pulm

Question 1

formula for physiologic dead space?

Answer 1

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

PaCO2 = alveolar PCO2
PECO2 = expired air PCO2

** Taco, Paco, Peco, Paco!

Question 2

formula for minute ventilation?

Answer 2

VE = VT * RR

Question 3

formula for alveolar ventilation?

Answer 3

VA = (VT - VD) * RR

Question 4

lung/chest wall dynamics at FRC?

Answer 4

inward lung pull = outward chest wall pull

systemic P = atmospheric

Question 5

lung pressures at FRC?

Answer 5

airway and alveolar P = 0

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

Question 6

dz that increase/decrease compliance?

Answer 6

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

Question 7

taut form of Hb?

Answer 7

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

Question 8

relaxed form of Hb?

Answer 8

oxygenated

positive cooperativity and negative allostery

Question 9

fetal Hb affinity for 2,3 BPG?

Answer 9

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

Question 10

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

Answer 10

methemoglobin - ferric (Fe 3+)

Question 11

cyanosis and chocolate colored blood?

Answer 11

methemoglobinemia

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

Question 12

Hb bound to CO?

Answer 12

carboxyhemoglobin

Question 13

CO causes what shift in Hb-O2 dissociation curve?

Answer 13

LEFT shift = decreased O2 unloading in tissues

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

Question 14

what causes right shift in Hb-O2 curve?

Answer 14

Acid
CO2
exercise
2,3 BPG
altitude
temperature

Question 15

formula for O2 content of blood?

Answer 15

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

Question 16

how much O2 can 1g of Hb bind?

Answer 16

1.34 mL O2

Question 17

when do you see cyanosis?

Answer 17

deoxygenated Hb > 5 g/dL

Question 18

what is approx O2 binding capacity?

Answer 18

20 mL O2/dL

Question 19

how does CO poisoning affect blood O2 parameters?

Answer 19

decreased Hb O2 saturation, decreased total O2

normal [Hb] and normal PaO2

Question 20

how does anemia affect blood O2 parameters?

Answer 20

decreased [Hb] and decreased total O2

normal Hb O2 saturation and PaO2

Question 21

how does polycythemia affect blood O2 parameters?

Answer 21

increased [Hb] and increased total O2

normal Hb O2 saturation and PaO2

Question 22

which gases are perfusion limited?

Answer 22

O2 (in normal lung)
CO2
N2O

Question 23

which gases are diffusion limited?

Answer 23

O2 (in emphysema, fibrosis)

CO

Question 24

formula for diffusion of gas?

Answer 24

Vgas = A/T * (difference in partial P)
A = area
T = alveolar wall thickness

• • emphysema causes decreased A
• • fibrosis causes increased T

Question 25

alveolar gas equation?

Answer 25

PAO2 = PIO2 - (PaCO2/R) ** at sea level, room air PAO2 = 150 mmHg - (PaCO2/0.8)

Question 26

causes of hypoxemia with normal A-a gradient?

Answer 26

high altitude | hypoventilation

Question 27

causes of hypoxemia with increased A-a gradent?

Answer 27

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

Question 28

causes of hypoxia?

Answer 28

decreased CO hypoxemia anemia CO poisoning

Question 29

V/Q at lung apex vs base?

Answer 29

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

Question 30

V, Q largest at bases or apices of lung?

Answer 30

both largest at base | perfusion has larger difference between base and apex

Question 31

how does exercise affect V/Q distribution?

Answer 31

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

Question 32

forms of CO2 in blood?

Answer 32

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

Question 33

Haldane effect?

Answer 33

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

Question 34

Bohr effect?

Answer 34

increased H+ from tissue metabolism --> favors O2 unloading

Question 35

changes in response to high altitude?

Answer 35

increase in: ventilation, EPO, 2,3BPG, mitochondria increase in renal HCO3 excretion to compensate for respiratory alkalosis ** chronic hypoxic pulmonary vasoconstriction --> RVH

Question 36

changes in response to exercise?

Answer 36

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