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USMLE Step 1 Random Facts > Respiratory > Flashcards

Flashcards in Respiratory Deck (78):
1

area of lung w/ largest physiologic dead space

apex

2

IC =

IRV + TV

3

FRC =

RV + ERV

4

VC =

IRV + TV + ERV

5

TLC =

IRV + TV + ERV + RV

6

Vd (physiologic dead space) =

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)

7

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

perfusion-limited

8

what causes equilibration to become diffusion-limited?

emphysema, pulmonary fibrosis, increased exercise

9

what does it mean to be diffusion-limited?

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

10

what does it mean to be perfusion-limited?

diffusion only increased IF blood flow increases

equilibration normally occurs along first 1/3 of capillary

11

primary TB likes to be where?

lower lung fields

12

2ndary TB likes to be where?

upper lobes

13

A-a gradient =

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

PAO2 = alveolar PO2
PaO2 = arterial PO2

14

PAO2 equation

= 150 - (PaCO2)/0.8

or

= PIO2 - (PaCO2)/R

PIO2 = PO2 in inspired air

15

causes of hypoxemia w/ normal A-a gradient?

high altitude
hypoventilation

16

causes of hypoxemia w/ increased A-a gradient?

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

17

minute ventilation =

TV x breaths/min

ALL air!

18

alveolar ventilation =

(TV - dead space) x breaths/min

ONLY AIR participating in gas exchange

19

diffusion of gas (Vgas) =

A/T x Dk (P1 - P2)

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

20

in diffusion limited states what's the main physiologic change

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

21

cause of primary pulm HTN

BMPR2 inactivating mut (inhib vasc SM prolif normally)
TGF-beta!!!

22

causes of 2ndary pulm HTN

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

23

PVR =

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

24

pulm wedge pressure is the same as what?

LA pressure

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