The respiratory system takes oxygen in, and gets carbon dioxide out of the body. It also transports air to the blood. We have discovered that the respiratory system works VERY closely with the circulatory system, and that the lungs are enclosed in a pair of tough pleural membranes. We wonder, if someone has a blood clot, will it stop oxygen flow within the circulatory system? Would would it cause them to have trouble breathing or stop breathing? What happens if air gets into the bloodstream.