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 lung pressures  



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Author4 Posts
  #1

wht happens to intraalveolar n intrapleral pressures in various stages of normal breathing n other abnormal conditions ??




  #2

Volume Pressure Alv Pressure Plural

FRC 0 -5 or so (755 mm)
TLC 0 -8 (752 mm)
RV -3 -6

In COPD emphys traction forces lost, pressure in alveolus more like intra plural (but not quite), elasticity going down, so volume TLC goes up
In restrictive, higher elastic resistance of the wall reduces the volume.


  #3

I meant to ask wht happens at the beginning of inspiration n end of expioration?n i didnt understnd the pressures u quoted :roll:


  #4

FRC pressures across alveolus are equal. Pleural pressuure is negative 5 mm Hg (760mm atmospheric-5mm=755) Lung elastic recoil pressure also 5 but directed inwards, hence +5
Begin resp.. chest wall expands, pleural space pulled apart, pleural pressure more negative, up to -8, alveouls pressure becomes negative approx = to intrapleural, but glottis is open, air runs in so pressure equlizes, at TLC even though pleural pressure is is max negative, the glottis equalizes the pressure with addition of air to alveolus.
THe rest ... just reverse.





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