The applications of point-of-care ultrasonography (POCUS) of the upper airway are growing over the last decade. It's clinical applications include both diagnosis of upper airway pathology as well as pre-intubation airway examination and provision of ultrasound markers of difficult laryngoscopy and/or intubation.

However, it is differentiated from the comprehensive ultrasound examinations traditionally performed by radiologists because it is targeted to answer a specific clinical question in real time. Moreover, ultrasound-guided techniques require knowledge of sonoanatomy and ultrasound operational skills. However, clinicians lack the standardized training that ultrasound technicians and radiologists receive. POCUS training is rarely done in a standardized manner, and even more so, POCUS is rarely conducted under expert's supervision.

The current study investigates the feasibility of upper airway POCUS performed on healthy volunteers by anaesthesia residents using a predefined scanning protocol after attending a structured training course. Assessment of anaesthesia trainees' competence and minimum training requirements were the aim of the study.

Point-of-care (POCUS) of the upper airway has proven a useful tool for airway management as well as diagnosis of upper airway pathology. Although anaesthesiologists are familiar with the use of ultrasound, with peripheral nerve blockade and vascular access representing the most popular applications in anaesthesiology, POCUS is not yet routinely used for airway evaluation. However, the reliability of such examination, which is clinician performed and interpreted, is highly dependent on the operator. Ultrasound-guided techniques require knowledge of sonoanatomy and ultrasound operational skills. Clinicians lack the standardized training that ultrasound technicians and radiologists receive. POCUS training is rarely done in a standardized manner, and even more so, POCUS is rarely conducted under expert's supervision. Insufficient ultrasonographic skills increase the risk of misdiagnosis compromising patient care.

This is a prospective observational study conducted in the University Hospital of Ioannina to investigate the feasibility of upper airway POCUS performed on healthy volunteers by anaesthesia residents using a predefined scanning protocol after attending a structured training course. Assessment of anaesthesia trainees' competence and minimum training requirements are the aim of the study.

All subjects will be healthy volunteer members of the Operating Room (OR) staff. The training course will be shaped in a stepwise manner, beginning with an "education day" that includes a didactic lecture and a hands-on workshop, followed by a "performance week" for competence assessment. During "education day" a predefined scanning protocol will be taught and practiced. An experienced in neck ultrasound radiologist (instructor) will demonstrate the scans and will supervise all trainees. The predefined scanning protocol includes identification of specific structures [(i) visualization of the hyoid bone, (ii) visualization of vocal cords, (iii) localization of thyrohyoid membrane and visualization of epiglottis and pre-epiglottic space, (iv) visualization of cricothyroid membrane, and (v) visualization of thyroid gland)], as well as performance of specific measurements [(i) distance from hyoid bone to skin, (ii) distance from anterior commissure to skin, (iii) distance from epiglottis to skin, and (iv) distance from thyroid isthmus to skin].

During "performance week" all trainees will perform upper airway POCUS to members of the OR staff. The predefined protocol will be applied in each case. A single scan will be allowed for each subject. All subjects will have ultrasound measurements recorded separately by the six trainees and the instructor. The data will be collected at bedside and each participant will be blinded to each other's assessments. Trainees' performance will be assessed by paired calculations of the trainee - instructor differences in all ultrasound measurements of interest.

Inclusion Criteria:

- healthy adult volunteers (ASA physical status I and II)

Exclusion Criteria:

• history of congenital or acquired airway abnormalities
• modified Simplified Airway Risk Index (SARI) > 4
• mallampati score > 3
• Body mass index (BMI) > 35 Kg/m2

Healthy adult volunteers, all members of the Operating Room (OR) staff, not anticipated to have difficult laryngoscopy and/or intubation based on their clinical upper airway evaluation.