Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2000-02-10
2003-02-04
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S2140RC
Reexamination Certificate
active
06515273
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention in general relates to sensors for measuring oxygen content in the blood, and, in particular, relates to an apparatus and method for monitoring the life of a pulse oximetry sensor.
2. Background
Early detection of low blood oxygen is critical in a wide variety of medical applications. For example, when a patient receives an insufficient supply of oxygen in critical care and surgical applications, brain damage and death can result in just a matter of minutes. Because of this danger, the medical industry developed pulse oximetry, a noninvasive procedure for measuring the oxygen saturation of the blood. A pulse oximeter interprets signals from a sensor attached to a patient in order to determine that patient's blood oxygen saturation.
A conventional pulse oximetry sensor has a red emitter, an infrared emitter, and a photodiode detector. The sensor is typically attached to a patient's finger, earlobe, or foot. For a finger, the sensor is configured so that the emitters project light from one side of the finger, through the outer tissue of the finger, and into the blood vessels and capillaries contained inside. The photodiode is positioned at the opposite side of the finger to detect the emitted light as it emerges from the outer tissues of the finger. The photodiode generates a signal based on the emitted light and relays that signal to the pulse oximeter. The pulse oximeter determines blood oxygen saturation by computing the differential absorption by the arterial blood of the two wavelengths (red and infrared) emitted by the sensor.
The foregoing conventional sensor is typically detachable from the oximeter to allow for periodic replacement. Periodic replacement is advantageous for a wide variety of reasons. For example, the sensor can become soiled, thereby possibly inhibiting sensor sensitivity or causing cross-patient contamination. Furthermore, the electronic circuitry in the sensor can become damaged, thereby causing sensor failure or inaccurate results. Moreover, the securing mechanism for the sensor, such as an adhesive substrate, can begin to fail, thereby improperly positioning the sensor in proximity to a measurement site and providing inaccurate data. Accordingly, periodic replacement of the sensor is an important aspect of maintaining a sterile, highly sensitive, accurate pulse oximetry system.
However, a conventional pulse oximetry sensor is wholly reliant on an operator for timely replacement of soiled, damaged, or otherwise overused sensors. This approach is problematic not only from the standpoint of operator mistake or negligence, but also from the perspective of deliberate misuse for cost saving or other purposes.
Based on the foregoing, significant drawbacks exist in the reliance on the operator for the periodic replacement of conventional pulse oximetry sensors. Accordingly, a need exists for a pulse oximetry sensor having the ability to monitor its own usable life.
SUMMARY OF THE INVENTION
Accordingly, one aspect of the present invention is to provide an inexpensive, highly accurate sensor life monitoring system for monitoring the useful and safe life of a pulse oximetry sensor. According to one embodiment, the sensor life monitoring system includes a timer and a sensor life indicator. According to another embodiment, the timer includes a divide-by-n counter and a non-volatile RAM, while the sensor life indicator includes at least one LED or incandescent bulb.
Therefore, one aspect of the present invention is a pulse oximetry sensor comprising a drive connection carrying a drive signal, wherein the drive signal has pulses. The pulse oximetry sensor further comprises a timer connected to the drive connection and configured to generate a timer output signal after a predetermined number of pulses are generated in the drive signal; and a sensor life indicator connected to the timer output signal and configured to provide an indication when the timer output signal is generated. The pulse oximetry sensor further comprises an LED network connected to the drive connection and configured to project light through a measurement site when pulsed by the drive signal; and a photodetector configured to detect the projected light and output a signal representative of constituents or characteristics of the measurement site.
Another aspect of the present invention is a sensor life monitoring system comprising a timer connected to a sensor drive signal; and a sensor life indicator connected to the timer such that the sensor life indicator is configured to indicate the expiration of the useful or safe life of a pulse oximetry sensor.
Another aspect of the present invention is a pulse oximetry system that comprises a pulse oximeter; a sensor connected to the pulse oximeter; and a sensor life monitor connected to the sensor and configured to monitor the useful and safe life of the sensor.
Another aspect of the present invention is a method of manufacturing a sensor. The method comprises connecting a timer to one of a sensor input and a sensor output; and connecting an indicator to the timer such that when the timer expires, the indicator is activated.
Another aspect of the present invention is a method for monitoring the life of an oximetry sensor. The method comprises monitoring a parameter responsive to repeated use of a sensor. When the parameter indicates that the sensor has expired, the method generates an expiration indication.
Another aspect of the present invention is an oximetry sensor life indicator that comprises a non-volatile counter connected to receive a drive signal having a plurality of transitions where the counter changes a count value in response to the transitions. The oximetry sensor life indicator further includes a sensible indicia connected to the counter, where the sensible indicia has a first state, and a second state and the sensible indicia changes from the first state to the second state to indicate the end of life of the oximetry sensor when the count value in the counter reaches a predetermined value.
Another aspect of the present invention is an oximetry system comprising an oximeter; a sensor attached to the oximeter through a cable; a timer connected to at least one of a sensor drive signal and a sensor return signal; and a sensor life indicator connected to the timer.
Another aspect of the present invention is an oximetry system comprising a sensor having a timer, wherein the timer produces a sensor expiration signal. An oximeter is connected to the sensor and is configured to receive the sensor expiration signal from the timer.
Another aspect of the present invention is an oximetry system comprising a sensor having a reset indicator. An oximeter is connected to the sensor and is configured to monitor whether the reset indicator has been set.
Another aspect of the present invention is a pulse oximetry system comprising a pulse oximeter and a sensor connected to the pulse oximeter. The sensor is adapted to measure a physiological parameter. The pulse oximetry system also comprises a memory device connected to the sensor and adapted to measure the useful life of the sensor.
Another aspect of the present invention is a pulse oximetry system comprising a sensor having an emitter, a detector, and a memory device storing a characteristic of the sensor. The pulse oximetry system also comprises a pulse oximeter connected to the sensor and adapted to read the characteristic of the sensor and the output of the detector. The pulse oximetry system also comprises a database connected to the pulse oximeter and adapted to store the characteristic along with a longevity measurement corresponding to the sensor.
For the purposes of summarizing the invention, certain aspects, advantages, and novel features of the invention have been described. Of course, it is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, the invention may be embodied or carried out in a manner that achieves or optim
Knobbe Martens Olson & Bear LLP
Le Que T.
Masimo Corporation
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