Abstract

A patient vital signs monitoring system includes an elongated flexible esophageal stethoscope catheter including a mircophone and a thermister measuring means detachably connected to a processing monitor through a patient interface unit for electrical isolation of the patient from the processing system to assure patient safety from electrical currents. A single microphone, including an amplifier, picks up and transmits sound from the stethoscope catheter through a processing system including an audio filter system in the patient interface unit which filters out unwanted sounds and selectively amplifies either one or both of the heartbeat and breathing sounds and transmits signals indicative of these sounds to the monitor/transmitter unit through a fiberoptic link to the microprocessor where the signals are converted into counts per units of time (rates), which are, in turn, compared against reference upper and lower limits for generating alarm signals in response to critical deviations from preset norm. The monitor/transmitter unit is programmed to be self-monitoring by running initial tests of the system prior to going into the normal patient monitoring mode and by a continuous monitoring submode while in the monitoring mode. An IR transmitter in the monitor/transmitter unit transmits the vital breath and heart sounds by way of an infrared signal which is picked up by receiver carried by the operator and monitored by an earphone to eliminate interference from electrical systems and avoiding additional hardline electrical connection within the operating room. A self-destruct circuit within the patient interface unit destroys the microphone circuit within the esophageal stethoscope catheter during disconnect of the catheter in order to prevent reuse of the esophageal catheter.

Other References

• Linnarsson et al., "Oesophageal Probe. . . ", Med. & Biol. Eng. & Comp., 1982