Gas Transport Flashcards
What are the mechanisms for O2 transport in the blood?
- Dissolved
- Hemoglobin-bound
How much of the O2 does dissolved O2 make up?
0.3 mL/100 mL blood
This amount is essentially negligible.
What is Henry’s Law of gas solubility?
The concentration of a solute gas is proportional to is partial pressure above the solution.
What is the color of oxygenated Hb?
Red
What is the color of deoxygenated Hb?
Bluish
What is the significance of the O2 dissociation curve?
Its S-shaped slope facilitates the uptake of O2 at high pressures and the release at lower pressures
What is the normal P50 of O2?
27 mmHg - this is the partial pressure where Hb reaches 50% saturation
What happens with a right shift of the O2 dissociation curve?
It decreases the affinity of Hb for O2 and increases the P50 as a result.
What happens with a left shift of the O2 dissociation curve?
It increases the affinity of Hb for O2 and decreases the P50 as a result.
What happens to the O2 dissociation curve with exercise?
The curve will shift to the right and affinity for O2 will decrease due to increases in temperature, PCO2, 2,3-DPG and [H+]
What is the Bohr Effect?
Hb’s O2 binding affinity is inversely proportional to the acidity and CO2 concentration.
What occurs to the O2 dissociation curve in the presence of CO?
O2 curve will shift left and the O2 binding affinity of Hb will be greatly increased which will interfere with the unloading of O2.
What do victims of CO poisoning generally present with?
They are generally red due to O2 still being in the blood but it is just that it cannot be unloaded normally.
Where does hypoxemia become very dangerous?
Around 90% as the PO2 drops down to 60 mmHg
What is the normal O2 content in the venous blood?
75% saturation
What happens to the venous saturation in an anemic patient?
Anemic patient has less O2 extracted at 75% saturation than a normal person so compensation is done so that more O2 is extracted in the venous blood and saturation goes to 54% to extract the same amount of O2 as a normal person
Does saturation vary with the concentration of Hb?
No
What factor does depend on the concentration of the Hb?
O2 extracted
What are the mechanisms for CO2 transport?
- Dissolved
- As carbamino compounds
- Bicarbonate
How much of the CO2 is dissolved in the blood?
10%
Why is there more CO2 dissolved in the blood than O2?
CO2 is more soluble than O2
Is the conversion of CO2 to bicarbonate fast in the plasma?
No
Is the conversion of CO2 to bicarbonate fast in the RBC?
Yes. There is carbonic anhydrase in order to catalyze the reaction.
What is the Haldane Effect?
Reduced Hb can bind more CO2 than oxy-Hb
What is the majority of CO2 transported as?
Bicarbonate
What is the chloride shift?
As HCO3 increases in RBCs, it will diffuse out and Cl- will diffuse into the cells
What is the Haldane Shift?
In pulmonary capillaries where the environmental PO2 is high, the presence of oxygen decreases the affinity of hemoglobin for CO2 and assists in the unloading of CO2 from the blood to the alveolar spaces.
What is the Bohr Shift?
Conversely, in tissue capillaries where the environmental PCO2 is high, the presence of carbon dioxide decreases the affinity of hemoglobin for O2 and assists in the unloading of O2 from the blood to the tissue spaces.
What is the cause of hypoxic hypoxia?
Conditions of decreased PO2 which causes insufficient O2 delivery to tissues.
What can cause hypoxic hypoxia?
COPD
Pulmonary Fibrosis
Suffocation
What is a typical symptom of hypoxic hypoxia but is not required?
Cyanosis
What is the cause of circulatory/stagnate hypoxia?
It is due to reduced blood flow to tissues or that the supply rate is too slow.
What can cause circulatory hypoxia?
Vascular Disease
Cardiac Insufficiency
What is the cause of anemic/hypemic hypoxia?
Too little blood so that sufficient levels of O2 cannot be carried.
What can cause anemic hypoxia?
Anemia
CO Poisoning
What is the cause of histotoxic hypoxia?
Inability of the cell to use O2
Inhibit the O2 transport and usage in the mitochondria where the PO2 is normal
but the cells cannot use it
What can cause histotoxic hypoxia?
Poisoning (cyanide, etc)
What is the O2 saturation?
It is the amount of HbO2 divided by the O2 capacity and equal to the O2 binding sites of Hb occupied by O2
