Transpulmonary Pressure

[E.S.Prakash]

Khoo Piggy, Year 2 asks: What is Transmural Pressure? Is it the same as Transpulmonary Pressure?

Reply: Transmural is a general term that means across the wall of a structure; the wall could be blood vessel wall, wall of the alveolus etc. 

Transpulmonary Pressure is the pressure across the lungs and is the difference between Alveolar Pressure and Intrapleural Pressure. 

During normal inspiration, lung expansion is driven by a positive transpulmonary pressure that allows the lungs to fill when airways are open; actually, the primary change is that the intrapleural pressure becomes more negative because of contraction of the diaphragm and or muscles of inspiration. 

During eupneic (passive) expiration, "transpulmonary pressure" is lesser than the pressure generated by elastic recoil of lungs; mechanistically speaking, the alveolar pressure becomes positive during expiration because of the elastic recoil of the lung parenchyma. 

There are more related terms like Transthoracic Pressure, Transrespiratory Pressure; you may like to check out NMS Physiology by John Bullock et al (a copy is available in our Library; you can read some pages online via the Google Book service)

Prakash

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