Anatomy for the
Anesthetist
Marianne Cosgrove,
CRNA, DNAP, APRN
Components of the Respiratory
System
The nose
 The pharynx
 The larynx
 The trachea
 The bronchi
 The lungs

Conducting Portion of the
Respiratory System
nasal cavities
 oral cavity
 pharynx
 larynx
 trachea
 bronchial tree

Lining of the Respiratory Tract

Nonciliated stratified squamous epithelium
– anterior nose, oropharynx, laryngopharynx

Ciliated pseudostratified squamous
epithelium
– posterior nose, nasopharynx, laryngeal mucosa above cords

Ciliated pseudostratified columnar
epithelium
– larynx below cords, trachea, bronchiolar tree

Nonciliated cuboidal epithelium
– terminals and respiratory bronchioles
The Nose and Sinuses
The external nose
 The internal nose

– bony septum
– nasal turbinates
– posterior nares

The paranasal sinuses
–
–
–
–
maxillary
frontal
sphenoid
ethmoid
Functions of the Nose
Warms inspired air
 Humidifies air
 Cleans inhaled air
 Organ of olfaction
 Resonator for speech

The Pharynx
…a musculomembranous tube extending
from the undersurface of the skull to the
level of C6 and lower border of the cricoid
cartilage where it is continuous with the
esophagus.
The Pharynx

Divisions
– nasopharynx
– oropharynx
– laryngopharynx

Innervation
– sensory
• via glossopharyngeal (cranial nerve IX)
– motor
• via vagus (cranial nerve X)

Primary motor function
– swallowing
Divisions of the Pharynx
 nasopharynx
– Behind posterior nares and above soft palate
 oropharynx
– Extends from the soft palate to the base of the
tongue
Divisions of the Pharynx cont’d

laryngopharynx
– Extends from the base of the tongue to the
opening of the esophagus
– Contains the landmarks for endotracheal
intubation: epiglottis, aryepiglottic folds,
arytenoid cartilages
Landmarks for Intubation
Esophagus

upper 1/3 striated muscle
– voluntary
– airway protection against regurgitation via the
cricopharyngeus muscle (A.K.A. upper esophageal
sphincter (UES))
• motor innervation via the RLN

lower 2/3rds
– involuntary; tone/contraction under ANS control

distal 3-5 cm  lower esophageal sphincter
(LES)
– A functional structure; may be manually opened with
~ 18 cm H2O pressure
Classifications of the Airway
Mallampati
Cormack-Lehane
The Larynx
…consists structurally of a framework of
articulating cartilages linked together by
ligaments which move in relation to each
other by the action of laryngeal muscles.
The Larynx

Location
– adult
• anterior neck at the level of C4-6
– child
• anterior neck at the level of C3-5
The Larynx

Blood supply
– Arterial
• subclavian artery to inferior thyroid artery to inferior
laryngeal artery
– Venous
• inferior laryngeal vein to brachiocephalic vein to
SVC
The Laryngeal Cartilages

Singular cartilages
– thyroid
– cricoid
– epiglottis

Paired cartilages
– arytenoids
– corniculates
– cuneiforms
Thyroid Cartilage

Largest cartilage
– Two broad sheets of cartilage which unite in a V shape
anteriorly to form the “Adam’s Apple”
– Attached to the hyoid bone by the thyrohyoid
membrane
– Attached to the cricoid cartilage by the cricothyroid
membrane
– Provides the anterior attachment for the vocal cords
Cricoid Cartilage

Consists of the only complete ring in the larynx
which broadens into a plate like structure on the
posterior aspect; A.K.A. “The Signet Ring
Cartilage”

forms the inferior and posterior borders of the
larynx

Is the narrowest portion of the pediatric airway
Epiglottis

Leaf like, elastic
– Projects obliquely upward behind the tongue and in
front of the entrance to the larynx
• Functions to cover the glottic opening to prevent entrance of
solids and liquids into the airway during swallowing
Attached to the posterior surface of the thyroid
cartilage above the vocal cords
 First cartilage encountered during laryngoscopy

Arytenoid Cartilages

Pyramidal in shape; sit on cricoid cartilage
– Each has a muscular process which is the
insertion of the posterior and lateral
cricoarytenoids
– Each has a vocal process which is the posterior
attachment of the vocal cords
Corniculate Cartilages

Cone shaped structures situated in posterior
part of the aryepiglottic folds

Each is attached to the apex of an arytenoid
cartilage
Cuneiform Cartilages

Elongated structures located slightly
posterior to the corniculates at the base of
the epiglottis
C3
C4
C6
The Laryngeal
Cartilages
Netter, Plate 71
Other Laryngeal Structures
Aryepiglottic folds
 Ventricular folds (false vocal cords)
 Vocal folds (true vocal cords)
 The glottis

– *The rima glottis is the narrowest portion of the adult
airway

cricothyroid membrane
– palpated between the lower border of the thyroid
cartilage and the cricoid ring
– allows for easy surgical access to the airway via
cricothyrotomy in “can’t ventilate, can’t intubate”
scenario
Muscles of the Larynx
muscle
action
effect
Posterior cricoarytenoids
(2)
Rotate arytenoids outward ABduction
(widens rima)
Lateral cricoarytenoids
(2)
Rotate arytenoids inward
ADduction
(approximates vocal
cords)
Transverse arytenoid (1)
Approximate arytenoids
ADduction
(approximates vocal
cords)
Thyroarytenoids (2)
Draw arytenoids forward
Relaxes and shortens
cords
Cricothyroids (2)
Draw up arch of cricoid
and tilt lamina back
Tenses and elongates
cords
Posterior, Lateral Views of Laryngeal
Muscles
Netter, Plate 72
Lateral Dissection of Laryngeal
Muscles
Netter, Plate 72
Superior View of Laryngeal Muscles
Netter, Plate 73
Action of Posterior and Lateral
Cricoarytenoids
Netter, Plate 73
Action of Cricothyroid Muscles
Netter, Plate 73
Action of Transverse Arytenoid, Thyroarytenoid
Muscles
Netter, Plate 73
Innervation of the Larynx

Superior laryngeal nerve
– A branch of the vagus nerve; contains internal
and external branches
• Internal branch supplies sensory innervation
above the vocal cords
*stimulation may precipitate
laryngospasm
• External branch supplies motor innervation
to the cricothyroid muscles
Innervation of the Larynx
 Recurrent laryngeal nerve
– A branch of the vagus nerve
– Supplies motor innervation to all muscles of the
larynx except the cricothyroid muscles
– Supplies sensory innervation to the larynx
below the vocal cords
– May be damaged during thyroid/parathyroid
surgery
Damage to the Recurrent
Laryngeal Nerve
Unilateral transection = hoarseness
 Bilateral damage from ischemia = complete
airway obstruction from laryngospastic
cords
 Bilateral transection = flaccid vocal cords

– May have some passage of air
Laryngeal Nerves
Netter, Plate 74
The Trachea




Cartilaginous and membranous tube extending
from the vocal cords to the carina to form the
right and the left mainstem bronchi
Lies anterior to the esophagus and is protected
anteriorly with cartilaginous rings
Posterior wall is membranous
The carina lies at the level of T5
Airway Measurements
female
Incisors to vocal 10-14 cm
cords
male
12-16 cm
Incisors to
carina
26-28 cm
24-26 cm
The Bronchi

Mainstem (A.K.A primary bronchus)
– Right
• Shorter, wider, and less acute angle off trachea
– In adults, forms a 25 degree angle
– In children less than 3 years old, forms a 50
degree angle
• Divides into 3 lobar branches
• Inhaled foreign bodies are more likely to enter the R
mainstem bronchus
The Bronchi

Mainstem (A.K.A primary bronchus)
– Left
• Longer, narrower, more horizontal than right
–In adults and children, forms a 40-60
degree angle off trachea
• Divides into two lobar branches
The Tracheobronchial Tree, Respiratory
Bronchioles, and Alveoli

Continued branching produces:
– Segmental bronchi
– Small bronchi
– Bronchioles
– Terminal bronchioles
– Respiratory lobules
The Terminal Bronchioles
The tracheobronchial tree ends at the 16th
level from the trachea at the level of the
terminal bronchioles
 Diameter is <1 mm, cilia disappears,
cartilage is absent


This marks the end of anatomic dead
space
Anatomic Dead Space
Equal to approximately 1cc/lb in both adults
and children
 Examples:

– 70 Kg pt = 155 lbs
Approximate anatomic dead space = 155 cc
- 4 kg infant = 9 lbs
Approximate anatomic dead space = 9 cc
The Respiratory Lobule

Comprised of:
– respiratory bronchiole
– alveolar duct
– alveolus (air sac)
The Respiratory Bronchiole
Where actual respiratory exchange begins
 Muscle layer of bronchial tree is thickest
here (relatively speaking)

– Forms a thin band around the openings of the
alveolar ducts
– No muscle is found beyond this point
Classification of airways by order of branching
Common name
Generation of airway
Trachea
0
Main bronchi
1
Lobar bronchi
2-3
Segmental bronchi
4
Small bronchi
5-11
Bronchioles, terminal
bronchioles
12-16
Respiratory bronchioles
17-19
Alveolar ducts
20-22
Alveolar sacs
23*
Trachea and
Major Bronchi
The Lungs

Lie free in the pleural cavity attached only at
the hilum
– The bronchi, major vessels, and lymphatics
enter and leave here

Each lung has a concave base
– Rests upon the diaphragm

Each lung has an apex
The Right Lung

Three lobes
– Right
– Middle
– Lower

Broader, shorter than the left lung due to
elevation of the diaphragm from the liver
– The right apex extends further above the
clavicle than the left
The Left Lung

Two lobes
– Upper
– Lower

Smaller than the right due to the position of
the heart
The Thoracic Cavity

Three divisions separated from each other
by partitions of pleura
– Pleural space
• Contains the lungs
– Pericardial space
• Contains the heart, pericardium
– Mediastinal space
• Contains the major vessels, lymphatics
The Bronchial Circulation
Feeds the parenchyma of lung
 Venous return to the pulmonic vein

– Accounts for a normal 1-3% shunt
(deoxygenated blood mixing with arterial blood)

Not to be confused with pulmonary
circulation
– Where respiration occurs
Shunt vs. Dead Space

Shunt
– perfusion without aeration

Dead space
– aeration without perfusion
• A.K.A. an area of bi-directional air flow
The Pleura

A double layered serous membrane
– Parietal
• Lines the entire thoracic cavity, inner surface
of ribs, superior surface of diaphragm
– Visceral
• Adheres to the surface of each lung
– The pleural space is a potential space between
the pleura
• A small amount of serous fluid is present
Muscles of respiration

diaphragm
– responsible for 70% of tidal volume

accessory muscles of respiration:
inspiration
expiration
sternocleidomastoid
scalenes
pectoralis major
pectoralis minor
serratus anterior
serratus posterior superior
upper iliocostalis
external oblique
internal oblique
rectus abdominus
lower iliocostalis
lower longissimus
serratus posterior inferior
Cardiac Anatomy
Coronary Arteries
Other Zones of
Anesthetic
Interest…
Major Nerve Plexuses
A
nerve plexus is a network of
intersecting nerves which
combine sets of spinal nerves
that serve the same area of the
body into one large grouped
nerve
Cervical plexus (C1-C5)
A
plexus of the ventral rami of the first
four cervical nerves
–Branches:
• Lesser occipital nerve (C2)
• Greater auricular nerve(C2,3)
• Transverse cervical nerve (C2,3)
• Supraclavicular nerves (C3-4)
Supplies the skin behind the ear, at the angle of the jaw, in the
anterior and lateral triangles of the neck to shoulder and below the
clavicle
Cervical Plexus, cont’d
 Branches,
cont’d
–Muscular
• Ansa cervicalis
• Hypoglosssal
• Thyrohyoid, genohyoid
Innervate the
rhomboids, serratus
anterior, SCM,
trapezius, levator
scapulae, and
scalenus medius
Cervical Plexus, cont’d
–Communicating
• From the SNS (superior cervical
sympathetic ganglion)
–C1 communicates with hypoglossal
»supplies geniohyoid and thyrohyoid
–C2 and C3 form ansa hypoglossi
»supplies sternohyoid, sternothyroid,
and omohyoid muscles
Cervical Plexus, cont’d
–Mixed (sensory, motor, and
sympathetic)
–Phrenic nerve (C5)  diaphragm
Cervical plexus
contributes to brachial plexus
The Brachial Plexus

Supplies the upper limb with sensory and
motor innervation

A branching network of nerves derived from
the anterior (ventral) rami (roots) of spinal
nerves C5, 6, 7, 8, and T1
Brachial Plexus Divisions
Roots (Randy)
– C5-T1
 Trunks (Travis)
– Upper, middle, lower
 Divisions (Drinks)
– Anterior, posterior
 Cords (Coffee)
– Lateral, medial, posterior
 Branches (Black)

The Brachial Plexus
clavicle
Distribution of terminal nerves
cords
lateral
branches
musculocutaneous
median
posterior
axillary
radial
medial
median
ulnar
innervation to
UE flexors (m)
lateral aspect forearm from
elbow to wrist (s); *most difficult
to block
medial aspect forearm (s)
see below
shoulder (m,s)
UE extensors (m)
thumb, 2nd finger, inner medial
3rd finger (s)
dorsal-distal half 2nd, 3rd fingers;
medial ½ 4th finger (s)
ventral-thumb, 2nd, 3rd, and ½ of
4th finger (s)
4th, 5th fingers, lateral hand (s)
Brachial Plexus Block

Four approaches:
1) Interscalene
- Trunks emerge between anterior and middle
scalenes; proximity of RLN, stellate ganglion, phrenic
nerve, and vertebral artery predisposes to high rates of
incidental blockade or intravascular injection
2) Supraclavicular (AKA subclavian)
- Plexus is compacted here; provides excellent blockade;
high incidence of pneumothorax (1-6%)
3) Infraclavicular
- Risk for pneumo, hemo, chylo (L sided) thorax
4) Axillary
- Remember the musculocutaneous nerve!
1) Visit www.nysora.com
Celiac (solar) Plexus

Formed (in part) by the greater and lesser
splanchnic nerves of both sides, and also
parts of the right vagus nerve
 includes a number of smaller plexuses which
supply viscera:
–
–
–
–
–
–
–
–
–
hepatic
splenic
gastric
pancreatic
suprarenal
renal
testicular/ovarian
superior mesenteric plexus
inferior mesenteric plexus
Lumbosacral plexus

Lumbar plexus (T12-L4)
– Main branches
• iliohypogastric
• ilioinguinal nerve
• genitofemoral nerve
– Dorsal divisions
• lateral femoral cutaneous
• femoral nerve  adductors of hip, extensors of knee, and
skin over medial surfaces of thigh and leg
– saphenous is main branch
– Ventral divisions.
• obturator nerve  adductors of hip and skin over medial
surface of thigh
• accessory obturator nerve
Lumbar plexus, cont’d
Sacral plexus (L4-S4)
gluteal nerves  adductors and extensors of
hip and skin over posterior surface of thigh
 sciatic nerve  (L4-S3) 2 nerves contained
within a sheath
 common peroneal
 tibial
– flexors of knee and ankle, flexors and
extensors of toes, and skin over anterior
and posterior surfaces of leg and foot

– posterior and medial cutaneous nerve  skin over
medial surface of leg
– pudendal nerve (S2-4)
Sacral Plexus
The Great Veins of the Neck

Internal jugular
– Right IJ best for cannulation and passage of a
PA catheter

External jugular
– Beware of the large valve at the junction of the
EJ and the subclavian
Anterior jugular
 Subclavian

The Great Veins of the Neck
The Thoracic Duct
Aortic Arch
Brachiocephalic=Innominate
The Antecubital Fossa
The Circle of Willis
…an anastomosis of the internal carotids and
the vertebral arteries which is found at the
base of the brain. All cerebral arteries are
derived from this anastomosis.
This circle is directly responsible for cerebral
perfusion.
During carotid X-clamping, collateral flow to
the circle is via the contralateral carotid and
the vertebro-basilar system.
Cerebral Perfusion Pressure
CPP = MAP - ICP
or CVP, whichever is
higher
The Circle of Willis
CSF circulation
CSF secreted by choroid plexus
to
Lateral ventricles 1 & 2
to
Foramen of Munro
to
3rd ventricle
to
Aqueduct of Sylvius
to
4th ventricle
to
Foramina of Luschka and
Magendie
to
Subarachnoid space
to
Reabsorption by arachnoid villi
The Cranial Nerves
…with regard to their regions of innervation,
are nerves of the head. They spread
through the head-neck region, except for
the parasympathetic portions of the vagus
nerve which pass to the abdominal organs.
Cranial Nerves I-VI
Cranial nerves
Type
I. Olfactory
S
smell
II. Optic
S
sight
III. Oculomotor
M
eye movement,
pupil constriction
IV. Trochlear
M
eye movement
V. Trigeminal
B
chewing, great
sensory of face
M
eye movement
(three branches)
ophthalmic (S), maxillary (S), mandibular
(M & S)
VI. Abducens
Function
Cranial nerves VII-XII
Cranial nerves
Type
Function
VII. Facial
B
taste, great motor
of the face
S
hearing, balance
(five branches)
temporal, zygomatic, buccal, mandibular, cervical
VIII. Acoustic
(A.K.A. vestibulocochlear)
IX.
B
Glossopharyngeal
swallowing,
afferent carotid
body and sinus
X. Vagus
B
“Great Wanderer”
afferent and
efferent
M
larynx and
pharynx
tongue
(branches: superior laryngeal
and recurrent laryngeal nerves
may be injured during
intubation)
XI. Accessory
(A.K.A. spinal accessory)
XII. Hypoglossal
(may be injured during intubation)
M
The Spine
Largest interspace is
L5-S1 (A.K.A. Taylor’s
space)
Spinal cord

Extends from the foramen magnum to the
level of L1 (adults), L3 (children)
– Terminates to conus medullaris and filum
terminale
• lower spinal nerves form the cauda equina
– “Tuffier’s line” – the plane which crosses the
iliac crests bilaterally
• Approximately the L4 level in most individuals
• Cord may extend below the L1 level in obese pts
• Conus is at approximately L3 in children
Tuffier’s Line
( ~T7)
Spinal Cord termination
Blood supply
• Derived from a single anterior and
paired posterior spinal arteries
–Anterior spinal artery
»formed from the vertebral artery
»supplies anterior 2/3rds of the
cord
–Posterior spinal arteries
»Arise from cerebellar artery
Additional blood supply to the cord

Intercostals (thorax)
 Lumbar arteries (abdomen)
 Artery of Adamkiewicz (great ventral radicular
artery, arteria radicularis magna)
– arises from the aorta
– unilateral—usually from the L side
– provides the major blood supply to the anterior,
lower 2/3rds of the spinal cord
Cross section of spinal cord
Substantia gelatinosa
Found in the dorsal horn of the spinal
cord
 Plays a major role in processing and
modulating nociceptive input from
cutaneous nociceptors
 Major site of action for intrathecal
opioids
 AKA “Rexed’s Lamina II”

Vertebra—superior view
Vertebra--lateral view
Vertebra and disc
Spinal Ligaments
Spinal anesthesia
Epidural Anesthesia
Epidural Anesthesia
Epidural Anesthesia
epidural space
venous plexus
ligamentum flavum
Epidural space widens as it descends the cord; widest at L2-3
Schematic of Spinal vs. Epidural
Anesthesia
Miscellaneous…
Diaphragmatic Innervation

Phrenic nerve (R & L branches)
– Arises from C3, 4, 5
• This is the source of motor innervation
(“C3,4,5 keeps a man alive”)
– Sensory innervation
• Lower 6 intercostal nerves
Cardioaccelerator nerves

Arise from T1-4

Bradycardia usually noted in quadriplegia or
high level of spinal anesthesia
Landmarks for Sensory Levels
T4
Nipple
T6
Xiphoid
T7
Lower border of scapula
T8
Lower border of rib cage
T10
Umbilicus
L4
Iliac crest
Dermatome Man
Peripheral Nerve Stimulation

Most common site of placement of PNS is
along the groove of the ulnar nerve
– Elicits a response from the
adductor pollicis brevis

May use the facial nerve distribution for
placement if arms are not accessible
– Elicits a response from the
• orbicularis oculi
• corrugator supercilii
Arterial Supply of the Hand
Sites for arterial cannulation

Radial artery
– Most commonly selected site

Ulnar artery
– Major blood supply of the hand
– Difficult to cannulate; deep, tortuous

Brachial artery
– Large, easy to cannulate
– Risk of median nerve damage


Axillary artery
Femoral artery
– Good to use in low flow states

Dorsalis pedis artery
– May have distortion of waveform; falsely high SBP 2º
distance from aorta
Positioning

neuropathies following surgery are from:
– stretching of nerves for sustained periods of time
– pressure on nerves for sustained periods of time
• leads to ischemia of the nerve  neuropathy
• alopecia of occipital area; particularly in low-flow states

anesthetized pts are unable to compensate for
awkward/painful positions
– muscle relaxation allows for positioning that would
otherwise not be tolerated by the pt

proper positioning considered a “shared
responsibility” among OR team
(however…)
Positioning

upper extremity
– *ulnar nerve is the most frequently damaged in
pts in the supine position
– neuropathy may manifest as sensory and/or motor
deficit
• usually transient
– 70-90% of injured pts are male
– other predisposing factors to development of injury:
•
•
•
•
extremes of weight (particularly obese pts)
extended bedrest (before and/or after surgery)
long surgery
preexisting neuropathy in the contralateral limb
Brachial plexus injury

most associated with median sternotomy
– particularly with dissection of IMA
• probably 2º uneven retraction of chest wall

increased risk with
– arm abduction > 90º from side
• compounded if head is turned contralaterally
– prone position with arms on rests beside head
• may occur with arms at sides if shoulders allowed to
prolapse forward with no support
Positioning

lower extremity
– lithotomy position carries a high risk of
perioperative nerve injury
• usually mild/self limiting
• severe  footdrop
– common peroneal nerve
• *most commonly injured nerve in the lower
extremities
• relatively superficial
– wraps around the head of the fibula on the lateral aspect
of the knee
Lower extremity nerves, cont’d

sciatic nerve
– adjacent to the hamstrings
– stretch from hyper flexion of the hip, especially when
coupled with an extended leg/flexed foot

femoral nerve
– more commonly injured with deep, lower abdominal
retraction
• sustained compression of the iliac or femoral arteries leads to
ischemia
– pronounced abduction of thigh (frog leg)
Lower extremity nerves, cont’d

obturator
– injured with pronounced abduction of the thigh
– neuropathies are usually sensory (numbness inner
aspect of thigh)

lithotomy position caveats:
– padding of bony prominences is essential
– position changes of the LEs must be made
simultaneously

1º risk factor for the development of neuropathy
following lithotomy is obesity
Supine position

minimal circulatory and ventilatory changes noted
– FRC may be slightly  due to cephalad displacement
of diaphragm/abdominal contents
– stress on lower back
• may be attenuated with mild knee flexion
– pressure on heels
– legs crossed: sural (upper leg) and peroneal (lower leg)
pressure
– upper extremities should be neutral
• if supinated, abduction from body not to exceed 90º
• pronation may cause undue pressure on the ulnar groove
• individualize to each pt
Trendelenburg

head down; associated with many physiologic
changes
–  pulmonary compliance, FRC from diaphragmatic
displacement
–  myocardial O2 demand
• from  preload, slight impedance of forward LVSV
– may ultimately  CO
– ICP, IOP
• leads to facial, scleral edema; possible retinal detachment,
POVL
– ? R mainstem intubation vs. extubation
–  risk of passive regurgitation; possible aspiration
– arms should be secured if abducted
– shoulder braces should be placed on acromio-clavicular
processes with padding
Prone

face down; head and neck should remain in a neutral position
– turned head may obstruct vertebral artery flow and jugular drainage

upper extremities are best placed at sides
– should not be abducted > 90º if extended alongside the head

physiologic changes include
–  FRC with  intraabdominal pressure
• ***FRC may actually be unchanged or facilitated in absence of increased IAP
–  intraabdominal pressure
• may impede venous return via IVC; thereby reducing preload/CO
• collaterals via epidural vessels; may see  intraoperative blood loss
from congestion
•  pulmonary compliance
– pooling of blood in lower extremities
– facial/ocular edema
• retinal artery occlusion may lead to blindness
– risk compounded by overhydration with crystalloid, prolonged periods of
hypotension, direct pressure on the orbits, EBL > 2.5 l, prolonged surgery
– pressure on breasts, genitalia
–  risk for airway compromise during position changes or
intraoperatively
• pt should be log rolled after induction with neck maintained in a neutral
position
Sitting

venous air embolism (VAE) is the 1º
complication associated with this position
– occurs when the operative site is above the level of
the heart
• treatment:
–
–
–
–

have the surgeon flood the operative site with saline
discontinue N2O
aspirate air through a central venous catheter
resuscitate with fluids, ionotropic support, (+) pressure
ventilation
other effects of sitting include:
– BP, preload, CO from pooling
– CPP (brachial reading underestimates pressure
at the Circle of Willis!)
– intrathoracic blood volume; V/Q mismatching
Lateral decubitus

side lying; physiologic changes generally pulmonary;
overall V/Q mismatch from:
–  pulmonary compliance with  perfusion to the upper lung
  dead space
–  pulmonary compliance and FRC with  perfusion to the
dependent lung   shunt


compression of IVC
pressure on axilla on dependent side
– brachial plexus injury common
– pulse oximetry on dependent hand recommended to assess
perfusion
– Axillary roll – a misnomer!


pressure on medial aspects of knees
potential injury to dependent eye/ear