Vent and Perfusion

Question 1

Pulmonary circuit different than systemic circuit how?

Answer 1

1) lower pressures and resistance
2) less smooth mm in pulm arteries and arterioles
3) SNS affect on pulm circuit are minimal

Question 2

Pulmonary circuit has low resistance, why?

Answer 2

large cross sectional area of plum capillaries

Question 3

Pulmonary circuit has low pressure, why?

Answer 3

resistance is low,

thin walled capillaries can not tolerate high pressure

Question 4

Pulmonary vasculature characteristics? (2)

Answer 4

1) highly compliant Ѧ blood reservoir
2) can not autoregulate pressure and Po2

(compared to autoreg in systemic vascular beds)

Question 5

Resistance of plumonary circ and blood flow affected by? (3)

Answer 5

1) vascular pressures
2) gravity
3) P_Ao₂

Question 6

↑ pulmonary vascular pressures results in what?

Answer 6

↓ pulmonary vascular resistance thru:

↑ distension or recruitment

Question 7

Recruitment is?

Answer 7

in response to ↑ pulmonary pressure (arteries or veins),

more capillaries open to ↓ pulm vascular resistance.

Response is more useful at lower pressures.

Question 8

Distention is?

Answer 8

in response to ↑ pulmonary pressure (arteries or veins),

capillaries already partially open are expanded to ↓ pulm vascular resistance.

Response is more useful at higher pressures

Question 9

Gravity lowers pulmonary vascular resistance how?

Answer 9

distributes blood from apex to base of lung

↑ flow = ↓ resistance

Question 10

What happens to P_A, P_a and P_V w/ change in lung position (relative to gravity)?

Answer 10

P_A remains constant

P_a and P_V both ∆

Question 11

Gravity in Zone 1?

Answer 11

(apex)

vessels collapse = θ flow

contributes to alveolar dead space

P_A > P_a > P_V

Question 12

Gravity Zone 2?

Answer 12

θ flow but

proportional to P_a - P_A

P_a > P_A> P_V

Question 13

Gravity Zone 3?

Answer 13

(base)

driving force is P_a - P_V

P_A dose not affect flow

P_a > P_V > P_A

Question 14

Effects of hypoxic vasoconstriction (P_Ao₂) on pulmonary vascular resistance?

Answer 14

↓ P_Ao₂ below 70 mmHg ->

smooth mm contracts in pulm vasculature ->

blood sent to better ventilated alveolar ->

local control of vascular resistance

OPPOSITE of response of system circulation to hypoxia

Question 15

Hypoxic vasoconstriction responsible for? (3)

Answer 15

1) plumonary HTN at high-altitude
3) chronic hypoventilation (COPD)
4) in utero keeps blood flow to fetal lungs at minimum

Question 16

Alveoli at apex of lung:

Intrapleural pressure?

Volume?

Compliance?

Answer 16

-10 cm H2O

larger vol due to more neg intrapleural pressure

partially expanded so compliance is reduced

Question 17

Alveoli at base of lung:

Intrapleural pressure?

Volume?

Compliance?

Answer 17

-2.5 cm H2O

smaller vol due to less neg pressure

more compliant Ѧ better ventilated

Question 18

Vent/Perfusion ratio

Answer 18

ºV = vent reaching alveoli

(4.2 L/min)

ºQ = blood flow thru lungs

(cardiac output) (5 L/min)

ºV/ºQ = 0.84 in upright lung

Question 19

Vent/Perfusion ratio

Answer 19

ºV = vent reaching alveoli

(4.2 L/min)

ºQ = blood flow thru lungs

(cardiac output) (5 L/min)

ºV/ºQ = 0.84 in upright lung

Question 20

vent and perfusion ↓

from where to where?

Answer 20

base ( 3)

perfusion changes more rapidly than ventilation

Question 21

High ºV/ºQ does what to:

ventilation and perfusion?

P_Ao₂ and P_Aco₂?

Answer 21

vent > perfusion

high P_Ao₂

low P_Aco₂

Question 22

Low ºV/ºQ does what to:

ventilation and perfusion?

P_Ao₂ and P_Aco₂?

Answer 22

perfusion > ventilation

low P_Ao₂

high P_Aco₂

Question 23

Apex ºV/ºQ ratio is?

Pao₂?

Paco₂?

Answer 23

high (3.0)

highest (130 mmHg)

lower (28 mmHg)

Question 24

Base ºV/ºQ ratio is?

Pao2?

Paco2?

Answer 24

low (0.6)

lowest (89 mmHg)

higher (42 mmHg)

Question 25

Wasted ventilation is?

Happens?

Answer 25

vent > needed to saturate blood delivered to alveoli

happens in alveoli w/ high ºV/ºQ

Question 26

Shunt is?

ºV/ºQ?

O2 supplementation tx?

Answer 26

perfusion w/o ventilation:

e.g. bronchial blood flow, defective ventral septum

ºV/ºQ = 0

does not respond to supplemental O2,

non-vent alveolar are never ventilated

Question 27

Areas w/ low ºV/ºQ add blood that is?

Respond to O2 tx?

Answer 27

poorly oxygenated

does respond to supplemental O2

Question 28

O2 supplementation ↑ what?

Improves what?

Answer 28

F_Io₂ of inspired air

oxygenation in areas of low ºV/ºQ