Resp Final Flashcards
Larynx: Anatomic Location
Adult: located anterior to 3rd-6th cervical vertebre
At birth: level at C3-4
A-O extension
normally 35 degrees
MP Class. 1 & 2
full view of uvula and tonsillar pillars, soft palate
partial view of uvula or uvular base, partial view of tonsils, soft palate
MP Class. 3
soft palate only
MP Class. 4
hard palate only
Recurrent Laryngeal nerve (CNX)
trachea below VC’s
Internal branch Superior Laryngeal nerve (CNX)
mucus membrane above the VC’s, glottis
Glossopharyngeal nerve (CN IX)
lingual back 1/3, pharyngeal, tonsillar nerves) – oral pharynx, supraglottic region
Sphenopalatine ganglion
middle division of CN V) – nasal mucosa, superior pharnx, uvula, tonsils
Internal SLN
provides sensation to supraglottic & ventricle compartment, STIMULATION CAUSES LARYNGOSPASM
External SLN
provides motor innervation of cricothyroid muscle
Left RLN
passes @ Aortic Arch
Provides Sensory innervation to infraglottis
Motor innervation to all larynx except cricothyroid muscle
Stimulation causes abduction of VC
Damage to RLN cause VC adduction
Trachea
Extends from C6 to T5
At carina (level T5-7) divides into 2 bronchi @ 25cm from teeth
Airway structures that participate in gas exchange
Respiratory Bronchiole
Alveolar Duct
Alveoli
Lung segment with thick smooth muscle (Contraction)
Bronchiole
Phrenic nerve
(C 3,4,5) transmits motor stimulation to diaphragm
Intercostal nerves
(T 1-11) send signals to the external intercostal muscles
The act of inhaling is?
negative-pressure ventilation
FRC =
ERV + RV
Spirometry cannot measure
Residual Volume (RV) thus Functional Residual Capacity (FRC) and Total Lung Capacity (TLC) cannot be determined using spirometry alone
FRC and TLC can be determined by
1) Helium dilution, 2) Nitrogen washout, or 3) body plethysmography
Look at Flow Volume Loop and Obstructions
Slide 19 & 20
Functions of Surfactant (3)
Lowers surface tension of alveoli & lung
Promotes stability of alveoli
Prevents transudation of fluid into alveoli
Poiseuille’s Law
r is radius of tube (to 4th power)
***reducing r by 16% will double the R
***reducing r by 50% will increase R 16-fold
Two mechanisms employed to decrease PVR when PVP rises
Recruitment & Distention (Slide 25)
Pulmonary Hemodynamics
Slide 23 & 24
Pulmonary Cap. characteristics
70-80% of alveolar surface area covered by capillary bed
Functional capillary volume
Capillary volume increases by opening closed segments (recruitment)
70 ml (1 ml/kg body weight) normal volume at rest 200 ml at maximal anatomical volume
Lung Zones
Slide 28
Zone 3 best in upright lung: Pa>Pv>PA
PVR Vasoconstrictors
Reduced PAO2 Increased PCO2 Thromboxane A2 α-adrenergic catecholamines Histamine
PVR Vasodilators
Increased PAO2
Prostacyclin
Nitric oxide
Alveolar hypoxia produces
hypoxic pulmonary vasoconstriction (HPV)
- Localized response of pulmonary arterioles
- Contraction of smooth muscle in small arterioles in hypoxic region
How does HPV improve V/Q
Shift of flow to better ventilated pulmonary regions
Normal alveolar PO2
Minimum ml O2/min
100mmhg
250ml O2/min
Normal alveolar Pco2
Normal CO2 production
40
200ml/min
Alveolar air is expired at
end of exhalation
Fick’s Law
Diff. = (A * Dpp * D) / T
Diff. is diffusion of gas through a tissue membrane
A is cross sectional area of membrane
Dpp is the driving pressure (partial pressure difference)
D is gas coefficient
T is tissue thickness or length through membrane
Physiologic Shunt =
perfusion but no ventilation
V/Q is below normal
Slide 37
Physiologic Dead Space =
ventilation but no perfusion
V/Q greater than normal
Slide 38
Saturation & Corresponding PAO2 Values
100 100+
95 75
90 60
75 40 (mixed venous blood in pulm. artery)
60 30
50 27 (Hb P50 point)
HGB 02 Curve Slide 42
Curve affected in two ways, what are they and which is worse?
Shift in position
Change in shape
A change in shape indicates a greater interference with O2 transport than curve shift
What happens with a right shift
Hb has less affinity for O2, releases O2, saturation will be less for a given PO2
Increased CO2/Temp/H+/2,3 DPG
What happens with a left shift
Hb has higher affinity for O2, binds O2, saturation will be higher for a given PO2
CO2/Temp/H+/2,3 DPG
CaO2 Equation
CaO2 = O2 content in blood (ml/dL)
CaO2 =
SO2 * [Hb] * 1.31) + (PO2 * 0.003
Most C02 is transported as?
Bicarb (70%)
Carbonic Acid (23%)
C02 (7%)
The DRG controls
inspiration & respiratory rhythm
DRG receives signals from three sources
Peripheral chemoreceptors
Baroreceptors
Lung receptors
Chemo sensitive area responds to what?
C02 & H+
CO2 has potent direct effect, via [H], on the chemosensitive area
C02 is what to the blood brain barrier?
highly permeable to blood-brain barrier so blood & brain concentrations are equal
Carotid Bodies are where and respond to what?
stimulated by hypoxemia
Bifurcations in common carotid
Afferent nerve fibers pass via CN IX to act on DRG
Aortic Bodies where and stimulated by what?
hypoxemia
Aortic arch
CN X to DRG
Chemoreceptor Impulse Rate is sensitive to drops in PaO2 from a range?
60 mmHg to 30 mmHg (hypoxia)
High Risk PFT results
FEV1 < 2L
FEV1/FVC < 0.5
VC < 15cc/Kg in adult & < 10cc/Kg in child
VC < 40 to 50% than predicted
Intubation Criteria
Slide 54
Extubation Criteria
VSS, awake & alert,
resp. rate < 30
ABG on FiO2 of 40% PaO2 >70 and PaCO2 <55
MIF is more negative than -20cm H2O
Vital capacity (VC) > 15cc/Kg
ABG Values
pH: 7.35 – 7.45
PCO2: 35 – 45 mmHg
PO2: 75 – 105 mmHg
Bicarbonate: 20 – 26 mmoles/L
Base excess: -3 to +3 mmoles/L
an increase of PCO2 by 10 mmHg causes a?
decrease in pH by 0.08, likewise, a decrease of PCO2 by 10 mmHg will increase pH by 0.08
A-a gradient is a measure of what?
efficiency of lung
Normal A-a = approximately (Age / 3)
Look at slide 58
a decrease in bicarb. by 10 mmoles does what?
decreases the pH by 0.15, likewise, an increase in bicarb. By 10 mmoles increases pH by 0.15
Total body bicarb. deficit equation?
(base deficit * wt in Kg * 0.4), in mEq/L,
usually replace ½ of deficit
Puzzle slide for acid base (Slide 60)
Slide 60
Pulse ox wavelengths
940nm = infrared light, oxyhemoglobin absorbs more of this light, corresponds to 100% saturation
660nm = red light, deoxyhemoglobin absorbs more of this light, corresponds to 50% saturation
Carboxyhemoglobin (COHb)
a SpO2 of 100%, this is an overestimation of the true oxygenation, co-oximeter used to distinguish between the two
Methemoglobin (MetHb)
Fe2 changed to Fe3
absorbs equally at both wavelengths, 1:1, shows a SpO2 of 85%,
Tx’d with low dose methylene blue or ascorbic acid
Fetal _______ and ___________ do not effect pulse Ox
hemoglobin and bilirubin
Capnography rapidly and reliably indicates _______ _______ but does not reliably detect _______ ________
esophageal intubation, endobronchial intubation
What is the gold standard for tracheal intubation
EtCO2
Capnogram
AB segment = beginning exhalation, dead space gas
BC segment = exhalation, mixing of gases
CD segment = alveolar plateau, alveolar rich gas
D point = highest [CO2]
DE = start inspiration
Difficult Airway Algo. (Slide 65)
Slide 65
In the ________ & _______ the _______ lung is better perfused (gravity) & ventilated
Awake, Lateral
dependent
Factors that inhibit HPV
Very high or very low pulmonary artery pressures
Hypocapnia
High or very low mixed venous PO2
Vasodilators: nitroglycerin (NTG), nitroprusside (SNP), b-adrenegic agonists (dobutamine), calcium channel blockers
Inhalation agents
Hypoxia during one lung ventilation*** Slide 68
Slide 68
MH Triggers
by inhaled agents (not N2O) and/or succinylcholine
MH First sign, most sensitive
unexplained tachycardia
MH Most Specific
increasing EtCO2 = hypercapnia, 2-3X
MH S/s
decrease in SaO2 & SpO2, rigidity despite muscle relaxant onboard, dysrhythmias, tachypnea, cyanosis, sweating, unstable BP, mottling of skin, trismus (masseter spasm) after succinylcholine, darkening of blood in surgical field, decreased mixed venous saturation, cola-colored urine, heating and exhaustion of CO2 absorber, hyperthermia
MH Labs
Labs: initial metabolic acidosis then a combined metabolic & respiratory acidosis, hyperkalemia, hypercalcemia, hyperphosphatemia, creatinine kinase (CK) > 1000 IU, myoglobinuria, hypoxemia
Factors that increase MAC
Age: term infant to 6 months of age has the highest MAC requirement
Hyperthermia
Chronic EtOH abuse
Hypernatremia
Drugs that increase CNS catecholamines
Factors that decrease MAC
Hypothermia: for every 1 deg. C drop in body temp – MAC decreases 2 to 5%
Elderly
Pregnancy
Acute EtOH ingestion
Hyponatremia
Severe hypoxemia – PaO2 < 38 mmHg
No effect on MAC
Thyroid gland dysfunction Duration of anesthesia Gender Hyperkalemia Hypokalemia Hypocarbia Hypercarbia
Second Gas effect
The ability of a large volume uptake of a first gas (N2O) to accelerate the rate of rise of the alveolar partial pressure of a concurrently administered companion gas (agent) thus speeding induction
Second gas effect example
Example: (alveolar space): 70% N2O, 30% O2 and ISO 1%____rapid uptake of ½ of the N2O _____35% N2O, 30% O2, and ISO now 1.53%
Diffusion Hypoxia
Avoided by administering 100% O2 following N2O use
Nicotine ________ sympathetic ganglia – catecholamines
stimulates.
catecholamines released from adrenal medulla – increasing HR, BP, and SVR – persists 30 minutes after last cigarette
What to do with bad COPD
Pre-O2 well and avoid instrumentation of airway until deep level of anesthesia
Preop smoking cessation education
Advise stopping at least 12 hours prior to surgery
Cessation of > 8 weeks will reduce post-op pulmonary complications
Bronchospasm & what drugs to avoid
avoid *histamine releasing drugs
Pentothal (STP), Morphine (MSO4), Atracurium, Mivacurium, Neostigmine
Tx with nebulized albuterol especially before extubation
