There is no need for complicated equations and mathematical models. Exhaled nitric oxide can be partitioned with two simple exhalations

Background: By measuring eNO at multiple flows and applying mathematical models of eNO exchange dynamics, the signal can be partitioned into its proximal airway [Jno (nl/sec)] and distal airway/alveolar contributions [CA(NO) (ppb)]. This method is time consuming, requires at least 3 exhalations and is affected by a number of limitations such as axial diffusion and turbulent flow. We eveloped a more practical method based on the production of NO (Vno) at two exhalation flow rates. Methods: In a group of 27 normal subjects (38±2 yr; 20 male), 13 steroid naive asthmatic patients (34±3 yr; 6 male, FEV1 70±4% predicted), 14 patients with chronic obstructive pulmonary disease (COPD) (65±2 yr; 10 male, FEV1 58±3%), and 12 patients with cystic fibrosis (21±4 yr; 8 male, FEV1 60±3%) we compared CA(NO) and Jno with the variation of total NO production at 50 and 200 ml/s [Vno50-200 (nl/s)]. Vno was measured by calculating the average area under the curve (NO concentration/time) of two successive exhalations at each flow rate. Results: Vno50-200 was strongly correlated with Jnoin normal subjects (r=0.94, p Conclusions: The flow dependent component of exhaled NO, which is affected by its bronchial production, can be estimated by measuring Vno50-200. This method is simple, does not require sophisticated equipment or equations and is in agreement with Jno calculated mathematically.