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step 1 - physiology > pulm > Flashcards

pulm Flashcards

1
Q

formula for physiologic dead space?

A

VD = VT * (PaCO2 - PECO2) / (PaCO2)

PaCO2 = alveolar PCO2
PECO2 = expired air PCO2

** Taco, Paco, Peco, Paco!

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2
Q

formula for minute ventilation?

A

VE = VT * RR

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3
Q

formula for alveolar ventilation?

A

VA = (VT - VD) * RR

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4
Q

lung/chest wall dynamics at FRC?

A

inward lung pull = outward chest wall pull

systemic P = atmospheric

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5
Q

lung pressures at FRC?

A

airway and alveolar P = 0

intrapleural P < 0 (~ -5) –> prevents PTX

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6
Q

dz that increase/decrease compliance?

A

increase: emphysema, aging
decrease: fibrosis, PNA, edema

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7
Q

taut form of Hb?

A

deoxygenated
low affinity for O2
favored by increased Cl, H, CO2, 2,3BPG

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8
Q

relaxed form of Hb?

A

oxygenated

positive cooperativity and negative allostery

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9
Q

fetal Hb affinity for 2,3 BPG?

A

lower affinity for 2,3 BPG –> higher affinity for O2 (LEFT shift in dissociation curve)

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10
Q

oxidized form of Hb, decreased affinity for O2, increased affinity for cyanide?

A

methemoglobin - ferric (Fe 3+)

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11
Q

cyanosis and chocolate colored blood?

A

methemoglobinemia

    • tx with methylene blue
    • can be induced with nitrites/thiosulfate and benzocaine –> treat cyanide poisoning
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12
Q

Hb bound to CO?

A

carboxyhemoglobin

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13
Q

CO causes what shift in Hb-O2 dissociation curve?

A

LEFT shift = decreased O2 unloading in tissues

** CO has 200x greater affinity for Hb than O2

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14
Q

what causes right shift in Hb-O2 curve?

A 
Acid
CO2
exercise
2,3 BPG
altitude
temperature
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15
Q

formula for O2 content of blood?

A

O2 content = (O2 binding capacity * % saturation) + dissolved O2

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16
Q

how much O2 can 1g of Hb bind?

A

1.34 mL O2

17
Q

when do you see cyanosis?

A

deoxygenated Hb > 5 g/dL

18
Q

what is approx O2 binding capacity?

A

20 mL O2/dL

19
Q

how does CO poisoning affect blood O2 parameters?

A

decreased Hb O2 saturation, decreased total O2

normal [Hb] and normal PaO2

20
Q

how does anemia affect blood O2 parameters?

A

decreased [Hb] and decreased total O2

normal Hb O2 saturation and PaO2

21
Q

how does polycythemia affect blood O2 parameters?

A

increased [Hb] and increased total O2

normal Hb O2 saturation and PaO2

22
Q

which gases are perfusion limited?

A

O2 (in normal lung)
CO2
N2O

23
Q

which gases are diffusion limited?

A

O2 (in emphysema, fibrosis)

CO

24
Q

formula for diffusion of gas?

A 
Vgas = A/T * (difference in partial P)
A = area
T = alveolar wall thickness
    • emphysema causes decreased A
    • fibrosis causes increased T
25
Q

alveolar gas equation?

A

PAO2 = PIO2 - (PaCO2/R)

** at sea level, room air PAO2 = 150 mmHg - (PaCO2/0.8)

26
Q

causes of hypoxemia with normal A-a gradient?

A

high altitude

hypoventilation

27
Q

causes of hypoxemia with increased A-a gradent?

A

V/Q mismatch
diffusion limitation
R-to-L shunt

28
Q

causes of hypoxia?

A

decreased CO
hypoxemia
anemia
CO poisoning

29
Q

V/Q at lung apex vs base?

A

apex: V/Q = 3 (ventilation > perfusion)
base: V/Q = 0.6 (perfusion > ventilation)

30
Q

V, Q largest at bases or apices of lung?

A

both largest at base

perfusion has larger difference between base and apex

31
Q

how does exercise affect V/Q distribution?

A

vasodilation of apical capillaries –> increased perfusion –> V/Q at apex approaches 1

32
Q

forms of CO2 in blood?

A

HCO3 = 90%
HbCO2 = 5% (CO2 binds at N-terminus of globin –> favors taut form)
dissolved CO2 = 5%

33
Q

Haldane effect?

A

Hb oxygenation in lungs –> H+ dissociation from Hb –> CO2 formation –> CO2 release from RBCs

34
Q

Bohr effect?

A

increased H+ from tissue metabolism –> favors O2 unloading

35
Q

changes in response to high altitude?

A

increase in: ventilation, EPO, 2,3BPG, mitochondria
increase in renal HCO3 excretion to compensate for respiratory alkalosis

** chronic hypoxic pulmonary vasoconstriction –> RVH

36
Q

changes in response to exercise?

A

increase in: CO2 prod, O2 consumption, ventilation rate, pulm blood flow
decrease in pH
V/Q ratio more uniform b/w apices and bases

    • PaO2 and PaCO2 STAY THE SAME
    • increase in venous CO2 and decrease in venous O2

step 1 - physiology (8 decks)

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