@article {Paredip4781, author = {Paolo Paredi and Omar Usmani and Katharine Hurt and Neil Pride and Peter Barnes}, title = {There is no need for complicated equations and mathematical models. Exhaled nitric oxide can be partitioned with two simple exhalations}, volume = {38}, number = {Suppl 55}, elocation-id = {p4781}, year = {2011}, publisher = {European Respiratory Society}, abstract = {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{\textpm}2 yr; 20 male), 13 steroid naive asthmatic patients (34{\textpm}3 yr; 6 male, FEV1 70{\textpm}4\% predicted), 14 patients with chronic obstructive pulmonary disease (COPD) (65{\textpm}2 yr; 10 male, FEV1 58{\textpm}3\%), and 12 patients with cystic fibrosis (21{\textpm}4 yr; 8 male, FEV1 60{\textpm}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\<0.001), asthma (r=0.98, p\<0.001), COPD r=0.93, p\<0.001), and CF patients (r=0.74, p\<0.05). This agreement was confirmed by the Bland and Altman test. Vno50-200 did not correlate significantly with CA(NO) in any of the study groups.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.}, issn = {0903-1936}, URL = {https://erj.ersjournals.com/content/38/Suppl_55/p4781}, eprint = {https://erj.ersjournals.com/content}, journal = {European Respiratory Journal} }