Airway Evaluation and ManagementKey Learning Objectives

•Review the anatomy relevant to airway management•Understand the components of an airway examination•Learn the principles of mask ventilation and intubation

Introduction

Despite the site of surgery or the anesthetic technique chosen, every patient receiving anesthetic care is exposed to a varying degree of risk of airway compromise. That is, all levels of sedation, general anesthesia, and regional anesthesia carry with them at least a small risk of airway obstruction and apnea.

Therefore, every anesthesia provider must examine each patient in anticipation of a need to mechanically ventilate and intubate, regardless of whether or not such interventions were part of the primary anesthetic plan. A thorough airway examination and history, combined with expert airway management, guard against the life-threatening risks of airway obstruction and apnea.

Airway Anatomy

The human airway is a dynamic structure that extends from the nares to the alveoli.

Obstruction can occur at any point because of anatomic collapse or a foreign body

which includes liquids such as mucous, blood, and gastric contents

Pharynx

The pharynx is basically a wide musculartube forming the common upper pathway of alimentaryand respiratory tracts. It extends from the base of the skullto the level of C6. The pharynx lies posterior to, and communicates with,the nose, mouth and larynx. This relationshipdivides the pharynx into three sections: naso-, oro andLaryngo pharynx. The posterior surface of the pharynxlies on the prevertebral fascia and cervical vertebrae.

Larynx

The larynx is a functional sphincter at the beginning of the respiratory tree to protect the trachea from foreign bodies. It is lined by ciliated columnar epithelium and consists of a framework of cartilages

linked together by ligaments which are moved by a series of muscles.

Cartilages of the larynx

The thyroid cartilage is said to be shaped like a

shield. It consists of two plates that join in the

midline inferiorly to form the thyroid notch (Adam’s

apple). Each plate has a superior and inferior horn or cornua at the upper and lower limit of its posterior border, respectively. The inferior horn articulates with the cricoid cartilage.

The cricoid cartilage is shaped like a signet ring, with the large laminal portion being posterior.

Each lateral surface features a facet that articulates with the inferior horn of the thyroid cartilage. The upper border of the lamina has an articular facet for the

arytenoid cartilage.

There is a pair of arytenoid cartilages, each shaped like a triple-sided pyramid possessing medial, posterior and anterolateral surfaces.

Each arytenoid cartilage projects anteriorly as the vocal process and in a similar fashion laterally as the muscular process.

The posterior and lateral cricoarytenoid muscles are inserted into the muscular process.

The epiglottis is a leaf-shaped cartilage. It has a lower tapered end which is joined to the thyroid cartilage by the thyroepiglottic ligament.

The free upper end is broader and projects superiorly behind the tongue.

The lowest part of the anterior surface of theepiglottis is attached to the hyoid by the

hyoepiglottic ligament. Two other minor cartilages are the corniculate and

the cuneiform.

Ligaments of the larynx

Extrinsic ligaments are the:

thyrohyoid membrane, cricotracheal, cricothyroid, and hyoepiglottic ligaments.

The intrinsic ligaments of the larynx are of minor importance, being the capsules of the small synovial joints

Muscles of the larynx

• Extrinsic group:Sternothyroid, thyrohyoid and inferior

constrictor is a constrictor of the pharynx• Intrinsic group: These are paired, with the

exception of the (transverse arytenoid).Cricothyroid, posterior cricoarytenoid,

lateral cricoarytenoid, aryepiglottic, thyroarytenoid

Nerve supply

The mucous membrane of the larynx above the vocal cords is supplied by the internal laryngeal nerve, that below by the recurrent laryngeal nerve.

All muscles of the larynx are supplied by the recurrent laryngeal nerve except for the cricothyroid, which is supplied by the superior (also known as external) laryngeal nerve.

Trachea

The trachea descends from the lower border of the cricoidcartilage (C6) to terminate at its bifurcation into the twomain bronchi at the sternal angle (T4). The length of theadult trachea varies between 10 and 15 cm. The walls ofthe trachea are formed of fibrous tissue reinforced by 15–20 incomplete cartilaginous rings. Internally the tracheais lined by respiratory epithelium. The trachea may bedivided into two portions, that in the neck and that in thethorax.

Bronchial tree

Extrapulmonary bronchiAt the carina, the two main bronchi arise. The rightmain bronchus is shorter, wider and more upright thanthe left. The right pulmonary artery and azygos vein areintimately related to the right main bronchus. The leftmain bronchus passes under the aortic arch anterior tothe oesophagus, thoracic duct and descending aorta. Thestructure of the extrapulmonary bronchi is very similar tothat of the trachea.Intrapulmonary bronchiBranching of the intrapulmonary bronchi gives rise tofunctional units – the bronchopleural segments.

Tracheal intubation

usually simply referred to as intubation, is the placement of a flexible plastic or rubber tube into the trachea to maintain an open airway or to serve as a conduit through which to administer certain drugs.

Endotracheal tubes

Modified for variety of specialized applications:

Flexible, wired-reinforced (armored), rubber,

Microlaryngeal, oral/nasal RAE, double lumen, cuffed non cuffed.

All endotracheal tubes has a radio-opaque line.

Airflow resistance depends on tube diameter, curvature and length.