Disclosed is a method and device for assessing respiratory data in a monitored subject. The disclosed method comprises collecting respiratory data of the subject at different levels of exertion with a physiological monitoring system (15-19), the respiratory data at least relating to instantaneous lung volume and comprising the end expiratory lung volume (EELV) after expirations； collecting exertion level data of the subject at the different levels of exertion, the exertion level data at least relating to instantaneous oxygen demand and/or heart rate； establishing a parametric relation (14, 15) between the collected respiratory data and the collected exertion level data, the parametric relation being described by one or more parameters； and assessing the respiratory data of the subject in terms of the value of the one or more parameters. The method and device allow a reliable measuring of dynamic hyperinflation in subjects without requiring much attention on the part of the subject.
