Surgery – Truss – Pad
Patent
1995-08-24
1997-06-17
Manuel, George
Surgery
Truss
Pad
A61B 800
Patent
active
056388241
DESCRIPTION:
BRIEF SUMMARY
This invention relates to ultrasonic monitors. The invention is primarily concerned with ultrasonic movement monitors such as a monitor for monitoring breathing movement of a subject, which may be a human or other animal. However, the invention also relates to the measurement of the properties of fluids with ultrasonics, such as fluid viscosity measurement.
It has been proposed to monitor the breathing of a baby by monitoring ultrasonic waves reflected from the baby, in order to detect apnoea, the cessation of respiration. An alarm signal is initiated when breathing has ceased, to call the parent, or nurse in a hospital, so that urgent attention can be given.
In systems such as those proposed in Specifications Nos GB 2 192 713 and U.S. Pat. No. 4 197 856, a continuous ultrasonic wave is employed, and a phase-locked-loop is provided whereby the frequency of the ultrasonic source is varied. The analogue output signal of the phase-locked-loop represents the movement of the object in the time domain.
The known systems tend to produce false alarm signals because they can respond to movements of nearby objects, such as a person walking past a baby's cot. Attempts to render the existing systems more discriminating can lead to a loss in sensitivity to the baby's breathing.
According to a first aspect of the invention a movement monitor for monitoring the movement of an object comprises an ultrasound emitter and an ultrasound receiver adapted to receive sound waves reflected from the object, pulse energisation means for causing the emitter periodically to emit a burst of ultrasound pulses, and detection means responsive to the receiver to monitor the output of the receiver and to indicate an abnormal movement or lack of movement.
When the movement to be monitored is a cyclic movement the time period between successive bursts of ultrasound is arranged to be substantially less than the cycle time.
In addition to indicating abnormal movement or lack of movement, the detection means may be arranged to indicate normal movement.
Although the invention has been developed for use as a movement monitor, we consider that there would be advantages in applying digital phase discrimination analysis techniques to the measurement of properties of fluids. We have realised that if an ultrasonic wave is transmitted through a fluid from an emitter to a receiver, and the condition of the fluid changes in some way, the change can result in a phase shift in the received signal.
According to a second aspect of the invention an ultrasonic monitor comprises an ultrasound emitter and an ultrasound receiver, a fluid chamber interposed in the sound path between the emitter and receiver whereby ultrasound passes through the fluid in the chamber, digital phase monitoring means responsive to the input to the emitter and to the output from the receiver and adapted to monitor the changes in the phase relationship between said input and said output.
Such a monitor may be used, for example, to monitor changes in the fluid in said chamber, such as temperature change, which will alter the sound velocity and consequently alter the phase relationship between said input and said output. Viscosity or composition changes in the fluid too may be associated with changes in sound velocity, and thus be measurable.
Such a monitor may, for example, be used to measure the velocity of a fluid by arranging for the ultrasound to be transmitted parallel to the direction of fluid travel in the chamber, thereby to alter the effective ultrasound velocity through the chamber. Since fluid velocity can be a measure of the viscosity of a fluid, for a given applied pressure difference to the fluid, the phase changes between said input and said output may also be arranged to be a measure of viscosity change.
An ultrasonic monitor in accordance with the second aspect of the invention may incorporate a fixed ultrasound reflector whereby the waves pass in two directions through the fluid from the emitter to the receiver, which can then be positioned adjacent to the emitter.
In a
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patent: 4107659 (1978-08-01), Massa
patent: 4399703 (1983-08-01), Matzuk
patent: 4738266 (1988-04-01), Thatcher
patent: 4819652 (1989-04-01), Micco
patent: 5455588 (1995-10-01), Lew et al.
Advanced Monitors Holdings Limited
Anderson Ronald M.
Manuel George
Summers John Brian
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