HN220 Lecture Notes - Lecture 26: Transpulmonary Pressure, Intrapleural Pressure, Pleural Cavity
Document Summary
Forces for pulmonary ventilation: air moves in and out of lungs by bulk flow, pressure gradient drives flow, air moves from high to low pressure. Inspiration: pressure in lungs less than atmospheric pressure: expiration: pressure in lungs greater than atmospheric pressure. Intra-alveolar pressure = palv: pressure of air in alveoli. Intrapleural pressure = pip: pressure inside pleural sac, transpulmonary pressure = palv pip, distending pressure across the lung wall, atmospheric pressure, 760 mm hg at sea level, decreases as altitude increases. Increases under water: other lung pressures are given relative to atmospheric pressure (set patm = 0 mm hg) Intra-alveolar pressure: pressure of air in alveoli, given relative to atmospheric pressure, varies with phase of respiration, during inspiration = negative (less than atmospheric, during expiration = positive (more than atmospheric, difference between palv and patm drives ventilation. Increases distending pressure across lungs: causes lungs (alveoli) to expand, increasing volume.
