NBCRNA APEX Exams: Key Terms & Definitions in Medicine

What muscle abducts the vocal cords?

posterior cricoarytenoid

What is the only muscle that tenses (elongates) the vocal cords?

cricothyroid "cords tense"

What muscle opens the glottis?

thyroepiglottic

What two muscles close the glottis?

aryepiglottic

oblique arytenoid

What muscles adduct the vocal cords and arytenoids?

- there are two

lateral cricoarytenoid

transverse arytenoid

What muscle shortens the vocal cords? (relaxes?)

- there are two

thyroarytenoid "they relax"

vocalis

The cricothyroid muscle is innervated by?

external branch of SLN

- the only branch that tenses (elongates) the VCs

The internal branch of the SLN is purely?

- sensory or motor?

sensory

Recurrent laryngeal innervates...

below vocal cords --> the trachea

Branches off vagus in thorax

Motor: all intrinsic except cricothyroid

Glossopharyngeal innervates...

the vallecula

topside of epiglottis

soft palate

oropharynx

post 1/3 of tongue

tonsils

afferent limb of gag reflex

CN IX - sensory

Superior laryngeal innervates...

posterior epiglottis --> vocal cords

Internal branch is sensory - underside of epiglottis

External branch is motor - cricothyroid muscle

Trigeminal (V) V3 innervates...

anterior 2/3 tongue

Trigeminal nerve (V) contains what 3 branches?

V1 ophthalmic (anterior ethmoidal) - nares/ant 1/3 septum

V2 maxillary (sphenopalatine) - turbinates/septum

V3 Mandibular (lingual)

Superior laryngeal nerve block:

3ml at the inferior aspect of the greater cornu of hyoid bone bilaterally

- helps tolerate FO intubation once past the oropharynx

Glossopharyngeal block:

1-2 ml at the tonsillar pillar bilaterally

Transtracheal block:

3-5 ml through the cricothyroid membrane

What is most likely to injure the left RLN while sparing the right RLN?

Mitral stenosis (LA enlargement compresses the nerve and may present as hoarseness)

PDA ligation

Aortic arch aneurysm

Thoracic tumor

Causes of left OR right RLN injury:

parathyroid or thyroid surgery

external pressure from LMA/ETT

neck tumor

neck extension

Where does the right RLN loop?

left RLN loop?

under the right subclavian artery

- left under the aorta (more susceptible to injury)

For the patient in sitting position, order the cartilages from superior to inferior:

cricoid

epiglottis

arytenoid

corniculate

epiglottis

corniculate

arytenoid

cricoid

How many unpaired cartilages present in the larynx?

Paired?

3 unpaired

3 paired

9 cartilages total

Where is the adult larynx located?

Infant larynx?

C3-C6

Infant is C2-C4

What is the narrowest part of the airway? adult/infant

Vocal cords for adult

Cricoid for infant, if paralyzed = vocal cords

Risk factors for intraoperative laryngospasm?

GERD

Exposure to 2nd hand smoke

recent URI

Age < 1 year

HYPOcapnia

light anesthesia

saliva or blood in the upper airway

What is the definition of laryngospasm?

Sustained and involuntary contraction of the vocal cord Adductors that result in the inability to ventilate.

Tensor palatine opens?

nasopharynx

Genioglossus opens?

the oropharynx

Hyoid muscles open?

the hypopharynx

Landmarks for the Larson's maneuver?

posterior: mastoid process

superior: skull base

Anterior: ramus of mandible

Muller's maneuver?

inhaling against a closed glottis

Which type of pneumocystis produce surfactant?

type 2

Three types of pneumocytes?

type 1 - 3

type 1 - cover 80% of alveolar surface

type 3 - macrophages that fight lung infection

Most common etiology of hypoxemia in the PACU?

V/Q mismatch: specifically atelectasis

Result as FRC becomes smaller and there is less radial traction to hold the airways open:

result is atelectasis, R -> L shunt, and hypoxemia

Intrapleural pressure becomes positive during:

The ONLY time intrapleural pressure becomes positive is during forced exhalation, and pneumothorax

What is transpulmonary pressure?

alveolar pressure - intrapleural pressure

- always positive, keeps airway open

- Intrapleural always negative - keeps lungs inflated

What muscles provide the most significant contribution to forced exhalation?

rectus abdominus

Contraction of the inspiratory muscles reduces thoracic pressure and increases thoracic volume, what law is this?

boyles law

What muscles contract during inspiration?

diaphragm and external intercostals (tidal breathing)

accessory muscles: sternocleidomastoid and scalenes

Muscles of exhalation?

active exhalation: abdominal muscles

internal intercostals serve as secondary role in active

Alveolar compliance =

alveolar volume / alveolar pressure

The best ventilated alveoli are the?

most compliant!

- exchange more gas, volumes change more.

these alveoli reside at the steep slope of the curve

The least ventilated alveoli are the?

least compliant!

- exchange less gas, volumes change very little

reside near the top of the curve

Dead space is...

ventilation without perfusion

Shunt is...

perfusion without ventilation

Perfusion is what L/min?

Ventilation?

perfusion = 5L/min (greatest at lung base - gravity)

ventilation = 4L/min (greatest at base - higher compliance)

Compared to spontaneous ventilation, what happens to the Vd/Vt ratio when a patient is placed on a ventilator?

The ratio increases.

What does the Vd/Vt ratio mean?

fraction of the tidal volume lost to dead space

- gas not involved in alveolar gas exchange

Calculations for Vd/Vt ratio?

Vd = 2ml/kg

Vt = 6ml/kg

ex: 150/450 = 0.33%

Mechanical ventilation increases what west zone?

1

- increases alveolar pressure and this increases ventilation relative to perfusion. Increases to 0.5 or 50%

A patients PaCO2 has increases while his etCO2 has decreased, what is likely to contribute to this phenomenon?

Hypotension

COPD

amniotic fluid embolism

When asked about an increased PaCO2-etCO2 ratio, what is it referring to?

what increases dead space ventilation or West Zone 1

What is the most common cause of increased dead space under GA?

other causes?

decreased cardiac output

- other causes: COPD, pulmonary embolism

Anticholinergics, mechanical ventilation, neck extension, adding an HME between y-piece and ETT, and an incompetent unidirectional valve

Where does dead space begin?

at the y-piece

What is the consequence of adding a HME btw the ETT and y-piece?

PaCO2 increases (increased alveolar conc of CO2)

PaO2 decreases

*It increases apparatus dead space

What happens when PaCO2 increases?

increased alveolar concentration of CO2, which causes the alveolar partial pressure of oxygen to DECREASE

What variables are required to calculate the partial pressure of alveolar oxygen?

PAO2 - PP of O2 inside the alveolus

FiO2

Pb - barometric pressure

PH2O -humidity of inspired gas (assume 47)

PaCO2 - PP of CO2 in the blood

RQ - (CO2 production/O2 consumption = 0.8)

What is the alveolar gas equation?

PAO2 = FiO2 x (Pb - PH20) - (PaCO2/RQ)

PAO2 = 0.21 x (760-47) - (PaCO2/0.8)

PAO2 = 0.21 x (713) - (PaCO2/0.8)

What does the alveolar gas equation give context to?

to evaluate the PaO2 provided by an ABG

You can calculate the A-a gradient

How to identify an abnormal A-a gradient?

normal: A-a gradient < FiO2

Abnormal: A-a gradient > FiO2

What is the A-a gradient?

difference between PAO2 and PaO2

helps diagnose the cause of hypoxemia

Causes of a increased A-a gradient?

aging

vasodilators

R -> L shunt (can't fix with supplemental O2) (PFO, DA, VSD)

Diffusion limitation - alveocapilary thickening

Why is the alveolar gas equation important? Examples.

Hypoventilation --> hypercarbia and hypoxemia

supplemental O2 can reverse hypoxemia but NOT hypercarbia....which can go undetected with a pt on supplemental O2

Shunt increases by ____ % for every ____ mmHg of A-a gradient

1% for every 20 mmHg

What venous systems contribute to anatomic shunt?

Empties directly into left side of the heart:

Thebesian veins (drains left heart)

bronchiolar and pleural veins (drains bronchial circ)

Causes of R --> L shunt and increased A-a gradient?

atelectasis

pneumonia

bronchial intubation

intracardiac defect

What are the 3 causes of anatomic shunt?

1. venous blood that empties into the LA

2. R --> L shunt d/t intracardiac lesion (PFO, DA, VSD)

3. AVM that develops as a consequence of liver dx

Venous admixture increases when:

expiratory reserve volume decreases

Whenever you see shunt or venous admixture, what should you think of?!

FRC!!!

Decreased ERV = decreased FRC

Pulmonary vascular resistance is DIRECT/INVERSELY proportional to lung volume?

What does this mean clinically?

Inversely

When FRC decreases, PVR increases.

Venous admixture increases b/c less blood coming into contact with oxygenated alveoli

Clinically: faster rate of arterial desat during arena and an increased A-a gradient

Residual volume is what percentage of TLC?

20%

IRV - volume

3000ml - amount of gas that can be forcibly inhaled after a tidal inhalation

Vt - volume

500 - amt of gas that enters and exits the lungs during tidal breathing

ERV - volume

1100 - volume of gas that can be forcibly exhaled after a tidal exhalation

RV - volume

1200 - volume of gas that remains in lungs after complete exhalation, can't leave the lungs

Closing volume

variable - volume above RV where the small airways begin to close

TLC - volume

5800 IRV+Vt+ERV+RV

VC - volume

4500 IRV+Vt+ERV

IC - volume

3500 IRV+Vt

FRC - volume

2300 RV+ERV

Closing capacity

variable - RV+CV

Causes of decreased FRC!

GA

obesity

pregnancy

neonate

supine, lithotomy, T-burg

paralysis

light GA

High IVF

High FiO2

decreased pulmonary compliance

Causes of increased FRC:

old age

prone, sitting lateral, reverse Tburg

COPD

PEEP

sigh breaths

The etCO2 is 5%, what is this in mmHg?

What law?

38mmHg

Daltons law of partial pressure

Basically (5*760)/100

How much oxygen is consumed by a 70kg healthy adult at rest?

answer in ml/100g/min

0.357 ml/100g/min

VO2 as ml/min = 250ml/min

3.5 ml/kg/min

VO2 as ml/kg/min: 250/70 = 3.57 ml/kg/min or just 3.5

VO2 as ml/100g/min: change kg to 100g

3.57 ml/kg/min = 0.357 ml/100g/min

or if you used 3.5, 0.350 ml/100g/min

EMLA cream toxicity does what to P50 and oxyhemoglobin dissociation curve?

Why?

Tx?

decreases P50 and shifts the curve to the left

EMLA --> prilocaine, which is metabolized to o-toluidine and causes methemoglobinemia

Methemoglobin decreases P50

Tx: Methylene blue 1-2 mg/kg

Bohr effect

describes how changes in acid (PCO2 or H+) alter the carrying capacity of O2 in the blood. It explains why hemoglobin releases O2 at the tissue level and binds O2 in the lungs

REMEMBER: bOHr = Oxygen and Hgb

Haldane effect

describes how changes in PO2 in the blood alter the carrying capacity of CO2 in the blood, and it explains why venous blood can carry more CO2 than arterial blood

Hamburger phenomenon

describes how Cl- is exchanged for HCO3- to maintain electroneutrality when the erythrocyte acts as a buffer

What is the inspiratory pacemaker?

dorsal respiratory center = resp pacemaker

- active during respiration

Ventral respiratory center

active during exalation - in the medulla, tractus solitarius

quiet during normal breathing

Pontine respiratory centers include?

pneumotaxic center and apneustic center

- regulate DRG

Pneumotaxic center?

upper pons

inhibits the DRG (inhibits the PM)

triggers end expiration

strong stimulus = rapid shallow breathing

weak - slow and deep breathing

apneustic center?

lower pons

stimulates the DRG

antagonizes pneumotaxic center

inhibited by pulmonary stretch receptors

What phenomena is responsible for tachypnea that accompanies PE?

J-receptor stimulation

What is J-receptor stimulation?

causes tachypnea, activated by PE or during pulmonary vascular congestion, such as CHF

Hering-Breuer inflation reflex does what?

stops inspiration when the lungs become hyperinflated

Describe hypoxic pulmonary vasoconstriction.

What activates it?

Effect begins?

minimizes shunt by reducing blood flow through poorly ventilated alveoli.

- a low alveolar PO2 (not arterial) is the trigger that activates HPV

- effect beings almost immediately and reaches full effect in 15min

What are some examples that inhibit HPV, therefor increasing shunt?

How do IV anesthetics affect HPV?

Halogenated anesthetics > 1-1.5 MAC

phosphodiesterase inhibitors

dobutamine

vasodilators - nipride

IV ANESTHETICS DO NOT INHIBIT HPV!

What are three causes of hypercapnia?

Increased CO2 production

Decreased CO2 elimination

Rebreathing