RESUMEN
Disease of the peripheral (or small) airways is fundamental in asthma, being closely related to symptoms (or lack of control of them), airway hyperresponsiveness, spirometric abnormalities, risk of loss of control, or exacerbations and inflammation. Current technology now allows routine measurement of peripheral airway function. Having a working concept of peripheral airways disease in asthma is arguably very useful to clinicians and beneficial to patients because it allows a more comprehensive assessment of asthma severity (rather than just symptoms alone, which is the norm), tracking of progress or deterioration, and assessing response to treatment. Oscillometry is a sensitive way to monitor the peripheral airways, whereas multiple breath nitrogen washout parameters are excellent measures of future risk. In the longer term, physiologic measurements will be crucial in research to define causes and find new disease-modifying treatments.