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31 Cards in this Set

  • Front
  • Back
What is the pressure reference point in pulmonary medicine?
ambient air pressure

e.g.: Patm = 740 = 0
What does it mean to have "negative pressure in the lungs"
pressure is less than ambient air pressure
general equation for distending pressure
distending pressure = pressure inside - pressure outside
lung distending pressure, aka:
transpulmonary pressure (PTP)
PTP =
PTP = Palveolar - Pip
Intrapleural pressure must be _____ to keep the lungs distended
Intrapleural pressure must be SUB-ATMOSPHERIC to keep the lungs distended
What must be true for distending pressue to be positive?

How does lung achieve this?
Pressure inside > pressure outside

by keeping Pip < Patm
Just before inspiration begins, Palveolar =
Just before inspiration begins,

P(alveolar) = Patm
Lung volume just prior to inspiration =
FRC
7 steps of inspiration
inspiratory muscles contract
chest wall expands and diaphragm lowers
intrapelural pressue (Pip) becomes more negative than -5 cm H2O
tranplumonary pressure increases (becomes more positive than +5 cm H2O)
lungs expand
alveolar pressure decreases below Patm
air flows into lungs
Physical law describing flow of air into lungs during inspiration
Ohm's Law:

Flow = Driving force * conductance
= driving force/resistance
= (Patm - P(alveolar))/airway resistance
What must happen wrt pressures to cause expiration?
P(alveolar) must rise above Patm
7 steps of expiration
inspiratory muscles relax
chest wall moves inward/diaphragm upward
Pip becomes less negative
PTP decreases
lungs decrease in size
Palveolar increases
air flows out of the lungs
compliance =

lung compliance =
compliance = change in volume/change in distending pressure

lung compliance = change in vol./change in PTP = slop of line in lung vol. vs. PTP graph
restrictive pulmonary disease is characterized by abnormally...
restritive pulmonary disease is characterized by abnormally LOW LUNG COMPLIANCE
Lungs in restrictive pulmonary disease require an abnormally large ______ to inflate
distending pressure
Which pressure must be greater than normal to inflate lungs in restrictive disease?
distending pressure, aka: PTP
TO achive normal FRC in restrictive disease, which pressure must be LOWER than normal?
Pip
How does the body make Pip lower than normal in restrictive disease?
powerful contraction of inspiratory muscles
3 clinical examples of restrictive disease
pulmonary fibrosis (fibrous replaces elastic tissue)

pulmonary edema (tissue water-logged, stiff)

infant respiratory distress syndrome (inadequate sufactant, high surface tension in fluid lining alveoli, stiff alveoli)
Clinical values characterizing restrictive disease
FEV1/FVC is NOT REDUCED

&
TLC decreased a lot
residual volume decreased some
ergo, FVC is decreased
Obstructive pulmonary disease is characterized by abnormally...
obstructive disease is characterized by abnormally HIGH AIRWAY RESISTANCE
Is there a problem holidng lungs at FRC in obstructive disease?
No
which cells in alveoli does surfactant cover?
all of them - thin walls, too!
what leads to obstruction, restriction AND alveolar diffusion limitation?
pulmonary edema
equation for oxygen consumption
??
pulmonary vascular resistance =
(pulm artery pressure - LA pressure)/CO
The air in Lansing has ____ PO2 in comparison with the air on a mountain top.
The air in Lansing has a HIGHER PO2 in comparison with the air on a mountain top.
normal PaO2
100 mmHg
normal PaCO2
40 mmHg
normal [HCO3-]
24 mM