Respiratory System: Karius contribution

Question 1

What part of this path way is considered “dead space” ?

nasal cavity –> nasopharynx –> larynx –> trachea –> bronchi –> bronchioles –> acinus

Answer 1

everything up to the acinus bar the respiratory bronchioles which do contain some alveoli

Question 2

how much air does anatomical dead space hold in the average person?

Answer 2

~ 150 ml

Question 3

alveolar dead space

Answer 3

alveoli that do not participate in gas exchange although they should/can. should have some but not too much

Question 4

Alveolar ventilation is (three things)

Answer 4

volume of air reaching the alveoli
V(dot)Alv: volume of air reaching alveoli per minute
4 L/min average

units should be ml air/min

Question 5

Q

what it Q and how is it calculated?

Answer 5

perfusion: the process of delivering blood to a capillary bed

from Right Ventricle
5 L/blood min

CO = SV x HR

left and right ventricles should match

Question 6

what is the “point of the lungs” ?

Answer 6

to bring together ventilation and perfusion

Question 7

Diffusion of Gases

Diffusion formula with units

Answer 7

J (ml/min) =

(Surface Area) x Diffusion coefficient x (Pressure 1 - Pressure 2) / distance

equation solved for each gas individually

Question 8

Gas exchanged under normal conditions

Answer 8

250 ml O2/min

200 ml CO2/min

Question 9

S.A =

Answer 9

surface area of alveoli = total number of alveoli in lungs

also effected by number of open capillaries

Question 10

what “roughly” is the amount of blood in the capillaries at a given moment?

Answer 10

around 70 ml but during exercise can be as much as 200 ml

Question 11

how do you explain resistance in emphysema patients?

Answer 11

decreased surface area of alveoli

Resistance = 1 / ( r^4)

Question 12

diffusion distance =

Answer 12

thickness of alveolar barrier

Question 13

thickness of alveolar barrier includes

Answer 13

fluid layer, alveolar epithelium, interstitial space, blood vessel endothelium

around .6 microns

Question 14

how does the deposition of collagen in the interstitial space alter diffusion distance?

Answer 14

it increases it

Question 15

diffusion coefficient of each gas

D depends on two general factors

Answer 15

the solubility of the gas in water and molecular weight of the gas

Question 16

solubility of O2 versus CO2

weight of O2 versus CO2

Answer 16

O2 far less soluble than CO2

CO2 weighs more

Question 17

the solubility coefficient of CO2 vs O2

Answer 17

CO2 is 20x the D of O2

in other words, the solubility of CO2 is greater so the diffusion is greater by 20 times

Question 18

the pressure gradient in the diffusion equation

Answer 18

P1 - P2

represents pressure gradient across alveolar membrane

Question 19

Pressure of venous O2

Answer 19

40 mm Hg

Question 20

Pressure of alveolar O2

Answer 20

104 mm Hg

Question 21

Alveolar vs venous O2 pressure

Answer 21

104 - 40

Question 22

Pressure of venous CO2

Answer 22

45 mm Hg

Question 23

Pressure of alveolar CO2

Answer 23

40 mm Hg

Question 24

Alveolar vs venous CO2 pressure

Answer 24

40 - 45 = -5 mm Hg

Question 25

An RBC spends how much time in a pulmonary capillary?

Answer 25

under normal (non-exercising) conditions, around .75 seconds, but it only needs .25 seconds to go from 40 mmHg to 100 mmHg (from venous through alveolar capillary)

Question 26

"buffer zone"

Answer 26

this refers to the amount of time the RBC is in the alveolar capillary that isn't being used, because it fills up entirely in .25 sec but its in the cap for .75 sec

Question 27

When will someone with lung disease discover problems and why?

Answer 27

During exercise. The reason is that during resting conditions, the RBC spends around .75 seconds in a pulmonary capillary, but only needs .25 sec of that to achieve full oxygen saturation; this leaves a wide buffer zone of time for a person with lung disease to fill their RBCs with O2, but not during strenuous exercise.. During exercise, the RBC spends around .25 seconds in the pulmonary capillary during exercise, almost the exact amount of time required to achieve 100% O2 saturation of hemoglobin. Someone with lung disease will not be able to satisfy their O2 requirements in that span because the safety zone is reduced, so they will encounter problems.

Question 28

What is the DLO2 The average diffusion gradient of oxygen in the lungs

Answer 28

21 ml O2/min/mmHg measured at rest

Question 29

what compound is used to measure DL02 in order to indirectly measure O2?

Answer 29

CO carbon monoxide avidly binds to Hb DLO2 = (roughly) DLCO X 1.23

Question 30

Why is CO2 not quite as visible a sign of lung disease initially?

Answer 30

``` Pa1CO2 = 45 mm Hg Pa2CO2 = 40 mm Hg ``` the equilibrium is almost immediate, so lung disease has to be very extensive before any signs of CO2 deficiency appear

Question 31

how is DLO2 measured? what calculations have to be made?

Answer 31

1.23 x DLCO (diffusion in lungs of carbon dioxide)

Question 32

diffusion of CO2 =

Answer 32

400 ml CO2/min/mm Hg

Question 33

how does surfacant effect surface tension?

Answer 33

air bubbles want to form a giant bubble rather than remain diffuse, and this creates large areas of liquid exclusion (water here, liquid over here). so it prevents large bubbles from forming in the air/blood interface). pressure = 2T/r if surfacant reduces tension caused by water bubbles, it directly effects pressure

Question 34

why is surfcant important for alveoli ?

Answer 34

they vary in size, so a big alveolus will have less pressure causing a pressure gradient to be established: little alveoli will see air forced from their space toward big alveoli, causing damage and disequilibrium and dead space

Question 35

in which alveoli is surfacant most important?

Answer 35

small alveoli, because mm Hg = 2T/r, the tension is reduced so the pressure gradient isn't established causing the small alveoli to lose air