Alveolar Gas Exchange

Question 1

Alveolar ventilation equation

Answer 1

PAo2 = PIo2 - (PaCO2 / R)

Question 2

PIo2 how to calculate it and what is it

Answer 2

PIo2 = (760 - 47) x 0.21 0.21 = percent o2 47= water vapor P

Question 3

R is usually what

Answer 3

(200ml/min) / (250ml/min) = 0.8

Question 4

how to know if alveolus is damaged

Answer 4

difference between the alveolar and arterial P PAo2 - Pao2 = should be less then 20 if over 20 there is alveolar damage if normal and dyspnea = low O2 in atm. or impaired RR breathing ability

Question 5

what is the normal alveolar ventilation what is the normal alveolar perfusion

Answer 5

1. 4L/min (air that reaches the alveoli) 2. 5 Blood/min (CO, from RV)

Question 6

how do you calculate the diffusion rate

Answer 6

diffusion Rate = J (exchange between air and blood)

Question 7

normal J for O2 and CO2

Answer 7

O2 : 250mL/min CO2 : 200mL/min *change independently of eachother*

Question 8

what 2 factors depend on the ALVEOLAR STRUCTURE

Answer 8

SA of air exchange distance (for exchange, alveolar wall)

Question 9

what changes the SA

Answer 9

1. number of avleoli taking part in gas exchnage 2. number of open pulmonary capillaries

Question 10

normal amount of blood in pulmonary capillaries

Answer 10

70ml

Question 11

normal amount of blood in pulmonary capillaries during exercise

Answer 11

up to 200ml, more capillaries open

Question 12

what influences distance of exchange

Answer 12

1. thickness of alveoli wall (fluid) 2. BV (capillary) wall 3. alveolar endothelium 4. interstitial fluid (should be very thin)

Question 13

pulmonary fibrosis and interstitial fluid

Answer 13

collagen is deposited in the interstitial fluid increasing thickness alot Also called interstitial lung disease

Question 14

average distance for gas exchange

Answer 14

0.6 microns

Question 15

the diffusion coefficient for each gas depends on what 2 things

Answer 15

1. solubility of gas (CO2 is 20x more soluble) 2. molecular weight of gas (CO2 is heavier)

Question 16

P1-P2 is what and what is it normally for O2

Answer 16

pressure across alveolar membrane (inside alv to outside blood) =PAo2 - Pvo2 = 104 - 40 = 60mmHg

Question 17

normal P1-P2 for CO2

Answer 17

PACO2 - PvCO2 = 40 - 45 = -5 (interpleural P)

Question 18

how long does if take for blood to get through one entire pulmonary capillary

Answer 18

0.75 sec

Question 19

how long does O2 need to diffuse across from alv to blood how long does CO2 need

Answer 19

O2 : 0.25sec CO2 : almost immediately

Question 20

how long does if take for blood to get through one entire pulmonary capillary during exercise

Answer 20

0.25sec, just enough time for all O2 to diffuse from alv to blood * someone with lung disease will first have Sx during exercise

Question 21

what happens in COPD/emphysema and diffusion rate

Answer 21

diffusion rate is lowered and O2 needs more time to diffuse (more then 0.25sec)

Question 22

how to calculate Diffusion Capacity in O2

Answer 22

V(dot)O2 x (P1-P2) = 250mL/min x 60mmHg = 21mL/min/mmHg at rest

Question 23

how to quickly calculate Diffusion capacity for O2

Answer 23

* use CO, PaCO= 0mmHg* DLo2 = 1.23 (DLco)

Question 24

normal DLco2 is what

Answer 24

DLco2 = 400mL/min/mmHg (20x more then 21 which is for O2)

Question 25

reason in pnemonia or COPD there is found to be a NORMAL O2 and lowered CO2

Answer 25

as O2 gas diffusion rate decreases 1. PaO2 drops 2. peripheral chemoreceptors activated and increase RR + TV + f 3. PaO2 goes back to normal however the increases TV and RR causes a bunch of CO2 loss since its diffusion rate did not get effected from the start

Question 26

in pnemonia or COPD there is found to be a NORMAL O2 and lowered CO2 Eventually what happens

Answer 26

low CO2 = high pH peripheral chemoreceptors responds only cant all the way becuz it will hinder body from getting adequate O2

Question 27

normal baby HR is what

Answer 27

120 or higher

Question 28

reason you need surfactant

Answer 28

the air (in alv) and tissue/wall (water in this case) cause the alv wall to bubble up like water = alveoli collapse surfactant reduces the surface tension b/w water(tissue) and air

Question 29

LaPlace's Law on P in alv

Answer 29

P = 2T/r T = surface tension r= radius \* higher radius --\> decrease P \* higher surface tension --\> increase P

Question 30

reason you need surfactant

Answer 30

Surfactant LOWERS surface tension in SMALL ALVEOLI ----\> so their P is lowered and equal to the big alveoli

Question 31

what happens if you have no surfactant

Answer 31

the small alveoli have high P the large alveoli have low P AIR DIFFUSES ----\> large alveoli (that makes the small alveoli smaller = collapse of small alveoli) = LOWERS SA

Question 32

how does surfactant only effect the small alveoli

Answer 32

the closer the drops of surfactant are to one another the stronger it works , the drops are closer together the smaller alveoli

Question 33

what can you give the baby if you know they dont have developed type 2 cells to make surfactant in time of delivery

Answer 33

Steroids that increase surfactant

Question 34

what is surfactant composed of

Answer 34

phospholipid Dipalmitosphatidylcholine + Surfactant Proteins : SPB is the one lowering ST\*\*\*\* SPB is stored in the lamellar bodies and secreted