Background and objective: Two methods have been developed to account for the impact of airway nitric oxide (NO) production on alveolar NO (CANO) concentration. In the first (Condorelli method), CANO is corrected using bronchial NO flux (J’awNO) values, whereas in the second (Kerckx method), knowledge of the exhaled NO concentration at a flow of 50 ml/s (FENO50) is required. The aim of the present study was to determine the influence of each correction method on CANO values.

Methods: Ninety-one adults (27 asthmatics, 46 patients with allergic rhinitis, and 18 healthy volunteers) were studied. FENO50 was obtained according to a standardized method and exhaled NO was measured at multiple flows (100, 200, and 300 ml/s). CANO was adjusted for the trumpet shape of the airway tree and axial diffusion from central to peripheral airways using both the Condorelli and Kerckx methods.

Results: The mean (95% CI) CANO value obtained with the Condorelli method was 1.27 ppb (0.93-1.60), compared to 0.87 ppb (0.55-1.19, P<.001) with the Kerckx method. Differences in CANO values obtained with each method were identified in individuals with high FENO50 values (n=55) and in those with normal FENO50 values (n=36), but were significantly greater in the first group (P=.01).

Conclusions: Our findings suggest that CANO values obtained with the 2 methods reported to adjust for the trumpet shape of the airway tree and axial diffusion from central to peripheral airways are not equivalent and cannot be used interchangeably.

Key words: Nitric oxide. Alveolar nitric oxide. Bronchial nitric oxide. Asthma. Allergic rhinitis.