Abstract: A pulsed ultrasound Doppler blood flow sensing device includes a band pass filter for extracting only the Doppler frequency shift signals from the sampled and held signals, the band pass filter having a band pass characteristic in which a variation of an attenuation degree is almost flat over at least a frequency band between -f.sub.r /2 and +f.sub.r /2 except for a region in proximity to frequency O. A display displays blood flow signals which represent the obtained Doppler frequency shifts and have frequencies at least between the frequencies -f.sub.r and +f.sub.r.

Abstract: A method and apparatus for analyzing cardiac electrical activity and other life signs, and triggering a therapeutic current. A signal representative of cardiac electrical activity is analyzed by two distinct analog circuits and a logic protocol is provided to indentify cardiac arrhythmia based on the outputs of the circuits and the presence or absence of respiration. One circuit employs comparison of the electrical signal with a previous peak value thereof, and is characterized by its tendency to double-count some QRS complexes. The other circuit compares the sum of the rectified and low-pass filtered signal plus the derivative of the signal to a reference level, and compares the rectified and filtered signal to a threshold level, to identify QRS complexes while largely ignoring ventricular fibrillation.