Lecture 4- Clinical application in ventilation and lung mechanics Flashcards
conducting portion of the resp tract
nasal cavity pharynx larynx trachea primary bronchi sedcondary bronchi bronchioles terminal bronchioles
resp portion
resp bronchioles
alveolar ducts
alveoli
alveoli made up of
type 1 pneumocytes- gas exchange
type 2 pneumocytes- surfactant
QUIET INSPIRATION
• Inspiratory muscles contract Chest wall expands, taking lung with it (need pleural seal)
– To expand chest wall need functioning nerves, muscles, bones
– To expand lungs need to overcome
Elastic properties of alveolar walls
Surface tension of alveolar fluid
• Then air flows in:
• Overcoming airways resistance
QUIET EXPIRATION
• Passive process:
– Needs elastic recoil of Lungs
– Need to overcome airways resistance
compliance is a measure of
- Compliance is a measure of distensibility- change in volume relative to change in pressure
e.g. low compliance in
brand new balloon
e.g. high compliance in
older balloon (easier to blow up)
elastance is a measure of
elastic recoil
the tendency of something that has been distended to return to its original size
o In tissue with high compliance
easier to stretch, elastic recoil is less
o In tissues with low compliance
- elastic recoil is high (tendency to return to original size)
Lung Elasticity represents
mechanical properties of the lungs to be expanded (distended) by pressures surrounding or inflating the lungs, and to collapse
as soon as pressures disappear (lung recoil and distensibility)
E.g. the higher the compliance (the more distensible)
the worse the elastic recoil – e.g. go back to original shape
E.g. the lower the compliance (less distensible- harder to inflate)
the better the elastic recoil e.g. lung fibrosis
ventilation also dependent on airways resistance which depends on
o Surface tension within airways o Diameter airways Mucous in airways Pulmonary pressure gradients Radial traction
lung compliance is inverselys related to
connective tiussue surroundig alveoli- elastoc fibres inc collagen and other matrix elemets within the lug parenchyma
the more elastic fibres in the connective tissue surrounding the alveoli
the lower the compliance- harder to inflate lungs
The greater the alveolar surface tension, the
lower the lung compliance. (inversely related)
o Surfactant decreases surface tension, therefore increasing compliance
lung elastic recoil is directly related to the amount of
connective tissue surrounding alveoli - elastic fibres including elastin & collagen and other matrix elements within the lung parenchyma (the more connective tissue the higher the elastic recoil)
lung elastic recoil is ALSO directly related to
alveolar fluid surface tension
o If we have a condition where there is little surfactant- high alveolar surface tension- low compliance - lung elastic recoil will be increased
lung elastic recoil is inversely related to
lung compliance
0 the higher the compliance, the less elastic recoil
small bronchus have
small islands of cartilage and glands in submucosa
bronchioles have
no caritlage or no glands
how do bronchioles stay open on expiration if they have no cartilage
radial traction