Negative Pressure Breathing

[betterfuture]

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Can someone just give me a quick explanation of negative pressure breathing. This Kaplan book does not do justice to the mechanism of breathing; it is honestly confusing me with their wording.

 

[theonlytycrane]

As the diaphragm flattens, the volume of the chest walls expand out and increase. The intrapleural space increases in volume as well which decreases the pressure in this space. Since the air in the lungs is still at atmospheric pressure, but the pressure in the intrapleural space has dropped, the lungs expand into the intrapleural space which drops the pressure in the lungs. Air rushes into the lungs due to the pressure differential. When the diaphragm relaxes, air is pushed out by the reverse mechanism.

 

[betterfuture]

When you say "lungs expand into the intrapleural space which drops the pressure in the lungs" does that mean the lungs increase in their volume so the intrapleural space volume decreases?

 

[Astra]

Can someone just give me a quick explanation of negative pressure breathing. This Kaplan book does not do justice to the mechanism of breathing; it is honestly confusing me with their wording.

This is how breathing works.

Your diaphragm constricts. This causes your lung volume to increase.

What happens when you increase volume? Pressure decreases.

What is the preferred flow of gas? High to low pressure.

Therefore, air rushes inside your lungs.


The relative lower pressure compared to the atmosphere is called NEGATIVE PRESSURE BREATHING.


Your diaphragm now relaxes.

This causes you lung volume to decrease.

The air rushes out.

This is exhalation.


Think of the diaphragm as a rubber band that controls lung volume.

 

[betterfuture]

@Astra118 So why do they include intrapleural space in their explanation. It just confuses me because I am used to thinking like how you wrote.

 

[Astra]

@Astra118 So why do they include intrapleural space in their explanation. It just confuses me because I am used to thinking like how you wrote.

The intrapleural space is covering and pushing down on the lungs.

If this space expands, then there is less push on the lungs.

If there is less push on an object, it has a chance to expand. And this allows the lungs to expand and give us negative pressure

 

[betterfuture]

Ohh okay I see now! Thanks!!

 

[aldol16]

This is an excellent opportunity for the MCAT to test your knowledge of Boyle's law as it applies to physiology - so definitely an MCAT favorite!

 

[drdab]

As the diaphragm flattens, the volume of the chest walls expand out and increase. The intrapleural space increases in volume as well which decreases the pressure in this space. Since the air in the lungs is still at atmospheric pressure, but the pressure in the intrapleural space has dropped, the lungs expand into the intrapleural space which drops the pressure in the lungs. Air rushes into the lungs due to the pressure differential. When the diaphragm relaxes, air is pushed out by the reverse mechanism.

What I don't understand is how can we apply Boyle's law here when infact there is fluid in the pleural space & not air????