Spirometry is still the most often used test to assess airway diseases although it is often reported that it does not adequately reflect patient symptoms. Other disadvantages of spirometry include the lack of sensitivity in detecting disease onset and the dependence on patient effort, which is required for forced expiratory maneuvers and which can be difficult for very young or highly obstructed patients. In their publication “Dismantling airway disease with the use of new pulmonary function indices”, Sabine C. Zimmermann and colleagues from the University of Sydney, Australia report on two emerging lung function tests, which are more suitable to understand, characterize and monitor chronic airway diseases such as asthma and COPD: The forced oscillation technique (FOT) and the multiple breath nitrogen washout (MBNW). FOT measures the respiratory system impedance by applying pressure variations at the airway opening. MBNW measures the ventilation heterogeneity, or in other words, the efficiency of gas mixing within the lungs, and it gives rise to indices, which reflect ventilation heterogeneity within the small airways where disease originates or manifests. Both tests are non-invasive and effort-independent for the patient, and the availability of modern test devices such as the EXHALYZER®D have promoted their transition from research applications to routine use in clinical medicine.