Demographic data, including age, gender, weight (kilograms), body height (centimeters) and neck circumference (NC), will be recorded. Weight and height will be recorded with the patients wearing light clothes, but no shoes. Body mass index (BMI) will be then calculated as weight (kg) divided by height squared (mt2). NC will be measured (in cm) with a flexible tape at the level of the cricothyroid membrane after a gentle expiration by the subject while standing upright. History of hypertension, diabetes, hyperlipidemia or any other cardiovascular diseases will be recorded according to medical records or statements by the patients. All participants will be asked to complete the Epworth Sleepiness Scale (ESS), a subjective self-reported measure of excessive daytime sleepiness, within the same session before the ultrasound examination.