Exam #3: Respiratory Mechanics Flashcards
What anatomical events occur during expiration?
Diaphragm relax
What anatomical events occur during inspiration
Diaphragm contraction
What is the function of the rib cage?
Sustain negative pressure around the lung
What are the muscles of inspiration?
Diaphragm
External intercostals
Scaleni
SCM
What happens in diaphragmatic paralysis?
- Conditions established for development of pneumonia
- External intercostals, SCM, & scalini muscles become active in quiet inspiration to compensate
What happens in sub-diaphragmatic abscess
- Conditions established for development of pneumonia
- External intercostals, SCM, & scalini muscles become active in quiet inspiration to compensate
What is the effect of intercostal muscle paralysis?
Little
What does visible contraction of the scaleni muscles indicate?
Dyspnea
What are the muscles of expiration?
Abdominal wall muscles
What happens in congenital absence of abdominal wall muscles?
Fatal
What is the intrapleural pressure?
Negative
Suction activity
What is the transmural pressure?
Pressure between alveoli pressure & pleural pressure
*This is the driving force of respiration
How does negative intrapleural pressure lead to alveolar ventilation?
Pressure at the pleural surface is transmitted through the alveolar walls
What can cause a positive intrapleural pressure?
Pneumothroax
What happens to lung pressure during inspiration?
Negative alveolar pressure brings air in
When is the transpulmonary pressure largest?
End of inspiration
How does the pleural pressure change with inspiration?
Decrease
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
What is the difference between passive & active expiration?
- Expiration is a passive process normally
- Expiration is active is pathological states
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
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
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
How is compliance measured clinically?
Expiration limb of the pressure volume curve
What are the determinants of lung compliance?
Elastin
Collagen