Alveolar Ventilation and Perfusion

Question 1

what is the leading cause of low blood oxygen

Answer 1

-V/Q inequality

Question 2

PaO2 level that is hypoxemia

Answer 2

• <80 mmHg

Question 3

the total pressure of a mixture of gasses is the sum of

Answer 3

• the partial pressures exerted by each gas

Question 4

what is conditioning?

Answer 4

• warming, cleansing, and humidifying inspired air

Question 5

what is the partial pressure of water vapor

Answer 5

• 47 mmHg

Question 6

what happens when you introduce water vapor into a mixture of dry gases

Answer 6

• dry gas partial pressure falls accordingly

Question 7

what does the blood deliver to the lungs

Answer 7

• CO2

Question 8

what do the lungs give to the blood

Answer 8

• O2

Question 9

what is alveolar ventilation

Answer 9

• volume of air reaching alveoli to participate in gas exchange x respiratory rate

Question 10

the first 150 mL of air that is inspired is

Answer 10

• expired air from the previous breath

Question 11

amount of CO2 produced by the body’s metabolism per minute compared to the amount of CO2 eliminated by alveolar ventilation - during steady state

Answer 11

• equal

Question 12

relationship between alveolar ventilation and PACO2

Answer 12

• inverse

Question 13

increased PaCO2 will result in at change in pH

Answer 13

• fall in blood pH

Question 14

can doubling ventilation double PAO2

Answer 14

• no

- cannot rise higher than PO2 of humidified air (150)

Question 15

regulation of ventilation by the CNS is driven primarily by

Answer 15

• arterial PCO2

Question 16

hyperpnea

Answer 16

• increase in rate and depth of alveolar ventilation caused by a rise in metabolism

Question 17

tachypnea

Answer 17

• rapid, shallow breathing to maintain sufficient gas exchange

Question 18

apnea

Answer 18

• cessation of breathing

Question 19

hypoapnea

Answer 19

• slow, shallow breathing

Question 20

PaCO2 of hyperventilation

Answer 20

• less than 35 mmHg

Question 21

PaCO2 of hypoventilation

Answer 21

• greater than 45 mmHg

Question 22

if the lung is functioning perfectly, what will be the partial pressures of gas in the pulmonary blood versus alveolar gas

Answer 22

• equal

Question 23

what does the A-a difference compare

Answer 23

• calculated PAO2 and PaO2

Question 24

partial pressure of CO2 in alveolar gas versus that in the arterial blood

Answer 24

• equal

Question 25

in a subject standing or sitting upright, where is ventilation greatest why?

Answer 25

- base of the lung | - gravity pulls lung downward and creates more negative interpleural pressure at the apex that holds alveoli more open

Question 26

at end expiration, which alveoli are held more open

Answer 26

- alveoli at top of lung

Question 27

alveoli at the base

Answer 27

- more compliant | - greater increase in volume for a given increase in pressure.

Question 28

pressure, volume of the pulmonary circulation

Answer 28

- low pressure, high volume

Question 29

what does the low pressure of pulmonary circulation help prevent

Answer 29

- fluid extravasation (pulmonary edema)

Question 30

pulmonary arterioles shape, size

Answer 30

- numerous, short, thin walled

Question 31

auto regulation of pulmonary arterioles

Answer 31

- lack autoregulation

Question 32

compliance of pulmonary arterioles

Answer 32

- high compliance

Question 33

pulmonary capillary compliance to arterial pressure

Answer 33

- high compliance

Question 34

capillaries are also uniquely susceptible to

Answer 34

- alveolar air pressure

Question 35

where are extra-alveolar vessels located

Answer 35

- not adjacent to alveoli

Question 36

extra-alveolar vessels when lung volume increases

Answer 36

- increase in caliber and decrease in resistance

Question 37

extra-alveolar vessels when lung volume decreases

Answer 37

- decrease in caliber and increase in resistance

Question 38

alveolar vessels are located

Answer 38

- adjacent to alveoli

Question 39

alveolar vessels when lung volume increases

Answer 39

- decrease caliber and increase resistance

Question 40

alveolar vessels when lung volume decreases

Answer 40

- increase caliber and decrease resistance

Question 41

negative alveolar pressure during inspiration will do what to alveolar vessels

Answer 41

- dilate and decrease resistance

Question 42

positive alveolar pressure during expiration what do what to alveolar vessels

Answer 42

- collapse alveolar vessels and increase resistance

Question 43

high alveolar pressures at high lung volumes create

Answer 43

- lung zones with high vascular resistance and low blood flow

Question 44

high intravascular pressure will do what to alveolar vessels

Answer 44

- increase caliber of compliant ones | - lower resistance

Question 45

increases arterial or venous pressure leads to what in pulmonary vascular resistance

Answer 45

- a decrease in pulmonary vascular resistance

Question 46

what can increased intravascular pressures also do

Answer 46

- recruit previously non-perfused pulmonary capillaries

Question 47

capillaries because the lung is a very low pressure hemodynamic system

Answer 47

- many capillaries may be minimally perfused

Question 48

many capillaries may be minimally perfusion during

Answer 48

- periods of low activity and quiet breathing

Question 49

perfusion pressure and vascular resistance in upper zones of lung

Answer 49

- low perfusion pressure | - higher vascular resistance

Question 50

capillaries in upper lung respiratory units

Answer 50

- susceptible to collapse under influence of alveolar air pressure

Question 51

perfusion pressure and vascular resistance in lower zones of lung

Answer 51

- higher perfusion pressure | - low resistance

Question 52

vascular resistance in zone 1 why

Answer 52

- high. vasculature is snapped close. | - alveolar pressure higher than pulmonary arterial and pulmonary venous pressure

Question 53

result of collapse of alveolar capillaries and expansion of zone 1

Answer 53

- increase physiologic dead space

Question 54

pressures in zone 3

Answer 54

- pulmonary venous and arterial pressure higher than alveolar pressure

Question 55

lung perfusion is highest where

Answer 55

- zone 3

Question 56

why is there a dip in blood flow at the very bottom of the lung

Answer 56

- extra alveolar vessels are compressed at low lung volumes

Question 57

pressure in zone 2

Answer 57

- alveolar pressure intermediate to arterial and venous pressure

Question 58

arterial pressure in zone 2

Answer 58

- high enough to keep capillary open | - closer to the bottom

Question 59

arterial pressure in zone 2 at you go up up the lung

Answer 59

- decreases as you go up the lung | - artery will collapse and pinch off blood flow

Question 60

blood flow in zone 2 dependent on

Answer 60

- difference between arterial and alveolar pressures

Question 61

V/Q is highest at

Answer 61

- apex

Question 62

V/Q is lowest at

Answer 62

- base

Question 63

alveoli in apex of lung

Answer 63

- low compliance - low ventilation - low blood flow - high PAO2

Question 64

alveoli in base of lung

Answer 64

- high compliance - high ventilation - high blood flow - low PAO2

Question 65

hypoxia (low areas of O2 tension) will have what effect on the vasculature result

Answer 65

- vasoconstriction | - directs blood away and toward more well ventilated areas to preserve V/Q

Question 66

consequence of hypoxic pulmonary vasoconstriction

Answer 66

- increases pulmonary artery pressure

Question 67

result of long standing pulmonary hypertension

Answer 67

- cor pulmonale (right ventricular hypertrophy)