An esophageal cardiac pulse probe includes a lumen for insertion into the esophagus, the end of the lumen preferably being closed by a flexible diaphragm. Pressure variations imparted to the fluid within the lumen in response to sounds from the heart and the lungs are transmitted to an electrical transducer...http://www.google.es/patents/US4409986?utm_source=gb-gplus-sharePatente US4409986 - Esophageal cardiac pulse monitoring apparatus and method
Esophageal cardiac pulse monitoring apparatus and method
