Gas transport - Quiz 5 Flashcards
What is Tissue Oxygenation?
Process of moving O2 & CO2 in and out of body tissues
Distance of diffusion before it gets too slow?
> 100 micrometers
What are the Types of Hypoxia?
- Hypoxic Hypoxia
- Stagnant (Ischemic) Hypoxia
- Anemic Hypoxia
- Histotoxic Hypoxia
What is hypoxic hypoxia
Not enough O2 uptake from lungs to blood (Low PO2)
EX: COPD
What is Stagnant Hypoxia
Ischemic Hypoxia (Low Perfusion)
Not enough blood flow to organ
EX: Arteriosclerosis PVD
What is Anemic Hypoxia?
Not enough blood oxygen carrying capacity (Low HGB)
EX: Inactivated HGB
What is Histotoxic Hypoxia
Inteference with Mitochondrial Respiration
Ex: Cyanide Poisoning
What proteins carry the most O2?
Hemoglobin
Normal: 150g/L or 15g/dL
Carries 65x more O2 than plasma
Hemoglobin Characteristics
4 subunits = 2 alpha + 2 beta
Four Heme Groups - Iron-Porphyrin at O2 binding site
What is the Normal Adult Hgb Configuration?
Normal Adult = HbA = a2B2
What is the only thing that can bind to O2 in an iron containing porphyrin ring?
Ferrous Iron (Fe2+)
How many goblin protein chains can each heme combine with?
One
How much O2 can each gm of Hemoglobin carry?
1.31 - 1.39 mL of O2
What is Oxyhemoglobin?
When O2 is binds with hemoglobin.
Binds reversibly
How fast does binding and unbinding of Hgb to O2 happen?
Milliseconds
Important for gas exchange
Loose bonds b/t Fe2+ & O2
Oxygen carried in molecular state
What is the shape of the HbO2 equilibrium curve?
Sigmoid
Rxn b/t four heme groups
Heme group’s O2 binding capacity enhancement
O2 Saturation = ? PaO2
100% =
95% =
90% =
75% =
60% =
50% =
100% = 100
95% = 75
90% = 60
75% = 40 (mixed venous blood in pulm artery)
60% = 30
50% = 27
Oxygen Hemoglobin Dissociation Curve:
pH: Up
CO2: Down
DPG: Down
Temp: Down
Left Shift - Holds on to O2 for greater transport
Oxygen Hemoglobin Dissociation Curve:
pH: Down
CO2: Up
DPG: Up
Temp: Up
Right Shift - Enhances release and uptake of O2 (Bohr Effect)
Ligands
Iron attracted more to ligands than to O2
EX: Carbon Monoxide, Nitric Oxide
What is the initial pressure difference that causes O2 to diffuse into pulmonary capillary?
104 - 40 - 64 mmHg
What happens when O2 is used by the cells?
Virtually all of it becomes CO2 , increasing PCO2 –> causes it to diffuse to capillaries –> then to lungs to be expired
Why does blood in the lung require less time to become fully oxygenated during exercise?
Diffusion capacity increases 3x due to increased surface area (recruitment)
How is tissue PO2 determined?
Balance between
Rate of O2 Transport to tissues
and
Rate of O2 used by tissues
Why is the pressure difference needed for CO2 diffusion A LOT less than that of O2?
CO2 diffuses 20x faster
(Alveolar CO2 is 40, capillary CO2 is 45… only 5 mmHg difference)
How much O2 is carried by 100 mL of plasma?
0.003 mL of O2
What is the max amount of O2 can Heme carry in a normal man and woman?
Man: 20 mL O2 per 100 mL of blood
Woman: 19 mL O2 per 100 mL of blood
How many oxygen molecules can bind to Hemoglobin?
Four
What is Oxygen Saturation?
Ratio of bound Oxygen to Total amt that can be bound to Hgb
What is Oxygen Capacity
Max amount of O2 bound to Hgb
What is shunt flow and how does it effect the blood entering the left heart?
The 2% of blood that came from aorta supplying the deep lung tissues.
Mixes with pulm. venous blood dropping PO2 from 104 mmHg to 95 mmHg
Carbon Monoxide
Iron attracted 250x more than it does Oxygen
Doesnt separate readily
Needs hours for body to get rid of it
Nitric Oxide
Binds 200k times stronger
Irreversible Binding
Used to treat Pulm. HTN
What is Methemoglobinemia?
Condition where the Hemoglobin CANNOT let go of oxygen
Treat with Methylene Blue
Which way does oxygen dissociation curve shift with PRBCs or stored blood?
Left Shift d/t decrease in DPG
How to calculate O2 content (CaO2) in blood?
CaO2 = (SO2 x [Hgb] x 1.31) + (PO2 x 0.003)
SO2 = O2 Sat (%)
How to calculate Oxygen Delivery (DO2)
CaO2 x CO
How do muscle cells, Myoglobin, relate to O2
Has increased infinity for O2 at lower PO2
and
Temporarily stores O2 in muscle
What reduces Hgb’s ability to transport O2?
Cardiac Output
Anemia
What is the volatile waste product of Cellular Metabolism
Carbon Dioxide
What is converted to CO2 to be exhaled in the lungs?
Carbonic Acid
What is the Total Amount of CO2 transported in the blood?
200 mL/min of CO2 made in resting adult
x6 for exercise
What is the average amount of CO2 transported to lungs?
4 mL per 100mL of blood
What is the function of the large amount of CO2 that remains in the blood?
Bicarbonate Buffer
Maintenance of Hydrogen Ion Concentration
85%
CO2 Transport
- Tissues use O2 and Produce CO2
- CO2 + H2O (Carbonic Anhydrase) –> H2CO3 (Carbonic Acid)
- H2CO3 splits into H+ & HCO3- (Bicarb)
- Bicarb exits cell, Cl- enters to balance
- Cell goes to Pulmonary Capillary
- Cl- exits and Bicarb Re-Enters
- HCO3- (Bicarb) + H+ –> H2CO3 (Carbonic Acid)
- Carbonic Anyhydrase splits H2CO3 –> CO2 + H2O
- CO2 leaves cell and goes into Alveoli
Bohr Effect
- Increase in CO2 causes O2 displacement
- Right shift
- Increase in H+ ion
- Increase in Carbonic Acid
Haldane Effect
- O2 + Hgb displaces CO2 from blood
- Hgb is stronger acid, makes it less likely to combine with CO2
- Releases exces Hydrogen Ions
What is the metabolic arteriovenous O2 difference in Respiratory Gas Transportation?
50 mL/L
What is the metabolic arteriovenous CO2 difference in Respiratory Gas Transportation
40 mL/L
What is the PO2 in the Tissue?
10 mmHg
What is the PCO2 in the Tissue
50 mmHg
Percentages of the Different Ways CO2 is Transported
- CO2: 7%
- Hgb - CO2: 23%^
- HCO3-: 70%
