How to Open an Atelectatic Lung
The lung is composed of millions of alveoli, which can be seen separately. LaPlace was the first to draw attention to the pressure in a bubble, which depends on the surface tension at the air-liquid interface and the radius; this relation was later called after its discoverer: the Law of Laplace, p = 2γ/r (where p = pressure, γ = surface tension, r = radius). In other words, at the same radius, the pressure necessary to avoid bubble collapse is higher as surface tension increases. As long as the surface tension is not zero, there still is a retractive force that normally could lead to bubble collapse. That this model is also valid for the lung was shown by von Neergaard, who eliminated the air-liquid interface by filling the lung with fluid, and discovered that the pressure required to fill a lung with fluid is only one-third to one quarter that to fill a lung with the same volume of air.
KeywordsVentilator Setting Open Lung High Tidal Volume Surface Tension Increase Surfactant Deficiency
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