In this study the changes in upper airway geometry and resistance between images, obtained in upright and supine position, will be evaluated. Therefore a Cone Beam Computed Tomography (CBCT) scan and a low dose Computed Tomography (CT) scan will be taken in a population of 20 subjects. The upright morphology will be obtained using CBCT scan while the supine upper airway geometry will be determined using a standard High Resolution Computed Tomography (HRCT) scanner.

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.