The cervical spine (neck region) consists of seven bones (C1-C7 vertebrae), which are separated from one another by intervertebral discs. These discs allow the spine to move freely and act as shock absorbers during activity.
Establishing a definitive airway is defined as placement of an ETT in the trachea with cuff inflated below the vocal cords. Relative to the ETT, the LMA is more prone to displacement and malposition. As such, it does not provide definitive airway security in terms of placement or dependable ventilation.
Oropharyngeal leak pressure (OLP), measured by closing the expiratory valve of the anesthetic circle system at a fixed gas flow rate and noting the equilibrium airway pressure, is used to quantify the efficacy of airway sealing in SGA devices.
The pharynx, commonly called the throat, is a passageway that extends from the base of the skull to the level of the sixth cervical vertebra. It serves both the respiratory and digestive systems by receiving air from the nasal cavity and air, food, and water from the oral cavity.
Bound superiorly by the epiglottis and inferiorly by the junction between the glottic inlet and oesophagus, the laryngopharynx typically contains the bulk of the LMA mask. The mask’s bowl aligns with the laryngeal inlet, while the lateral aspects of the cuff abut the pyriform fossa forming an airtight seal. This seal is called the primary seal. The distal cuff tip should occupy the entire hypopharynx forming an oesophageal seal to protect the laryngeal inlet from aspiration from below. This oesophageal seal is also known as the secondary seal.