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USMLE Step 1 Random Facts > Respiratory > Flashcards

Respiratory Flashcards

1
Q

area of lung w/ largest physiologic dead space

A

apex

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2
Q

IC =

A

IRV + TV

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3
Q

FRC =

A

RV + ERV

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4
Q

VC =

A

IRV + TV + ERV

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5
Q

TLC =

A

IRV + TV + ERV + RV

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6
Q

Vd (physiologic dead space) =

A

Vt x [(PaCO2 - PECO2)]/PaCO2

Vt = tidal vol
PECO2 = expired air CO2
PaCO2 = arterial CO2

=anatomic dead space + functional dead space (ex. in apex of lung)

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7
Q

equilibration of O2 in NORMAL individual @ rest is what-limited?

A

perfusion-limited

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8
Q

what causes equilibration to become diffusion-limited?

A

emphysema, pulmonary fibrosis, increased exercise

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9
Q

what does it mean to be diffusion-limited?

A

gas doesn’t equilibrate by the time blood reaches end of capillary

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10
Q

what does it mean to be perfusion-limited?

A

diffusion only increased IF blood flow increases

equilibration normally occurs along first 1/3 of capillary

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11
Q

primary TB likes to be where?

A

lower lung fields

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12
Q

2ndary TB likes to be where?

A

upper lobes

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13
Q

A-a gradient =

A

PAO2 - PaO2
should be 10-15mmHg
increased in right to left shunt, diffusion limitation, V/Q mismatch

PAO2 = alveolar PO2
PaO2 = arterial PO2
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14
Q

PAO2 equation

A

= 150 - (PaCO2)/0.8

or

= PIO2 - (PaCO2)/R

PIO2 = PO2 in inspired air

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15
Q

causes of hypoxemia w/ normal A-a gradient?

A

high altitude

hypoventilation

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16
Q

causes of hypoxemia w/ increased A-a gradient?

A

V/Q mismatch (pneumonia, COPD, pulm embolism)
R–>L shunt (EIsenmenger synd)
pulmonary fibrosis (diffusion limited)

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17
Q

minute ventilation =

A

TV x breaths/min

ALL air!

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18
Q

alveolar ventilation =

A

(TV - dead space) x breaths/min

ONLY AIR participating in gas exchange

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19
Q

diffusion of gas (Vgas) =

A

A/T x Dk (P1 - P2)

A = area (decreased in emphysema)
T = thickness (increased in pulmonary fibrosis)
Dk (P1 - P2) = diff in partial pressure

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20
Q

in diffusion limited states what’s the main physiologic change

A

increased partial pressure difference b/w alveolar air + pulm capillary blood

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21
Q

cause of primary pulm HTN

A

BMPR2 inactivating mut (inhib vasc SM prolif normally)

TGF-beta!!!

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22
Q

causes of 2ndary pulm HTN

A

COPD
mitral stenosis
recurrent thromboemboli (decreases cross-sectional area of pulm bed)
autoimmune disease
L –> R shunt
sleep apnea
living @ high altitudes (hypoxic vasoconstriction)

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23
Q

PVR =

A

[P(pulm artery) - P(pulm wedge pressure)]/cardiac output

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24
Q

pulm wedge pressure is the same as what?

A

LA pressure

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25
Resistance (R) =
(change in P)/Q Q = flow
26
as viscosity increases, R -->
increases
27
as vessel length increases, R -->
increases
28
as vessel RADIUS increases, R -->
decreases (prop to the 4th power)
29
O2 content of blood =
(O2 binding capacity x %sat) + dissolved O2
30
1g of Hb can normally bind how much O2
1.34mL O2
31
as Hb falls, what changes happen in blood O2
O2 content decreases | O2 sat and arterial pO2 DON'T change!!
32
PAO2 =
150 - PaCO2/0.8
33
if PaO2/FiO2 =
300-500 (normal) | <200 (severe hypoxia)
34
increased A-a gradient usually seen in what state
hypoxemia
35
O2 changes in anemia
decreased TOTAL O2 content | no change in PaO2, O2 sat
36
O2 changes in COPD
decreased PaO2 physio shunt --> decreased O2 extraction ratio decreased blood O2 content
37
O2 changes in exercise
decreased venous PO2 (bc increased demand) right shift of curve PaO2 doesn't change
38
as V/Q --> 0, what happens?
airway obstruction, aka SHUNT! | 100% O2 doesn't improve condition bc air can't REACH alveoli
39
as V/Q --> infinity, what happens?
blood flow obstruction aka PHYSIOLOGIC DEAD SPACE | 100% O2 DOES improve if <100% dead space bc blood rerouted to other areas of lung w/ better O2 content
40
physio @ zone 1 (apex) of lung
``` PA > Pa > Pv physiologic dead space V/Q > 1 pulmonary capillaries collapsed decreased perfusion ```
41
physio @ zone 2 of lung
Pa > PA > Pv | pulsatile blood flow (increases as BP increases)
42
physio @ zone 3 (base) of lung
Pa > Pv > PA decreased ventilation V/Q < 1 SHUNTING
43
ventilation and perfusion are BOTH greatest @
base of lung than at apex
44
majority of CO2 transported in blood as
bicarb
45
cabaminohemoglobin (aka CO2 bound to Hb) is bound to Hb at what position?
@ N-terminus of GLOBIN not heme
46
Haldane effect?
lungs --> oxyg of Hb promotes dissociation of H+ from Hb --> leads to CO2 formation --> CO2 released from RBC
47
Bohr effect?
periph tissue --> increased H+ from tissue (from increased pCO2) --> shifts curve right --> unloads O2 (due to histidine side chains found on alpha + beta Hb subunits)
48
RBC exports bicarb out cell by exchanging for
plasma Cl-
49
body response to high altitude
decreased PAO2 --> decreased PO2 increased ventilation --> decreased PCO2 increased erythropoietin --> increased Hct, Hb increased 2,3-BPG (unload more O2) increased mitochondria increased renal excretion of bicarb (to comp for resp alkalosis) chronic hypoxic vasoconstriction --> RVH
50
body response to exercise
increased O2 consumpt + increased CO2 prod increased ventilation rate V/Q ratio uniform throughout lung (bc capillaries dilated in apices to lessen O2 wasting) increased pulm BF bc of increased cardiac output decreased pH (2ndary to lactic acidosis) increased venous CO2, decreased venous O2, decreased venous pH; NO change in PaO2, PaCO2
51
Homan's sign?
dorsiflexion --> calf pain | for DVT!
52
triad for fat embolus
hypoxemia neuro abnorm petechial rash (TCP - from platelets coating fat microglobules)
53
amniotic fluid emboli can cause?
DIC
54
2 histo findings in asthma
``` Curshmann spirals (shed epith forming mucus plugs) Charcot-Leyden crystals (from breakdown of eosinophils in sputum) ```
55
anthracosis
coal mines black lung, but asympt no increased risk of lung cancer UPPER lobes
56
silicosis
foundries, sandblasting macrophages --> release fibrogenic factors --> fibrosis silica can disrupt phagolysosome --> impair macrophages --> increased risk of TB increased risk of bronchogenic carcinoma UPPER lobes "eggshell" calcifications in hilar LN
57
all pneumoconioses increase risk of?
cor pulmonale | Caplan's synd (pneumoconiosis w/ rheumatoid arthritis - present w/ intrapulm nodule)
58
asbestosis
shipbuilding, roofing, plumbing calcified parietal pleural plaques (not precancerous) increased of bronchogenic carcinoma (1), mesothelioma (2) LOWER lobes asbestos bodies - golden-brown rods ("dumbbell shaped") [aka ferruginous bodies - bc contain Fe]
59
Berylliosis
aerospace manufacturing non-caseating granulomas (from CMI) increased risk of lung cancer
60
RF for neonatal RDS
maternal diabetes, pre-maturity
61
therapeutic supplemental O2 in neonatal RDS can lead to?
retinopathy bronchopulmonary dysplasia due to ROS!!
62
low compliance is when
stiff lung and means extra work is required to bring in a normal volume of air (ex. pulm fibrosis)
63
high compliance is when
due to the poor elastic recoil --> no problem inflating the lungs but have extreme difficulty exhaling air **extra work is required to get air out of the lungs. Compliance also increases with increasing age
64
2 lung cancers not ass w/ smoking
BRonchial carcinoid | BRonchoalveolar carcinoma
65
tumors located peripherally
adenocarcinoma | large cell carcinoma
66
tumors located centrally
small cell | squamous cell
67
bronchoalveolar subtype carcinoma from what cells?
Clara cells
68
adenocarcinoma ass w/ what mutation
activating k-ras
69
squamous cell carcinoma of lung arises from?
hilar mass from bronchus
70
mesothelioma features?
hemorrhagic pleural effusions + pleural thickening can arise in tunica vaginalis (sac around testes) as well psammoma bodies
71
SVC synd signs
facial plethora JVD edema of UE
72
pneumonia caused by exacerbation of COPD =
H.influenza
73
granulomatous rxn w/ eosinophils
hypersensitivity pneumonitis
74
chlyothorax findings
milky fluid | increased TG content (from chylomicrons)
75
one cause of spontaneous pneumothorax
rupture of apical blebs (ass w/ paraseptal [distal acinar] emphysema)
76
straddle embolus occludes what
bifurcation of pulm arteries
77
EKG changes/lab changes seen in PE
wide S in lead I large Q, inverted T in lead III "SIQ3T3" elevated D-dimer
78
when in pulmonary vascular resistance lowest?
@ FRC

USMLE Step 1 Random Facts (35 decks)

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