Diagnosis of EIB
Diagnosis of EIB among young athletes does not presently differ from adult athletes. In the physical examination, especially at rest, patients suffering from EIB do not exhibit abnormalities. Diagnosis can be made when respiratory symptoms occur during exercise and are linked to confirmation with an exercise challenge test, performed by a standardized protocol.
Several tests can be used to assess the occurrence of bronchospasm in EIB-positive athletes. One such test is spirometry, which usually does not rule-out the occurrence of EIB and can give false negative results.
Regular exercise is a factor that improves functions of the respiratory tract. Athletes are characterized by higher cardiovascular and respiratory system parameters, meaning their baseline spirometry parameters can be higher than in general population21.
Provocation tests provide a basis for diagnosing bronchospasm during exercise and are divided into two groups: direct andindirect . The first group contains a metacholine challenge, which is direct bronchoprovocation test, designed to stimulate a response of the respiratory tract to the administration of methacholine. A fall in FEV1 ≥ 20% from the baseline value is considered positive.
Indirect tests consist of an exercise challenge via treadmill (in accordance with the recommendations of the American Thoracic Society, ATS), a free running exercise challenge, eucapnic voluntary hyperventilation (EVH), hypertonic saline challenge, and the mannitol test.
The most recommended by scientific societies is the exercise challenge on treadmill or a cycle ergometer, which consists of six to eight minutes of physical effort, with a heart rate of 80% to 90%. Respiratory response is measured by performing repetitive spirometry, usually after 5, 10, 15 and 30 minutes of exercise. The test is considered positive with decline in FEV1 ≥ 10% from the baseline value, according to the recommendations of the American Thoracic Society22.
The free running exercise is based on repetitive peak expiratory flow (PEF) measurements after physical exercise lasting approximately 6 minutes, but mainly depends on the subject’s motivation to complete the test with maximal effort23.
Eucapnic Voluntary Hyperventilation (EVH) is a test specially developed for EIB diagnosis that indirectly causes bronchospasm. During the test, a patient is required to breathe for six minutes at 85% maximum voluntary ventilation rate with a controlled concentration of carbon dioxide. Inhaled air should contain 21% oxygen, 5% carbon dioxide and 74% nitrogen. After three, five, 10 and 15 minutes, maximal voluntary flow-volume loops should be assessed. As in the exercise challenge on treadmill, EVH is considered positive when FEV1 ≥ 10% decreases from baseline value. Good standardization and sensitivity are the reasons for which EVB is the preferred diagnostic test used by many researchers. EVH is limited by its requirement for special equipment and more demanding procedures, including proper training of testing personnel.
The hypertonic saline challenge and mannitol tests are indirect tests that involve the inhalation of hypertonic saline and mannitol, respectively. The tests are considered positive when there is a fall in the baseline value in FEV1 ≥ 15%24,25.