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Flashcards in Resp - Gas Exchange Deck (49):
1

things affecting diffusion rate

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

2

diffusion limited exchange

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

3

perfusion limited

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

4

O2 diffusion/perfusion limited

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

5

O2 forms in blood and how much in each

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

6

PO2 measures...

dissolved O2 in blood

7

Hb - when to take up or release O2

take up when PO2 is high
release when PO2 is low

8

SO2

% saturation of Hb
SO2 = HbO2 content/HbO2 capacity

9

Hb cooperative binding

binding an O2 makes Hb more likely to bind another

10

O2 diss curve: plateau

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

11

O2 diss curve: steep section

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

12

Hb helps diffusion how

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

13

O2 diss curve: right shift consequences

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

14

P50

PO2 when Hb is 50% saturated

15

O2 diss curve: right shift causes

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

16

O2 diss curve: left shift consequences

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

17

Bohr effect

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

18

CO2 forms in blood

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

19

bicarb steps in RBCs

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)

20

chloride shift

for each bicarb leaves RBC, a Cl comes in
maintains electroneutrality of RBC

21

Haldane effect

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

22

bohr/haldane together

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

23

effects of CO2 being more soluble

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

24

CO2 binding to Hb

bind to globin (not heme)
deoxy binds more CO2 than oxy

25

capnia and ventilation relationship

hypercapnia (hypovent)
hypocapnia (hypervent)

26

causes of hypercapnia

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

27

causes of hypocapnia

hyperventilation from:
anxiety
fever
aspirin (salicyclics) poisoning

28

hyperpnea

increased ventilation to match increased metabolic demand (exercise)

29

blood gas values

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

30

Acid base conditions

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

31

compensation defenses

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

32

Henderson-Hasselbach eq

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

33

resp acidosis mech

retain CO2
HH down
pH down

34

causes of retaining CO2 (resp acid)

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

35

resp acidosis buffer

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

36

resp acidosis compensation

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

37

resp alkalosis mech

low CO2
HH up
pH up

38

causes of low CO2 (resp alk)

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

39

resp alkalosis compensation

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

40

sign of compensation

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

41

Resp acidosis values

PCO2 up
pH down
HCO3 norm

42

Resp alkalosis values

PCO2 down
pH up
HCO3 norm

43

Metabolic acidosis values

PCO2 norm
pH down
HCO3 down

44

Metabolic alkalosis values

PCO2 norm
pH up
HCO3 up

45

metabolic acidosis causes

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

46

metabolic acidosis compensation

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

47

metabolic alkalosis causes

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

48

metabolic alkalosis compensation

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

49

O2 content eq

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