Lecture 17: Gas Exchange: O2 Flashcards
Dalton’s law
gas’s pressure is proportional to its conc
partial pressure
pressure exerted by each gas of total gas pressure
partial because of indiv gas when there is more than one
atmopsheric pressure at 2389 ft
700 mmHg
Pps of deoxyg blood
PO2 40 mmHg
PCO2: 45 mmHg
Pps of oxyg blood
PO2: 100 mmHg
PCO2: 40 mmHg
How much fresh air enters with inspiration?
about 55mL
mixes w/ FRC (2400 mL)
very little compared to whas already there (FRC)
When fresh air enters, [O2]…
inc slightly
When fresh air enters, [CO2]…
dec slighltly
When fresh air enters, average alveolar value
DOES NOT CHANGE much
constant situation means we have predictable rate of exchange
expired air comparied to inspired air conc
lower [O2]
higher [CO2]
why lower [CO2] inspired than expired
b/c O2 removed from lungs by blood during inspiration
CO2 movement during breath
moves from blood to lungs and is exhaled
gases in lungs (tissue and lung levels)
constantly taking O2 out and putting CO2 in
O2 at tissues
leaves capps and goes into cells
CO2 at tissues
enters caps
venous blood concs
high CO2 low O2 (comes into caps at 100, leavs at 40)
Fick method
O2 consumption= blood flow x (tissue oxygen extraction)
aka C.O. x ([arterial O2] - [mixed venous O2])
most direct and accurate way to measure whole body O2 uptake
O2 consumption
measured using Fick method
depends on level of activity
see slide 10
10
Fick relationship
CO2 production measured
values go up (down in O2 one)
Fick relationship equation
CO2 production= blood flow x (tissue CO2 production)
aka C.O. X ([CO2 mixed venous] - [co2 arterial])
O2 concs at rest vs. max
rest: 250
max: 3500
more than 10 fold increase
CO2 concs at rest vs max
rest: 200
max: 3800
close to 20 fold increase
amounts of O2 consumed and CO2 produced are
NOT EQUAL
respiratory quotient (RQ) equation
amount CO2 made/O2 consumed
RQ varies with
nutrient type
pure fat RQ
0.7
7 mL pure CO2 produced for every 10 mL pure O2 used
pure carb RQ
1.0
CO2 produced and O2 consumed are about equal
partial pressuure O2 in atmosphere
21
partial pressure N2 in atomsphere
79
atomospheric PO2 vs. alveolar PO2
atmosphere: 159
alveoli: 105
atomospheric PCO2 vs. alveolar PCO2
atmosphere: 0.3
alveoli: 40
why oxygen PP doesn’t match between alveolar and oxy blood
nutritient exchange in lung to feed lungs
best place to look for mixed venous blood
right ventricle, right atrium, pulmonary artery
with oxygen we make
water
we get CO2 from
the fuel we use
