APK 2105C Lecture Notes - Lecture 39: Intrapleural Pressure, Transpulmonary Pressure
16 Jun 2018
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Chapter 14, Lecture 3
Pulmonary Ventilation
• Mechanics of breathing
o Flow = pressure gradient / resistance
o Air flow = Patm – Palv / resistance
▪ Because Patm is constant, changes in Palv determine the direction of air
movement
▪ Palv < Patm = air into lungs
▪ Palv > Patm = air out of lungs
o Determinants of Palv
▪ Alveolar volume (size)
• Changes in volume of alveoli are produced by changes in volume
of TC
o Boyle’s law
o Increase
volume of
TC = pull
open lungs =
intrapleural
pressure,
alveolar
expands,
inspiration
o Decrease
volume of
TC = close
lungs a little
• Respiratory muscles
expand of compress
the TC
• Thoracic volume
impacts alveolar volume
o Diaphragm contracts, goes down = inspiration
o Diaphragm relaxes, goes back up = expiration
▪ Quantity of air molecules in alveoli
▪ Breath volume increases =
inspiration
• Neural control of ventilation
o Motor neurons signal neural input
o Inspiratory muscles get signal and contract
o Chest wall expands and causes intrapleural
fluid to get pulled—increased volume in
intrapleural cavity
o Increase in transpulmonary pressure
o Increased alveoli volume, flow of air into
alveoli
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