Angiography provides important information regarding the perfusion and patency of distal arteries (e.g. femoral artery). Coronary angiography is used to determine the patency and configuration of the coronary artery lumens. Cricoid force greater than 40 N can compromise airway patency and make tracheal intubation difficult. Similarly, airway patency and venous return may be compromised by circumferential burns involving the neck. Safety and patency of mechanical (stapled) bowel anastomoses has been widely studied. This technique shown to improve vein graft patency and less development of intimal hyperplasia. Autopsy was not performed, and the long-term patency of the anastomosis was not established. Tubal insufflation is a standard procedure for testing patency. Rapid assessment of airway patency and respiratory effort must be performed. Environmental conditions and overall patient health may also affect the patency of the graft. Supportive measures include observation of vital signs, especially Glasgow Coma Scale and airway patency. In mice, this is accomplished by turning off the mechanism which maintains the ductus's patency. The function is thought to maintain the patency of blood vessels during occlusal loading. Great care needs to be taken during the planning phase to maximize airway patency. He described the Eustachian tube and the maneuver to test its patency (openness).