June 4, 2009 Two Indiana University studies have explored the potential use of two simple tests for not only predicting whether someone has exercise-induced asthma (EIA) but also its severity, without subjecting the patient to an exercise challenge.
One test involves measuring exhaled breath levels of nitric oxide. The other involved measuring the pH level of exhaled breath. Researchers found that both tests could be effective at predicting EIA and its severity. Both tests can be performed in a doctor's office while the patient is at rest.
With EIA, vigorous exercise triggers an acute narrowing of the airway afterward, making breathing difficult. Around 80 percent of people with asthma have this condition, also called exercise-induced bronchoconstriction. EIA also is found in an estimated 10 percent or more of elite athletes and as much as 10 percent of the general population without asthma.
Previous research has shown that pre-exercise fraction of exhaled nitric oxide (FENO) levels, which is a marker of airway inflammation, is elevated in people who have EIA. FENO levels also are associated with post-exercise closure of large airways. This study demonstrated the same positive relationship between FENO and closure of small airways after exercise. The study involved 12 people with EIA and six people without EIA. Their FENO levels were measured before the study participants underwent a eucapnic voluntary hyperventilation challenge for six minutes. "Our study found that exhaled nitric oxide may be a useful tool in predicting EIB and the magnitude of both large and small airway changes as a result of exercise," said lead author Louise Turner, a doctoral student in the Department of Kinesiology. "It involves the use of a simple piece of equipment and does not require exercise." Co-authors of the study include Sandra Tecklenburg-Lund, Joel M. Stager and Mickleborough, all of IU's Department of Kinesiology in the School of Health, Physical Education and Recreation. The study, "Exhaled Nitric Oxide Is Correlated With Changes in Small And Large Airway Obstruction," was presented during the Respiratory Session on May 29.
The second study found that study participants with EIA had significantly lower levels of exhaled pH, which might "indicate acidification of the airways in individuals with airway hyperresponsiveness," according to the study. The pH level also was related to the degree of closure of the small airways. This study involved 23 participants who had asthma and EIA and eight people who did not. The study participants were asked to breathe normally for 10 minutes while their exhaled breath was collected. They then underwent a eucapnic voluntary hyperventilation challenge for six minutes. Their pulmonary function was measured several times before and after the hyperventilation. Coauthors include lead author Tecklenburg-Lund, Turner, Stager and Mickleborough. The study, "Exhaled Breath Condensate pH is Correlated With Post-exercise Small Airway Obstruction," was presented during the Respiratory Session on May 29.
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