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NSU AA Denver > 2025 Airway Management Exam 1 > Flashcards

2025 Airway Management Exam 1 Flashcards

Anatomy and Physiology of Airway

1
Q

Upper Respiratory System

A

Nose
Mouth
Sinuses
Pharynx
Larynx

Frontal Sinus
Sphenoid Sinus
Nasal conchae: Superior, Middle, Inferior
Nasal Cavity
External Nares
Internal Nares
Entrance to Auditory Tubes
Oral Cavity
Hard Palate
Soft Palate
Pharynx: Naso, Oro, Laryngo (Hypo)
Epiglottis
Glottis
Vocal Fold

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2
Q

Framework of Nose

A

Bony: Frontal Bone, Nasal Bones, Maxilla
Cartilaginous: Lateral nasal cartilages, Septal cartilage, Alar cartilage
Dense Fibrous Connective Adipose Tissue

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3
Q

Upper Airway Functions

A

Heat
Respiratory
Humidification
Filtration
Olfaction
Reservoir for secretions: Paranasal sinuses, Nasolacrimal ducts
Phonation: Modification of speech

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4
Q

Nose Anatomy

A

Nasal Septum: R and L nasal cavities
Turbinates aka Conchea

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5
Q

Nose Blood Supply

A

Anterior Ethmoid Artery
Posterior Ethmoid Artery
Sphenopalatine Artery
Greater Palatine Artery
Superior Labial Artery
… all flow into Kiesselbach’s Plexus

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6
Q

Kiesselbach’s Plexus

A

Aka Little’s Area
Most common source of clinically significant epistaxis

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7
Q

Pharynx

A

The pharynx is the part of the digestive system situated posterior to the nasal and oral cavities and posterior to the larynx.

12-15 cm long

Extends from the base of the skull down to the inferior border of the cricoid cartilage (around the C6 vertebral level), where it becomes continuous with the esophagus

It is therefore divisible into nasal, oral, and laryngeal parts:
(1) nasopharynx,
(2) oropharynx
(3) laryngopharynx

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8
Q

Pharynx Function

A

The pharynx is the common channel for:
Deglutition (swallowing)
Respiration

Food and air pathways cross each other in the pharynx

In the anesthetized patient, the passage of air through the pharynx is facilitated by extension of the neck.

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9
Q

Swallowing Process

A

BEGINNING DEGLUTITION
Pharynx ascent
Dilation with tensing of soft palate
Tongue moves upward
No air enters nasopharynx
Larynx ascends
Elevation of hyoid-laryngeal complex

BOLUS ENTERS PHARYNX
Pharynx descends
Constrictors contract from to top to bottom to transport bolus towards UES

BOLUS ENTERS ESOPHAGUS

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10
Q

Nasopharynx

A

Posterior portion of the nasal cavity, with which it has a common function as part of the respiratory system.

Primarily of respiratory function

Eustachian tubes open into the nasopharynx

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11
Q

Oropharynx

A

Extends inferiorly from the soft palate to the superior border of the epiglottis

Primarily of digestive function

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12
Q

Laryngopharynx (Hypopharynx)

A

Extends from the superior border of the epiglottis to the inferior border of the cricoid cartilage, where it becomes continuous with the esophagus

Lies between C4-C6

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13
Q

Oral Cavity and Dentition

A

Know the Picture (Slide 23)

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14
Q

Tooth Numbering

A

Top Back Right to Top Back Left (1-16)
Bottom Back Left to Bottom Back Right (17-32)

Type of Teeth (Top and Bottom)
Central Incisor
Lateral Incisor
Cuspid or Canine
First Premolar
Second Premolar
First Molar
Second Molar
Third Molar or Wisdom Teeth (17-21yo)

Peds = 20 teeth
Adults = 32 teeth (28 if wisdom teeth removed)

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15
Q

Tongue Nerve Supply

A

SENSORY NERVES
Anterior 2/3 of tongue
Lingual nerve (CN V Trigeminal – sensation)
Facial nerve (CN VII Facial – mostly taste)
Posterior 1/3 of tongue
Glossopharyngeal nerve (CN IX)

MOTOR NERVES
Hypoglossal nerve (CN XII) – mostly
Superior Laryngeal nerve (CN X Vagus) – minimal

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16
Q

Cranial Nerves

A

Olfactory nerve (CN I): The nerve that carries smell information from the nose to the brain

Optic nerve (CN II): The nerve that carries visual information from the retina to the brain

Oculomotor nerve (CN III): The nerve that controls four of the six eye muscles

Trochlear nerve (CN IV): The nerve that helps move the eye down and out

Trigeminal nerve (CN V): The largest cranial nerve that provides sensory information to the face and controls the muscles used for chewing

Abducens nerve (CN VI): The nerve that controls the lateral rectus muscle of the eye

Facial nerve (CN VII): The nerve that extends from the brain stem

Vestibulocochlear nerve (CN VIII): The nerve that carries information about sound and balance from the inner ear to the brain

Glossopharyngeal (IX): Primarily responsible for sensory functions in the pharynx and posterior tongue, including taste

Vagus (X): A mixed nerve that controls various involuntary functions in the body including heart rate, digestion, and breathing

Accessory (XI): Primarily motor, controlling the muscles of the neck.
Hypoglossal (XII): Responsible for controlling the muscles of the tongue

Hypoglossal (XII): Responsible for controlling the muscles of the tongue.

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17
Q

Larynx

A

The larynx is the organ that connects the lower part of the pharynx with the trachea

Begins at C4-C6

It serves as a:
Valve to guard the air passages
especially during swallowing
Maintenance of a patent airway
Vocalization

Laryngeal Functions
Air passage into and out of the lungs
Protection of lungs from liquids and solids
Phonation
Effort closure: Coughing, Lifting, Defecation

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18
Q

Larynx Cartilages

A

The larynx possesses:
3 paired cartilages
Arytenoid
Corniculate
Cuneiform

3 single cartilages
Thyroid
Cricoid
Epiglottic

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19
Q

Types of Larynx Cartilage

A

Types of Cartilage
Hyaline
Calcifies - beginning in middle life
Ossifies - as age advances
If become calcified, become viable radiographically
Cricoid, Arytenoid, Thyroid

Elastic
Neither calcifies nor ossifies
Maintains functional form throughout life
Epiglottic, Corniculate, Cuneiform

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20
Q

Epiglottic Cartilage

A

TYPE
Elastic cartilage

GENERAL SHAPE
Leaf

ARTICULATIONS
None

ATTACHMENTS
Hyoepiglottic ligament
Thyroepiglottic ligament

FUNCTIONS
Protects against food entering the larynx

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21
Q

Thyroid Cartilage

A

STRUCTURE - OTHER
Superior cornu (horns) – suspend thyroid cartilage from hyoid bone
Inferior cornu (horns) – suspend cricoid cartilage from thyroid cartilage

ARTICULATIONS
Inferior cornu & cricoid cartilage

ATTACHMENTS
Thyrohyoid membrane cephalad
Cricothyroid membrane caudad
Vocal cords – midline, interior

FUNCTIONS
Protects larynx
Suspends 7 (of 8) laryngeal folds

TYPE
Hyaline cartilage

GENERAL SHAPE
Shield

UNIQUE ASPECT
Largest laryngeal cartilage

STRUCTURE – PHYSICAL EXAM
Alae (wings) - 2
Prominentia laryngis (Adam’s apple); midline fusion of alae
Thyroid notch

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22
Q

Cricoid Cartilage

A

STRUCTURE – PHYSICAL EXAM
Midline, rounded prominence below prominentia laryngis
Can be depressed into esophagus
Only Complete Ring
C5-C6

ARTICULATIONS
Thyroid cartilage’s inferior cornu
Arytenoid cartilage’s bases

ATTACHMENTS
Cricothyroid membrane – cephalad
Trachea - caudad

TYPE
Hyaline cartilage

GENERAL SHAPE
Signet ring

UNIQUE ASPECT
Only circumferential laryngeal structure

STRUCTURE – PHYSICAL EXAM
Midline, rounded prominence below prominentia laryngis
Can be depressed into esophagus

FUNCTIONS
Supports arytenoid cartilages

Must be able to identify for cricothyrotomy

Pressure on this structure for Rapid Sequence Induction (RSI) – Sellick’s maneuver

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23
Q

Corniculate Cartilages (horn-like)

A

GENERAL SHAPE
Conical nodules

UNIQUE ASPECT
Cartilages of Santorini (Italian
anatomist, 1700s)

STRUCTURE – PHYSICAL EXAM
Tubercles appear beside interarytenoid incisure

STRUCTURE – OTHER
Located in aryepiglottic folds

FUNCTIONS
Spring-like action (stressed by adduction of arytenoid cartilages) produces recoil assistance with mediolateral separation of arytenoids and reopening of glottis

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24
Q

Cuneiform Cartilages (wedge-shaped)

A

GENERAL SHAPE
Small, elongated STRUCTURE –

PHYSICAL EXAM
Tubercles appear lateral to
corniculate tubercles

STRUCTURE – OTHER
Located in aryepiglottic folds

ATTACHMENTS
Arytenoid cartilages

FUNCTIONS
Stiffens aryepiglottic folds
Spring-like action facilitates reopening of glottis

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25
Q

Innervation of the Airway

A

Superior laryngeal nerve (SLN) – Internal Branch
Pierces thyrohyoid membrane
Sensory
Supraglottic region

SLN – External Branch
Motor
Cricothyroid muscles

Recurrent Laryngeal Nerve (RLN)
Motor: All intrinsic laryngeal muscles except cricothyroids
Sensory: Infraglottic

Lecture 1, Slide 40, 41, 42

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26
Q

Larynx Cartilages

A

Know how to identify

Lecture 1, Slides Throughout

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27
Q

Innervation Complications

A

SLN damage occurs (thyroidectomy, neoplasm, or trauma) and contraction of cricothyroid muscle bilaterally – results in acute airway obstruction

Complete paralysis of RLN and SLN – midway position of vocal cords – seen after NMB given (cadaveric position, seen with administration of NMB)

A contraction of ALL the laryngeal muscles – Laryngospasm (cords close)

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28
Q

Lower Airway

A

Trachea
Also known as the windpipe, this tube carries air from the upper respiratory system to the lungs. The trachea is made of cartilage rings that keep it from collapsing or over-expanding.

Bronchi
These passageways carry air to the lungs. The left bronchus carries air to the left lung, and the right bronchus carries air to the right lung. (Primary, Secondary, Tertiary)

Bronchioles
These are smaller branches of the bronchi that clean, warm, and moisten the air that’s inhaled.

Alveoli
These tiny air sacs in the lungs are where oxygen is absorbed and carbon dioxide is released.

Lungs
These spongy organs are where the exchange of gases between the blood and air takes place.

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29
Q

Trachea

A

~12-15 cm long, 1.5-2cm internal diameter

Extends from the cricoid cartilage to the bronchial bifurcation (Carina)
Carina: T5 at expiration, T6 at inspiration

16 to 20 C- shaped cartilages

Trachealis muscle runs vertically for the posterior aspect

5th thoracic vertebra – trachea bifurcates into R & L mainstem bronchi

R mainstem bronchus and tracheal axis is more acute
R mainstem bronchus intubation
Greater risk for aspiration of food liquids

Adult Angle of R Bronchus: 20 degrees; L Bronchus 40 male/50 female

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30
Q

Pediatric Airway

A

Head
Very large (in relation to body)
Occiput elevates head
Little muscle tone
Tendency for cervical flexion
Tendency for airway obstruction

Nose
Obligate nasal breathing
Nasal passages smaller

Tongue
Larger (in relation to oral cavity)

Larynx
Is situated at a higher level than in adults, infant it is funnel shaped

Epiglottis
Omega shaped
Horizontally oriented
Longer
Stiffer

Vocal cords
Antero-inferior plane
C3-C4 Glottic Opening, in adults C4-C5, Premature Infant C3

Narrowest part in pediatrics:
cricoid cartilage
Narrowest part in adult:
rima glottidis

Trachea and Mainstem Bronchi
Shorter and narrower
Right mainstem has less acute angle
Diameter of larynx affected more by edema

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31
Q

Airway Length and Purposes

A

Airway extends from the nose and mouth to the alveoli

Upper = filter/humidify/warm
Lower = ventilation/oxygenation

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32
Q

Bronchi

A

1st bifurcation at carina leads to R & L lung

R main bronchus less angled than L
Easier to R mainstem intubate

RUL of lung only 2.5cm from carina

Walls in larger airways contain:
smooth muscle
elastic tissue
cartilage

33
Q

Lungs

A

Right
3 lobes
10 broncho-pulmonary segments

Left
2 lobes
9 broncho-pulmonary segments

23 airway divisions between trachea and alveoli

Gas movement
Tidal flow – larger airways
Diffusion – smaller airways (division 17 and smaller)

34
Q

Tracheobronchial Tree

A

23 divisions/generations

Cartilaginous support lost at bronchioles (becomes only smooth muscle)

Gas exchange begins on pulmonary bronchioles (generations 17-19)

Trachea - 0
Primary Bronchus - 1
Secondary Bronchus - 2
Tertiary Bronchus - 3
Bronchiole - 4
Terminal Bronchiole - 5-16
Respiratory Bronchiole - 17-19
Alveolar Duct - 20-22
Alveolar Sac - 23

35
Q

Pleura

A

Pleura
Double layer surrounding the lungs

Visceral (defined as relating to organ) pleura – lung

Parietal (defined as relating to cavity) pleura – lines thoracic cavity

Intrapleural space
Small amount of lubricating fluid

36
Q

Location of Lungs and Pleura

A

Clavicle to 8th rib anteriorly
10th rib laterally
T12 posteriorly

37
Q

Pneumothorax

A

Air in Pleural Space

38
Q

Alveoli

A

Size is a function of both gravity and lung volume

Average diameter ~0.05-
0.33mm

Largest at apex of lung (more negative intrapleural pressure) & smallest at base of lung

Gas exchange on thin side (no intestitium and few organelles) (~0.4μm thick)

Thick side provides support (interstitial space) (1-
2 μm)

50-100m2 surface area for gas exchange

39
Q

Laplace’s Law

A

Tension within wall of sphere filled to a particular pressure depends on the radius of the sphere

P = 2T/R

Formula that describes why small alveoli tend to collapse (atelectasis)

Lecture 2, Slide 13

40
Q

Pulmonary Epithelium

A

Type I pneumocytes
Flat cells, form tight junctions with one another
Prevent passage of large oncotically active molecules into alveolus

Type II pneumocytes
More numerous
Occupy <10% of alveolar space
Cuboidal cells
Produce and secrete surfactant
Able to undergo cell division
Produce type I pneumocytes
Resistant to hypoxia

41
Q

Interstitial Space

A

The space between cells in the body

42
Q

Pulmonary Circulation

A

Gas exchange with alveoli

Low pressure (25/10mmHg)

Can accommodate large increase in blood flow with no change in pressure
Does so by vascular distension and recruitment of unperfused capillaries

Hypoxia is the main stimulus for an increase in pulmonary vascular resistance via hypoxic pulmonary vasoconstriction
Only vascular bed where hypoxia/hypercarbia lead to vasoconstriction; everywhere else in the body hypercarbia and hypoxia causes vasodilation to occur.

43
Q

Bronchial Circulation

A

Supplies parenchyma of the lung itself

Drains to L heart with pulmonary vein
Deoxygenated blood = physiological shunt

Descending thoracic aorta gives rise to the L and R bronchial arteries
Supply oxygenated blood to lungs (connective tissue, septa, bronchi) and after joins pulmonary veins without oxygenation

44
Q

Control of Ventilation In Brain

A

Located in Brain Stem

MEDULLA
Breathing Regulation
Dorsal respiratory group (DRG)
Inspiratory center
“pacemaker” for respiratory system

Ventral respiratory group (VRG)
Expiratory coordinating center

PONTINE CENTERS
Apneustic center
Sends impulse to DRG, designed to sustain inspiration

Pneumotaxic center
Limit depth of inspiration

45
Q

Chemical Control of Ventilation

A

Peripheral chemoreceptors
Composed of carotid and aortic bodies
Respond to:
lack of oxygen
↑ CO2
↑ H+

Central chemoreceptors
Located in medulla
Respond to CO2, H+

46
Q

Mechanism of Breathing

A

INSPIRATION
Initiated by creating sub-atmospheric pressure (-5 cm H2O) in alveoli by increasing volume of thoracic cavity by action of inspiratory muscles

Diaphragm generates the negative intrathoracic pressure
Primary ventilatory muscle
Innervation from C3-5
(“C3-4-5 keeps the diaphragm alive”)

External intercostal muscles
Innervation by intercostal nerves (T1-T12)

EXPIRATION
Initiated by creating intra-alveolar pressure that is higher than atmospheric pressure & flow to mouth results

During relaxed breathing, initiated by relaxation of diaphragm and external intercostals

Normally passive process

47
Q

Accessory Muscles of Breathing

A

CERVICAL STRAP MUSCLES
Most important inspiratory accessory muscles
Primary inspiratory muscles when diaphragm is impaired
Omohyoid
Sternohyoid
Thyrohyoid

ABDOMINAL MUSCLES
Most powerful muscles of active expiration
Important for expulsive efforts (i.e. coughing)

Other muscles with less contribution:
Sternocleidomastoid
Intercostals
Large back and intervertebral muscles of shoulder girdle

48
Q

Lung Volumes and Capacities

A

Tidal Volume (VT)
Each normal breath
~500mL (~ 6-8mL/kg)

Inspiratory Reserve Volume (IRV)
Maximal additional volume that can be inspired above tidal volume
~3000mL

Expiratory Reserve Volume (ERV)
Maximal volume that can be expired below tidal volume
~1100mL

Residual Volume (RV)
Volume remaining after maximal exhalation
~1200mL

Total lung capacity (TLC)
RV+ERV+VT+IRV
~5800mL

Functional Residual Capacity (FRC)
RV+ERV
~2300mL

Lecture 2, Slide 25

49
Q

Functional Residual Capacity (FRC)

A

Lung volume at end of a normal exhalation

Measured by nitrogen wash-out, helium wash-in, or total body plethysmography

During apnea this is the reservoir of O2

GA ↓ FRC ≈ 400mL, supine position ≈ 800mL

Factors that alter FRC
Body habitus – directly proportional to height
Obesity dec FRC, 2° reduced chest compliance
Posture – decr. when moved from upright to supine/prone
2° reduced chest compliance
Lung disease – decr. Restrictive disorders
Diaphragmatic tone – contributes either way
Ascites, abdominal surgery, & pregnancy

50
Q

FRC and O2 Stores

A

When apneic, existing O2 stores consumed by cellular metabolism
Rate of O2 consumption at rest is 1 MET (Metabolic equivalent)
Approximately 3.5ml/min/kg of O2
Average 70kg adult ~ 250ml of O2/min

If 21% FIO2
->0.21 x 2300mL = 483mL of O2 in lungs
Time to consumption of O2 stores: 483/250 = 1.9 mins

If 100% FIO2
-> 1.0 x 2300mL = 2300mL of O2 in lungs
Time to consumption of O2 stores: 2300/250 = 9.2 mins

51
Q

Closing Capacity

A

Closing Capacity(CC)
Volume at which small collapsible airways begin to close in dependent parts of the lung
Alveoli continue to be perfused, but no longer ventilated
intrapulmonary shunting
hypoxia

Measured using tracer gas (Xenon-133) which is inhaled near residual volume and then exhaled from total lung capacity

Normally well below FRC
Inc. with age
44yo CC=FRC in supine position
66yo CC=FRC in most upright individuals

Increased by smoking, obesity, aging, and supine position

52
Q

Vital Capacity

A

Maximum volume of gas that can be exhaled following maximal inspiration

Dependent on respiratory muscle strength and chest- lung compliance

Normal ~60-70mL/kg

53
Q

Forced Vital Capacity

A

Measuring vital capacity as an exhalation that is hard and as rapid as possible

54
Q

Forced Expiratory Volume (FEV1)

A

Forced volume in 1 second (can go to 2 or 3s)

COPDers have a lower FEV1 than normal

Less than 50% of normal indicates greatest risk of complications

55
Q

Ratio of FEV1/FVC

A

Ratio of FEV1/FVC ≥80% in normal adults is proportional to degree of airway obstruction

Lecture 2, Slide 31

56
Q

Flow-Volume Loop

A

A “flow volume loop” is a graphical representation of airflow (measured in liters per second) plotted against lung volume (in liters) during a forced breath in and out, essentially showing how quickly air can be moved at different lung volumes, which is used to diagnose and localize airway obstructions in the lungs by analyzing the shape of the loop produced during a test; a normal loop has a characteristic shape, while abnormalities like “dips” or flattened sections indicate potential issues like asthma or upper airway obstruction depending on where the abnormality occurs on the loop.

Lecture 2, Slides 32, 33

57
Q

Restrictive Lung Disease

A

Decreased lung compliance or increase in lung resistance

FEV1/FVC normal

Volume is the problem

Static lung compliance

Ventilator Management:
Increase O2, PEEP, RR
Decrease TV

Extrinsic Pulmonary Disorders
Pleura, chest wall, diaphragm
Pleural Effusions
Pneumothorax
Masses

Intrinsic Pulmonary Disorders
Pulmonary Edema
Pneumonia
Pneumonitis-(aspiration)
ARDS

58
Q

Obstructive Lung Disease

A

Most common

Increased resistance to airflow

Results in air trapping (can’t breathe out)

FEV1/FVC decreased

Flow is the problem

Associated with Dynamic Compliance

Ventilator Management:
Increase I:E Ratio and decrease RR to allow more time to exhale
Allow higher EtCO2 because of dead space volume gradient

Asthma
Emphysema
Bronchitis
Cystic Fibrosis

59
Q

Pulmonary Compliance

A

The relationship between the ∆P and the resultant volume increase ∆V of the lungs and thorax

Compliance = change in volume (V)/ change in pressure (P)

Either dynamic (peak) or static (plateau)

60
Q

Static Compliance

A

Volume/(Plateau Pressure – PEEP)

Reflects elastic resistance of lung and chest wall

Plateau pressure is when air flow stops

Alveoli only

Pneumonia, effusion, atelectasis

61
Q

Dynamic Compliance

A

Volume/(Peak Inspiratory Pressure-PEEP)

Reflects static compliance and airway resistance

Always lower than static compliance because PIP is always higher than plateau pressure

Peak pressure is generated when air flows

Airways AND alveoli

Asthma, bronchospasm, obstruction
AND Pneumonia, effusion, atelectasis

62
Q

Airway Resistance

A

Poiseuille’s Law… Lecture 2, Slide 40

Force through orifice is
Proportional
to change in pressure
to radius of orifice to 4th power
Inversely proportional
to viscosity
to length

63
Q

Laminar Flow

A

Occurs when gas passes down parallel-sided tubes at less than a certain critical velocity
Airways below main bronchi

64
Q

Orifice Flow

A

Occurs at severe constrictions such as a nearly closed larynx or a kinked ET

65
Q

Turbulent Flow

A

When flow exceeds the critical velocity it becomes turbulent (i.e. flow in the trachea)

Four conditions change laminar flow to turbulent
high gas flows
sharp angles within the tube
branching in the tube
a change in tube diameter

66
Q

Alveolar Ventilation in Lungs

A

R lung > L (53% vs. 47%)

Lower < upper

Pleural pressure ↓ 1 cmH2O for every 3 cm decrease in lung height

67
Q

Distribution of Ventilation and Perfusion

A

5 L/min blood flow to lungs
~70-100mL in pulmonary capillaries undergoing gas exchange

Capillaries perfuse more than 1 alveolus

Hypoxic pulmonary vasoconstriction
Blood flow to an unventilated area is shut down and diverted
Decreases perfusion to non-functioning areas to overcome ventilation perfusion mismatch
Anesthesia can alter this compensatory mechanism
Hypoxia and acidosis
-> pulm. vasoconstriction
Hypocapnia
-> pulmonary vasodilation
Systemic circulation has opposite effect

68
Q

Zones of West

A

3 zones of perfusion – regardless of position

Lower portions
more blood flow
less ventilation

Higher portions
less blood flow
more ventilation

Zone 1 – upper = PA>Pa>Pv
Alveolar pressure continually occludes pulm. capillaries

Zone 2 – middle = Pa>PA>Pv
Pulm. capillary flow is intermittent and varies with respiration

Zone 3 – lower = Pa>Pv>PA
Pulm. capillary flow is continuous

69
Q

Ventilation and Perfusion Ratios

A

V = Alveolar ventilation ~4L/min
Q = Pulmonary capillary perfusion ~5L/min

V/Q ratio relates to the efficiency with which lung units resaturate venous blood with O2 and eliminate CO2

Overall 0.8 for individual lung units
Can range from
1:1 = Normal, 0.3 to 3.0, most ~1.0
1:0 = Dead Space
0:1 = Shunt

0 = no ventilation, absolute shunt
∞ = no perfusion, absolute dead space

70
Q

Dead Space

A

The portion of VT that does not participate in gas exchange

Anatomic dead space
The gas that ventilates the conducting airways (oro-nasopharynx to terminal bronchioles)

Alveolar dead space
Alveolar gas that doesn’t take part in gas exchange b/c of
underperfused alveoli (West zone 1)
“wasted ventilation”
Can be caused by large tidal volumes/PEEP

Physiologic dead space
Sum of anatomic and alveolar dead space

Normally ~33%

71
Q

Calculate Dead Space

A

PaCO2- etCO2 gradient
Normally 3-5 mmHg

Bohr Equation=Physiological dead space

72
Q

Alveolar Gas Equation

A

At sea level
PAO2 = 0.21(760-47) – 40/.8
PAO2 = 99.7 mmHg

Lecture 2, Slide 51

73
Q

Arterial Oxygen Tension

A

PaO2 = 120 – (Age/3)
Normally 60-100 mmHg

A-a gradient
PAO2-PaO2
Normally ~15
Increases w/ age

74
Q

A-a Gradient Example

A

A 40 year old patient comes in with signs of hypoxia due to a narcotic overdose. ABG show 7.3 ph, co2 of 55, Pao2 of 65, pulse ox is reading 88% and RR is 5 on room air. Calculate the A-a gradient.

A-a oxygen gradient = [(FiO2x [Patm - PH2O]) - (PaCO2÷ R)] - PaO2
[(0.21) x (760-47) – (55 ÷ 0.8)] – 65=15.98

Normal A-a gradient, we can then conclude, is due to hypoventilation and not a gas exchange issue.

75
Q

A-a Gradient Example

A

A patient with pulmonary edema is on 80% oxygen (intubated) and their abg shows ph 7.31/ co2 55/pao2 65/86% pulse ox reading.

-a oxygen gradient = [(FiO2x [Patm - PH2O]) - (PaCO2÷ R)] - PaO2A-a gradient = [(0.80) x (760-47) – (55 ÷ 0.8)] – 65=436.65

This proves the patient is not being hypoventilated but instead has an issue with gas exchange. The pulmonary edema must be treated to see their pulse ox reading increase.

76
Q

R to L Shunts

A

Desaturated mixed venous blood from the right heart returns to the left heart without being resaturated with O2 in the lungs

CAN produce hypoxia (cannot be overcome by increasing FIO2)

Areas where V/Q = 0
(blood shunted away from ventilated areas)
2-5% of cardiac output is normally shunted through postpulmonary shunts which include:
Thebesian
Bronchial
Mediastinal
Pleural veins

77
Q

L to R Shunts

A

Cannot produce hypoxia
Septal defect (SD)

78
Q

Blood Oxygen Content

A

CaO2 = (1.39 x Hgb x SaO2) + (PaO2 x .003)
Expressed in units of mL/dL or mL/100mL

Important aspect of equation reflects that simply increasing dissolved O2 is 1000x less effective than binding O2 to hemoglobin (Hgb)

In other words, increasing blood carrying capacity more effective to improve oxygenation than increasing amount of dissolved blood (ie, Increasing FiO2)

NSU AA Denver (1 decks)

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