PubMed · 1109595
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1975. Biomedical engineering and scientific technical progress.. https://pubmed.ncbi.nlm.nih.gov/1109595/
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The design of a fetal heart rate (FHR) monitor using fetal electrocardiogram (FECG) scalp electrodes is described. It is shown that the design approach followed two stages: generation of FHR pulses at R-R intervals and FHR computation. The former uses a simple hardware approach for QRS detection and R-wave enhancement, while the latter requires a software implementation in order to produce FHR traces on a beat to beat basis. The QRS detection is based on bandpass filtering using switched mode capacitor technique; the R-wave enhancement and amplitude information are achieved by differentiation followed by fullwave rectification and peak detection. An adaptive threshold together with a comparator circuit are used to generate FHR pulses at R-R intervals. Beat to beat variations of FHR traces are produced by hardware and software implementation on a Z80 microprocessor board. Results obtained by the FHR monitor are evaluated and contrasted to other commercial FHR monitors.
User-induced errors are common when women repetitively employ conventional probe type thermometers to chart their basal body temperatures in an effort to indicate ovulation. An alternative technique employing a two-part telemetric thermometer is proposed, with low-power, SAWR-controlled UHF radio as the transmission medium. Worn overnight in the vagina, the 1 microW erp telemetry transmitter sends pulse modulated data continuously to a microcontroller in a nearby receiver; a real time clock enables programmable sampling and storage of the subject's temperature to 0.1 degrees C resolution. Initial clinical results indicate an enhanced performance compared to oral and axillary temperature trends taken by a mercury-in-glass thermometer. Polar plots of both the isolated and body-worn telemetry transmitter are presented; body induced attenuations of up to 30 dB were measured.