• small airway
• gas exchange
• Asthma

SUMMARY

Background: Involvement of small airways has been hypothesized to be responsible of poor asthma control in subgroups of patients, also due to the difficulty of inhaled drugs to reach peripheral airways.
Aim: To evaluate in a sample of moderate-severe asthmatic patients under treatment with inhaled corticosteroid/long acting beta2-agonist (ICS/LABA) combinations, the relationship between asthma control, as assessed by traditional clinical, functional and biological findings, and some measurements of small airway involvement.
Patients and methods: 31 asthmatic patients regularly treated with ICS/LABA combinations were evaluated for the level of asthma control according to GINA guidelines, by a 4-month period of diary card and peak expiratory flow (PEF) monitoring, FEV1 and exacerbation rate; sputum eosinophils and fractional exhaled nitric oxide (eNO50) were also measured. Small airway involvement was assessed by single breath nitrogen washout (CV, ΔN2%), alveolo-arterial O2 and arterial-alveolar CO2 gradients (AaDO2, aADCO2), and alveolar concentration of nitric oxide (CalvNO).
Results: According to GINA guidelines, patients were defined as well controlled (N=10), partly controlled (N=11) and not controlled (N=10). No significant difference was observed among the groups as regards markers of small airway involvement, as well as for biomarkers. When well controlled and partly controlled were considered together, not controlled patients showed a significantly higher AaDO2 difference. A significant correlation was observed between AaDO2 and FEV1 %pred, sputum eosinophil percentage, and rescue medication use.
Conclusions: Small airway involvement as assessed by AaDO2 may be observed in clinically not controlled moderate-severe asthmatics under ICS/LABA combination treatment, despite a not significant difference in FEV1 and airway biomarkers.