Airway closure Flashcards
What is the physiological basis of airway closure?
Pressure drops as fluid flows through a tube
P1 > P2
AKA- As gas flows through a tube, pressure falls. In the airway, pressure decreases as gas flows along the bronchioles.
Forces keeping airway open during inspiration and forces causing closure during forced expiration:
During forced expiration intrapleural pressure becomes what?
Positive
30 cm H20 in picture
Forces keeping airway open during inspiration and forces causing closure during forced expiration:
the high intrapleural pressure (30 cm H2O) is transmitted to the what?
Alveoli
38 cm H2O in this picture
Forces keeping airway open during inspiration and forces causing closure during forced expiration:
As the air flows along the airway, the pressure in the airway begins to what?
fall
(remamber as fluid or gas flows through a tube, pressure falls)
Forces keeping airway open during inspiration and forces causing closure during forced expiration:
At some point in the airway the intrapleural pressure sufficiently exceeds airway pressure, and the airway does what?
closes
Forces keeping airway open during inspiration and forces causing closure during forced expiration:
in the diagram the airway closes when the pressure falls to 19cmH2O
why does the trachea not close then?
b/c it has rings
what part of the airway is suceptable ro collapsing
bronchioles to alveoli
why do the mainstems not collapse?
b/c they have rings also
Closing volume (CV) and Closing Capacity (CC):
at some point during forced expiration, airways begin to close. The volume that can subsequently be exhaled is called the
closing volume
Closing volume (CV) and Closing Capacity (CC):
What makes up the closing capacity
the closing capacity is the closing volume plus the residual volume
CC = CV + RV
Closing volume (CV) and Closing Capacity (CC):
the CV and CC are measures how?
nitrogen washout test
and
helium dilution method
Closing volume (CV) and Closing Capacity (CC):
what happens if your CC is higher than your FRC?
you have no reserve (no FRC)
Closing volume (CV) and Closing Capacity (CC):
what typw of pt may have a CC higher than FRC
Elderly
Closing volume (CV) and Closing Capacity (CC):
since older peoples CC exceeds their FRC what does this mean in relation to thir airway closure?
they close without forced expiration
Young VS Eldery CC
