PSIO 532 Study Guide - Midterm Guide: Alveolar Pressure, Mucus, Intrapleural Pressure
PSL – Respiratory Physiology
Airway Resistance Factors
4 variables are depicted for inspiration and expiration:
Volume is the integration of the flow signal; aveolar pressure and intrapleural pressure
For a given change in volume, if airway resistance exists within the system, you will have
to generate a greater change in pressure (there has to be a greater reduction in
intrapleural pressure → become more negative)
Alveolar pressure must fall to establish a pressure gradient in order for inspiration to
occur
Alveolar pressure decreases as a consequence of a decrease in intrapleural pressure at
the onset and throughout inspiration
If there was no airway resistance, intrapleural pressure would follow the profile
labelled ABC (dashed line), which is determined by the elastic recoil of the lung; in this
case, the intrapleural is less negative (generating less pressure) because of the absence
of airway resistance
However, increased pressure is required to overcome airway resistance and
consequently the changes in pressure during inspiration are indicated by the profile
labelled AB'C → this means we have to generate a more negative intrapleural
pressure because of the presence of airway resistance
Factors that Determine Airway Resistance
► Physical Dimensions of the tracheal bronchial tree
o Branching patterns of airway geometry and the impact it has on airway
resistance
o Lung volume – radial traction of the surrounding lung tissue
o Dynamic compression of the airways; pressure that surrounds the airway →
what impact it has on either increasing the diameter of the airway or causing a
collapse of the airway itself
► Airway smooth muscle tone
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