Onset of action of inhaled corticosteroids on bronchial and alveolar nitric oxide output

Abstract

Exhaled nitric oxide (FENO) is a marker of airway inflammation in asthma. Measuring FENO at multiple flow rates enables calculation of NO-parameters like bronchial NO output (JawNO), bronchial wall (CawNO) and alveolar (CANO) NO-concentrations, and bronchial diffusion factor of NO (DawNO). FENO is known to rapidly reduce after administration of inhaled corticosteroids (ICS) in asthma. However, little is known on the effect of ICS on other NO-parameters. We assessed 1) the onset of the ICS-treatment on the NO-parameters and 2) whether the changes in bronchial NO-output are due to changes bronchial wall NO-concentration or diffusion factor. FENO and other NO-parameters were measured in 23 children with asthma or asthma-like symptoms at baseline and after 1, 3 and 7 days of treatment with inhaled fluticasone propionate 250 mg b.i.d. There was a decrease in JawNO (from 680 (244/1791) (median (1st/3rd quartile)) to 357 (165/753) pl/s, p ICS-treatment reduces FENO50 and JawNO rapidly and the decline is caused by decreased bronchial wall NO-concentration while bronchial NO diffusion factor remained unchanged. These findings suggest that CawNO could be a more specific marker of airway inflammation and treatment response than JawNO or FENO50, which are both determined also by DawNO that was found to be resistant to the treatment with ICS.