Deeper you go under water, does the water pressure increase or decrease?
Increase
Higher you climb the Himalayas, does the air pressure increase or decrease?
Decrease
Is atmospheric pressure higher in Denver or Mesa?
Mesa, because we are lower in altitude vs Denver is high up there
What is the atmospheric pressure near sea level?
760 mmHg
Is pressure greatest at lowest or highest altitude?
Lowest
What is the fractional concentration of oxygen in air?
21%
What is the fractional concentration of nitrogen in air?
78%
What is the fractional concentration of carbon dioxide in air?
0.03% -- effectively zero!
True/False: atmospheric air is simply just oxygen gas and nothing else
False; atmospheric air is a mixture of gasses—nitrogen, oxygen and some carbon dioxide
What is the equation for partial pressure?
Partial pressure = total pressure x fractional concentration of gas
What is Dalton’s Law?
Total pressure is sum of partial pressure of gas mixtures
What is the partial pressure of oxygen in atmospheric air?
PO2= 760 mmHg x 0.21= 159.6 mmHg
Atmospheric pO2 is _____ tracheal pO2
Greater than
True/false: Water vapor is present in the trachea so water vapor displaces atmospheric air, thereby reducing tracheal pO2
True
At 37C, aka body temp, what is the amount of water vapor in the airway?
47 mmHg
Water vapor in humidified tracheal air is in which state?
Gaseous
How would you calculate pO2 in the trachea?
Must subtract water vapor in the airway, which is 47 mmHg
Tracheal pO2= (760-47) x 0.21 = 150 mmHg
Why is pO2 in trachea calculated differently from pO2 in atmosphere?
Because respiratory system releases water vapor into the airways and this water vapor exerts partial pressure within the airway, so atmospheric air is displaced
Why is water vapor in the airways important?
Water vapor prevents epithelial tissue of airways from getting dried out while breathing
Tracheal pO2 is ____ alveolar pO2
Greater than
Why is alveolar pO2 less than Tracheal pO2?
Because alveoli exchange gas with blood, so there is less oxygen in the alvoli as compared to trachea
Tracheal pCO2 is _____ alveolar pCO2
Less than
Gas exchange occurs by _______, not ________.
Diffusion; active transport
Venous pO2 entering the alvoeli is about _____.
40 mmHg
After gas exchange has taken place between the blood and alveoli, what is the partial pressure of O2 in arterial? In alveoli?
Equal in both (100 mmHg in textbook picture)
What is the pCO2 between alveoli and arterial blood after gas exchange?
Equal, just like pO2 are equal in both after gas exchange
Venous pO2 (before gas exchange) is ____, and arterial pO2 (after gas exchange) is ____.
40; 100 mmHg
Venous pCO2 (before gas exchange) is ___, and arterial pCO2 (after gas exchange) is___.
46; 40 mmHg
How come there is a greater difference (60 mmHg) between arterial and venous pO2, than there is a difference (6 mmHg) between arterial and venous pCO2, before and after gas exchange?
Because CO2 is more soluble in liquid so it does not exert much partial pressure
True/false: gases behave according to their partial pressures, not their concentrations.
True
Henry’s Law:
Concentration of gas in solution = partial pressure gradient x solubility
What does Henry’s Law actually mean in Catherine’s head?
Basically saying that concentration of gas in solution is dependent on how soluble that gas is, so the more soluble the gas, the greater the concentration of it in solution
True/ False: free floating gasses contribute to partial pressure
True
What role does hemoglobin play in terms of O2 partial pressure in blood?
Hgb increase the amount of O2 that our blood can hold without changing arterial pO2. This is because oxygen that are in the hemoglobin does not contribute to the partial pressure of arterial blood, only free O2 molecules contribute to the pressure gradient, allowing the blood to carry more O2 at once
____ molecules contribute to partial pressure gradient.
Free floating
What is Fick’s law of diffusion describe?
Rate of diffusion increases when partial pressure gradient increases
Rate of diffusion is proportional to partial pressure gradient, surface area and solubility
What is the relationship between the rate of diffusion and molecular weight?
Inversely proportional
What is the relationship between the rate of diffusion and thickness of the barrier?
Inversely proportional
What is the relationship between the rate of diffusion and partial pressure gradient?
Directly proportional
What is the relationship between the rate of diffusion and surface area?
Directly proportional
What is the relationship between the rate of diffusion and solubility?
Directly proportional
At the same partial pressures, which diffuse faster, O2 or CO2?
CO2, because CO2 is more soluble
How does emphysema affect gas exchange?
Reduces it because of reduced surface area due to destruction of alveoli
True/False: Rate of diffusion changes, gas levels in blood remain the same
False; gas levels in blood change too
In fibrotic lung disease, how is the rate of diffusion affected?
Slowed down because of thickened alveolar membrane as a result of decreaed lung compliance
How is the rate of diffusion affected in pulmonary edema?
Reduces it because of increased distance between the alveoli and arterial blood
Arterial pO2 is low
But pCO2 in arterial may be normal because of CO2 solubility in water, the distance ain’t no thang for CO2
What happens with the rate of diffusion in asthmatic patients?
Increased airway resistance, decreases airway ventilation, so pO2 is low in both alveoli and arterial
What are two ways that gases behave during gas exchange?
Diffusion limited (slow equilibration)
Perfusion limited (fast equilibration)
Is diffusion limited fast or slow equilibration?
Slow
Is perfusion limited fast or slow equilibration?
Fast
What is perfusion limited gas exchange?
Partial pressure gradient is not maintained
Gas exchange limited by the amount of blood that perfuses the alveoli
What are example of gasses that undergo perfusion limited gas exchange?
NO, CO2, O2 (resting) – these gasses quickly equilibrate between alveoli and pulm capillaries, eliminating the partial pressure
What is diffusion limited gas exchange?
Occurs when the partial pressure gradient is maintained, so gas exchange is limited
What are example of gasses and condition that would undergo diffusion limited gas exchange?
Oxygen during strenuous exercise, CO, emphysema and pulmonary fibrosis
Why is carbon monoxide diffusion limited?
Because it is sticky for hemoglobin and binds to it, resulting it less free floating CO that contribute to partial pressure gradient
True/false: anything that reduces the rate of diffusion could create diffusion-limited gas exchange if the partial pressure fails to equilibrate
True
Is alveolar air replaced slowly or quickly?
Slowly
What happens to the blood delivered to the lungs when we exhale? Does it still get oxygenated?
Yes it still gets oxygenated because alveolar air is replaced slowly
Air remains in the alveoli and still gets to be oxygenated
True/False: arterial pO2 DOES change with the respiratory cycle
FALSE; artier pO2 does NOT change with respiratory cycle, arterial pO2 remains constant during inhalation and exhalation
Arterial pO2 does/does not vary during respiratory cycle
DOES NOT
The faster we breathe, the _____ alveolar air gets replaced with fresh air.
Faster
When we breathe fast, what happens to alveolar pCO2 and pO2?
Alveolar pCO2 goes down
Alveolar pO2 goes up
Because air gets replaced with fresh air faster
True/false: CO2 enters the alveoli from inhaled breath
False, there is NO CO2 entering from atmospheric air (essentially 0 CO2 in atm)
Where does alveolar pCO2 come from?
Blood; after gas exchange with blood, determined by metabolic rate of tissues
How is the amount of CO2 that leaves the alveoli determined?
By how fast air is moved into and out of the alveoli – aka alveolar ventilation
