Waters III

Question 1

T or F. All O2 delivered from the lungs is delivered to tissue. (or in other words, no O2 is seen in venous circulation)

Answer 1

F. Only about 250ml/min of O2 is delivered out of 1000mL/min in arterial circulation

Question 2

T or F. There is more CO2 in arterial circulation that O2 at any given time

Answer 2

T. Counter-intuitive but there is way more Co2 in the blood (arterial and venous) than O2.

NOTE: There is more Co2 in venous circulation than arterial

Question 3

What is respiratory quotient (RQ)?

Answer 3

The ratio of CO2 produced to O2 consumed by tissue

Question 4

What is a normal RQ?

Answer 4

0.8 (200ml/min produced to 250ml/min used)

Question 5

RQ for carbs? fat? protein?

Answer 5

carbs=1
fat=0.7
protein=0.8

so for fat and protein, t takes more O2 to produce 1 co2

Question 6

Gas exchange between alveolar gas and blood and between blood and tissue is entirely by ____.

Answer 6

diffusion

Question 7

What is the eqn. for Po2?

Answer 7

atmospheric pressure x fraction of O2 molecules in DRY air

or 159 mm Hg usually

Question 8

What happens when air is inspired?

Answer 8

it is warmed to 37C and humidified (aka water vapor is formed)

Question 9

What happens to Po2 when air is inspired?

Answer 9

lowers to 150 mm Hg

(760-47 (for water vapor))*0.21

Question 10

Eqn for conc. of a gas in solution (Henry’s law)

Answer 10

equals a*Px where a=solubility of the gas in solution

thus, two different gases at the same partial pressure can have different concentrations (i.e. CO2 is way more concentrated in water than O2)

Question 11

What is Fick’s Law of Diffusion?

Answer 11

gas flow (volume/time)= (A/thickness)Diffusion constant(P1-P2)

where P1-P2 = conc. gradient

Question 12

What variables of Fick’s eqn. does emphysema affect?

Answer 12

decreased A

Question 13

What variables of Fick’s eqn. does fibrosis affect?

Answer 13

increased thickness

Question 14

T or F. Co2 diffuses up to 20x faster than O2

Answer 14

T.

Question 15

What is the Po2 in alveoli? Why isn’t it the same as the atmosphere?

Answer 15

About 105mm Hg because there is mixing with deoxygenated air

alveolar Co2 (PAco2) is around 40 mm Hg

Question 16

What is the PO2 in arterial (PaO2) blood?

Answer 16

100 mm Hg

Question 17

What is the Pco2 in arterial (Paco2) blood?

Answer 17

40 mm Hg

Question 18

What is the PO2 in venous blood?

Answer 18

40 mm Hg

Question 19

What is the PCO2 in venous blood?

Answer 19

46 mm Hg

Question 20

Eqn for PAco2

Answer 20

k*(CO2 production rate/alveolar ventilation)

where k= 863 mm Hg at BTPS

Question 21

What is ‘hypoventilation’?

Answer 21

increase in PAco2 due to alveolar ventilation not keeping up with Co2 production

Question 22

What factors determine PAo2?

Answer 22

• Pio2 of inspired air (less at high altitude)
• Alveolar ventilation (lower increases PAco2 and decreases PAO2)
• cellular oxygen consumption (higher consumption = higher)

Question 23

Eqn for PAo2

Answer 23

= Pio2- (PAco2/R), where R takes into account Co2 production/O2 consumption

Question 24

What is hypoxemia?

Answer 24

lower than normal Po2 (100 mm Hg)

Question 25

What is the A-a gradient?

Answer 25

PAO2- PaO2 (alveolar- arterial)- used toe examine causes of hypoxemia

Question 26

What is hypoxia?

Answer 26

decrease in O2 delivery to, or utilization by, tissue. Due to decreased blood flow or decreased O2 binding to hemoglobin

Question 27

What is hypercapnia?

Answer 27

higher than normal arterial Pco2. Most often due to hypoventilation

Question 28

Normally oxygen is perfusion limited in the sense that all blood leaving pulmonary capillaries are saturated with O2 due to the short amount of time/distance needed to bind O2 (about 0.3 seconds compared to the 0.75s blood spends in the capillary). What conditions promote diffusion-limited transfer of O2?

Answer 28

• fibrosis
• emphysema
• high altitude
• intense exercise

Question 29

T or F. Pulmonary vascular resistance (PVR) is very low compared to systemic resistance

Answer 29

T. So you can change the resistance easily is needed

Question 30

Eqn for PVR

Answer 30

(pulmonary artery pressure-left atrial pressure (aka pulmonary wedge pressure)) / Cardiac output

Question 31

What is pulmonary HTN defined as?

Answer 31

above 25 mm Hg at rest

Question 32

What causes primary pulmonary HTN?

Answer 32

inactivating mutation in the BMPR2 gene which promotes vascular smooth muscle cell proliferation

Question 33

How is pulmonary blood flow regulated?

Answer 33

hypoxia-induced pulmonary vaso-CONSTRICTION

Question 34

Why would pulmonary vessels constrict with low oxygen?

Answer 34

want to re-route oxygen to low areas

Question 35

Which parts of the lungs receive the most blood flow?

Answer 35

the base due to gravity

Question 36

Where are pulmonary capillaries most susceptible to collapse in the vertical lung upon standing?

Answer 36

at the apex because PA is greater than Pa (which is greater than Pv)

Question 37

Pressures in zone 2 (middle) of the lung

Answer 37

Pa greater than PA greater than Pv

Question 38

Pressures in zone 3 (base) of the lung

Answer 38

Pa greater than Pv greater than PA

Question 39

How does alveolar ventilation change in the vertical lung?

Answer 39

the apical pleural pressure is more sub atmospheric than the base, so the alveoli tend to be more open (even in relaxed states) and thus not as compliant (already distended). Therefore alveoli at the BASE can inflate more and ventilate better