Exam #3: Respiratory Mechanics Flashcards Preview

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

What anatomical events occur during expiration?

A

Diaphragm relax

2
Q

What anatomical events occur during inspiration

A

Diaphragm contraction

3
Q

What is the function of the rib cage?

A

Sustain negative pressure around the lung

4
Q

What are the muscles of inspiration?

A

Diaphragm
External intercostals
Scaleni
SCM

5
Q

What happens in diaphragmatic paralysis?

A
  • Conditions established for development of pneumonia

- External intercostals, SCM, & scalini muscles become active in quiet inspiration to compensate

6
Q

What happens in sub-diaphragmatic abscess

A
  • Conditions established for development of pneumonia

- External intercostals, SCM, & scalini muscles become active in quiet inspiration to compensate

7
Q

What is the effect of intercostal muscle paralysis?

A

Little

8
Q

What does visible contraction of the scaleni muscles indicate?

A

Dyspnea

9
Q

What are the muscles of expiration?

A

Abdominal wall muscles

10
Q

What happens in congenital absence of abdominal wall muscles?

A

Fatal

11
Q

What is the intrapleural pressure?

A

Negative

Suction activity

12
Q

What is the transmural pressure?

A

Pressure between alveoli pressure & pleural pressure

*This is the driving force of respiration

13
Q

How does negative intrapleural pressure lead to alveolar ventilation?

A

Pressure at the pleural surface is transmitted through the alveolar walls

14
Q

What can cause a positive intrapleural pressure?

A

Pneumothroax

15
Q

What happens to lung pressure during inspiration?

A

Negative alveolar pressure brings air in

16
Q

When is the transpulmonary pressure largest?

A

End of inspiration

17
Q

How does the pleural pressure change with inspiration?

A

Decrease

18
Q

Outline the breathing sequence.

A

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
Q

What is the difference between passive & active expiration?

A
  • Expiration is a passive process normally

- Expiration is active is pathological states

20
Q

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

A

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

21
Q

What is compliance in relation to Hooke’s law?

A

Compliance is the slope of the pulmonary pressure volume curve.

Steeper slope= more compliance
Shallower slope= less compliance

22
Q

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

A

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

23
Q

How is compliance measured clinically?

A

Expiration limb of the pressure volume curve

24
Q

What are the determinants of lung compliance?

A

Elastin

Collagen

25
Q

Write the law of Laplace.

A

N/A

26
Q

How does alveolar radius relate to pressure?

A

Decreased radius increases the pressure tending to collapse an alveolus

27
Q

What is the function of surfactant?

A

Reduce alveolar surface tension & decrease collapsing force

28
Q

What cell type secretes surfactant?

A

Type II pneumocytes

29
Q

What is the main component of surfactant?

A

Lecithin

30
Q

How does Lecithin concentration vary with gestation?

A

Lecithin increases at 33 weeks

31
Q

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

A

Decrease in ratio means that surfactant production is NOT sufficient

–> Infantile Respiratory Distress Syndrome

32
Q

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

A

Lungs tend to collapse

Chest tends to spring out

33
Q

Draw the chest wall- lung combined compliance curve.

A

N/A

34
Q

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

A

Increased lung compliance

  • Loss of elastic fibers
  • Compliance increases
  • Higher FRC
  • Breathes at higher lung volumes
  • Barrel-shaped chest
35
Q

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

A

asdf

36
Q

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

A

Seen in pneumonia, pulmonary edema, & lung fibrosis

  • Decreased slope of pressure volume curve
  • Lower FCR
37
Q

What determines pulmonary resistance? Write pisouille’s law.

A

N/A

38
Q

Where are the greatest changes in resistance seen?

A

Broncioles

39
Q

What clinical conditions can increase resistance?

A

Asthma

Bronchitis

40
Q

What happens to resistance with PNS stimulation?

A

M3 activation

Asthma
Muscarinic agents

Increase resistance

41
Q

What happens to resistance with SNS stimulation?

A

B2 activation

Epinephrine
Albuterol

Decreased resistance

42
Q

What happens to pulmonary resistance in exercise?

A

Traction increases, leading to a decrease in resistance

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