Introduction
Asthma is a chronic disease characterized by airway inflammation and
diagnosed if a subject has a history of respiratory symptoms such as
wheezing, shortness of breath, chest tightness, and coughing as well as
variable airflow obstruction (1). Airflow obstruction can often be
reversed either spontaneously or with pharmacological treatment (1).
However, approximately 10% of infant subjects with asthma in a previous
study exhibited an expiratory airflow limitation that was not completely
reversible, despite optimal treatment being provided (2); this condition
is known as fixed airflow obstruction (FAO) (3).
FAO is diagnosed when a subjects’ ratio of the forced expiratory volume
in the 1st second (FEV1) to the forced
vital capacity (FVC) (FEV1/FVC) is below the lower limit
of the normal range (LLN) after optimal treatment (3). The development
of FAO has been explained by a type of pathological airway remodeling
that leads to structural changes in the airway and airflow restrictions
(4). The risk factors for FAO are multifactorial and differ between
adults and children (2, 5). The main risk factors for FAO in adults
include a subjects’ sex, his or her smoking habits, the presence of
rhinitis, atopy, and eosinophil inflammation; and the amount of
fractional exhaled nitric oxide (5). In children and adolescents, the
risk factors are related to asthma severity and the frequency of
exacerbations (2).
Previous studies have reported that subjects with FAO exhibit higher
asthma hospitalization rates and more severe symptoms such as dyspnea,
wheezing, and chest tightness than do their non-FAO peers (2, 4). The
fear of feeling asthma symptoms could inhibit many subjects from taking
part in regular physical activity due to exercise-induced
bronchoconstriction (6). The current guidelines encourage subjects with
asthma to engage in regular physical activity (1). An increase in a
subject physical activity level (PAL) improves his or her aerobic
fitness and health-related quality of life (HRQoL) and reduces the need
for inhaled corticosteroids, asthma exacerbations, and dyspnea symptoms
(7). In addition, adolescents with asthma who remain physically active
exhibit a slower annual decline in the FEV1 and
FEV1/FVC ratio values than do those who are physically
inactive (8). Although the benefits of regular physical activity are
well known, adults with asthma and FAO are physically inactive and
exhibit low levels of aerobic fitness (8, 9); however, the effects of
FAO in adolescents with asthma remain poorly known.
In the present study, we hypothesized that adolescents with asthma and
FAO have lower levels of aerobic fitness, PAL, muscle strength, and
HRQoL than do their peers with asthma but without FAO. Our study aimed
to compare adolescents with FAO and their non-FAO peers in terms of
aerobic fitness, PAL, muscle strength, and HRQoL.