PULMONARY 07: GAS TRANSPORT Flashcards
Oxygen is carried in what 2 forms:
Dissolved and bound to hemoglobin
Define PAO2
Alveolar partial pressure of oxygen
Define PaO2
Arterial partial pressure of oxygen - DISSOLVED
Define SaO2
Oxyhemoglobin or hemoglobin saturation - percentage of hemoglobin sites with oxyge nbound
This is dictated by PaO2 and PvO2
SpO2 is also called “peripheral” or “pulse” SO2
Define CaO2
Oxygen content, oxygen concentration - total oxygen in the blood per unit of volume (dissolved + oxyhemoglobin)
1mmHg of pO2 translates to 3uL O2 / 100mL of blood. That means that for the normal 100mmHg pO2, how much is in the blood? What does this mean for our oxygen needs vs what dissolves?
0.3mL / 100mL
The dissolved oxygen isn’t enough
What type of Hgb is most common in adults
HbA
Two states of hemoglobin molecularly speaking
Tense and relaxed state
Tense - low affinity
Relaxed - high affinity
binding of oxygen to hemoglobin does what to the state of hemoglobin
Increases amount of hemoglobin in relaxed state
At pressures of oxygen below 60mmHg, how is this affecting hemoglobin?
Small changes in oxygen pressure lead to a release of a huge amount of oxygen - faciliates release to organs/cells, but you don’t want this to be where the pressure of oxygen in the lungs is
A leftward shift in the hemoglobin - oxygen curve indicates what
More Hemoglobin-o2 binding
a rightward shift in the oxyhemoglobin dissociation cure indicates what?
Less hemoglobin oxygen binding
The point at which 1/2 hemoglobin is saturated is called what?
P50
Things that shift the oxyhemoglobin dissociation curve (4)
Temp
CO2
2,3 DPG
pH
For most factors, as factor X increases, hemoglobin binding to oxygen (increases/decreases)
Decreases
For the case of pH we’re thinking of it as concentration of protons (because this would actually be a decrease in pH)
As termperature increases, the oxyhemoglobin curve shifts what direction
Right
As co2 increases, what is the effect on the curve and how is it reacting with hemoglobin?
Rightward shift
It binds to amino termini (not the same place as oxygen binding)
Happens normally in systemic capillaries
Bohr effect
High CO2 leads to decreased pH; respiratory acidosis decreases O2 affinity - combination of CO and pH significantly changes binding curve shift
How does increasing 2,3 dpg affect oxyhemoglobin binding curve?
Rightward shift
It preferentially binds to deoxyhemoglobin and allosterically decreases affinity for O2
How does CO affect binding of O2 to hemoglobin
Dramatic INCREASE; hemoglobin has a WAY higher affinity for O2 so we can’t let go of it; however, CO also competitively binds for the same pocket, so you get less O2 binding overall
Therefore there’s less oxygen to begin with, and we can’t let go of what we’re carrying
What are 3 respiratory reasons being in a burning building is bad?
Carbon monoxide fucking with oxyhemoglobin curve and oxygen being carried
Fire burns O2, so there’s low O2 around
The smoke inhalation is going to deposit particles and block airways
Sickle cell Hemoglobin is denoted as what
HbS
What is the problem molecularly speaking with HbS?
Under normal conditions it’s normal. But in low O2, such as in tissues, some HbS converts into a crystalizing structure which is permanent and fucks with the shape of the RBC. The more the RBC’s ccle, the more they crystalize out of solution and make weird shapes.
What is Hb A1C
This is a standard blood test to look for diabetes. If you have high blood glucose, you get high levels of glucose-6-phosphate. This can glycosylate hemoglobin. The glycosylation itself is not pathalogical NECESSARIY, but we know that erythrocytes go in and out of cycle ~120 days ; therefore, you have a long term average readout for someone’s blood glucose level in this way
1g of Hb can bind how many mls of O2
1.34mL
To calculate oxygen content in arterial blood, we multiply what two things together?
O2 capacity of hemoglobin, and SO2 (oxygen saturation)
You don’t add what’s dissolved, it’s negligible
How much oxygen is extracted at tissues
4mL/100mL blood
If you have an anemic patient, how does this affect oxygen content?
For the same oxygen saturation, there is less total oxygen that can be used by the body
3 main ways carbon dioxide is transported in the blood
Dissolved
Bicarbonate
Carbamino compounds
What is the form MOST carbon dioxide is carried in the blood
bicarbonate
per 1mmHg PCO2, there is 0.067mL CO2/100mL in the blood. What does this mean about CO2 dissolving vs O2?
CO2 dissolves about 20x more readily than O2
CO2 conversion to bicarbonate PRIMARILY occurs where?
Erythrocytes using carbonic anhydrase (this would happen naturally in plasma, but VERY slow)
Most important protein carbon dioxide will bind to as a carbamino compound is what/
Hemoglobin
Hemoglobin can bind O2, or CO2 more?
CO2
This is not competitive, but stoichiometric (4co2/Hb)
Haldane effect
Unload more CO2 as we get to lungs in oxygen rich environment; bind CO2 in tissues with CO2 rich environment
Haldane vs Bohr
Haldane: Effect of O2 on Hb to increase/decrease binding to CO2
Bohr: Effect of CO2 on Hb to increase/decrease binding to O2
Therefore
Haldane: Important when considering CO2 unloading in lungs
Bohr: Important when understanding O2 unloading in tissues
