March 13, 2011 Cliff 2 Comments. The reason IVC collapse occurs is that a Starling Resistor is generated – when the pressure within a distensible tube drops below the pressure. For that talk, I started animating a slide on the physiology of IVC collapse & dilation, but did not finish it in time for my presentation. in spontaneously breathing subjects, intrathoracic pressure decreases during inspiration, thereby increasing venous return and inducing collapse of the IVC;. Inferior vena cava (IVC) is normally 1. Evaluation of the inferior vena cava (IVC) from the subcostal view is part of.