Term
| In what major forms is oxygen transported in the blood? |
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Definition
Oxygen content= O2plasma + O2Hb
1) Dissolved in plasma (ml O2/ 100ml blood)= 0.003x PaO2
- linear relationship between dissolved O2 and PaO2
2) Bound to Hb
- 1.34 ml O2 can saturate 1 gram of Hb
- Non-linear saturation kinetics (flattens above 50) |
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Term
| What factors regulate the relationship between the partial pressure of oxygen in arterial blood and Hb saturation? |
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Definition
Dropping arterial pressure below 40 mmHg will cause "unloading." If P50 is shifted to "left," it becomes more difficult to unload oxygen.
1) pH
2) Temperature of blood
3) [2,3 DPG]
Left shift (P50 is lower, Hb binds O2 tighter)
1) Decrease temp, decrease 2.3 DPG or increase pH
Right shift (greater partial pressure to achieve 50% saturation- give O2 up)
1) Increase temperature
2) Decrease pH
3) Increase 2-3 DPG |
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Term
| How is the total oxygen content of arterial blood expressed mathematically? |
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Definition
TOC= O2 plasma + O2 Hb
TOC= (0.003 X PaO2) + (1.34 X Hgb X SaO2/100) |
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Term
| What is total oxygen delivery (DO2) and how does it relate to hypoxia? |
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Definition
Product of arterial content (CaO2) and blood flow (CO)
1) O2 provided to each organ
DO2= CaO2 X CO X 10
2) Hypoxia can occur if either arterial blood content (anemia) decreases or CO decreases (HF) |
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Term
| How is CO2 from actively metabolizing cells carried to the lungs for excretion? |
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Definition
1) Diffuses across partial pressure gradient out of cell and into plasma, before entering RBC
a) small amount dissolves
b) some combines with Hb to form carbamino compound (Haldane effect)
c) some becomes H+ and HCO3- (fast with CA), and HCO3- is exchanged for Cl- in blood (chloride shift)
2) Blood that remains in plasma is transported as either
a) dissolved CO2 (0.067 X PaCO2)
b) bound to plasma proteins as carbamino compounds
c) hydrated to carbonic acid (slow without CA in plasma) |
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Term
| What do the Bohr and Haldane effects have to do with CO2 transport in the blood? |
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Definition
In RBCS, CO2 can dissolve (small amount), or
1) Combine with unsaturated Hb to form carbamino groups (Haldane effect)
2) Become hydrated to H+ and HCO3- (CA-mediated), where HCO3- is exchanged for extracellular Cl- and H+ binds to Hb, decreasing its affinity for O2 in alveoli (Bohr effect)
In tissues, increased PCO2 facilitates O2 unloading by hydrating Hb (Bohr) and un-oxygenated Hb facilitates CO2 loading (Haldane)
In lungs, Hb oxygenation facilitates CO2 unloading (Haldane) and decreased PCO2 facilitates O2 loading. |
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Term
| How do O2 and CO2 saturation kinetics differ in blood? |
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Definition
1) Oxygen saturation is readily achieved after critical PP is met (>60 mm Hg)
2) Multiple CO2 carrier systems assure that saturation of systems does not occur even in the presence of significant anemia |
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Term
| What happens to CO2/O2 handling in tissues and lungs, respectively? |
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Definition
Think about in terms of PCO2.
1) In tissues, PCO2 is high and pH is low. In RBCs, CO2 becomes H+ and HCO3-, and H+ complexes with Hb to release O2 to the tissue (Bohr). Deoxygenated Hb then picks up CO2 to form Carbamino groups (Haldane)
2) In lungs, PCO2 is low, and pH is higher. Decreased CO2 facilitates O2 loading onto Hb (Bohr), because less Hb will be hydrated, and this oxygenation facilitates CO2 unloading (Haldane) |
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Term
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Definition
Oxygen content of arterial blood
Oxygen carried by Hb + dissolved O2
= 1.34 X Hbg (g/dL) + (0.003 X PaO2) |
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