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The fetal electrocardiogram: the signal and its processing
On the undertaking of studying a biomedical engineering system, it is of value to be aware of the system's total domain; in other words, an examination of its medical, engineering, and biomedical engineering aspects enables a more appreciative and perhaps profitable understanding. It is with this perspective I approached the writing of a paper on the processing of the fetal electrocardiogram. This study is based on papers and laboratory work done under Dr. E.H. Hon. .After a brief description of the electrocardiogram, an examination is made into the importance of the fetal electrocardiogram. Different categories of fetal heart rate variation are defined; these classifications are then shown to be of diagnostic value for different conditions of fetal stress. The fetal electrocardiogram processing system is then described. After playing the recorded fetal signals on an analog tape unit, the waveforms are then conditioned, digitized, and averaged. The signal processor generates a “sampling window", based on the peak of the waveform, and provides a digital and analog output after every eight samples. The products of the processing system consist of two different strip chart recordings and a digital computer print-out. The strip chart recordings contain the raw data, time coding, sampling event marking, and analog averaged fetal electrocardiogram. The computer print-out contains the digitized converted fetal electrocardiogram information and various amplitude and duration parameters. A sample of data produced by the FECG processing can be found in the appendix.