Abstract: A probe in a hand held ultrasonic Doppler fetal heart beat detector and monitoring system comprising a crystal for transmitting ultrasonic energy, a variable power source connected to said crystal for driving the crystal at a selected power setting and a microprocessor for selecting a power setting for the variable power source.

Abstract: A noise controller for use in a probe in a hand held ultrasonic Doppler fetal heart beat detection and monitoring system where the probe includes a crystal for generating an input signal as a function of the ultrasonic energy in received ultrasonic wave and a detector for generating a first signal from the input signal. The noise controller comprises a volume controller for receiving the first signal and for processing the first signal to produce an analog signal as the output of the probe. A detector generates a second signal whenever break noise is detected in the first signal. A muting circuit immediately lowers the amplitude of the analog signal upon detection of break noise by the detector thereby substantially attenuated in the analog signal the break noise which occurred in the first signal.

Abstract: A transcranial Doppler (TCD) probe fixation assembly is provided comprising an assembly for holding a TCD probe. The probe holding assembly comprises in one embodiment a track assembly and in another embodiment a single bar assembly. The ends of both the track assembly and bar assembly are connected to an annular member. Strap retaining members are provided on the exterior of the annular member for strapping the TCD probe to a patient's head. In use, the position of the probe is selected by moving the probe linearly along the track and bar assemblies and by rotating the track and bar assemblies relative to the annular member. Thereafter, the probe is angulated until a desired signal is obtained, at which point it is locked in place.

Abstract: A TCD probe mounting assembly is provided comprising a TCD probe mounted in a pedestal which has affixed to the base thereof an adhesive material for adhesively securing the pedestal to a patient's head. The pedestal is designed to allow insertion of the TCD probe therein after the pedestal is secured to a patient's head and for holding the probe at a selected angulation by means of friction after the probe is inserted in the pedestal. An external compression device and strap member are supplied to provide alternative means for providing a force perpendicular to a patient's head in order to minimize the risk of air gaps between the probe and the patient's head.

Abstract: A method and apparatus for distinguishing ultrasound signals returned from bubbles and particles moving in a fluid from signals due to ultrasound transducer motion monitors the receiving ultrasound signal for signals which are of much larger amplitude than the signals observed when no gas bubbles or particles are present. When a large amplitude event is detected, the maximum amplitude of the forward flow signal (that is, the positive frequency portion of the power spectrum) is compared to the maximum amplitude of the reverse flow signal (negative frequency portion of the power spectrum). If these maxima are significantly different in amplitude, the event is counted as a bubble. If the maximum amplitudes of the forward and reverse flow signals are comparable, the event is classified as a motion artifact. Displays of the spectra are marked whenever an event is counted as an air or particulate emboli so as to call attention to the event and, optionally, to generate an audible or visual alarm.

Abstract: An ultrasonic transducer assembly comprising an injection-molded body member, a pair of piezoelectric ceramic members and a multi-pin connector is described. The piezoelectric ceramic members are electrically connected to the multi-pin connector by means of thin metallic ribbons. When assembled, the transducer assembly is detachably inserted in recesses provided therefor in the end of a hand-held probe.

Abstract: An ultrasonic transducer assembly comprising an injection-molded body member, a pair of piezoelectric ceramic members and a multi-pin connector is described. The piezoelectric ceramic members are electrically connected to the multi-pin connector by means of thin metallic ribbons. When assembled, the transducer assembly is detachably inserted in recesses provided therefor in the end of a hand-held probe.

Abstract: An inflatable plethysmographic cuff bladder comprising interior members for preventing the trapping of an inflating medium in the bladder when the inflating medium is rapidly evacuated therefrom. The interior members comprise members which project inwardly from facing interior walls of the bladder and members which are inserted in the bladder and extend outwardly toward the facing interior walls of the bladder. In all cases, the members cooperate to form channels assisting the flow of inflating medium from the bladder when the bladder is rapidly evacuated of the inflating medium.

Abstract: An apparatus for calibrating a photoplethysmograph system comprising a white card mounted in the cone of a speaker. The card is mounted a predetermined distance from a photoplethysmograph sensor for providing an output from the sensor corresponding to the DC or venous mode. An oscillation is provided for oscillating the white card at a frequency corresponding to the average heartbeat for producing on the output of the sensor a signal corresponding to an average heartbeat. By adjusting the gain of the photoplethysmograph apparatus to obtain a constant amplitude output from the system, a calibration signal is obtained.

Abstract: A method of and apparatus for calibrating and providing an output from a strain gauge (1) is described. In the method and apparatus there is provided a constant-current source (10). Coupled to the current source (10) is an amplifier (12,13) for providing an output corresponding to the difference between the voltage drop across the strain gauge (1) and a reference voltage from a source (14). The reference voltage is used to adjust the current in the strain gauge (1) from the current source (10). After the current is adjusted, further changes in the voltage drop in the strain gauge (1) relative to the reference voltage is used for providing an output of the voltage difference relative to the reference voltage. The adjusting of the magnitude of the current from the constant-current source (10) is provided by a calibrate-and-zero sample and hold circuit (16) having a sample and hold period sufficient to reduce to negligible levels the effects of the dielectric absorption of an associated capacitive means (20).