Peripheral inflammation in patients with asthmatic symptoms but normal lung function

Area of Science:

• Respiratory Medicine
• Pulmonology
• Biomarkers

Background:

• Asthma diagnosis relies on lung function, potentially excluding patients with symptoms and inflammation but normal spirometry.
• Exhaled nitric oxide (NO) measurement is a non-invasive tool to assess airway inflammation.

Purpose of the Study:

• To investigate whether alveolar and bronchial NO output are elevated in individuals with asthmatic symptoms and normal lung function.
• To compare NO parameters between patients with asthmatic symptoms, diagnosed asthma, and healthy controls.

Main Methods:

• Exhaled NO concentration was measured at three exhalation flow rates (100, 175, 370 mL/s) to determine alveolar NO concentration and bronchial NO flux.
• Study included 23 patients with asthmatic symptoms and normal lung function, 40 asthma patients, and 40 healthy controls.

Main Results:

• The asthmatic symptoms group exhibited significantly increased bronchial NO flux and alveolar NO concentration compared to healthy controls.
• Patients with diagnosed asthma showed higher bronchial NO flux but normal alveolar NO concentration compared to controls.
• In the asthmatic symptoms group, alveolar NO concentration correlated with blood eosinophil counts and inversely with small airway function.

Conclusions:

• Individuals with asthmatic symptoms and normal lung function display elevated alveolar NO concentration and mildly increased bronchial NO flux.
• These findings suggest peripheral airway inflammation in patients with undiagnosed asthma.
• Exhaled NO measurements may aid in identifying and diagnosing asthma in its early stages.