Surgery – Diagnostic testing – Flexible catheter guide
Reexamination Certificate
1999-09-23
2002-12-10
Shaver, Kevin (Department: 3736)
Surgery
Diagnostic testing
Flexible catheter guide
C600S500000, C128S900000
Reexamination Certificate
active
06491647
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a non-invasive device for measuring physiological processes. More particularly, it concerns a device that can be applied externally to the body of an animal or human to detect and quantify displacement, force, motion, vibration and acoustic effects resulting from internal biological functions. Specifically, an inexpensive device is disclosed that is compact, light, portable and comfortable, and operates satisfactorily even with imprecise location on the body, ambient noise, motion and light.
BACKGROUND INFORMATION
Traditionally, non-invasive gauging of physiological processes in vivo has been accomplished either with large, complex and expensive techniques such as X-ray, tomography, magnetic resonance and ultrasound, all of which demand the skills and infrastructure of a medical institution, or with simpler, more portable equipment. In the latter category, devices employing superficially attached electrophysiological electrodes (electrocardiogram (ekg), electroencephalogram (eeg), electromyogram (emg), electrooculogram (eog)) are prevalent, but require skill and surface preparation for proper electrode attachment and cause skin irritation with prolonged use. Small portable “light” devices using optical, ultraviolet and infrared spectroscopic and absorption techniques are also implemented widely based on the availability of miniaturized electromagnetic sources, detectors and support electronics. However, these devices are quite susceptible to interference from movement and/or ingress of ambient light. Motion, displacement, vibration and acoustic sensing techniques have also been developed extensively but have yet to see widespread adoption because their inherent sensitivity to movement, location and noise makes it difficult to interpret signal changes in a normal ambulatory environment. Such techniques range from commercially available, simple, passive actigraphy devices to complex servo-driven systems that react instantaneously to each force or displacement as it is generated by the body. The actigraph is typically a casing attached to the body containing a suspended accelerometer element that responds to all magnitudes and frequencies of motion. During physical activity, it therefore reflects the level of effort being exerted overwhelming any other physiologically derived signals, and during quiet rest periods it becomes sensitive to the body's internal “ballistics” such as breathing, tremor, and heart and arterial pulsation. The servo driven devices are generally invoked to quantify physiological parameters such as blood pressure where the force applied to the actuating element can be used as a measure of the force deriving from the biological function. Typically, these devices are quite bulky, demand external power or compressed air supply and require extensive computation capability. In between these extremes lies a spectrum of devices as described below, covering a range of complexity, accuracy and cost, and varying in effectiveness at combating extraneous signal pick-up. Because of the pre-eminent importance to modern medicine of evaluating cardiovascular function, emphasis has been placed on devices that measure heart rate, arterial pulse profile and blood pressure in the review that follows.
Commercially available devices exist which measure heart rate and provide the output on a wrist-mounted display similar in appearance to a wrist-watch. However, none exist which operate continuously and autonomously without ancillary equipment and without requiring some operation to be performed by the wearer.
Devices with Ancillary Equipment
1. Chest Band Pick-ups
A large number of products are available commercially from manufacturers like Acumen, Bodyguard, Cardiosport, Cateye, Polar, Performance, Sensor Dynamics, Sigma, Sports Instruments and Vetta, which sense the electrical activity of the heart through electrocardiogram type electrodes mounted in an elasticated chest band. The resultant electrical spikes are then identified and transmitted to a display that may be mounted anywhere within the range of the telemetered signal —in a wrist-watch type devise, a bicycle handlebar mounted readout, or a custom computer display on a piece of exercise equipment. However, even on far forward bicycle handlebars the signal can be lost. A typical device is described in U.S. Pat. No. 5,690,119 to Pekka.
While the devices typically provide steady and reliable readings, they are best suited to use for brief periods during exercise rather than as a continuous long-term or all-day monitor. In addition, the readings are affected by other users nearby utilizing similar heart rate monitors, electromagnetic radiation interference, particularly from power lines and motorized equipment. Accordingly, they typically will not work in an automobile, near TV's and computers, and on certain types of exercise equipment using electric motors and video screens. While less constraining than an ear clip or finger stall with their associated wires, the chest band takes time to put on under clothing and is a physical encumbrance to the exerciser. In addition, it typically only functions when good electrical contact is established to the skin, either by moistening with water or through sweat during vigorous exercise. During very vigorous activity such as mountain biking the chest-band will often slip down from the optimum pick-up location.
2. Handlebar Pick-ups
Certain types of exercise equipment, such as treadmills, stair-steppers, etc, are outfitted with electrically conducting handlebars that serve as crude electrocardiogram leads. The change in gross position of the cardiac dipole during the course of each beat is manifest as a measurable shift in surface potential between the right and left side of the body and can be picked up at the gripping surface of each hand.
Although this provides feedback while the exercise equipment is being used, all readings are lost when physical contact with the equipment is broken.
3. Ear Lobe Pick-ups
Some exercise equipment and heart rate monitors come with a small infrared transmitter (a light emitting diode is a typical example) and detector that clips onto the ear-lobe and picks up the fluctuation in IR transmission through the ear as the capillaries fill with blood and then drain during the cardiac cycle. The pulse data is hard-wired from the sensor to a display mounted on the wrist or other convenient location. A typical commercially available product of this type is the Cateye PL-6000.
In addition to being uncomfortable, and awkward (because a wire has to be run from the detector on the ear to a visible display), these devices are prone to interference from movement and changing ambient lighting conditions. The slightest head motion causes changes in the amount of IR radiation detected, hence the apparent pulse rate, due primarily to the light that leaks in around the edges of the detector window.
U.S. Pat. No. 5,490,505 to Diab et al. describes such a device, typically configured as a pulsoximeter on the finger or ear with two different wavelength LED's shining through the tissue to enable an attenuation measurement to be made after propagation through or reflection from the medium. Pulse rate is determined from the periodic attenuation associated with the increase and decrease in arterial flow during a pulse cycle. However the resultant plethysmographic waveform is readily overwhelmed by motion because movement exerts a strong influence on the dynamics of venous blood flow and hence venous blood attenuation of the LED wavelength. Accordingly, the patent describes complex and involved signal processing to recognize the true signal and extract it from exercise-generated noise.
U.S. Pat. No. 4,867,442 to Matthews describes an exercise aid configured as a sweatband around the head with IR or piezoelectric sensors on the ear to pick up pulse. However, the patent provides no enabling disclosure to overcome the motion induced artifacts which would obscure the pulse signal during exercise.
4. Finger Stall
Bridger Keith
Cooke Arthur V.
Kuhn Philip M.
Lutian Joseph J.
Passaro Edward J.
Active Signal Technologies, Inc.
Astorino Michael
Pietragallo Bosick & Gordon
Shaver Kevin
Towner, Esq. Alan G.
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