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Flashcards in Statics 2 Deck (20):
1

Tissue elastic forces percentage of total lung elasticity:

1/3 total lung elasticity
 

2

Fluid air surface tension percentage of total lung elasticity:

2/3 of total lung elasticity

3

The three structural components of lung compliance/elastic recoil:
 

  1. elastin
  2. collagen
  3. surface tension

4

Roles of pulmonary surfactant:

  • decreases work of inspiration by lowering the surface tension of alveoli
    • reduces elastic recoil of lung; lung more compliant. 
  • stabilizes alveoli by lowering even further the surface tension of smaller alveoli, equalizing the pressure inside alveoli of different sizes.

5

What two things help stabilize the alveoli and oppose alveolar collapse (atelectasis)?

  1. pulmonary surfactant 
  2. mechanical interdependence of the alveoli 

6

How does the mechanical interdependence of the alveoli help stabilize the alveoli and oppose alveolar collapse (atelectasis)?

  • If an alveolus begins to collapse, it increases the stresses on the walls of the adjacent alveoli, which would tend to hold it open.

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7

The volume of gas in the lungs at the end of a normal tidal expiration, when no respiratory muscles are actively contracting, is known as the:

  • functional residual capacity (FRC).
  • FRC is lung volume when outward recoil of chest wall = inward recoil of lungs.

8

As the person increases his or her lung volume, the total system recoil pressure becomes positive because of 2 factors: 

  • increased inward elastic recoil of lung because of stretched alveoli.
  • decreased outward elastic recoil of chest wall.

9

When does the chest wall get inward elastic recoil?

  • when inspiration leads to a lung volume >70% of total lung capacity (TLC).
     

10

At lung volumes below the FRC, the relaxation pressure measured at the mouth is negative because:

  • outward recoil of the chest wall is greater than the reduced inward recoil of the lungs.

11

Why does FRC decrease when supine?

  • abdominal contents push against relaxed diaphragm. 
  • decreases overall outward recoil of chest wall.

gravity no longer assists the diaphragm

12

Effect of emphysema on intrapleural pressure and FRC:

  • decreased elastic recoil of lungs.
  • intrapleural pressure becomes less negative at the FRC.
  • greater than normal FRC.

13

Effect of fibrosis on intrapleural pressure and FRC:

  • increased elastic recoil of lungs.
  • intrapleural pressure becomes more negative at FRC.
  • less than normal FRC.

14

The 2 main components of the work of breathing are:

  • elastic recoil of the lungs and chest wall 
  • resistance to air flow.

15

Work required for breathing is proportional to:

pressure change x volume change

16

Pressure change (work) required for breathing is:

  • trans-pulmonary pressure necessary to overcome both elastic work of breathing and resistive work of breathing.

17

The elastic work of breathing is the work done to overcome:

  • elastic recoil of chest wall.
  • surface tension of alveoli.

18

Restrictive diseases increase which type of respiratory work?

  • elastic
  • Obese: decreased outward chest wall elastic recoil.
  • Fibrosis: increased elastic recoil of the alveoli.

19

The resistive work of breathing is the work done to overcome:

tissue resistance and the airways resistance.

20

COPD/emphysema increase which type of respiratory work?

  • resistive work.
  • decreased elastic recoil makes overcoming airway resistance more difficult.