Single-breath nitric oxide measurements in asthmatic patients and smokers.

Exhaled nitric oxide (NO) concentrations were measured in asthmatic outpatients and in non-smoking and smoking healthy controls. In single exhalations, NO showed a peak suggestive of airway origin in both controls and asthmatic patients. The peak NO concentration was higher in asthmatic patients and lower in smokers than in non-smoking controls (p < 0.05). The findings support a role for NO in the host defence response in asthma and suggest that NO measurements can discriminate between different types of lung disorders.