Author:  Dave Rosenberg, M.D. Educational Pearls Poiseuille’s Law addresses the flow of a fluid through a tube. Many common ED presentations involve alterations in flow: asthma, MI, ischemic stroke, etc. According to the law, flow increases with the 4th power of the radius. That is to say, doubling the radius of the tube will increase the flow by 16x. Therefore, in situations that require re-opening of an anatomic tube (artery, airway), small changes in the size of the opening will result in dramatic effects. References: https://www.openanesthesia.org/poiseuilles_law_iv_fluids/