Lesson 9: Ventilation and Gas Exchange

Question 1

what do we really need to do in order to maintain blood gas homeostasis within the system?

Answer 1

ventilation

Question 2

what is ventilation?

Answer 2

the amount of air moved into/out of the alveoli

Question 3

how do we express ventilation?

Answer 3

as a rate
- a volume per minute

Question 4

how do you have a high ventilation?

Answer 4

if you have a high flow

Question 5

what is a minute ventilation a product of?

Answer 5

the size of your breath X the frequency of it

Question 6

what is the size of your breath referred to as?

Answer 6

tidal volume

• about 500 mils per breath

Question 7

how many L of air do we breath in and out everyday?

Answer 7

8640L/day

Question 8

what are the two types of ventilation?

Answer 8

• dead space
• alveolar ventilation

Question 9

what is dead space ventilation?

Answer 9

when we breath in, not all of it goes to the alveoli. some of the air gets trapped in the conducting zone and is then wasted

Question 10

what is alveolar ventilation?

Answer 10

the amount of air that is ventilated and gets to the alveoli

Question 11

alveolar and dead space ventilation together makes up?

Answer 11

our total ventilation per ml/minute

Question 12

about how much of the gas we breathe in does not make it to the gas exchange zones?

Answer 12

roughly 30%
- dead space ventilation

Question 13

how much air actually reaches the alveolar/capillary gas-exchange interface/zone?

Answer 13

350ml ventilated to and from the alveoli (ie. alveolar ventilation), 150ml wasted ventilation (ie. dead space ventilation)

Question 14

what happens if you have higher levels of dead space due to clinical diseases?

Answer 14

then you need to breath more to get enough air ventilation

Question 15

what is Ve?

Answer 15

the total volume of expired ventilation
- the total amount of air that we can measure with a spirometer

Question 16

why do we look at Ve and not Vi when we are looking at total ventilation?

Answer 16

because we exhale more CO2 so it is going to give us some index of how well we’re ventilation

Question 17

how do we calculate alveolar ventilation?

Answer 17

(tidal volume - dead space in a single tidal breath) x frequency

Question 18

what is the amount of air available for gas exchange characterized by?

Answer 18

alveolar ventilation (Va)

Question 19

what is air moved characterized by?

Answer 19

total ventilation (Ve)

Question 20

why do we breath?

Answer 20

to bring in oxygen and remove CO2 (biproduct of cellular respiration)
- cellular respiration

Question 21

how do we know if alveolar ventilation is sufficient?

Answer 21

you can look at your arterial oxygen levels
- oxygen saturation of hemoglobin

MORE IMPORTANTLY

• alveolar/arterial CO2 is within a narrow physiological range (36-40mmHg)

Question 22

why is alveolar ventilation important?

Answer 22

for the delivery and removal of air at the gas exchange level

Question 23

what would be the oxygen, hemoglobin saturation levels of someone that has good oxygen levels?

Answer 23

96-100% Hb saturated is the normal physiological range of arterial O2 content

Question 24

what relationship are we more closely paying attention too when looking at ventilation?

Answer 24

the relationship between the amount of air we are breathing and the actual metabolic CO2 production
- CO2 is actually what drives the breathing

Question 25

why do we not want a too high or too low CO2 in our alveoli and arteries?

Answer 25

because it means we are either not generating enough ventilation or too much ventilation which could dysregulate acid-base balance and lead to a series of events that disrupt cellular respiration (last part doesn't really matter)

Question 26

what is the alveolar ventilation equation / concentration or pressure of expired CO2 in alveoli?

Answer 26

(VCO2/Va) x K

Question 27

what is "PaCO2"?

Answer 27

the arterial/alveolar concentration/partial pressure of expired CO2

Question 28

what is VCO2?

Answer 28

the volume of expired CO2

Question 29

what does expired CO2 represent?

Answer 29

the metabolic CO2 that is produced in all the tissues pushed up through the venous circulation, diffused across the capillary alveolar interface and breathed out

Question 30

what is the gas exchange zone?

Answer 30

alveoli

Question 31

alveoli is made up of?

Answer 31

epithelial cells

Question 32

how many cells thick is alveoli?

Answer 32

1 cell thick (type 1)

Question 33

what are alveoli surrounded by?

Answer 33

capillaries

Question 34

how many times does the bronchioles/alveoli branch?

Answer 34

23 times - millions and millions of them so we have a huge surface area for gas exchange

Question 35

while gas exchange occurs at the lungs, it also occurs at?

Answer 35

the peripheral tissues - because we diffuse, we bring O2 into the lungs, goes through the circulation, the cardiovascular system and then also diffuses into the tissue

Question 36

at both the pulmonary capillary and tissue capillary levels, gas exchange involves the simple _________ of O2 and CO2 _________________________________.

Answer 36

1. diffusion 2. down partial pressure gradients

Question 37

the partial pressure exerted by each gas in a mixture equals?

Answer 37

the total pressure multiplied by the fractional composition of this gas in the mixture

Question 38

what are additional factors that affect the rate of gas transfer?

Answer 38

- as surface area increase, the rate increases - an increase in the thickness of the barrier separating air and blood decreases the rate of gas transfer - the rate of gas exchange is directly proportional to the diffusion coefficient for a gas

Question 39

what is the Law of Partial Pressure (Dalton's)?

Answer 39

in a mixture of gases the pressure of each gas is independent of the others - partial pressure = total pressure x gas fraction