Respiratory biophysics

Question 1

In terms of pressure and volume what are the difference between heart and lungs?

Answer 1

The lungs increase the cavity and decrease the pressure, while the heart decreases the cavity and increase the pressure.

Question 2

The pleural pressure is a negative pressure below the ____ pressure.

Answer 2

atmospheric pressure

Question 3

The ______ inside the lungs is the driving force to inflate the lungs.

Answer 3

negative pressure

like a vaccum, sucks air in

Question 4

mouth pressure___pleural pressure

Answer 4

mouth pressure > pleural pressure

Question 5

Δ P = P ___ - P __

This increases the flow.

Answer 5

Δ P = P mouth - P alveoli

Question 6

Elastic properties of the lung (recoil), will try to ___ the lungs so the ___ pressure balances it.

Answer 6

• colapse

- pleural

Question 7

____ pressure is the driving force that balances the lungs’ elastic forces.

Answer 7

Pleural

Question 8

Normal situation:
P bodysurface = P mouth = P atm

On ventilation:
P mouth __ P bodysurface

Answer 8

P mouth ≠ P bodysurface

Question 9

P pleura ___ P alveoli

Answer 9

P pleura < P alveoli

Question 10

Maximum elastic tension of the lung is at what moment of respiration?

Answer 10

Maximum inspired volume

Question 11

Inspiration: Δ P __ 0
Expiration: Δ P __ 0

Answer 11

• Inspiration: Δ P > 0
• Expiration: Δ P < 0

Δ P = P mouth - P alveoli

Question 12

Total R trachea ___ Total R alveoli

Answer 12

Total R trachea > Total R alveoli

Question 13

Generation ____ have the highest R

Answer 13

5-15

Question 14

The interphase between the air and the capillaries has a surface tension, this surface tension will make the alveoli tend to ____.

Answer 14

collapse

Question 15

The _____ reduces the effect of the surface tension

Answer 15

Surfactant

Question 16

Young LaPlace Law:

Answer 16

Δ P = 2 γ / r

γ = surface tension
r = radius

Question 17

P alveoli pressure for inspiration is____.

Answer 17

-1cmH2O

Question 18

P pleural pressure for inspiration is___

Answer 18

-6 to -10 cmH2O

Question 19

P alveoli for expiration is

Answer 19

+1 cm H2O

Question 20

P pleural for expiration is ___

Answer 20

• 3 to -5 cmH2O

Question 21

Surface tension appears in any ____ between two ____.

Answer 21

• interphase

- fluids (eg: air & water)

Question 22

Surface tension makes it seem as if there was an _____

Answer 22

elastic membrane

Question 23

The force of surface tension is directly related with the ____ “elastic membrane” is streched.

Answer 23

length

Question 24

F surface tension = γ ___

Answer 24

F surface tension = γ L

Question 25

Surface tension is ____ to the level of deformation

Answer 25

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.

Question 26

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.

Answer 26

P alveoli with bigger radius will have a more negative pressure so air would only go to the alveoli with bigger radius.

Question 27

The concentration of surfactant produced varies according to the ____ of the alveoli

Answer 27

radius

Question 28

Surfactant ____ surface tension, therefore ___ collapse of alveoli.

Answer 28

• reduces

- prevents

Question 29

Why does O2 reach the interphase?

Answer 29

Ideal gas beheviour, gas movement (velocity) depend on the temperature. Dalton equation.

Question 30

Dalton’s law _____ states that if we know the % of a molecule in a mix we can know the probability of hitting the surface.

Answer 30

P gas = PO2 + PCO2 + PN2 ….

Question 31

Why does oxygen cross the interphase

Answer 31

because O2 is permeable.

The concentration of O2 is lower in the blood, therefore it will go with its concentration gradient.

Question 32

Frick’s 1st Law of diffusion:

Answer 32

J = D (Δ [] )/( Δx)

J= flux
D = diffusion cte
(Δ [] )/( Δx) = concentration gradient

Question 33

How does O2 dissolve into blood and which are it’s limiting factors?

Answer 33

Because of affinity and temperature, O2 limit, most O2 Hb bound.

Question 34

Henry’s law:

Answer 34

[O2] = H PO2 
H = soulubility

Question 35

HCO2 = ___ HO2

H = solubility

Answer 35

HCO2 = 22 x HO2