Gas Transport Mechanisms Flashcards
Dalton’s Law of Partial Pressures
the total pressure of atmospheric gas is equal to the sum of the partial pressures of each gas subcomponent
760 mm Hg total
normal partial pressure of N2
596 mm Hg, 78.6%
normal partial pressure of O2
158 mm Hg, 20.8%
normal partial pressure of CO2
0.3 mm Hg, 0.04%
Atmospheric Pressure
normal partial pressure of H2O
5.7 mm Hg, 0.5%
Alveolar Gas: composition will
Alveolar Gas
compensation will differ from atmospheric gas
Why does aveolar gas differ from atmospheric gas?
- incomplete replacement of Alveolar air with Atmospheric air
- O2 is constantly being absorbed by Alverolar capillaries
- CO2 is leaving pumonary capillaries and entering alveoli
- atmospheric air is usually much drier than alveolar air
partial pressure of water will displace other gases there is moisture in the airway passages
Alveolar Gas Partial Pressure
N2: 573 mm Hg
O2: 100 mm Hg
CO2: 40 mm Hg
H2O: 47 mm Hg
Arterial Gas Partial Pressure
N2: 573 mm Hg
O2: 95 mm Hg
CO2: 40 mm Hg
H2O: 47 mm Hg (ignore)
O2 is less than alveolar gas because the lungs use oxygenated blood to supply their tissues
Venous Side of Capillaries Partial Pressures
N2: 573 mm Hg
O2: 40 mm Hg
CO2: 46 mm Hg
H2O: 47 mm Hg (ignore)
O2 gets dumped off in tissues, CO2 diffuses from tissues into capillaries
Why does CO2 diffuse into the lungs and O2 diffuse into the blood?
the differences in partial pressure
higher O2 in alveolar gas than blood
higher CO2 in blood than alveolar gas
3 forms of CO2 in the blood stream
- HCO3 - 70%
- bound to hemoglobin - 23%
- free gas, CO2 - 7%
Oxygen-Hemoglobin Dissociation Curve
expressed as % O2 saturation vs partial pressure O2
Oxygen-Hemoglobin Dissociation Curve
P50 Value
the pO2 where hemoglobin is 50% saturated
the higher the P50 value, the lower the affinity of hemoglobin for O2
Oxygen-Hemoglobin Dissociation Curve
Causes for a Right Shift
- Low pH (acid)
- Increase in CO2 (acid)
- Increase in Temperature
- Increase in 2,3 DPG (caused by increase in temp or decrease in pH)
higher P50, lower hemoglobin binding affinity
Oxygen-Hemoglobin Dissociation Curve
Fetal Hemoglobin has low 2,3 DPG binding therefore:
a higher binding affinity for O2 than maternal blood
left shift of curve
DPG at high altitude
increased 2,3 DPG production, O2 less tightly bound, easy to dump off O2 to tissues
Right Shift of curve
Erythropoietin
produces RBCs
Mountain Sickness
- Decreased BP
- decreased air pressure in alveoli
- Hyperventilation and alkalosis
- edema in lungs and nervous system
- potential for coma and death
Myoglobin vs Hemoglobin
Myoglobin has higher binding affinity for O2 than hemoglobin
Effect of Carbon Monoxide
- Forms Carboxyhemoglobin(210x more affinity for hemoglobin than oxygen)
- Displaces O2 binding
- When bound to 70-80% hemoglobin death results (anemic hypoxia)
treatment with hyperbaric chamber or transfusion
The Bends
elevated N2 dissolved in blood due to increased water pressure
causes arterial blockage, joint pain, explossive decompression, air embolism
happens when at depth for too long or rapidly rising to the surface
Nitrogen Narcosis
high concentrations of nitrogen have a narcotic effect on the nervous system
How to survive swimming to the surface from a submarine?
exhale as you swim up as air in lungs expands during ascent
Chloride Shift
- Excess HCO3- builds up in RBC
- HCO3- is exchanged with Cl- ions
- HCO3- enters plasma
Carbonic Anhydrase mediates
CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
