Airway and Respiratory Anatomy Flashcards
Trachea extends from where to where? Levels!
Cricoid cartilage at C6
Tracheal bifurcation at carina T5-6
Lies midline anterior to oesophagus
Length of trachea
15cm
5cm above sternal notch or 8cm if neck fully extended
Patency of trachea is maintained by what?
C rings of cartilage anteriorly
The thyroid isthmus overlies which tracheal rings?
2-4
Characteristics of right main bronchi
What relevance is this to aspiration?
Shorter wider and vertically placed compared to left
RUL arises 2.5cm from carina
More likely to aspirate into apical bronchus of right lower lobe as it is the first segmental bronchus arising posteriorly.
Lung lobes
Right - 3 split by horizontal and oblique fissure
Left - 2 plus lingula (middle lobe remnant)
What are the layers that enclose the lung?
Visceral
Parietal attached to chest wall and mediastinum
Pleural cavity in between layers which contains serous fluid
What causes negative intrapleural pressure?
Outward spring of rib cage and elastic recoil of lungs
Thoracic cage volume increases the negative intrapleural pressure and the lungs inflate
Which part of the lung remains vulnerable during some procedures?
2-4cm above mid third of clavicle exposed to intravenous procedures and nerve blocks (intercostal and brachial plexus)
Surgery on adrenal and kidney also problematic as lung extends to Costo diaphragmatic recess.
How many bronchopulmonary segments are there?
10 each with own blood supply and distinct lung parenchyma
Bronchioles is also called what? What condition occurs at this lung level?
Primary lung lobule
Asthma as it contains smooth muscle and no cartilage
Alveoli are lined with what?
Single layer of fine non ciliated cuboidal epithelium
Separated from capillary network by fine basement membrane
What produces lung surfactant?
Type II pneumocytes situated in alveoli
How does lung surfactant work?
Prevents air sacs from collapsing
Mediastinum is made up of how many compartments?
Space between the 2 pleural cavities
4 - ant, post, middle and superior
A mass in which mediastinal compartment would concern anaesthetists?
Anterior
Loss of muscle tone post-induction would allow mass to fall back against the heart and great vessels and major airway
What is the most important muscle of respiration?
Diaphragm
Contributes to 60-75% tidal volume
Flattens to push Abdominal contents down and ribs up and out
1.5cm in quiet resp, 13cm movement in deep resp
What is the nerve supply of the diaphragm?
What happens if this nerve is damaged?
C3-5 phrenic
Damage causes a upward ipsilatersl paradoxical movement of diaphragm
What else does the diaphragm contribute to?
LOS
Disrupted in hiatus hernia
What muscles help with forced expiration?
Abdominal and diaphragm
What limits diaphragmatic movement?
Abdominal distension -pregnancy/ obesity/ pneumoperitoneum
What is the function of the external intercostal muscles?
Slope down and forward to pull ribs up and out on inspiration
Increases anteroposterior and lateral thorax diameter
What are the functions of the internal intercostal muscles?
Slope down and back
Only use in active expiration pulling ribs down and in
What do the innermost intercostal muscles do?
Stabilise chest wall linking ribs
What is the nerve supply to the intercostal muscles?
Why do nerve blocks at this nerve not affect respiration significantly?
T1-T11
Diaphragmatic contribution 65-70%
Accessory muscles function how?
Scalene - elevate first 2 ribs
SCM - elevate sternum
Small muscles of head and neck and nasal flaring
What is the depth of trachea tube insertion?
F - 21cm at the lips
M - 23cm at the lips
What phase is a CXR taken in?
Full inspiration
At lest 6 ribs visible anteriorly and 10 posteriorly
What is the safe triangle in chest drain insertion?
Emergency - 2nd ICS Midclavicular line just above 3rd rib
Formal drain - 5th ICS (below 5th rib but just above 6th rib, midaxillary line
Airway assessment consists of what?
Mouth opening Dental MP Jaw protrusion Neck extension Thyromental distance
What anatomical variants prove tricky for airway management?
High arched palate Small mouth Receding chin Large tongue Beard Poor dentition TMJ disease Tonsilar hypertrophy
What acquired issues are difficult in airway management?
Burns Tumours Abscess Radiotherapy Scarring
What happens to the airway under anaesthesia?
Loss of muscle tone
Pharyngeal airway loses patency
What manoeuvres aid airway patency?
Jaw thrust
Chin lift
What adjuncts can be used to improve airway patency?
NPA/OPA
LMA
ETT
What is the function of the nose?
Warm humidify air by pseudostratified ciliated columnar epithelium and mucous serous glands
Smell
Speech resonation
What is the widest part of the nasal airway?
Below the inferior turbinate
What are the advantages and disadvantages of nasal intubation?
A- Better tolerated. Leaves oral cavity free for surgery
D- Bleeding, false passage in skull fractures, infection
What is the function of the palate?
Separates nose and mouth during swallowing
What does the hard palate consist of?
Palatine process of the maxilla and the horizontal sort of the palatine bone
What nerves supply the gag reflex?
Afferent - glossopharyngeal CN IX
Efferent - vagus CN X
Pharynx is made up of what?
Oropharynx, nasal pharynx and laryngopharynx
Where do fish bones lodge?
Piriform fossae, recesses either side of the larynx
What are the pillars of fauces?
Palatine tonsils lymphoid tissue between palatoglossal and palatopharyngeal arches
Hypertrophy in childhood
What is the nerve supply to the tonsils?
3 nerves
Glossopharyngeal, maxillary,mandibular
Anaesthetic to the tonsilar bed most effective analagesia
Swallow reflex
Closure of laryngeal sphincter
Upward movement of larynx behind base of tongue
Inhibited breathing
Lateral channeling of food by epiglottis into piriform fossae
Epiglottis lid over trachea
What are the articulating cartilages of the larynx?
Thyroid Cricoid Epiglottis Arytenoid (with superior cricoid) Corniculate Cuneiform visible on laryngoscopy at aryepiglottic folds
Where do the intrinsic muscles of the larynx attach
Arytenoids, pivot to adjust vocal cord position
What are the false cords?
Vestibular folds (mucous membrane that covers the free borders of the intrinsic ligaments of the larynx)
Where is the narrowest part of the airway?
The glottis - gap between true vocal cords
Also known as the Rima glottidus
What do the extrinsic larynx muscles do?
Attach to hyoid and work with other muscles to move the larynx up and down during swallowing
What do the intrinsic larynx muscles do?
Open the vocal cords during inspiration
Close cords and laryngeal inlet during swallowing
Alter tension of cords during phonation
What are the vocal cord abductors?
Posterior cricoarytenoids
How does abduction of vocal cords on inspiration occur?
Pull posterior ends of arytenoid cartilages together. Pivot then abducts the anterior ends of the cartilages to which vocal cords are attached.
What are the vocal cord adductors? (Close)
Lateral cricoarytenoids and transverse arytenoids
Aryepiglottis and thyroepiglottis do what?
Laryngeal sphincters -close laryngeal inlet during swallowing
Cricothyroid muscle does what?
Tensor of cords
Pivot at cricoid cartilage on the thyroid cartilage
What muscle relaxes the cords?
Thyroarytenoids
Vocalis muscle does what?
Fine tunes cords
What is the sensory supply to the larynx?
Vagus Branches to: Superior laryngeal nerve (Above cords) internal branch Recurrent laryngeal nerve (below cords)
What branches of the superior laryngeal nerve are there?
Internal - sensory to interior larynx and vallecula
External - motor supply to cricothyroid muscle
What happens with superior laryngeal nerve damage?
Temporary Hoarseness
Aspiration risk
What does RL nerve supply?
Sensation below vocal cords
Motor to all intrinsic muscles of larynx apart from cricothyroid
Bilateral vocal cord/ SLN palsy causes what?
Severe respiratory distress
Stridor due to flaccid cords
Cricothyroid membrane lies where?
Between thyroid and cricoid cartilage
Avascular band
What can be damaged in a surgical airway?
Vocal cords
Causes subglottic stenosis
What are the paths of the right and left RL nerves?
Right passes under subclavian artery then ascend to larynx in tracheo-oesophageal groove
Left passes under aortic arch to ascend in same groove
What equipment do you need for an emergency cricothyroidotomy?
6 ett
10 blade scalpel
GEB
Suction
Unilateral RL nerve damage results in?
Vocal cord palsy Hoarseness Poor glottis closure Poor cough (cannot generate positive intrathoracic pressure) Aspiration risk
Neurovascular bundle lies where in relation to run surface?
Inferior surface
