Respiratory Mechanics II

Question 1

Four Forces Overcome by Respiratory Muscles

Answer 1

1) Recoil of Lung
2) Recoil of Chest
3) Surface Tension
4) Airway Resistance

Question 2

Flow Rate Equation [ V* ] (laminar flow)

Answer 2

(mL/min) = ∆P(between two points) / R

Increase R = Decreased Flow Rate

Question 3

Resistance if calculated using Poiseuille equation. What is it and what are the relationships?

Answer 3

R = 8 (viscosity)(length) / (π)(radius^4)

increase radius = decreased resistance

Question 4

increasing [resistance] _________ [ V* - flow-rate]
decreasing [radius] ___ [resistance], ___ [ V* - flow-rate]
increasing [length] ___ [resistance], ___ [ V* - flow-rate]

Answer 4

increasing [resistance] __D__ [ V* - flow-rate]
decrease [radius] I [resistance], D [ V* - flow-rate]
decrease [length] D [resistance], I [ V* - flow-rate]

Question 5

Name 3 things that affect Radius of airway

Answer 5

1) Dynamic Compression
2) Bronchoconstrictors { }
3) Mucus / (other articles)

Question 6

NOTE: For laminar flow: V* is proportional to ∆P. If ∆P was plotted on the X axis and V* on the Y axis, what would be the slope?

Is this the case for turbulent flow? Can you hear Tf

Answer 6

Slope = 1

No, its less efficient

you can only hear turbulent flow

Question 7

Turbulence is calculated using Reynolds equation. What is it and what are the relationships? Where doe Tf occur

Answer 7

R (Tf chances) = 2 (radius)(V*)(density) / (viscosity)

larger space, faster speed, more Tf

*Tf occurs in trachea and branch points! Tf –> Laminar

Question 8

Why does Emphysema, cause “dynamic compression” when patients exert themselves.

Answer 8

recoil pressure transferred to the alveoli during expiration is reduced. During expiration Ppl becomes greater than decreasing PAlv (upstream) causing compression.

recoil pressure transfer goes from 12 —> 4;
16 (contraction) + 4 = PAlv = 20 –> upstream–> PAlv = 14; 16 > 14 –> Transmural pressure is (-) compression