UNIT 1 Respiratory Flashcards
Which muscles tense & relax the vocal cords? Which muscles abduct & adduct the vocal cords?
Tense & Relax:
- cricothyroid “cords tense”
- thyroarytenoid “they relax” & vocalis
Abduct & Adduct:
- thyroarytenoid & lateral cricoarytenoid: adduct
- posterior cricoarytenoid: abduct
Which muscles abduct & adduct the vocal cords?
posterior cricoarytenoid: “please come apart”
lateral cricoarytenoid: “let’s close the airway”
Describe the sensory innervation of the upper airway
Trigeminal (CN V)
V1 (opthalmic): nares & anterior 1/3 of septum
V2 (maxillary): turbinates & septum
V3 (manidbular): anterior 2/3 of tongue
Glossopharyngeal (CN IX)
posterior 1/3 of tongue, soft palate, oropharynx, vallecula, anterior of epiglottis
SLN
internal branch: posterior side of epiglottis –> level of VC
external branch: no sensory
RLN
below VC –> trachea
How does RLN injury affect integrity of the airway?
Bilateral:
acute = respiratory distress d/t unopposed action of the CT muscles)
chronic = no respiratory distress
Unilateral
no respiratory distress
How does SLN injury affect the integrity of the airway?
Bilateral:
hoarseness but no respiratory distress
Unilateral:
no respiratory distress
Name 3 airway blocks, and ID the key landmarks for each one.
- glosspharyngeal block: palatoglossal arch @ the anterior tonsillar pillar.
- SLN block: greater cornu of hyoid.
- Transtracheal block: CT membrane
What are the 3 paired & 3 unpaired cartilages of the larynx?
unpaired: epiglottis, thyroid, cricoid
paired: corniculate, cuniform, arytenoid
What is the treatment for laryngospasm?
100% FiO2 remove noxious stimuluation deepen anesthesia CPAP 15-20cmH2O open airway w/ head extension, chin lift Larson's maneuver succinylcholine
Describe how the respiratory muscles function during the breathing cycle.
Inspiration:
- diaphragm & external intercostals (tidal breathing)
- accessory: sternocleidomastoid & scalene m.
Expiration:
- usually passive
- active via abdominal musculature (rectus abdominis, transverse abdominis, internal & external obliques) & secondarily via internal intercostals
What is the difference between minute ventilation & alveolar ventilation?
MV: air in a single breath x # breaths per minute (Ve = Vt*RR)
AV: only measures the fraction of Ve that is available for gas exchanges (i.e. it removes anatomic dead space gas) (AV = (Vt-dead space)*RR)
Define the 4 types of dead space.
- Anatomic (air confined to the conducting airways)
- Alveolar (alveoli that are ventilated but not perfused)
- Physiologic (Anatomic + Alveolar Vd)
- Apparatus (Vd added by airway equipment)
Provide an example for each type of dead space.
- Anatomic = trachea
- Alveolar = Zone 1 alveoli
- Physiologic = see above
- Apparatus = face mask
What does the alveolar compliance curve tell you?
alveolar ventilation is a function of alveolar size & it’s position on the alveolar compliance curve.
- best ventilated alveolar are the most compliant (steep slope of curve)
- worst ventilated alveoli are the least compliant (flat portion of the curve)
What does the V/Q ratio represent?
V/Q is the ratio of ventilation to perfusion
- normal MV = 4L/min
- normal CO = 5L/min
- -> normal V/Q = 0.8
dead space V/Q –> infinity
shunt V/Q –> 0
Define the West zones of the lungs
Zone 1
PA>Pa>Pv
dead space (ventilation w/out perfusion)
Zone 2
Pa>PA>Pv
waterfall (normal physiology)
Zone 3
Pa>Pv>PA
shunt (perfusion w/out ventilation)
Zone 4
Pa>Pist>Pv>PA
pressure in the interstitial space (i.e. pulmonary edema) impairs ventilation & perfusion
Recite the alveolar gas equation
PAO2 = FiO2(Pb-PH2O)-(PaCO2/RQ)
tells us that hypoventilation can cause hypercarbia & hypoxemia.
normal = approx 106mmHg
Pb = 760mmHg sea level PH2O = 47mmHg RQ = CO2 elimination/O2 consumption = 200/250 = 0.8 - RQ = 1 --> over feeding - RQ < 0.7 --> starvation
What is the A-a gradient and what factors affect it?
difference b/n alveolar oxygen (PAO2) & arterial oxygen (PaO2)
- helps diagnose cause of hypoxemia by quantifying the amount of venous admixture
- it is normally 5-15mmHg
- it is increased by high FiO2, aging, vasodilators, R–>L shunting, and diffusion limitation
List the 5 causes of hypoxemia. Which ones are reversed w/ supplemental oxygen?
- Reduced FiO2
- Hypoventilation
- Diffusion Limitation
- V/Q mismatch
- Shunt
1-4 are reversed w/ supplemental oxygen.
Define the 5 lung volumes & give reference values for each.
- inspiratory reserve volume (3000mL)
- tidal volume (500mL)
- expiratory reserve volume (1100mL)
- residual volume (1200mL)
- closing volume (variable - approaches RV in healthy young patients)
Define the lung capacities & give reference values for each.
- total lung capacity (5800mL)
- vital capacity (4500mL)
- inspiratory capacity (3500mL)
- functional residual capacity (2300mL)
- closing capacity (variable)
What factors influence FRC?
FRC = RV + ERV (35mL/kg)
conditions that reduce FRC tend to reduce outward lung expansion and/or reduce lung compliance –> zone III (shunt) increases. PEEP restores FRC by reducing zone III
- position changes
- increased intraabdominal pressure/contents
- anesthesia/NMB
- surgical displacement
COPD or any condition that causes air trapping increases FRC
Why can’t spirometry measure FRC?
Because it contains RV & the RV cannot be measured by spirometry
What tests can measure FRC?
nitrogen washout
helium wash in
body plethysmography
What is closing volume & what increases it?
the point at which dynamic compression of the airways begins.
the volume above residual volume where the small airways begin to close during expiration
CLOSEP:
- COPD
- LVF
- Obesity
- Supine position
- extreme age
- pregnancy
State the equation and normal value for oxygen carrying capacity
CaO2 = SaO2Hgb1.34 + PaO2*0.003
normal = 20mL O2/dL
State the equation and normal value for oxygen delivery
DO2 = CaO2CO10
normal = 1000mL O2/min
Discuss the factors that alter oxyhemoglobin dissociation curve
Left shift (love, increased affinity, decreased offloading to the tissues)
- decreased temperature
- decreased 2,3-DPG
- decreased CO2
- alkalosis/decreased [H+}
- abnormal Hgb (HgbF, HgbCO, HgbMet)
Right shift (release, decreased affinity, increased offloading to the tissues)
- increased temperature
- increased 2,3-DPG
- increased CO2
- acidosis/increased [H+]
How is CO2 transported in the blood?
bicarbonate 70%
bound to Hgb 23%
dissolved in plasma 7%
CO2–> HCO3- requires carbonic anhydrase & release of HCO3- from RBC to plasma causes Cl- shift (aka Hamburger shift)
–> RBC increases in size
Describe the Bohr effect
describes O2 carriage
states that increased CO2 & decreased pH causes RBC to release O2
Describe the Haldane effect
describes CO2 carriage
states that increased O2 causes RBC to release CO2 (occurs in the lungs)
List the 3 primary causes of hypercapnia and provide examples of each
- increased CO2 production (sepsis, overfeeding, malignant hyperthermia, shivering, seizures, thyroid storm, burns)
- decreased CO2 elimination (a/w obstruction, increased Vd, increased Vd/Vt, ARDS, COPD, respiratory depression, drug OD, inadequate NMB reversal)
- rebreathing (incompetent one-way valve, exhausted soda lime)
Describe the 4 areas in the respiratory center
Medullary Respiratory Centers:
- Dorsal respiratory center: active during inspiration (respiratory pacemaker)
- Ventral respiratory center (active during expiration)
Pontine Respiratory Centers:
- Pneumotaxic center (upper pons): inhibits the DRC
- Apneuristic center (lower pons): stimulates DRC
Contrast the location & function of the central & peripheral chemoreceptors.
Central:
- located in the medulla
- responds to the [H+] in the CSF ([H+] is a function of the PaCO2 of the blood)
Peripheral:
- located in the carotid bodies: nerves of Hering –> CN IX (glossopharyngeal)
- located in the aortic arch (vagus CN X)
- respond to decreased O2, increased CO2, and increased H+
Which reflex prevents overinflation of the lungs?
Hering-Breuer inflation reflex
What is hypoxic pulmonary vasoconstriction?
minimizes shunt by reducing blood flow through poorly ventilated alveoli
a low PAO2 (NOT arterial) is the trigger that activates HPV.
- effect begins immediately & takes 15mins for full effect.