Small airway function, exhaled NO and airway hyper-responsiveness in paediatric asthma

Area of Science:

• Pediatric Pulmonology
• Respiratory Medicine
• Asthma Research

Background:

• Asthma is a chronic inflammatory airway disorder affecting peripheral airways.
• Current guidelines rely on symptoms and spirometry (FEV1) for diagnosis and treatment.
• FEV1 is an inadequate measure of small airway function, asthma control, and inflammation.

Purpose of the Study:

• To evaluate the role of small airway dysfunction and inflammation in pediatric asthma.
• To investigate the relationship between small airway dysfunction, airway inflammation, and airway hyper-responsiveness (AHR).

Main Methods:

• Small airway function assessed using the SF(6) multiple breath inert gas washout (MBW) technique (LCI, S(cond), S(acin)) in 47 asthmatic children and 74 controls.
• Exhaled nitric oxide at 50 mL/s (FENO(50)) measured to determine alveolar and bronchial NO flux (airway inflammation surrogate).
• Airway hyper-responsiveness (AHR) assessed via isocapnoic dry air hyperventilation challenge.

Main Results:

• 66% of asthmatic children showed impaired S(cond), and 38% had impaired S(acin).
• Increased LCI and decreased FEV1 were observed in 15% of asthmatic subjects.
• Subjects with AHR exhibited higher S(cond) and FENO(50) levels. Elevated FENO(50) and bronchial NO flux were noted in asthmatics versus controls.
• S(cond) correlated with FENO(50) and alveolar NO; S(acin) correlated with alveolar NO in asthmatic children.

Conclusions:

• Small conducting airway dysfunction is significantly associated with airway inflammation in pediatric asthma.
• These findings highlight the importance of small airway dysfunction in the pathophysiology of childhood asthma.
• Small airway dysfunction is linked to airway hyper-responsiveness, suggesting a comprehensive approach to asthma management is needed.