Tidal airway closure in asthma and COPD

Functional closure of small airways can occur during tidal breathingabove functional residual capacity (FRC) both in asthma and chronicobstructive pulmonary disease (COPD) patients, especially during ex-acerbations. Such event has several noxious consequences on gas ex-change, airway hyperresponsiveness and mechanical stress and strainwithin lung tissue and airway wall, mostly due to increase in ventila-tion heterogeneity. The availability of simple functional tests based onsequential measurements of lung volumes (i.e., FRC), by plethysmog-raphy and dilutional techniques may reveal and monitor easily tidalairway closure that can be and should be treated with the aim of abol-ishing or at least reducing this dangerous condition.