A Prospective Study Measuring Exhaled Nitric Oxide in Exercise-Induced Asthma

Overview

Exercise induced bronchospasm (EIB), also known as exercise induced asthma (EIA) is a transient obstruction to airflow triggered by exertion. It is now a well known identity, center of discussion in recent years, particularly in the athletes' world. It is more common in asthmatic individuals (regardless of severity of disease), but it is also seen in otherwise healthy subjects, leading to the general consensus that the pathophysiology is different than asthma. The concentration of exhaled nitric oxide (FeNO) in various airway \& respiratory disorders, particularly asthma, has been deeply studied. Its use for noninvasive monitoring of asthma control (reflecting airway eosinophilic inflammation) is being closely examined and put into clinical practice. FeNO is significantly elevated in asthma. Elevated FeNO levels have also been noted in patients hospitalized with a COPD exacerbation, acidosis, rhinitis, bronchiectasis, active pulmonary sarcoidosis, active fibrosing alveolitis, and acute lung allograft rejection. Decreased FeNO levels have been seen in patients with primary ciliary dyskinesia, cystic fibrosis, PiZZ phenotype-related alpha-1 antitrypsin deficiency, and pulmonary hypertension Two studies have addressed the variations on FeNO after EIB and they had contradictory results. Scollo et al. found no change in FeNO in either healthy or asthmatic children after a 6-min of vigorous exertion in an exercise laboratory when they studied 24 asthmatic and 18 control children. Terada et al. reported, for 39 subjects, a decrease in FeNO in subjects with EIB and an increase in healthy controls. It is well accepted that the pathophysiology of exercise induced bronchospasm it is not similar to that of asthma. Certainly the inflammation in the airway does not appear to be eosinophilic. Understanding the disease mechanism is a key factor to adequately manage it. This will be a prospective study measuring online exhaled nitric oxide involving children 8 to 21 years old. The study group will include any children coming for a pulmonary exercise test in the exercise laboratory located in the Pediatric Pulmonary Division office. The study will be conducted from the fall of 2009 until the spring of 2011. The change in the FeNO measurement will be correlated with the change in % predicted FEV1. We will consider significant a decrease in FEV1 post exercise of 15% and/or decrease on FEF25-75 of 20% that will persist until 15 minutes after completing exercise. We will also record any symptoms reported by the subject during or after the test. An exercise test is a standard of care when suspecting exercise-induced asthma. The subjects and their parents coming for exercise test will be offered the opportunity to participate in the study. The subject will come for the exercise test and will perform spirometry and FeNO measurement prior to start the test. According to our exercise laboratory protocol 1 minute of warm up at a low speed, followed by 6 minutes of high speed (enough to increase heart rate to 90% predicted or more) and 3 minutes of cool down at a low speed will be performed. Then spirometry will be repeated at 3, 5, 10 and 15 minutes and FeNO measurement will be taken at 5, 10 and 15 minutes. We will analyze the data to find if there is any significant change in FeNO measurements after exercise.