Resp - Gas Exchange

Question 1

things affecting diffusion rate

Answer 1

1. PP gradient (same)
2. SA (same)
3. thickness of membrane (opp)
4. diffusion constant (solubility of gas/mw) (same)
5. blood flow (same)

Question 2

diffusion limited exchange

Answer 2

ex: CO
binds to Hb so strong that PP gradient never changes
limited by amt that can diffuse

Question 3

perfusion limited

Answer 3

ex: N2O
doesn’t bind to Hb
as diffuses across, PP gradient goes down
limited by blood flow to keep gradient up

Question 4

O2 diffusion/perfusion limited

Answer 4

usually perfusion limited (like N2O)
equillibrate 1/3 way along cap
if disease makes it not equilibrate in time - now diffusion limited

Question 5

O2 forms in blood and how much in each

Answer 5

dissolved (0.3 ml/100 ml blood)
Hb bound (19.7)
total: 20 ml O2/100 ml blood

Question 6

PO2 measures…

Answer 6

dissolved O2 in blood

Question 7

Hb - when to take up or release O2

Answer 7

take up when PO2 is high

release when PO2 is low

Question 8

SO2

Answer 8

% saturation of Hb

SO2 = HbO2 content/HbO2 capacity

Question 9

Hb cooperative binding

Answer 9

binding an O2 makes Hb more likely to bind another

Question 10

O2 diss curve: plateau

Answer 10

reflects loading zone
saturate in lungs where theres high PO2
not much change in Hb sat from 60 - 100 (wiggle room)

Question 11

O2 diss curve: steep section

Answer 11

reflects unloading zone
gives up O2 easily w/ small changes in PO2
unload in tissue with low PO2

Question 12

Hb helps diffusion how

Answer 12

in lungs: acts as storage of O2 so that gradient stays higher for longer and O2 can come in

Question 13

O2 diss curve: right shift consequences

Answer 13

DECREASE O2 affinity
decrease Hb binding at given PO2
increase P50
–> unload

Question 14

P50

Answer 14

PO2 when Hb is 50% saturated

Question 15

O2 diss curve: right shift causes

Answer 15

up acid
up CO2
up temp
up 2,3 DPG
(all from exercise)

Question 16

O2 diss curve: left shift consequences

Answer 16

INCREASE O2 affinity
increase Hb binding at a PO2
decrease P50
–> uptake

Question 17

Bohr effect

Answer 17

acid up (pH down) –> up unloading (and reverse)
due to:
CO2 bound to Hb decreases affinity
H+ bound to Hb does same

Question 18

CO2 forms in blood

Answer 18

bicarb (60%)
dissolved in plasma (10%)
carbamino proteins (Hb) (30%)

Question 19

bicarb steps in RBCs

Answer 19

1. .CO2 goes into RBC
2. .CO2 + H2O –CA–> H2CO3 –> H + HCO3
3. HCO3 goes out and Cl- comes in
4. H binds to Hb (downs O2 affinity)

Question 20

chloride shift

Answer 20

for each bicarb leaves RBC, a Cl comes in

maintains electroneutrality of RBC

Question 21

Haldane effect

Answer 21

(low PO2 –>) Hb release O2 –> take up CO2 more easily

Question 22

bohr/haldane together

Answer 22

(low PO2 –>) Hb release O2 –> take up CO2 more easily –> CO2/H lower affinity –> Hb drop more O2

Question 23

effects of CO2 being more soluble

Answer 23

more dissolved in plasma

lungs can remove large amount of CO2 w/ small changes in PP

Question 24

CO2 binding to Hb

Answer 24

bind to globin (not heme)

deoxy binds more CO2 than oxy

Question 25

capnia and ventilation relationship

Answer 25

hypercapnia (hypovent) | hypocapnia (hypervent)

Question 26

causes of hypercapnia

Answer 26

``` VA = VE - VD hypoventilation from: low VE (sedatives, paralysis) high VD (COPD, restrictive) or combo ```

Question 27

causes of hypocapnia

Answer 27

hyperventilation from: anxiety fever aspirin (salicyclics) poisoning

Question 28

hyperpnea

Answer 28

increased ventilation to match increased metabolic demand (exercise)

Question 29

blood gas values

Answer 29

``` pH (7.35-7.45) PaCO2 (35 - 45) PaO2 (85-95) SaO2 (94-98%) (pulse ox) HCO3 (22-28) - Henderson-Hasselbach ```

Question 30

Acid base conditions

Answer 30

``` normal acute/chronic respiratory/metabolic acidosis/alkalosis 9 all together ```

Question 31

compensation defenses

Answer 31

1st: chemical buffering (seconds) 2nd: resp (minutes) 3rd: renal (days)

Question 32

Henderson-Hasselbach eq

Answer 32

pH = pK + log [HCO3]/0.3[PaCO2] | usually ratio = 20 --> pH 7.4

Question 33

resp acidosis mech

Answer 33

retain CO2 HH down pH down

Question 34

causes of retaining CO2 (resp acid)

Answer 34

VA down V/Q mismatch diffusion defect ex: obstruction, resp depressant, NM impairment

Question 35

resp acidosis buffer

Answer 35

can't use HCO3 (resp failure) | use non-bicarb (Hb in RBC)

Question 36

resp acidosis compensation

Answer 36

Renal can't change PaCO2 (resp problem) so up HCO3 PCO2 up stim kidney to conserve HCO3 and excretes H+

Question 37

resp alkalosis mech

Answer 37

low CO2 HH up pH up

Question 38

causes of low CO2 (resp alk)

Answer 38

increase VA | ex: anxiety, fever, altitude, acute asthma, CHF

Question 39

resp alkalosis compensation

Answer 39

renal can't change PaCO2 so lower HCO3 kidney secretes less H and generates less new HCO3

Question 40

sign of compensation

Answer 40

HCO3 and PCO2 rise or fall together and pH is normal | part comp if pH still abnormal

Question 41

Resp acidosis values

Answer 41

PCO2 up pH down HCO3 norm

Question 42

Resp alkalosis values

Answer 42

PCO2 down pH up HCO3 norm

Question 43

Metabolic acidosis values

Answer 43

PCO2 norm pH down HCO3 down

Question 44

Metabolic alkalosis values

Answer 44

PCO2 norm pH up HCO3 up

Question 45

metabolic acidosis causes

Answer 45

``` bicarb down (loss or used up against acids) ex: diabetes (ketoacidosis), diarrhea, strenuous exercise, uremic acidosis ```

Question 46

metabolic acidosis compensation

Answer 46

1st: pulm - up RR to down PaCO2 2nd: renal - eliminate ketones or H+

Question 47

metabolic alkalosis causes

Answer 47

up HCO3 ex: volume depletion - vomiting, furosemide, K or Cl loss no volume depletion - hyperaldosteronism, cushings

Question 48

metabolic alkalosis compensation

Answer 48

pulm: down RR to up PaCO2 renal: conserve H+, excrete excess HCO3

Question 49

O2 content eq

Answer 49

(Hb x 1.34 x SaO2) + PaO2 x 0.003)