Exam #3: Respiratory Mechanics Flashcards Preview

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Flashcards in Exam #3: Respiratory Mechanics Deck (42):
1

What anatomical events occur during expiration?

Diaphragm relax

2

What anatomical events occur during inspiration

Diaphragm contraction

3

What is the function of the rib cage?

Sustain negative pressure around the lung

4

What are the muscles of inspiration?

Diaphragm
External intercostals
Scaleni
SCM

5

What happens in diaphragmatic paralysis?

- Conditions established for development of pneumonia
- External intercostals, SCM, & scalini muscles become active in quiet inspiration to compensate

6

What happens in sub-diaphragmatic abscess

- Conditions established for development of pneumonia
- External intercostals, SCM, & scalini muscles become active in quiet inspiration to compensate

7

What is the effect of intercostal muscle paralysis?

Little

8

What does visible contraction of the scaleni muscles indicate?

Dyspnea

9

What are the muscles of expiration?

Abdominal wall muscles

10

What happens in congenital absence of abdominal wall muscles?

Fatal

11

What is the intrapleural pressure?

Negative
Suction activity

12

What is the transmural pressure?

Pressure between alveoli pressure & pleural pressure

*This is the driving force of respiration

13

How does negative intrapleural pressure lead to alveolar ventilation?

Pressure at the pleural surface is transmitted through the alveolar walls

14

What can cause a positive intrapleural pressure?

Pneumothroax

15

What happens to lung pressure during inspiration?

Negative alveolar pressure brings air in

16

When is the transpulmonary pressure largest?

End of inspiration

17

How does the pleural pressure change with inspiration?

Decrease

18

Outline the breathing sequence.

1) Brain initiates
2) Phrenic nerve
3) Diaphragm contracts (drops)
4) Throacic volume increases
5) Intrapleural pressure becomes more negative
6) Alveolar transmural pressure gradient increases
7) Aleveoli expand

19

What is the difference between passive & active expiration?

- Expiration is a passive process normally
- Expiration is active is pathological states

20

What is Hooke's law? How does it relate to pressure & volume?

For an elastic structure, the increase in length varies directly with the increase in force until the elastic limit is reached

21

What is compliance in relation to Hooke's law?

Compliance is the slope of the pulmonary pressure volume curve.

Steeper slope= more compliance
Shallower slope= less compliance

22

Draw the pressure volume curve for inspiration & expiration. Why are the curves different?

During inspiration you have to overcome the partially collapsed phase of the alveoli

23

How is compliance measured clinically?

Expiration limb of the pressure volume curve

24

What are the determinants of lung compliance?

Elastin
Collagen

25

Write the law of Laplace.

N/A

26

How does alveolar radius relate to pressure?

Decreased radius increases the pressure tending to collapse an alveolus

27

What is the function of surfactant?

Reduce alveolar surface tension & decrease collapsing force

28

What cell type secretes surfactant?

Type II pneumocytes

29

What is the main component of surfactant?

Lecithin

30

How does Lecithin concentration vary with gestation?

Lecithin increases at 33 weeks

31

What is the clinical significance of the sphingomyelin/ lecithin ratio?

Decrease in ratio means that surfactant production is NOT sufficient

--> Infantile Respiratory Distress Syndrome

32

What is the relationship between lung compliance & chest wall compliance?

Lungs tend to collapse

Chest tends to spring out

33

Draw the chest wall- lung combined compliance curve.

N/A

34

How does increased lung compliance alter the pressure-volume curve?

Increased lung compliance

- Loss of elastic fibers
- Compliance increases
- Higher FRC
- Breathes at higher lung volumes
- Barrel-shaped chest

35

How do changes in decreased chest wall compliance alter lung compliance?

asdf

36

How does a decrease in lung compliance alter the pressure-volume curve. Aside from fibrosis, when is this commonly seen?

Seen in pneumonia, pulmonary edema, & lung fibrosis

- Decreased slope of pressure volume curve
- Lower FCR

37

What determines pulmonary resistance? Write pisouille's law.

N/A

38

Where are the greatest changes in resistance seen?

Broncioles

39

What clinical conditions can increase resistance?

Asthma
Bronchitis

40

What happens to resistance with PNS stimulation?

M3 activation

Asthma
Muscarinic agents

Increase resistance

41

What happens to resistance with SNS stimulation?

B2 activation

Epinephrine
Albuterol

Decreased resistance

42

What happens to pulmonary resistance in exercise?

Traction increases, leading to a decrease in resistance

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