Exhaled nitric oxide in asthma: variability, relation to asthma severity, and peripheral blood lymphocyte cytokine expression.

Exhaled nitric oxide has been used as a means of indirectly measuring the underlying inflammation in asthma. The objectives of the study were to measure exhaled nitric oxide levels in asthma patients and healthy volunteers, to study peripheral blood lymphocyte cytokine expression, and to study the relationship between exhaled nitric oxide and intracellular cytokine expression. Exhaled nitric oxide was elevated in patients with moderate to severe asthma and with treatment decreased in the first week reaching to a near normal level by 4 weeks. Elevated exhaled nitric oxide was associated with decreased IL-4 and IL-13 cytokine expression by CD8 lymphocytes.