Gas Exchange & Transport And V/Q Mismatch Flashcards
Increased thickness of lung membrane =
Decreased diffusion (e.g pulmonary edema)
O2 and CO2 diffusion
Oxygen enters blood from alveolar air because PO2 is greater than that of the blood
Simultaneously CO2 molecules exit blood bc PCO2 of venous blood is much higher than alveolar air
Amount of O2 diffused into the blood each minutes depends on what factors
- Alveolar pressure gradient
- Total functional SA of membrane
- Respiratory minute volume
- Alveolar air
As altitude increases
Alveolar PO2 decreases, thus less O2 enters the blood, eventually the PO2 in air = PO2 of blood
Functional Surface area
Anything that decreases the functional SA of the respiratory membrane decreases amount of oxygen diffused into blood
E.g emphysema
Resp minute volume
Anything that decreases respiratory rate, tends to decrease blood oxygenation
E.g morphine slows resps
Hemoglobin
Contains iron and O2 has an affinity for Iron atoms allowing the iron to act as a sponge for O2 molecules
Alpha and beta amino acid chains in hemoglobin
CO2 has an affinity for these chains allowing HB to sponge CO2 and carry it well
How much does a fully saturated hemoglobin molecule unload
At rest - 25%
Exercise - 75%
O2 Disassociation curve
Describes the relationship between PO2 and O2 saturation
Rightward shift
Indicates the HB has a decreased affinity for O2
Means higher PO2 would be required to reach the same O2 saturation
Also easier for HB to release O2
Typical causes of a right shift
Exercise, stress, shock
CADET
C- CO2
A- Acid
D- DPG
E- Exercise
T- Temperature
What is DPG
this molecule stabilizes the deoxygenated form of hemoglobin. Decreased BPG concentrations create increased oxygen affinity
Left shift
HB has increased affinity for O2
Temperature
Higher - Right
Lower - Left
DPG
Higher - Right
Lower - Left
PCO2
Higher - Right
Lower- Left
Acidity
Higher pH (alkaline) - LEFT shift
Lower pH (acidosis) - RIGHT shift
Why CO2 needs to be transported
CO2 is very acidic and is transport in the blood to be eliminated by the lungs or kidneys
What ways is CO2 transported
Form of bicarbonate
Combined with hemoglobin
Dissolved in plasma
Dissolved CO2
Small amount of CO2 dissolves in plasma and is transported
This creates PCO2 of blood plasma
Carbamino compounds
25% of CO2 unites with hemoglobin to make Carbamino hemoglobin
Higher PCO2 - accelerates the binding process
Bicarbonate
2/3 of CO2 is carried in bicarbonate (HCO3-)
- CO2 dissolves in plasma and molecules bind with H2O to form carbonic acid
- some then split to form H+ and bicarbonate (H2CO3)
