Respiratory biophysics Flashcards
In terms of pressure and volume what are the difference between heart and lungs?
The lungs increase the cavity and decrease the pressure, while the heart decreases the cavity and increase the pressure.
The pleural pressure is a negative pressure below the ____ pressure.
atmospheric pressure
The ______ inside the lungs is the driving force to inflate the lungs.
negative pressure
like a vaccum, sucks air in
mouth pressure___pleural pressure
mouth pressure > pleural pressure
Δ P = P ___ - P __
This increases the flow.
Δ P = P mouth - P alveoli
Elastic properties of the lung (recoil), will try to ___ the lungs so the ___ pressure balances it.
- colapse
- pleural
____ pressure is the driving force that balances the lungs’ elastic forces.
Pleural
Normal situation:
P bodysurface = P mouth = P atm
On ventilation:
P mouth __ P bodysurface
P mouth ≠ P bodysurface
P pleura ___ P alveoli
P pleura < P alveoli
Maximum elastic tension of the lung is at what moment of respiration?
Maximum inspired volume
Inspiration: Δ P __ 0
Expiration: Δ P __ 0
- Inspiration: Δ P > 0
- Expiration: Δ P < 0
Δ P = P mouth - P alveoli
Total R trachea ___ Total R alveoli
Total R trachea > Total R alveoli
Generation ____ have the highest R
5-15
The interphase between the air and the capillaries has a surface tension, this surface tension will make the alveoli tend to ____.
collapse
The _____ reduces the effect of the surface tension
Surfactant
Young LaPlace Law:
Δ P = 2 γ / r
γ = surface tension
r = radius
P alveoli pressure for inspiration is____.
-1cmH2O
P pleural pressure for inspiration is___
-6 to -10 cmH2O
P alveoli for expiration is
+1 cm H2O
P pleural for expiration is ___
- 3 to -5 cmH2O
Surface tension appears in any ____ between two ____.
- interphase
- fluids (eg: air & water)
Surface tension makes it seem as if there was an _____
elastic membrane
The force of surface tension is directly related with the ____ “elastic membrane” is streched.
length
F surface tension = γ ___
F surface tension = γ L
Surface tension is ____ to the level of deformation
F surface tension = surface tension x length
F/L is a ratio that depends only on the intrinsic properties of the liquid, not on the geometry of the deformation.
Δ P = 2 γ / r, then if the change in pressure depends in the alveoli radius, what would happen to air flow in the absence of surfactant.
P alveoli with bigger radius will have a more negative pressure so air would only go to the alveoli with bigger radius.
The concentration of surfactant produced varies according to the ____ of the alveoli
radius
Surfactant ____ surface tension, therefore ___ collapse of alveoli.
- reduces
- prevents
Why does O2 reach the interphase?
Ideal gas beheviour, gas movement (velocity) depend on the temperature. Dalton equation.
Dalton’s law _____ states that if we know the % of a molecule in a mix we can know the probability of hitting the surface.
P gas = PO2 + PCO2 + PN2 ….
Why does oxygen cross the interphase
because O2 is permeable.
The concentration of O2 is lower in the blood, therefore it will go with its concentration gradient.
Frick’s 1st Law of diffusion:
J = D (Δ [] )/( Δx)
J= flux
D = diffusion cte
(Δ [] )/( Δx) = concentration gradient
How does O2 dissolve into blood and which are it’s limiting factors?
Because of affinity and temperature, O2 limit, most O2 Hb bound.
Henry’s law:
[O2] = H PO2 H = soulubility
HCO2 = ___ HO2
H = solubility
HCO2 = 22 x HO2
