Airway Anatomy, Physiology, and Pathophysiology - PDF

AIRWAY Anatomy, physiology and pathophysiology applied to anaesthesia and airway management Learning Objectives...

AIRWAY Anatomy, physiology and pathophysiology applied to anaesthesia and airway management Learning Objectives Anatomical and physiological knowledge helps us to improve patient safety by intervening rapidly General anaesthesia and paralysis are associated with alterations in the respiratory function (Breathing related to WHY are we learning this? Loading… Airway) Such knowledge has influence on clinical practice of airway management A high percentage of morbidity and mortality occurring in the perioperative period is associated with some form of respiratory dysfunction What does the AIRWAY comprise of? https://i.pinimg.com/originals/81/62/c1/8162c13c81db99824a92035b678ba54b.jpg Upper Airway Anatomy Loading… Tongue Involved in BREATHING & SWALLOWING The size of the tongue is significant: It has a lot of underlying muscle and tissue to facilitate movement and, when brain activity is suppressed, will be the greatest cause of an upper airway obstruction due to the loss of muscular tone and control It is connected to the mandible hence the reason why Jaw Thrust is effective https://www.researchgate.net/figure/The-geometry-of-the-tongue-and-mandible-captured-u Mimics-6_fig27_234134129 Reflexes Triggered by stimulation of key sensory nerves which send messages to the brain Medulla and Brain Stem to initiate motor movement of muscles to protect the airway These can be inhibited by: Deepening General Anaesthesia (inhibits brain activity in processing impulse) Using Local Anaesthetic (such as for awake intubation) to ‘block’ sensory messages to brain Pharyngeal reflex (Gag reflex) Retching Induced by sensory vagus and glossopharyngeal nerve located at base of tongue, uvula, tonsil and posterior pharyngeal wall Causes muscle contraction to eliminate foreign objects from oral cavity (healthy function to stop anything entering airway) The centre in the Medulla Oblongata for gag reflex is close to the vomiting, salivary and cardiac centres which all which may be stimulated during gagging See https://www.ncbi.nlm.nih.gov/books/NBK554502/ Prevents material from inappropriately entering the trachea by closing the vocal cords Stimulation of the mucosa surrounding the larynx and hypopharynx (lower Laryngeal part of pharynx) cause sensory nerves of the Superior Laryngeal Nerve to send a message to the medulla of brainstem. reflex (also Message then sent down Recurrent Laryngeal Nerve to contract thyroarytenoid muscle, which closes the vocal cords known as This is a primary cause of laryngospasm (patient not sufficiently reversed but reflexes present – react to foreign object of ET tube or mucous) Glottic closure Causes Cough reflex if patient is conscious: reflex) Receptors that pick-up signals of foreign objects are located at various locations of the upper and lower airway, but mainly: Carina, Tracheal mucosal lining, mucosa of larynx and even the pharynx, bronchioles and lower airways Coughs are generated in response to direct physical stimulation but also from chemical stimulation such as irritant gas and heat See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3415124/ See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4171040/#!po=8.65385 Overview Pharyngeal reflex Laryngeal reflex Intrinsic Muscles – Nerve Supply Vagus Nerve Loading… Recurrent Superior Laryngeal Nerve Laryngeal Nerve supplies all the intrinsic muscles of the larynx Supplies Cricothyroid Muscle except Cricothyroid Muscle Key Points Larynx Larynx forms protection for Vocal Cords (to be focused upon in greater detail) Angle of Right and Left main bronchus Cough reflex Larynx (Image on next slide) Complex organ which protects vocal cords Facilitates sound and speech Assists with coughing and straining Closes Glottis during swallowing Controls the tension of vocal cords during inspiration and expiration Comprises of: 1 x Bone 9 cartilages (3 single, 3 paired) Ligaments to connect Muscles to aid movement of cartilages 1x BONE HYOID Serves as an attachment to the tongue muscles Connected to Thyroid cartilage by Thyrohyoid membrane Only floating bone in body aiding speech and swallowing 9x Cartilages 3 single Cartilages: 1. THYROID CARTLIDGE 2. CRICOID CARTILIDGE 3. EPIGLOTTIS 3 paired Cartilages: ARYTENOID CARTILAGES https://prod-images- CORNICULATE static.radiopaedia.org/images/64899370/846c764df685f619583f2aaf94da7fdf25f6ca4b43e326886f3cc6f99426a40f_big_gallery.j peg CARTILAGES Function of Cartilages Thyroid Cartilage (Adams Apple): Protects vocal cords-speech-serves as attachment site for muscles and ligaments Cricoid cartilage: shaped like a signet ring and since it is relatively strong and is the only complete ring of cartilage in the airway, it is here that cricoid pressure (Sellick’s manoeuvre) is exerted during rapid sequence induction Epiglottis cartilage: Flap of tissue which connects to posterior wall of thyroid cartilage by a ligament. Moved by extrinsic laryngeal muscles during swallowing to cover opening of larynx and prevent food entering airway https://med.umn.edu/sites/med.umn.edu/files/figure-4-2.png B.U.R.P (Backward- Cricoid pressure differs to Upward- BURP Rightward- BURP is the pressure used to enhance view of vocal cords Pressure) Pressure placed on THROID Cartilage (Not Cricoid) Function of paired cartilages ARYTENOID CARTILAGES Vocal cord movement Attachment site for muscles and ligaments CORNICULATE CARTILAGES Sits at the end of arytenoid for connection of tissues CUNEIFORM CARTILAGES Connects epiglottis to laryngeal tissues https://image.slidesharecdn.com/larynxdr-160202061657/85/Larynx-Anatomy-8-320.jpg Bing Videos Vocal Cord anatomy in 2 min. AIRWAY Assessment Intubation Grade View Difficult Airway Society Guidelines (2015) Paediatric Difficult Airway Guidelines | Difficult Airway Society (das.uk.com) Guidelines for the management of difficult and failed tracheal intubation in obstetrics - 2015 | Difficult Airway Society (das.uk.com) PLAN A Think of airway anatomy and how this may complicate facemask ventilation and tracheal intubation, such as: Mouth opening No teeth Obesity-short neck Try different types of laryngoscopes Large tongue Beard Trauma *** CONSIDER POSITIONING https://i0.wp.com/airwayjedi.com/ wp- content/uploads/2016/12/p7_29.pn g?resize=780%2C822&ssl=1 PLAN B This is when you cannot facemask ventilate or intubate: Oxygenation must be maintained.. Attempt an LMA or I-gel Would surgery be continued?? PLAN C