MEDI111 Lecture Notes - Lecture 12: Breathing, Transpulmonary Pressure, Internal Intercostal Muscles
6 Aug 2018
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Document Summary
Mechanics of breathing: pulmonary ventilation consists of two phases: Inspiration gases flow into lungs: expiration gases exit the lungs. Intrapulmonary (intra-alveoli) pressure (ppul) is refers to pressure in the alveoli. It: fluctuates with breathing, always eventually equalizes with patm. If pip = ppul the lungs will collapse (ppul = pip) = transpulmonary pressure: during human ventilation, air flows because of pressure gradients, keeps the airways open, the greater the transpulmonary pressure, the larger the lungs. Involves inspiration and expiration: these are mechanical processes that depend on volume changes in the thoracic cavity, volume changes result in pressure changes, pressure changes result in gas flow to equalize pressure. Bo(cid:455)le(cid:859)s law: states the relationship between the pressure and volume of a gas, pressure (p) varies inversely with volume (v, p1v1 = p2v2. Inspiratory muscles contact: thoracic volume increases, lungs are stretched and intrapulmonary volume increases.
