PHYS20008 Lecture Notes - Lecture 15: Pulmonary Compliance, Airway Resistance, Rubber Band
8 May 2019
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Work of breathing is affected by 2 things: Airway resistance is going to increase with: Decreased airway diameter (this affects it massively) Also the only factor we can change makes it the main determinant of resistance. Lung compliance is the ability of lungs to stretch. Less compliance harder to stretch increased work to breath. Lung elastance is the ability of lungs to spring back after being stretched. Note: more compliance does not mean more elastance (in fact are often inversely proportional) The elasticity is caused by rubber band type structures around alveoli. Surface tension is cause by the water molecules along the inside surface wanting to move towards each other (adhesion + cohesion) This causes more resistance to being stretched and thus resists lung compliance. Law of laplace states that the larger the alveolus (diameter) the less resistance due to surface tension it will have. Since all our alveoli aren"t the same size, bigger ones are easier to inflate.
