PSL301: Respiratory 3 Flashcards
Dalton’s law of partial pressures tells us that total atmospheric pressure =
the sum of all partial pressures + water
PB = PO2 + PCO2 + PN2 + PH2O
pB - pH2O = pO2 + PCO2 + PN2
formula: partial pressure
fractional concentration * total pressure
Normal value for PB
760 mmHg
Normally, O2 makes up __% of air
21
Normally, CO2 makes up __% of air
0.04
Difference between fractional concentration and concentration
Fractional: gas in gas
Concentration: gas in liquid
Why is water included in the calculation of PB?
Air is humidified in the airway
what is the normal pH2O?
47 mmHg
How much O2 and CO2 is in the alveoli? (aka how much is available for exchange?)
100 mmHg O2
40 mmHg CO2
Not all the O2 breathed in will be available for exchange
What determines how much gas dissolves into solution?
- Partial pressure of the gas
- Solubility of the gas
- Temperature of the solution
What happens when gasses are at equilibrium?
the partial pressure will be the same in air and solution
LOWER/HIGHER partial pressure of a gas = increased solubility in water
Higher
What is more soluble, O2 or CO2?
CO2
Fick’s Law of Diffusion
Gas transfer = constant * pp gradient * area / wall thickness
Constant includes solubility of that particular gas
Fick’s Law of Diffusion tells us
amount of gas transfered
List the conditions that affect gas exchange
- Emphysema
- Fibrotic lung disease
- Pulmonary edema
- Asthma
How does emphysema affect gas exchange?
- alveoli destroyed
- less SA for gas exchange
Low/normal pO2 in lungs
Low pO2 in capillaries
How does Fibrotic lung disease affect gas exchange?
- thickened alveolar walls slow gas exchange
- loss of lung compliance may decrease ventilation
Low/normal pO2 in lungs
Low pO2 in capillaries
How does pulmonary edema affect gas exchange?
- more fluid in interstitial space, so distance travelled by O2 is longer
Normal pO2 in lungs
Low pO2 in capillaries
How does Asthma affect gas exchange?
- ventilation decreased
Low pO2 in lungs
Low pO2 in capillaries
How much O2 and CO2 are there left after passing the tissues?
pO2 = 40 pCO2 = 46
How is O transported in the blood?
> 98% bound to Hb
<2% dissolved in plasma
At lungs, __% of Hb is saturated with O
98
At tissues, __% of Hb is saturated with O
75
How much O2 is released at the tissues?
25%
What happens to the Hb saturation curve as pH goes down?
right shift
As temperature goes down, what happens to the Hb saturation curve?
left shift
What factors affect affinity of Hb for O2?
- pH
- temp
- pCO2
At higher pCO2, what happens to the Hb dissociation curve?
right shift
What is the effect of CO2 on Hb dissociation called?
Bohr effect
2 types of hemoglobin made during development
- fetal hemoglobin
2. maternal hemoglobin
The Hb dissociation curve of fetal hemoglobin looks like…
left shift
When is fetal hemoglobin produced?
During development inside mom; stopped as soon as baby is born
Why is fetal hemoglobin different from maternal?
Higher affinity for O2 means that it can steal the O2 from mom at the placenta
Effect of 2,3 DPG on Hb dissociation
right shift
How is CO2 transported in the blood?
7% dissolved in plasma
23% bound to Hb = carbaminohemoglobin
70% in plasma as bicarb
Which enzyme catalyzes CO2 conversion to bicarb?
Carbonic anhydrase (CA) CO2 + H20 H2CO3 H + HCO3-
Where is CO2 converted into bicarb?
erythorcytes
What buffers the H+ ions in RBC made during bicarb formation?
Hb
What happens when bicarb leaves the cell?
Chloride shift: Cl- enters in exchange
What is bicarb formation like at the tissues
CO2 enters the RBC and is converted to bicarb. The bicarb is released into plasma in exchange for Cl-
What is bicarb formation like at the lungs?
Bicarb enters the cell in exchange for Cl-. H+ is released from Hb to react with bicarb, forming CO2. CO2 is released by expiration.
What is the Haldane effect?
At any given pCO2, blood carries less CO2 at higher pO2
What is 1 application of the Haldane effect?
High pO2 at lungs means Hb blood will release CO2 to be exhaled.
