Clinical Study to Assess Change in Upper Airway Geometry Between Upright and Supine Position

Inclusion Criteria: * Written informed consent obtained. * Male or female subject aged ≥ 18 years. * BMI \< 25 kg/m2 (group 1), BMI ≥ 25 kg/m2 and \< 30 kg/m2 (group 2) and BMI ≥ 30 kg/m2 (group 3) at visit 0. BMI calculation should be repeated if the interval visit 0 - visit 1 \> 14 days. * Female subject of childbearing potential who confirms that a contraception method was used at least two months before visit 1. Exclusion Criteria: * Subject is under the age of legal consent. * Subject who is pregnant or is breast-feeding. * Subject with a history of surgery of the upper airway. * Subject with a history of any illness that, in opinion of the investigator, might confound the results of the study or poses an additional risk to the subject by participation in the study. * Subject is unlikely to comply with the protocol or unable to understand the nature, scope and possible consequences of the study. * Subject who received any investigational new drug within the last 4 weeks prior to visit 1. * Subject who has claustrophobia.