Key Points
Î Exercise-induced bronchoconstriction (EIB) describes acute airway
narrowing that occurs as a result of exercise. EIB occurs in a substantial
proportion of patients with asthma but may also occur in individuals without
known asthma.
Diagnosis
Î The diagnosis of EIB is established by changes in lung function provoked by
exercise, not on the basis of symptoms.
Î Serial lung function measurements after a specific exercise or hyperpnea
challenge are used to determine if EIB is present and to quantify the
severity of the disorder. It is preferable to assess FEV1, because this
measurement has better repeatability and is more discriminating than peak
expiratory flow rate.
Î The airway response is expressed as the percent fall in FEV1 from the
baseline value. The difference between the pre-exercise FEV1 value and the
lowest FEV1 value recorded within 30 minutes after exercise is expressed
as a percentage of the pre-exercise value. The criterion for the percent fall
in FEV1 used to diagnose EIB is ≥10%.
Î The severity of EIB can be graded as follows:
Percent fall in FEV1 from
the pre-exercise level Severity
10%-24% Mild
25%-49% Moderate
≥50% Severe
Î A number of surrogates for exercise testing have been developed that may
be easier to implement than exercise challenge. These surrogates include
eucapnic voluntary hyperpnea or hyperventilation, hyperosmolar aerosols,
including 4.5% saline, and dry powder mannitol.