resp-4 compliance & surfactant Flashcards
what is lung compliance
the measure of the elastic properties of the lungs and a measure of how easily the lungs can expand
compliance formula
change in lung volume / change in transpulmonary pressure
what is static compliance
lung compliance measued during periods of no gas flow
ins/ exp pause
how to determine static compliance of the lung
by P/V slope when measured at FRC (end of exp. effort)
when is dynamic compliance measured
during periods of airflow (transpulmonary pressure changes
what else does dynamic compliance measure
lung stiffness and airway resistance
when does dynamic compliance fall
lung is stiff or airways are resistant
dynamic and static compliance relationship
dynamic is always less than or equal to static
what is pneumothorax
loss of subatmosphere pressure in PIP so the lungs collapse
what is hysteresis
the difference between the inflation and deflation compliance paths
why does hysteresis exist
greater pressure difference is required to open a previously closed airway than to keepan open airway from closing
what determines lung compliance
elastic components of lungs and airway tissue (elastin, collagen)
surface tension at the air-water interface within the alveoli
where is elastic compliance localized
alveolar walls, around vessels and bronchi
what is collagen
like a strong twine, high tensile strength, inextensible, low elasticity
what is elastin
like a weak spring, low tensile strength, extensible, high elasticity
what happens when elastin and collagen decreases
lung compliance increases (floppy lungs)
what is emphysema
cause and effects
elastin &alveolar wall destruction
increased compliance
increased time to fill and empty lungs
what is pulmonary fibrosis
cause and effects
collagen deposition in alveolar walls
reduced compliance
higher PTP changes are necessary to generate changes in lung volume
what does surface tension do to lung compliance
surface tension decreases lung compliance
The surface tension at the air‐water interface
accounts for about (fill in the blank) of the elastic recoil
of the lungs
2/3
what is surface tension
a measure of the attracting forces acting to pull a liquids surface molecules together at an air-liquid interface
how is hysteresis and inflation pressures affected when lungs are inflated with liquid
no hysteresis and much lower inflation pressure
how does alveoli surface tension lead to alveoli collapse
because the surface tension creates an inward recoil
what is laplaces equation
P=2T/r
t is constant
r is radius
small bubble radius does whast to pressure
more pressure required to keep the bubble inflated
describe the equilibrium between alvolar surface tension and pressure
At equilibrium, the tendency of increased pressure to expand the alveolus
balances the tendency of surface tension to collapse it
what does surfactant do to surface tension and compliance
lower it so the alveoli are stable against collapse
raises lung compliance (Easier to expand the lungs)
is surfactant hydrophobic or hydrophilic
it is both
what are the most important parts of the pulmonary surfactant
the phospholipids (DPPC) apoproteins and calcium ions
does surfactant thickness increase or decrease with an increase in surface area
Thickness of surfactant decreases with
increase of surface area
how is pressure equalized between alveoli of different alveoli
thicker layer of surfactant in smaller alveolar (smaller collapse easier)
(T/r ratio remains constant)
what does surfactant improve
compliance (by reducing surface tension of alveolar fluid)
stabilizes the alveolar
what may be the cause of infant respiratory distress syndrome
lack of surfactants in premature infants
what is dynamic stabilization (surfactant)
concentration of surfactant aries with inflation and delation, helps make elastic recoil
where is ventilation highest? how did they find out?
ventilation is higher at the bottom (most air per volume)
they measured it with xenon tests
how does PIP change throughout the lungs
The weight of the lungs increases pressure in regions near bottom (makes PIP
less negative) therefore less pressure pulling it open than regions at top of
lung.
how does PIP explain how the bottom of the lungs receive more air
the alveoli at the bottom start more deflated, so they can expand more (PIP less negative, PTP is smaller)
