Lesson 10: Gas Exchange

Question 1

how goes gas exchange at the lungs happen?

Answer 1

via diffusion (passive)

Question 2

what are some things that can cause issues with diffusion of gases?

Answer 2

• if the space between the alveoli and the capillary is too big (thicker space)

Question 3

the partial pressures of what are key for understanding gas exchange efficiency and gas transport?

Answer 3

oxygen and co2

Question 4

the concentration of of O2 and CO2 is dependent on?

Answer 4

the pressure

Question 5

what is the equation for calculating partial pressure?

Answer 5

total pressure x gas fraction

Question 6

is pressure higher or lower as you get higher?

Answer 6

lower. less pressure pushing down on you

Question 7

true or false: the concentration (gas fraction) of oxygen in the room is the same as the concentration of oxygen on the peak of Mount Everest?

Answer 7

true

Question 8

why do people need oxygen tanks when they go climb mount everest to keep their oxygen and blood oxygen levels if the gas fraction is always the same?

Answer 8

they need to overcome the partial pressure drop

Question 9

atmospheric air is composed of? (the air we inhale)

Answer 9

nitrogen oxygen and co2 predominantly.
- 79.04% nitrogen
- 20.93% oxygen
- 0.03% CO2

Question 10

when the cabin pressure is lost in an airplane, they give you masks. what does the oxygen mask do?

Answer 10

its supplemental oxygen to help get our partial pressure up. its 80-100% oxygen. (atmospheric pressure stays low so we need to higher oxygen fraction)

Question 11

what is our PO2 at sea level?

Answer 11

760 mmHg x 0.2093 = 159 mmHg

(much lower on Mount Everest)

Question 12

what do you need to do if you want to increase the partial pressure of O2?

Answer 12

you need to increase the oxygen fraction (that is why people need oxygen tanks when they climb mount everest.)

Question 13

expired air is composed of?

Answer 13

• 79.95% nitrogen
• 15.85% oxygen
• 4.2% CO2

Question 14

what does it represent when you have exhaled less oxygen than what you have taken in?

Answer 14

represents that you have taken oxygen, deliver it, and consume some of it to create ATP for cellular function

Question 15

what does it represent when you have exhaled more co2 than what you have taken in?

Answer 15

represents metabolic CO2 productive
- throughout the tissues you have internal cellular respiration

Question 16

what does our expired airs composition depend on?

Answer 16

physiological state
- exercising, resting, etc.

Therefore, we cannot measure expired partial pressures unless given the gas fractions.

Question 17

what is our window of regulated arterial PCO2 value?

Answer 17

36-40mmHg

Question 18

what pressure difference in what is what helps to facilitate diffusion?

Answer 18

pressure differences in the alveoli and the capillaries

Question 19

what is Henrys Law?

Answer 19

the volume of gas dissolved in a liquid is proportional to the partial pressure of the gas

Question 20

what is the equation to solve for concentration of gas in a liquid (ml/dl)?

Answer 20

Pgas x k

Question 21

what is ‘k’?

Answer 21

solubility coefficient of the gas in the liquid

Question 22

why does O2 and CO2 have different solubility coefficients?

Answer 22

because their partial pressure gradients/concentration gradients in the capillaries and the alveoli are smaller than it is for oxygen

Question 23

what would happen if CO2 and O2 had the exact same solubility coefficients?

Answer 23

we would have issues with dissolving and thus diffusion and transport of O2 and CO2

Question 24

** Higher K (solubility coefficient of the gas in the liquid) means?

Answer 24

less pressure required to dissolved gas

Question 25

what is PaO2?

Answer 25

the arterial partial pressure of O2

Question 26

what is PAO2?

Answer 26

its the partial pressure in alveolar O2

Question 27

what is PvO2?

Answer 27

the venous partial pressure of O2

Question 28

*** what is the partial pressure of oxygen in the alveoli?

Answer 28

generally about 100mmHg

Question 29

what is the PO2 in the venous circulation?

Answer 29

about 40, lower than the alveolar so diffusion happens because of the gradient

Question 30

assuming that we have perfect levels of diffusion in the lungs, what is the arterial PO2?

Answer 30

the same as the alveolar PO2 in the setting of a normal lung

Question 31

in what scenario will there be a difference in the alveolar and arterial PO2?

Answer 31

interstitial lung disease - any disease that will affect the rate of diffusion

Question 32

what PCO2 in the arterial blood is?

Answer 32

about 40mmHg

Question 33

what is PCO2 in the venous blood?

Answer 33

about 46mmHg or higher

Question 34

we can change PO2 and PCO2 a lot through?

Answer 34

ventilation

Question 35

what is hyperventilation?

Answer 35

- over ventilation - ventilation > CO2 production (causing a decrease in arterial PCO2, and increase your arterial PO2 because you are overbreathing) - different than higher in respiration that occurs with exercise

Question 36

how is hyperventilation different from over breathing during exercise?

Answer 36

because it is called hyperpnea during exercise - ventilation is directly proportional to CO2 and O2 production so it does not affect homeostasis. Arterial blood gas values will stay the exact same.

Question 37

what is hypoventilation?

Answer 37

- under ventilation - ventilation < CO2 production

Question 38

how does decreased PO2 in inspired air (altitude) affect PAO2 and PaO2?

Answer 38

decreases it - it is going down because atmospheric pressure does down as altitude goes up

Question 39

how does increasing alveolar ventilation and unchanged metabolism affect PAO2 and PACO2?

Answer 39

- increase PO2, decrease PCO2

Question 40

how does increasing metabolism and unchanged ventilation affect PAO2 and PACO2?

Answer 40

decrease O2, increase CO2 (when you do not breathe, your CO2 accumulates)

Question 41

how does increasing your metabolism and ventilation (VA) affect PAO2 and PACO2?

Answer 41

(you are exercising) - there is no change, they both rise in perfect synchrony - blood gas remains

Question 42

where does blood need to go so that gas exchange can occur?

Answer 42

the capillaries to be perfused

Question 43

what is ventilation perfusion matching?

Answer 43

the matching of the airway, the airflow to the alveoli and the blood flow to the capillary or to the tissue

Question 44

what is perfusion?

Answer 44

blood flow to a tissue or an organ

Question 45

its the relationship between what that allows us to have hopefully perfect gas exchange?

Answer 45

ventilation and perfusion - disturbance in the relationship = alter gas exchange

Question 46

how is ventilation:perfusion affected with a shunt (no air flow, but has blood flow)?

Answer 46

the blood does not get oxygenated, so V/Q = 0/1 and PaO2 is low

Question 47

how is ventilation:perfusion affected with pure dead space (air flow, but has no blood flow)?

Answer 47

V/Q = 1/0. no blood to get oxygenated. - increase alveolar and plus physiological dead space - ventilation goes down to take place in gas exchange with the capillaries but there is no blood flow there available. so the ventilation/gas in there doesn't take place in gas exchange. wasted

Question 49

Why don’t we just breath more faster so we get more intake or oxygen?

Answer 49

Our oxygen levels are exactly where we need it to be. Breathing more will have 0 physiological benefit for us.