Airway and alveolar nitric oxide production, lung function, and pulmonary blood flow in sickle cell disease.

Background: Children with sickle cell disease (SCD) often have obstructive lung function abnormalities which could be due to asthma or increased pulmonary blood volume; it is important to determine the underlying mechanism to direct appropriate treatment. In asthmatics, exhaled nitric oxide (FeNO) is elevated. FeNO, however, can also be raised due to increased alveolar production. Our aim, therefore, was to determine if airway or alveolar NO production differed between SCD children and ethnic and age-matched controls.

Methods: Lung function, airway NO flux and alveolar NO production, and effective pulmonary blood flow were assessed in 18 SCD children and 18 ethnic and age-matched controls.

Results: The SCD children compared to the controls had a higher respiratory system resistance (P = 0.0008), alveolar NO production (P = 0.0224), and pulmonary blood flow (P < 0.0001), but not airway NO flux. There was no significant correlation between FeNO and respiratory system resistance in either group, but in the SCD children, there were correlations between alveolar NO production (P = 0.0006) and concentration (P < 0.0001) and pulmonary blood flow.

Conclusion: Airway NO flux was not elevated in the SCD children nor correlated with airways obstruction, suggesting that airways obstruction, at least in some SCD children, is not due to asthma.