Multum non multa: airway distensibility by forced oscillations

Airway distensibility although appears to be unaffected by airway smooth muscle tone probably related to airway remodelling, after bronchodilator treatment is significantly increased in subjects with asthma. We assessed airway distensibity and its first moment derivative in two patients with mild intermittent asthma and normal spirometry. The increase in airway distensibility after bronchodilation measured at the tidal volume range during quiet breathing by forced oscillations was not accompanied by a change in its first moment, while the latter showed a significant increase in a second patient after anti-inflammatory treatment. It appears that airway distensibility is sensitive to reduction of bronchial smooth muscle tone after bronchodilation, but in addition its first moment might provide information on a change of both bronchial smooth muscle tone and small airways inflammation.