Cardiac monitor is used to monitor patients with cardiac problems. This instrument finds use when monitoring important physiological parameters in the intensive care unit (ICU) like the heart rate or shape of the electrical waveform produced by the heart. This is done to observe the presence of arrhythmias or to be indicative of a serious condition. In hospitals, they are known as cardiac care units or coronary care units (CCU). These instruments are also called cardioscopes and they comprise of:
- Disposable type pre-gelled electrodes to pick up the ECG signal.
- Amplifier and a cathode ray tube (CRT) for the amplification and display of the ECG which enable direct observation of the ECG waveform.
- A heart rate meter to indicate average heart rate with audible beep or flashing light or both with each beat.
- An alarm system to produce signal in the event of abnormalities occurring in the heart rate
The cardioscopes are quite similar to the conventional oscilloscopes used for the display of waveforms in electronic laboratories. They have the usual circuit blocks like vertical and horizontal amplifiers, the time base and the EHT (Extra High Tension) for the cathode ray tube. However, they differ in two important aspects as compared to the conventional oscilloscope instrument. Cardioscope has slower sweep speeds and along persistence screen. The slow sweep is an outcome of the low frequency character of the ECG signal. The slow sweep speed necessitates the use of a long persistence screen so as to enable a convenient observation of the waveform. Without along persistence screen, one can only see a moving dot of light instead of a continuous trace.
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