Heavy physical exercise decreases nitric oxide levels in the nasal airways in humans

A continuous production of nitric oxide (NO) takes place in human nasal airways. NO in the nasal airways is mainly derived from the paranasal sinuses. The factors that regulate NO synthesis in the upper airways are presently not known. We have investigated the effects of physical exercise on NO levels in the nasal airways. Nasal cavity NO levels were measured by chemiluminescence technique in five healthy non-smoking male subjects before, during and after 5 min of maximal exercise (245 W) on an ergometer cycle. In addition, in one subject NO levels were measured directly in the maxillary sinus during exercise. Nasal cavity NO levels were decreased by 47% after only 1 min of exercise compared with the control situation. A maxima 76% reduction was found at the end of the exercise period and thereafter NO levels slowly increased, reaching basal levels again in about 15-20 min. NO levels in the sinus decreased in a similar manner during exercise. The decrease in nasal cavity NO levels cannot be explained merely by dilution of nasal air due to changes in nasal cavity volume or increased ventilation. We conclude that the excretion of NO in the nasal airways is decreased acutely during heavy short term physical exercise.