisticated equipment monitored their breathing and other vital signs. The
researchers measurements included analyzing the air each child exhaled.
During or after exercise, children with asthma cannot exhale as much air as
fast as children without the condition can. Seventeen children had normal
breathing function. They did not have the shortness of breath they had previously
experienced, but the symptom was reproduced in the 15 other children. However,
only four of those children had findings consistent with asthma, including
cough and wheezing, and a marked drop in the rate at which they could exhale
either during or immediately after the exercise test.
The remaining 11 children had tightness in their chest
and/or shortness of breath, but no wheezing or coughing and no change in their
lung function measurements of air flow. However, these children did have significantly
lower carbon dioxide levels than those measured in the other children, suggesting
that the children with lower carbon dioxide levels were hyperventilating.
When questioned, the children who had exercise-induced
hyperventilation said they felt discomfort while they were pushing themselves
generally during competitive exercise. Other studies have looked at adults
who felt chest discomfort while exercising, which raised concerns about cardiac
disease, but testing showed the adults in fact had exercise-induced hyperventilation.
"In cases of exercise-induced hyperventilation,
people breathe faster than they need to because they perceive theyre
having difficulty breathing when in fact theyre experiencing a normal
level of discomfort for an extreme level of exercise," Weinberger said.
He added that children with the pseudoasthma syndrome of hyperventilation
should be told they dont have asthma and taught how to pace themselves
through appropriate conditioning and training.
Children with exercise-induced hyperventilation should
also stop taking medications meant to treat asthma conditions. A few children
in the study previously misdiagnosed with exercise-induced asthma had been
put on every type of bronchodilator inhaler without a change in their symptoms,
"Given how widespread asthma is, it is natural
for physicians and people to consider a diagnosis of asthma even if the only
symptom is shortness of breath," he said. "But if a patient has
only that symptom and does not respond to treatment with inhalers, then the
physician should consider other diagnoses."
With the subsequent addition of even more sophisticated
means of assessing exercise physiology in the UI Pediatric Pulmonary Function
Laboratory, Weinberger and his colleagues can distinguish between two reasons
for decreased carbon dioxide in children. In addition to seeing the primary
exercise-induced hyperventilation reported in the study, the researchers also
found that some adolescents simply appear to over-respond to normal discomfort
from maximal effort, not realizing that they are "hitting the wall"
in their effort to succeed in their athletic effort.
He added that people with exercise-induced asthma
should understand that it is readily treatable and should not keep them from
taking part in normal activities, including competitive athletics. As with
all medical conditions, people should consult their physicians before making
any changes in their or a childs health care routine.