Human Phys 6.6 Flashcards
What percentage of dissolved O2 accounts for total O2 content in the blood?
2%
What form of O2 produces a partial pressure?
Dissolved gas
What drive diffusion?
Partial pressure
What is O2 bound to?
Hemoglobin
What percentage does bound gas account for?
98%
Does bound gas contribute to partial pressure?
No
What does CO2 get modified into?
HCO3 by carbonic anhydrase
What is perfusion limited gas exchange limited by?
Amount of blood
What is diffusion limited gas exchange limited by?
Strenuous exercise
Emphysema and fibrosis
What is the only way to get more diffusion?
Get more blood flow
What does pulmonary blood flow determine?
O2 transfer
What do both O2 and CO2 bind to for transport?
Hemoglobin
Why does O2 reach diffusion equilibrium while CO2 does not?
Hemoglobin in mixed venous blood is already about 75% saturated with O2
When does blood become almost fully saturated with oxygen?
By the time it passed through 1/3 of the pulmonary capillary and little additional oxygen normally enters the blood during the later 2/3
How long does the blood stay in the lung capillaries to cause full oxygenation?
3x as long
How many molecules of O2 can each molecule of hemoglobin bind?
4 molecules of O2
What is the PO2 when the arterial blood reaches the peripheral tissues?
95mmHg
What is the PO2 in the interstitial fluid that surrounds the tissue cells?
40mmHg
What is the % saturation?
Function of PO2 of blood
P50
The PO2 at which hemoglobin is 50% saturated
What does an increase in P50 indicate?
Drop in affinity
What can we tolerate significant drops of PO2 in without significant changes in O2 carried by hemoglobin?
From 100-60mmHg
What does a right shift of the O2 hemoglobin dissociation curve mean?
Hemoglobin more likely to let go O2 (low affinity)
What does a left shift of the O2 hemoglobin dissociation curve mean?
Hemoglobin hangs on to O2 (high affinity)
What causes a right shift in the O2 hemoglobin dissociation curve?
Increase PCO2
Increase temperature
Increase 2.3-DPG
Decrease pH
What causes a left shift in the O2 hemoglobin dissociation curve?
Decrease PCO2
Decrease temperature
Decrease 2.3-DPG
Increase pH
What is the amount of dissolved CO2?
5%
What is the amount of CO2 bound to hemoglobin?
3%
What is the amount of CO2 modified to bicarbonate?
90%
How much faster can CO2 diffuse than O2?
20x faster
What are the pressure differences needed to cause CO2 diffusion?
Much less than those needed to cause O2 diffusion
Diffusion of O2 to capillary blood
PO2 = 160
Enters trachea and PO2 drops to 150
Reaches alveolar air PO2=100 and PCO2= 40
Mixed venous blood comes in with a PO2=40 and PCO2=46
O2 moves in CO2 moves out and as the blood passes alveolar air and changes blood to PO2=100 and PCO2=40
What does it mean when systemic arterial blood equals the alveolar air?
Blood is fully oxygenated
