Microvascular auscultation. A new technique, using a diplo-microphone, for analysis of blood flow at suture lines in small arteries.

A new atraumatic method for patency and blood flow control of microvascular anastomoses has been developed. Sounds proximal and distal to a suture line are separately detected by means of two specially modified miniature microphones built together as an auscultation unit and named a diplo-microphone. Transmission of the two amplified signals to a loudspeaker as well as to an oscilloscope screen allows analysis of patency at the anastomosis. Photos taken of the sound waves are individual records characterizing blood flow on both sides of the suture line. The new method has been tested in carotid arteries of Wistar rats. Sounds at stenoses and end-to-end anastomoses have been detected, and several characteristics of postoperative sound waves have been worked out. The new method has turned out to be more sensitive in detecting medium-sized stenoses than radical pressure tests performed with forceps. Construction and application of a diplo-microphone are described. Auscultation results of normal and stenosed arteries are discussed.