PNB 2265 Lecture Notes - Lecture 17: Intrapleural Pressure, Surface Tension, Phrenic Nerve
13 Mar 2017
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Ventilation: respiratory mechanics: air moves in and out of lungs by bulk ow: f = ^p/r. Pressures: atmospheric pressure (patm) = 0, alveolar pressure (palv) -> change this to cause air ow. Aka intrapulmonary pressure; pressure within alveoli, equalizes with patm: intrapleural pressure (pip) Pressure in intrpleural uid, about 4mmhg less than patm (up to ~7mmhg less during inspiration: transpulmonary pressure (ptp) = palv - pip (crosses lung wall) Holds lungs open: chest wall (pcw) = pip - patm. Mechanism of negative pressure in intrapleural space (pip: two forces try to pull lungs (via visceral pleura) away from thorax wall (parietal pleura) Surface tension of alveolar uid ( tries to collapse alveoli: transpulmonary pressure - opposing force that keeps lungs open. Surface tension created by pleural uid glues visceral pleura (and lungs) to parietal pleura. Pneumothorax: accumulation of air in the pleural space.
