Pulmonary 7 - Lecture 29 Flashcards
What are two ways that oxygen is carried in blood?
- Dissolved
2. Bound to Hemoglobin
What is a way to measure PaO2?
Using Dissolved Oxygen
- small percentage of total O2 & is almost negligible under normal conditions
What is the composition of oxygen?
4 heme groups containing Iron (Fe3+)
- 2 alpha globin chains
- 2 beta-globin chains
HbA
What type of hemoglobin do children less than 1 year have?
HbF
- 2 alpha
- 2 gamma globin chains
Binded Hb is what color? Doxygenated Hb?
Red if Saturated
Blue if desaturated
What are the changes of Hb saturation at partial pressures > than 60 mmHg?
Less than 60?
- Greater than 60 = SMALL CHANGES in Hb saturation (plateau)
- Less than 60 = LARGE changes in Hb saturation with SMALL changes in pressure
- release of O2 in large amounts
Why does the Hb dissociation curve have such a steep slope?
Due to the COOPERATIVELY of oxygen molecules
At 50 % saturation, what is the P02 of Oxygen? As we shift right or left, how does this value change?
27 mmHg!
Memorize this
RIGHT: pO2 (p50) INCREASES (lower affinity)
LEFT: pO2 (p50) DECREASES
- higher affinity
What causes a RIGHTward shift in the Oxygen Dissociation Curve? (6)
- Exercise
- More CO2 production
- Lower pH
- Less O2
- Increase in Temp
- 2,3,-DPG
- causes a decrease in Hb affinity so that more O2 can be dropped off
How do the following shift the oxygen dissociation curve?
- Decrease in temp
- Decrease in pCO2
- Decrease in 2,3,-DPG
- Increase pH
LEFTWARD shift, increases affinity
How is the affinity of CO as compared to O2?
200 times greater affinity!
- at 1 mmHg of CO all binding sites are occupied
In the presence of small amounts of CO, how is affinity for O2 change and unloading?
O2 affinity INCREASES
unloading decreases!
- CO shifts curve LEFT
- unloading is blocked so SUFFOCATIOn ensues (no cyanosis since all Hb is still saturated)
When you reduce saturation to 94.5, how does the PO2 change? What about 90%?
PO2 drops to 80 mmHg
- HYPOXEMIA
PO2 drops to 60 mmHg = DANGER!!
How does oxygen delivery change in anemic patients?
Overall amount of oxygen delivery falls DOWN
What does the overall amount of O2 in the blood directly correlated with?
The amount of Hb in blood stream!
- less Hb (as in anemia) means less O2 bound and lower O2 concentration
What are the 3 ways CO2 is carried in the blood?
- Dissolved
- as Bicarbonate
- Carbamino Compounds with Proteins
Amount of CO2 and O2 dissolved follows what law?
HENRY’s law
C=kP
What can be dissolved more in blood: O2 or CO2? Why?
CO2!
- 20 times more soluble than O2
How does CO2 exist in plasma? in Erythrocytes?
- majority as CO2
- slow conversion to carbonic acid - Carbonic Anhydrase (CA) exists to convert CO2 to Carbonic Acid (H2CO3) –> which spontaneously dissociated to bicarbonate (HCO3-)
What is the most important protein? What can HB bind more, CO2 or O2?
Global of hemoglobin
- binds Carbaminohemoglobin
- can bind more CO2 due to the HALDANE affect
What is the majority of CO2 transported in the blood? (what form?)
- 60-70% as HCO3-
- 30-30% as Carbamino
- 60-70% as HCO3-
What happens when intracellular H+ and HCO3- increase? What anion begins to move in?
HCO3- diffuses out
- Cl- moves in to maintain electrical neutrality (negative charges move in, since HCO3 - is moving OUT)
= CHLORIDE SHIFT
–> curve moves RIGHT
With an increase in H+ and a decrease in pH and increase in CO2, what kind of shift occurs in the oxygen dissociation curve? How does p50 change?
curve shits RIGHT
- p50 increases
- O2 delivery facilitated
Because some Hb are loaded with H+, what is unloaded as a result?
CO2 unloading!
- hemoglobin is as important for oxygen delivery as it is for CO2 delivery
What is the haldane affect?
The lower the O2 saturation, the larger the CO2 concentration!
if Po2 is low, pCO2 is HIGH
How do the dissociation curves of CO2 and O2 relate?
No plateau phase in CO2!
CO2 line is linear and can bind much more CO2
- small changes in partial pressures cause SMALL differences)
In oxygen, differen saturation means DRASTICALLY different partial pressure
What is Tissue Hypoxia?
Insufficient oxygen is available to maintain adequate aerobic metabolism!
- higher pressure of O2 in capillaries and lower pressure of O2 in tissues, so the O2 diffuses down the gradient into the tissues!
O2 consumption continues at the same rate in tissue hypoxia until when?
Until PO2 is < 3 mmHg
What is Hypoxic Hypoxia? Name 3 examples
What is a typical clinical symptom?
Diseases/Conditions with decreased PaO2 leading to insufficient O2 delivery to tissues
- Suffocation
- COPD
- Pulmonary fibrosis
Clinal symptom: CYANOSIS
due to lack of oxygen and increased deoxyhemoglobin
(6g/dl of deoxyhemoglobin is required)
What are the 4 major types of tissue hypoxia?
- Hypoxic Hypoxia
- Circulatory (Stagnate) Hypoxia
- Anemic (Hypemic) Hypoxia
- Hystotoxic Hypoxia
What is circulatory or stagnate hypoxia?
State 2 clinical examples
Reduced blood flow to tissues
- Vascular Disease
- Cardiac Insufficiency (heart failure)
Flow to the tissues is extremely SLOW so oxygen rate is not enough to supply organs with sufficient oxygen
What is Anemic (Hypemic) Hypoxia?
Name 2 clinical examples
Inability of blood to carry sufficient oxygen
- Anemia (not enough RBC’s)
- CO poisoning (binding sites of Hb blocked! = suffocation)
What is Histotoxic Hypoxia? What is this due to?
Inability of the cell to utilize oxygen
- due to POISONING
- Cyanide
- Sodium Azide
Inhibit oxygen transport in the mitochondria!
- pO2 is normal and venous blood has a high O2, but cells cannot utilize the oxygen!
What is the O2 saturation?
The amount of O2 combined with Hb / O2 capacity
this is equal to the O2 binding sites of Hb occupied by O2
Most of the CO2 in blood is transported how? Where?
- Bicarbonate
2. Erythrocytes
Because the tissue Po2 pressure is very low, how is O2 transfer facilitated form the capillary to the tissue?
via the PRESSURE GRADIENT!
- Po2 in tissues about 5 mmHg
higher PO2 in capillary
What are 3 factors that determine O2 delivery to the tissues?
- Oxygen Content
2. Blood Flow
What is the Hb concentration under the following conditions:
- Anemia
- Normal
- Polycethemia
How do Oxygen Saturation and Oxygen concentration change?
- Hb = 10 g/dL
- SO still 100
- O2 concentration DECREASED (less Hb) - Normal Hb = 15
SO = 100 (97%) - Polycythemia Hb = 20 g/dL
- SO still 100
- O2 concentration INCREASED
How does CO change the Oxygen content in blood?
- Has high affinity for Hb
- if 1/3 of Hb is bound to CO, the curve shifts LEFT and Hb increases affinity for O2 and prevents unloading at the tissues!
= suffocation
Where is the only place bicarbonate cannot form? Why?
PLASMA
- no Carbonic Anhydrase to catalyze the reaction
How does the Arterial Venous Difference for PCO2 compare to PO2?
- SMALL difference in PCO2
(40 arterial and 47 venous) - Large difference in PO2
(40 venous & 100 arterial)
DESPITE THIS difference in CONTENT: the exchange of O2/CO2 in arterial & venous blood is the same
What is the affect of CO on Hb and on the oxygen dissociation curve?
- High affinity for Hb so takes up Hb easily and prevents O2 binding
- Shifts O2 curve LEFT making it difficult for Hb to unload O2!
