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before inspiration alveloar pressure(PA) is atmospheric and intraplural pressure(PpL) is -5cm of H2O.At the end of an inspiration in a healthy person ,with glottis open, these readings would be:
A. PA of +2,Ppl of -8 cm of H2O.
b.PA of -2,Ppl of -8 cm of H2O.
c. PA of 0, Ppl of +5 cm of H2O.
d.PA of 0,Ppl of -5 cm of H2O
e. PA of 0, Ppl of -8 cm of H2O.

* also tell what will be the PA and Ppl during expiration.


Should be e. AT end-inspiration, alveolar pressure must be 0, since no flow is occurring. Also, pleural pressure must be more negative, since it has done 'work' on the system (my rationalization).

During expiration, both alveolar pressure and pleural pressure become more positive, and both are above 0.

I hope this is right, it is off the top of my head.



At any time during resp.cycle,when the glottis is open and no air is moving,PA is equal to atmospheric pressure or 0 cm of H2O.

During inspiration a decrease in Ppl(increase in lung volume decreases it)
During expiration PA>0 and Ppl returns to -5 cm of H2O.
I hope this will help

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