The stethoscope--the anesthesiologist's best friend.
D000776:Anesthesiology; D001314:Auscultation / Q000266:history / Q000295:instrumentation*; D004562:Electrocardiography; D006326:Heart Auscultation; D049672:History, 19th Century; D049673:History, 20th Century; D008991:Monitoring, Physiologic; D013016:Sound