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62 Cards in this Set

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  • Back
2 forms of oxygen in the blood:
-Bound to hemoglobin
How much oxygen in the blood is
Bound = 19.7 ml/100 ml
Dissolved = 0.3 ml/100 ml
Total = 20 ml/100 ml blood
For an arterial O2 content of 20, what is the PO2 at the mixed venous point? O2 saturation? O2 content?
PO2 = 40
O2 saturation = 75
O2 content = 15 ml/dl
What is the PO2 at the arterial point? O2 saturation? Content?
PO2 = 100
O2 saturation = 100
O2 Content = 15 ml/dl
What is the PO2 at the P50?
24 mm Hg
What is the difference between bloodgas partial pressure and bloodgas contents?
Pressure reflects the kinetic energy of DISSOLVED gas.
Content reflects the TOTAL amt of gas in the blood.
4 factors that affect the affinity of hemoglobin for O2:
1. PCO2
2. [H+]
3. Temp
4. 2,3-DPG
What is the bohr effect?
PCO2 and H+
How is hemoglobin's affinity for O2 quantitated?
By the P50
What is the P50?
The pressure of O2 when hemoglobin is 50% saturated
What is the normal P50?
What is the P50 when the curve is shifted to the left? Why?
Lower - 20, because the O2 pressure at which Hb releases its oxygen is lower due to higher affinity.
What is the P50 when the curve is shifted to the right? Why?
Higher - 26, because the O2 pressure at which Hb releases its oxygen is higher due to decreased affinity.
Why is a change in Hb affinity for O2 beneficial to O2 transport during conditions like muscle exercise and high altitude?
Because when the P50 is highest, O2 affinity is decreased & the PO2 gradient for diffusion from capillaries to tissues is highest - increases performance.
What is the effect of anemia on delivery of O2?
-Hb is decreased
-Total O2 content is decreased
-Arterial PO2 is still 100 but contains less content - 10
-Arterial - Veinous O2 content is normally 5, so veinous content is 5 ml/100 ml; that corresponds to PO2 of 25 mm Hg - the pressure of O2 in the tissues is very low.
What is the affect of CO poisoning on delivery of O2?
-The total O2 content is decreased bc Hb's storage capacity is taken up by CO - the veinous O2 content = 5
-ALSO, CO enhances Hb's affinity for O2 which compounds the effect and reduces the veinous PO2 to 17
What is the normal blood Hb?
15 g/100 ml
What is the Hb in anemia?
7.5 g/100 ml
What is the normal difference in oxygen content of arteries vs veins?
5 ml/100 ml
What is the normal o2 content in arteries? veins?
Arteries = 20 ml/dl
Veins = 15 ml/dl
What is the O2 content in arteries and veins in CO poisoning and anemia?
Arteries = 10 ml/dl
Veins = 5 ml/dl
What is the mixed venous PO2 normally? In anemia? In CO poisoning?
Normal: 40
Anemia: 25
COHb: 17
What are 4 major factors that affect the decrease in PO2 as blood traverses the systemic capillaries?
1. Metabolic rate of the tissue
2. Arterial O2 content
3. Hemoglobin affinity
4. Rate of capillary bloodflow
How does oxygen delivery change during exercise when metabolic rate increases?
Arterial O2 content doesn't change but Hb affinity decreases and capillary bloodflow increases.
What happens to end capillary PO2 during exercise?
It is decreased because more oxygen is taken out of the blood
In what form is the majority of CO2 in the blood carried? How much?
In the form of Bicarbonate - 70%
What are 2 other forms of CO2 in the blood other than Bicarb? How much of each?
-Bound to hemoglobin - 25%
-Dissolved - 5%
What is the Haldane effect?
The effect that increasing PO2 has on PCO2 (inverse)
What is carbonic anhydrase?
An enzyme that increases the rate of hydration of CO2
Why is RBC carbonic anhydrase important to CO2 transport?
If absent, less CO2 is carried from the tissues to the lung in the form of bicarb; venous PCO2 and dissolved CO2 will increase more than normal.
What is the chloride shift in the blood?
The movement of bicarb out of the red cell in exchange for chloride in plasma.
What is the function of the chloride shift?
To keep the concentration of bicarb in RBCs low so the CA reaction will keep going forward.
What is the Haldane effect?
The effect of reducing Hb bound to O2 on the amt of CO2 and H+ that can be bound.
2 sites where mixed venous blood can be obtained:
-Right heart
-Pulmonary artery
Normal Arterial Po2:
95 mm Hg
Normal Mixed venous PO2:
40 mm Hg
Normal Hemoglobin (arterial and mixed venous)
15 g/ 100 ml
Normal arterial oxygen saturation %
Normal mixed venous oxygen saturation %
Normal arterial bound O2
Normal mixed venous bound O2
Normal arterial total O2
Normal mixed venous total O2
Normal arterial PCO2
Normal mixed venous PCO2
Normal arterial dissolved CO2
Normal mixed venous dissolved CO2
Normal total arterial CO2
Normal total mixed venous CO2
What is the arterial-mixed venous O2 content difference?
20 - 15.2 = 4.8
What is the arterial-mixed venous CO2 content difference?
52-48 = 4
Why does the arterial-mixed venous O2 content difference exceed the CO2 content difference?
Because of the respiratory quotient - humans use more oxygen than they put out CO2
What is the respiratory quotient in humans? Why?
0.7 - because of the fat in our diet.
What would the respiratory quotient be if we only ate carbs?
Why is the arterial-mixed venous PO2 difference ~60 mm Hg while the PCO2 difference is only ~5?
Because of the difference in the characteristics of the O2 and CO2 dissociation curves in the physiologic range.
Considering the arterial-venous difference, how can one increase O2 delivery to cells in a normal healthy individual? (2 ways)
-Increase bloodflow
-Increase Hb concentrations
What type of symptoms would a patient with COPD have? Why?
Exertional dyspnea - because he has decreased arterial PO2 which stimulates his drive for breathing.
What type of symptoms would a patient with anemia have? Why?
Fatigue and low work tolerance; because there is compromised delivery of oxygen to the tissues.
Why wouldn't a patient with anemia have exertional dyspnea?
Because they have normal arterial PO2 and so the drive for breathing isn't increased.
If a patient had all normal blood gas, pH, and Hb levels, but a very low arterial O2 content, what would you suspect?
CO poisoning
What patient would be most/least effected by increasing inspired PO2? (COPD, anemia, CO poisoned)
Most = CO poisoning
Least = anemia
What is the standard treatment for CO poisoning?
Administration of 100 % O2