A simple and inexpensive operating-room EKG telemetry system.

THE INCBEASING COMPLEXITIES of modern surgery have been accompanied by parallel developments in the realm of anaesthesiology. Today it would be very rare for a patient to be denied surgery because of the possibility that he might not tolerate anaesthesia. Our increasing boldness in the management of the poorrisk patient :is in large part due to the better methods of assessing the patient's condition on a continuing basis. We have seen the introduction of various monitors giving us moment-to-moment information on the patient's state. The constant guides thus provided have no doubt prevented many operating room eatasta'ophes. Many of the monitors have been of a bulky nature, and often quite expensive. Most of the time they are awkward to use because of the many connections and electrical wires creating a hazardous maze in the operating room. The complexities of all these electrical connections to the patient carry a further shock hazard which must not be overlooked. 1 Anything that either simplifies the size of monitor units or their method of connection to a patient is of interest to us. There are many occasions when the anaesthesiologist would like to observe electrocardiographic action continuously during anaesthesia, or in the immediate preor postoperative periods. Too frequently, the inconveniences of the patient cable-leads and the time necessary to connect them up are deterrents. Yet it cannot be denied that many cardiac problems during anaesthesia can be prevented or modified ff electrocardiographic information is continuously available. The purpose of this article is to present a simple and compact method of eliminating the patient cables entirely. It utilizes a simplified telemetry system of Canadian design and manufacture ( Fig. 1 ). Quickly applied disposable-type electrodes are used. The ones known as "Derma-Circs" (trade name) are recommended because they give minimal artefact. These are self-adhering, and it takes but a moment to place a small amount of non-irritating electrode jelly in the centre of these electrodes, applying one near the top of the sternum and the other on the chest wall in the vicinity of the apex beat. Two small wires clip on to these electrodes and connect to the transmitter by means of special Amphenol Micro-Med 221 connectors. The telemetry transmitter itself is the size of a small match box and weighs 30 gm. The ihigh quality of the electrical characteristics of the transmitter high input impedance (1 megohm) and wide band (0.5 to 10,000 Hz) enable this device to transmit the biological signal to a remote receiver without the introduction of unwanted artefacts. Because the transmitter is completely isolated from all other systems and is battery operated, the rejection of non-physiological signals, such as 60 Hz line interference, is extremely good. The transmitter is very