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62 Cards in this Set
- Front
- Back
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2 forms of oxygen in the blood:
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-Dissolved
-Bound to hemoglobin |
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How much oxygen in the blood is
-Bound -Dissolved -Total |
Bound = 19.7 ml/100 ml
Dissolved = 0.3 ml/100 ml Total = 20 ml/100 ml blood |
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For an arterial O2 content of 20, what is the PO2 at the mixed venous point? O2 saturation? O2 content?
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PO2 = 40
O2 saturation = 75 O2 content = 15 ml/dl |
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What is the PO2 at the arterial point? O2 saturation? Content?
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PO2 = 100
O2 saturation = 100 O2 Content = 15 ml/dl |
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What is the PO2 at the P50?
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24 mm Hg
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What is the difference between bloodgas partial pressure and bloodgas contents?
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Pressure reflects the kinetic energy of DISSOLVED gas.
Content reflects the TOTAL amt of gas in the blood. |
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4 factors that affect the affinity of hemoglobin for O2:
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1. PCO2
2. [H+] 3. Temp 4. 2,3-DPG |
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What is the bohr effect?
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PCO2 and H+
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How is hemoglobin's affinity for O2 quantitated?
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By the P50
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What is the P50?
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The pressure of O2 when hemoglobin is 50% saturated
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What is the normal P50?
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24
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What is the P50 when the curve is shifted to the left? Why?
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Lower - 20, because the O2 pressure at which Hb releases its oxygen is lower due to higher affinity.
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What is the P50 when the curve is shifted to the right? Why?
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Higher - 26, because the O2 pressure at which Hb releases its oxygen is higher due to decreased affinity.
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Why is a change in Hb affinity for O2 beneficial to O2 transport during conditions like muscle exercise and high altitude?
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Because when the P50 is highest, O2 affinity is decreased & the PO2 gradient for diffusion from capillaries to tissues is highest - increases performance.
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What is the effect of anemia on delivery of O2?
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-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. |
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What is the affect of CO poisoning on delivery of O2?
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-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 |
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What is the normal blood Hb?
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15 g/100 ml
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What is the Hb in anemia?
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7.5 g/100 ml
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What is the normal difference in oxygen content of arteries vs veins?
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5 ml/100 ml
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What is the normal o2 content in arteries? veins?
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Arteries = 20 ml/dl
Veins = 15 ml/dl |
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What is the O2 content in arteries and veins in CO poisoning and anemia?
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Arteries = 10 ml/dl
Veins = 5 ml/dl |
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What is the mixed venous PO2 normally? In anemia? In CO poisoning?
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Normal: 40
Anemia: 25 COHb: 17 |
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What are 4 major factors that affect the decrease in PO2 as blood traverses the systemic capillaries?
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1. Metabolic rate of the tissue
2. Arterial O2 content 3. Hemoglobin affinity 4. Rate of capillary bloodflow |
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How does oxygen delivery change during exercise when metabolic rate increases?
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Arterial O2 content doesn't change but Hb affinity decreases and capillary bloodflow increases.
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What happens to end capillary PO2 during exercise?
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It is decreased because more oxygen is taken out of the blood
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In what form is the majority of CO2 in the blood carried? How much?
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In the form of Bicarbonate - 70%
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What are 2 other forms of CO2 in the blood other than Bicarb? How much of each?
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-Bound to hemoglobin - 25%
-Dissolved - 5% |
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What is the Haldane effect?
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The effect that increasing PO2 has on PCO2 (inverse)
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What is carbonic anhydrase?
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An enzyme that increases the rate of hydration of CO2
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Why is RBC carbonic anhydrase important to CO2 transport?
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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.
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What is the chloride shift in the blood?
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The movement of bicarb out of the red cell in exchange for chloride in plasma.
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What is the function of the chloride shift?
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To keep the concentration of bicarb in RBCs low so the CA reaction will keep going forward.
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What is the Haldane effect?
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The effect of reducing Hb bound to O2 on the amt of CO2 and H+ that can be bound.
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2 sites where mixed venous blood can be obtained:
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-Right heart
-Pulmonary artery |
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Normal Arterial Po2:
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95 mm Hg
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Normal Mixed venous PO2:
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40 mm Hg
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Normal Hemoglobin (arterial and mixed venous)
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15 g/ 100 ml
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Normal arterial oxygen saturation %
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98%
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Normal mixed venous oxygen saturation %
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75%
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Normal arterial bound O2
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19.7
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Normal mixed venous bound O2
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15.1
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Normal arterial total O2
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20.0
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Normal mixed venous total O2
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15.2
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Normal arterial PCO2
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40
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Normal mixed venous PCO2
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45
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Normal arterial dissolved CO2
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2.52
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Normal mixed venous dissolved CO2
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2.84
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Normal total arterial CO2
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48
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Normal total mixed venous CO2
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52
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What is the arterial-mixed venous O2 content difference?
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20 - 15.2 = 4.8
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What is the arterial-mixed venous CO2 content difference?
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52-48 = 4
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Why does the arterial-mixed venous O2 content difference exceed the CO2 content difference?
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Because of the respiratory quotient - humans use more oxygen than they put out CO2
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What is the respiratory quotient in humans? Why?
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0.7 - because of the fat in our diet.
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What would the respiratory quotient be if we only ate carbs?
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1
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Why is the arterial-mixed venous PO2 difference ~60 mm Hg while the PCO2 difference is only ~5?
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Because of the difference in the characteristics of the O2 and CO2 dissociation curves in the physiologic range.
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Considering the arterial-venous difference, how can one increase O2 delivery to cells in a normal healthy individual? (2 ways)
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-Increase bloodflow
-Increase Hb concentrations |
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What type of symptoms would a patient with COPD have? Why?
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Exertional dyspnea - because he has decreased arterial PO2 which stimulates his drive for breathing.
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What type of symptoms would a patient with anemia have? Why?
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Fatigue and low work tolerance; because there is compromised delivery of oxygen to the tissues.
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Why wouldn't a patient with anemia have exertional dyspnea?
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Because they have normal arterial PO2 and so the drive for breathing isn't increased.
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If a patient had all normal blood gas, pH, and Hb levels, but a very low arterial O2 content, what would you suspect?
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CO poisoning
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What patient would be most/least effected by increasing inspired PO2? (COPD, anemia, CO poisoned)
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Most = CO poisoning
Least = anemia |
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What is the standard treatment for CO poisoning?
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Administration of 100 % O2
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