The CLE-test was described in detail by the authors Heimdal et al. in the "Laryngoscope" in 2006 and the scoring system by Maat et al. in the "European Archives of Otorhinolaryngology" in 2009. In short, the test combines a full cardio-pulmonary treadmill exercise set-up with continuous real-time transnasal video-laryngoscopy applied from rest to peak exercise to rest. A camera and a microphone placed in front of the subject enable recording of simultaneous video images of the external upper part of the body as well as recordings of the respiratory sounds. The subjects run on a treadmill according to a standardized protocol, incrementing speed and/or grade every minute with the aim to obtain peak oxygen consumption (peakVO2) after 6-12 min of exercise. The test is considered successful if the patient experience respiratory complaints, or indicate exhaustion, preferably supported by a plateau in oxygen consumption and/or the heart rate. All recordings continue until normal breathing is regained.