Resp 1- Static Mechanics of Breathing Flashcards
what are the physical forces that influnce breathing ?
Static: Elasticy/ Compliance/ Surface tension
Mechanical properties of the lung that influrnce gas flow but are independent of volume changes
Dynamic: Flow/ Resistance/ Turbulence
Mehcnical propertise affecting the flow of air into and out of th elung as volume changes with time.
Elasticity of the lungs is a static force what links it to the chest ? how much fluid is in the cavity
Plueral sac links elastic forces in the chest wall and lungs.
15 ml
elastic forces link what 2 things ?
pleural pressure to alveolar pressure
define elastic recoil in the lungs
elastin in the alveoli acts as an inwards collapsing force
balance of elastic recoil and opposing elastic recoil of the ribs outwards is called ?
sub-atmospheric intreapleural pressure
how does elastic retraction link to pressure
elastic retraction enables alveolar pressure to go above atmosphere perssure.
equation for complaince is ?
change in volume/ change in pressure
what does high compliance mean ?
lungs with high compliance is easy destended- high complaince balloon is easily inflated as its elasticity is low
what is low compliance ?
lungs with low compliance are difficult to distend- low compliance balloon has high elasticty thereofre harder to blow up
summarise the realtionship between complaince and elastcity
inverse relationship
how is compliance measured ?
it is measured under conditions of NO GAS FLOW
how is compliance affect by emphysema and fibrosis
Emphysema: high compliance which means it is easier for you to take up O2 but harder for you to breath out.
fibrosis: low complaince hard to take up O2 but easily removed
what are the affects of emphysema on the lungs?
mucus in bronchioles
Enlarged alveoli
fewer capillaries
what is pulmonary complaince produced by
Elastin connective fibres and Alveolar surface tension
how does high surface tension affect complaince
it reduces compliance
lable the diagram:
erythrocytes/ alveolus type 1/2 alveolar cells/ alverolar linining with pulmonary surfactant/ alveolar macrophage/ interstitial fluid/ pulmonary capillary.
what is transplumonary pressure
the pressure difference between the alveolar pressure and the intrapleural perssure
what does inflating lunsg with liquid do ?
it helps to overcome recoil effect by dissipating surface tension.
what is hysteresis ?
breathering in costs more enegry than breathing out. there is a lag phase due to surface tension effect during inhalation
define law of laplace
states that the tension within the wall of a sphere filled to a particular pressure depends on the thickness of the sphere
how is small diamtere of the alveolus ?
smaller diameter bubble have higher surface tension. therefore variation in the alveolar size/volume cause small alveoli to collapse into bigger ones
how is perssure in a bubble calculated
2x surface tension / radius bubble
what stabilises alveolar strucutre and how is it done
Pulmonary surfactant and it reduces surface tension of the water molecules by decreaseing densitry of water molecules a the airwarter surface. due to the hydrophbic tail reducing the vector
what is pulmonary surfactnat made from ?
Dipalmitoyl phosphatidyl choline (DPPC) which is packed around surfactant proteins (A-D)
what secrets surfactant
type 2 alveolar epithelial cells.
what are the 2 role of surfactant
- Prevents collapse of alveoli during lung expansion and contraction
- reduces pressure required to inflate lungs
how is surfactant linked to alveoli radius
decrease in radius leads to crowding on surfactant molecules to reduce tension
