Using The CAPMON System

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Background

CAPMON stands for Computer-Aided Physiological Monitoring. The unit consists of a set of sensors that are made up of both an emitter that sends out a beam of infrared light, and a detector that receives the light beam that is reflected back to the sensor. The sensors are connected to a converter that translates the analog information (the light) into digital information that can be understood by a computer.  Software in the computer then records and analyses the information so that it can be displayed on-screen.

Heartbeats are measured by placing the sensor on the shell of an invertebrate (in this case a crab or mussel) directly over the heart.  The infrared beam is emitted through the shell and onto the heart muscle tissue. The changes in the shape of the heart that coincide with the filling and emptying of the heart chamber (i.e., the heartbeat) will change the amount of light (the quantity) that is reflected back to the sensor.  These quantitative changes are measured by the detector.

It is important to note that measuring the wave shape of a crab’s heartbeat cannot be compared to a human electrocardiogram (ECG) because the methods of measurement are different.  An ECG records and displays electrical impulses from the human heart, whereas the CAPMON uses light relection to measure the change in the shape of the heart, which correlates with a beat cycle. Thus the wave shape produced on the computer screen will change depending on the position of the sensor.  This means that a heartbeat cycle can be recognized, but we cannot derive any information about the more subtle operations of the heart, as we can with an ECG.

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8-Channel