Asthma attacks worsened by obesity

NEW YORK (Reuters Health) -
In asthma patients, dynamic
hyperinflation, following a test measure airway
hypersensitivity, is greater in obese individuals than in their
nonobese counterparts, which helps explain why asthma is
perceived to be more severe in patients with a higher body mass
index (BMI), investigators in New Zealand report.

A BMI is the ratio between height and weight, and is used
to classify people as underweight, overweight or normal weight.

"The greater dynamic hyperinflation means that obese
individuals lose the ability to inhale as deeply or exhale as
fully as normal weight individuals," Dr. D. Robin Taylor
explains in an American Thoracic Society statement.

Taylor's team at the University of Otago in Dunedin studied
the changes in airway expansion and lung volume that occur with
acute constriction of the bronchial tubes in a group of 30
adult women with asthma. Ten women each were classified as
normal weight, overweight, or obese, and lung volumes were
measured.

The degree of bronchial constriction following the airway
sensitivity test did not vary by group, the team reports in the
American Journal of Respiratory and Critical Care Medicine. The
only significant difference among the subjects was a decrease
in vital capacity that significantly corresponded with
increasing BMI.

Lung volume measurements also showed that the volume of air
retained in the lung following exhalation was significantly
higher as BMI increased, while the amount of air that could be
inhaled was lower.

These variations "were significantly greater in relation to
BMI" after taking into account the effects of "airway
hyperresponsiveness, the severity of airflow obstruction, and
lung volume measurements, indicating the effect of BMI was an
independent one," the investigators note, meaning that BMI
alone was associated with the severity of asthma.

This puts obese individuals at greater disadvantage due to
enhanced gas trapping, they point out, a significant
contributor to difficulty in breathing.

Taylor and his associates also noted that conventional lung
function tests "may have limitations when used to evaluate
symptoms in obese patients with asthma, with the potential for
misinterpretation" in the absence of lung volume measurements.

source:news.yahoo.com