Diagnosis of obstructive sleep apnoea syndrome (OSAS) is technically demanding, costintensive and time-consuming. The measurement of volatile organic compounds by an electronic nose is an innovative method that determines distinct molecular patterns of exhaled breath in different patient groups. We addressed the following questions: What is the diagnostic accuracy of an electronic nose in the detection of OSAS and the ability to detect effects of standard therapy in patients with OSAS? Are these results related to changes in distinct markers of airway inflammation and extracellular remodelling?We included 40 OSAS patients and 20 healthy controls. Exhaled breath of all participants was analysed using the Cyranose 320 electronic nose. Pharyngeal washings were performed to sample the upper airway compartment. For statistical analysis linear discriminant analysis was employed.We identified a linear discriminant function separating OSAS from control (p,0.0001). The corresponding area under the receiver-operating curve was 0.85 (95% CI 0.75-0.96; sensitivity 0.93 and specificity 0.7). In pharyngeal washing fluids of OSAS patients, we observed higher levels of a 1 -antitrypsin and markers of extracellular remodelling compared to controls.The electronic nose can distinguish between OSAS patients and controls with high accuracy. @ERSpublicationsThe electronic nose can distinguish between OSAS patients and controls with high accuracy