Intrapleural Pressure - drdab

[ArchivalUser]

Hi,
Can anyone pls explain why is the intrapleural pressure normally -5 cm H20

[ArchivalUser]

Hi,
Norm IP is NEG ( OR less than atmospheric P)

How created? By elastic forces of lung & chest wall pulling in OPPOSITE direction on intrapleural space*. And space you know btw visceral & parietal pleura.

Now at FRC the system @equilibrium, the lungs with rubber properties (tend inclined to collapse) & wall with that rubber properties is try to to spring -> out. These 2 = & opposite force pulling * create nasa jet vacumm or as you can ans NEG P in that space…

That is the why u asking here, but if you still think its foggy read preach of Costanzo ...
Fin.

[ArchivalUser]

Hmm
But what i am confused with is doesn't the pleural space contain fluid in it, so then how can we apply boyle's law in the sense that as we cause the volume of the pleural cavity to increase we end up decreasing pressure ( making it more negative)????
Shall chk Costanzo & get back to u.
Thank u

[ArchivalUser]

OK
I think i'm getting ur explanation, i guess i drifted a bit too much into physics.
Merci beaucoup.

[ArchivalUser]

Pleural cavity is a virtual space between two pleural membranes parietal and viceral b/c of the opposing recoil of the lungs and the chest cavity one pulling on the other this creates a subatmospheric pressure of -5 cm of H2O at FRC which is in between the last tidal expiration an the next tidal inspiration.

There is no volume of air in the pleural space that is impossible in the normal pt. Now, if you are talking about a pneumothorax at that point a volume of air goes into the pleural space making the intrapleural pressure (PPL) positive instead and leading to a collapse of the lung unit affected.

In the normal lungs intrapleural p is always negative -5 at FRC or -10 at end of tidal inspiration. You can have a + ppl in a normal pt during a very forced valsalva maneuver during exhalation however.

Don't forget volume of air versus pressure when talking boyle's law refers to volume in the alveoli versus pressure in the alveoli (inverse relation of volume to pressure).

[ArchivalUser]

But in the topic on perfusion-ventilation they give that ipp is -5 in the middle of the lung ,-10 @ top of lung & -2.5cm water @ lung base & this is normally present .So i was getting confused with this concept assoc with mech of ventilation.
Anyways thanks for helping.