January 13 , 2012 Audio Lecture Notes
Intrapleural pressure increases from 754 to 756mmHg
Transpulmanary pressure = alv – Intrapleura
-It was 6mmHg at the end of breathing in and that’ why lung was bigger and recoil pressure
went to 6mmHg.
-When breathing out
-Intrapleural pressure increases to 756mm that drops transpl to 4mmHg recoil pressure
is still 6mmHg
-Recoil is greater than transpulmonary
-The pressure pushing out on the lung is less than elastic recoil therefore the lung collapses.
Alveoli get smaller, pressure in the alveoli it increases.
-Pressure goes from 760 to 761mmHg in alveoli .
- Pressure in alveoli (761) is greater than atmospheric(760) therefore there is a PRESSURE
Bulk flow formula
When you have a pressure gradient it is greater in the alveolus than it is outside the alveolus ,
air gets pushed out.
-Air is always PUSHED OUT.
-Expiration is a passive process since it takes energy to breathe in BUT relax to breathe out.
-Breathing out =RELAXING
-During strenuous exercise when you force the air out then you might be using energy but ITS
-If you control it you use energy but if you don’t then NO ENERGY is involved in expiration
-Example of diff number, DON’T MEMORIZE NUMBERS.
Atmosphereic air is 750 alveolar air is 750 at the end of the breath
Transpulamonry pressure went from 4 to 10. *Don’t get bogged down on numbers*
- The greater the change the bigger the lungs will get,.. If intrapleural pressure changes
2mmHg you might get small inflation of the lung. If the intrapleural pressure decreases
7mmHg since transpulmonary pressure will be greater until recoil equals same
-If transpulmonary pressure is 10 instead of 6 and lung will keep getting bigger recoil
-Recoil =(normal lung function) dependant upon the size of the lung -10 size is bigger lung
-If we want to breath deeper we make the chest bigger which cuases a bigger drop in
intrapleural pressure, you get a greater increase in transpulmonary which means recoil
pressure has to go higher and only way to do it is to make lung bigger.
-All this process is related to HEALTHY LUNGS.
-Two things that determine the pressure in the lung (alveoli)
(ii) Amount of Air in there
Once the pressure increases above atmospheric in the alveoli and air starts to go out the
pressure drops until it equals atmospheric (760) then the process starts again.
This is a voluntary process.
When you expire
- intreapleural pressure increases, transpulmonary pressure decreases
When you expire
Diaphragm & inspiratory intercoastels relax, chest gets smaller
intreplural spaces gets smaller and pressure goes up.
Relative Difference between healthy condition.
Atmospheric = Alveolar
Interpleural < Alveolar
Recoil pressure is dependent on the SIZE OF THE LUNG. The bigger it is the
greater the recoil pressure.
Lung gets bigger RECOIL pressure increases (like elastic bend).
Recoil always wants to equal TRANSPULMONARY PRESSURE.
Change in Transpulmonary (by changing intrapleural)
-causes change in the volume of the lung.
- that causes the air to MOVE not the lung and then recoil will MATCH IT.
How would you force more air into the lungs?
-By pushing air in you are making a new equilibrium.
-All gases make up the 760mm Hg (nitrogen, oxygen, CO all add up to 760mmHg)
-Negative Intrapleural pressure m