BIOL 221 Lecture 7: TOPIC 7 -13
3 Mar 2020
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Ventilation: Important Pressures
● Intrapleural (pleural) pressure (Ppl)
● less than intrapulmonary pressure by about 4 mm Hg due to:
● surface tension in alveoli
● elasticity of lungs
● elasticity of thoracic wall
● Palv and Ppl also measured in cm H2O
● 1 cm H2O = 0.74 mm Hg
○ Intrapleural pressure (Ppl), also called pleural pressure, is the
pressure of the fluid between the visceral and parietal pleurae.
○ That is, it is the pressure within the pleural cavity surrounding
the lungs.
○ It is normally less than intrapulmonary pressure by about 4 mm
Hg (5 cm H2O).
○ This is due to the surface tension in the alveoli, elasticity of the
lungs and elasticity of the thoracic wall.
○ The alveolar surface tension and elasticity of the lungs tend to
pull inward while the elasticity of the thoracic wall tends to pull it
outward.
○ Intra-alveolar pressure and intrapleural pressure are also
measured in cm H2O. One centimeter of water (cm H2O) equals
approximately 0.74 millimeters of mercury (mm Hg).
Intrapleural Pressure Disorders
Document Summary
Less than intrapulmonary pressure by about 4 mm hg due to: Palv and ppl also measured in cm h2o. 1 cm h2o = 0. 74 mm hg. Intrapleural pressure (ppl), also called pleural pressure, is the pressure of the fluid between the visceral and parietal pleurae. That is, it is the pressure within the pleural cavity surrounding the lungs. It is normally less than intrapulmonary pressure by about 4 mm. This is due to the surface tension in the alveoli, elasticity of the lungs and elasticity of the thoracic wall. The alveolar surface tension and elasticity of the lungs tend to pull inward while the elasticity of the thoracic wall tends to pull it outward. Intra-alveolar pressure and intrapleural pressure are also measured in cm h2o. One centimeter of water (cm h2o) equals approximately 0. 74 millimeters of mercury (mm hg). If intrapleural pressure = intra-alveolar pressure, lungs collapse (atelectasis)
