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FOLDING MEDICAL SENSOR AND
TECHNIQUE FOR USING THE SAME
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to medical devices and, more particularly, to sensors used for sensing physiological parameters of a patient.
2. Description of the Related Art 10 This section is intended to introduce the reader to various
aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better 15 understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In the field of medicine, doctors often desire to monitor certain physiological characteristics of their patients. Accord- 20 ingly, a wide variety of devices have been developed for monitoring physiological characteristics. Such devices provide doctors and other healthcare personnel with the information they need to provide the best possible healthcare for their patients. As a result, such monitoring devices have 25 become an indispensable part of modern medicine.
One technique for monitoring certain physiological characteristics of a patient is commonly referred to as pulse oximetry, and the devices built based upon pulse oximetry techniques are commonly referred to as pulse oximeters. Pulse 30 oximetry may be used to measure various blood flow characteristics, such as the blood-oxygen saturation of hemoglobin in arterial blood, the volume of individual blood pulsations supplying the tissue, and/or the rate of blood pulsations corresponding to each heartbeat of a patient. 35
Pulse oximeters typically utilize a non-invasive sensor that is placed on or against a patient's tissue that is well perfused with blood, such as a patient's finger, toe, forehead or earlobe. The pulse oximeter sensor emits light and photoelectrically senses the absorption and/or scattering of the light after pas- 40 sage through the perfused tissue. The data collected by the sensor may then be used to calculate one or more of the above physiological characteristics based upon the absorption or scattering of the light. More specifically, the emitted light is typically selected to be of one or more wavelengths that are 45 absorbed or scattered in an amount related to the presence of oxygenated versus de-oxygenated hemoglobin in the blood. The amount of light absorbed and/or scattered may then be used to estimate the amount of the oxygen in the tissue using various algorithms. 50
In many instances, it may be desirable to employ, for cost and/or convenience, a pulse oximeter sensor that is reusable. One such type of pulse oximeter sensor is a clip-style sensor which is held on a patient by the force provided by a spring or other biasing mechanism. Such a clip-style sensor may then 55 be removed by applying a countervailing force to the spring or biasing mechanism, thereby separating the ends of the sensor and allowing the sensor to be removed. In this manner, the clip-style sensor can be applied and removed many times, with the same or different patients. 60
Such reusable sensors, however, may be uncomfortable for the patient for various reasons. For example, the materials used in their construction may not be adequately compliant or supple or the structural features may include angles or edges. Furthermore, the reusable sensor should fit snugly enough 65 that incidental patient motion will not dislodge or move the sensor, yet not so tight that it may interfere with pulse oxim
etry measurements. Such a conforming fit may be difficult to achieve over a range of patient physiologies without adjustment or excessive attention on the part of medical personnel. In addition, lack of a tight or secure fit may allow light from the environment to reach the photodetecting elements of the sensor. Such environmental light is not related to a physiological characteristic of the patient and may, therefore, introduce error into the measurements derived using data obtained with the sensor.
Reusable pulse oximeter sensors are also used repeatedly and, typically, on more than one patient. Therefore, over the life of the sensor, detritus and other bio-debris (sloughed off skin cells, dried fluids, dirt, and so forth) may accumulate on the surface of the sensor or in crevices and cavities of the sensor, after repeated uses. As a result, it may be desirable to quickly and/or routinely clean the sensor in a thorough manner. However, in sensors having a multi-part construction, as is typical in reusable pulse oximeter sensors, it may be difficult to perform such a quick and/or routine cleaning. For example, such a thorough cleaning may require disassembly of the sensor and individual cleaning of the disassembled parts ormay require careful cleaning using utensils capable of reaching into cavities or crevices of the sensor. Such cleaning is labor intensive and may be impractical in a typical hospital or clinic environment.
Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms of the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
There is provided a sensor assembly that includes: a frame, wherein the frame is configured to move between an open and a closed configuration; a covering provided over at least part of the frame; at least one optical component disposed on the frame; and a retaining component configured to hold the frame in the closed configuration when engaged.
There is provided a sensor assembly that includes: a sensor body configured to move between an open and a closed position; an emitter disposed on the sensor body; a detector disposed on the sensor body; and a retaining component configured to hold the sensor body in the closed configuration when engaged.
There is provided a sensor assembly that includes: a frame configured to move between an open and a closed position; an emitter disposed on the frame; a detector disposed on the frame; and a covering provided over at least part of the frame to form a sensor assembly.
There is provided a method of manufacturing a sensor that includes: situating an emitter and a detector on a frame; and coating the frame with a coating material to form a sensor assembly, wherein the frame is substantially open when coated.
There is provided a method for acquiring physiological data that includes: emitting two or more wavelengths of light from an emitter of a sensor assembly, wherein the sensor assembly is held in a closed configuration by one or more retaining components; detecting transmitted or reflected light using a photodetector of the sensor assembly; and determining a physiological parameter based on the detected light.
There is provided a retaining component for use on a sensor assembly that includes: an elastic band configured to hold a sensor body in a substantially closed configuration.
There is provided a method of manufacturing a sensor body that includes: coating a frame with a coating material to form a sensor body, wherein the frame is substantially open when coated.
There is provided a sensor body that includes: a frame, 5 wherein the frame is configured to move between an open and a closed configuration; a covering provided over at least part of the frame; and a retaining component configured to hold the frame in the closed configuration when engaged.
There is provided a sensor body that includes: a sensor 10 body configured to move between an open and a closed position; and a retaining component configured to hold the sensor body in the closed configuration when engaged.
There is provided a sensor body that includes: a frame configured to move between an open and a closed position; 15 and a covering provided over at least part of the frame to form a sensor assembly.
There is provided a frame of a sensor that includes: a frame configured to move between an open and a closed configuration; and a retaining component configured to hold the frame 20 in the closed configuration when engaged.
There is provided a method for manufacturing a frame of a sensor that includes: forming a frame configured to move between an open and a closed configuration, wherein the frame comprises a retaining component configured to hold 25 the frame in the closed configuration when engaged.
BRIEF DESCRIPTION OF THE DRAWINGS
Advantages of the invention may become apparent upon 30 reading the following detailed description and upon reference to the drawings in which:
FIG. 1 illustrates a patient monitoring system coupled to a multi-parameter patient monitor and a sensor, in accordance with aspects of the present technique; 35
FIG. 2A illustrates a covered sensor in an open configuration, in accordance with aspects of the present technique;
FIG. 2B illustrates the sensor of FIG. 2A in a closed configuration;
FIG. 3 illustrates a covered sensor in a closed configura- 40 tion, in accordance with aspects of the present technique;
FIG. 4A illustrates a covered sensor in an open configuration, in accordance with aspects of the present technique;
FIG. 4B illustrates the sensor of FIG. 4A in an intermediate configuration; 45
FIG. 5A illustrates a covered sensor in an open configuration, in accordance with aspects of the present technique; and
FIG. 5B illustrates the sensor of FIG. 5A in a closed configuration.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise 55 description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made 60 to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a 65 routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
It is desirable to provide a comfortable and conformable reusable patient sensor, such as for use in pulse oximetry or other applications utilizing spectrophotometry, that is easily cleaned and that is resistant to environmental light infiltration. In accordance with some aspects of the present technique, a reusable patient sensor is provided that is based upon a frame upon which the sensor components, such as light emitting diodes and photodetectors, may be situated. To simplify construction, the frame may be constructed or formed in an open configuration, as opposed to the closed configuration employed when the resulting sensor is in use. In embodiments where the sensor is constructed from an open frame, a retaining or locking mechanism may be included on the sensor to hold the sensor in a closed configuration once folded or bent into the closed configuration.
Furthermore, the sensor may be covered, such as with a coating or overmold material, to provide patient comfort and a suitably conformable fit. In such embodiments, the frame may be covered in an open configuration to reduce the labor and complexity of the overmolding process. In addition, the retaining or locking mechanism may be provided as part of the frame that is covered, as part of the frame that is not covered, as part of the overmold material alone, or as a separate structure that is added combined with the covered sensor to hold the sensor in a closed configuration when in use.
Prior to discussing such exemplary sensors in detail, it should be appreciated that such sensors may be designed for use with a typical patient monitoring system. For example, referring now to FIG. 1, a sensor 10 according to the present invention may be used in conjunction with a patient monitor 12. In the depicted embodiment, a cable 14 connects the sensor 10 to the patient monitor 12. As will be appreciated by those of ordinary skill in the art, the sensor 10 and/or the cable 14 may include or incorporate one or more integrated circuit devices or electrical devices, such as a memory, processor chip, or resistor, that may facilitate or enhance communication between the sensor 10 and the patient monitor 12. Likewise the cable 14 may be an adaptor cable, with or without an integrated circuit or electrical device, for facilitating communication between the sensor 10 and various types of monitors, including older or newer versions of the patient monitor 12 or other physiological monitors. In other embodiments, the sensor 10 and the patient monitor 12 may communicate via wireless means, such as using radio, infrared, or optical signals. In such embodiments, a transmission device (not shown) may be connected to the sensor 10 to facilitate wireless transmission between the sensor 10 and the patient monitor 12. As will be appreciated by those of ordinary skill in the art, the cable 14 (or corresponding wireless transmissions) are typically used to transmit control or timing signals from the monitor 12 to the sensor 10 and/or to transmit acquired data from the sensor 10 to the monitor 12. In some embodiments, however, the cable 14 may be an optical fiber that allows optical signals to be conducted between the monitor 12 and the sensor 10.
In one embodiment, the patient monitor 12 may be a suitable pulse oximeter, such as those available from Nellcor Puritan Bennett Inc. In other embodiments, the patient monitor 12 may be a monitor suitable for measuring tissue water fractions, or other body fluid related metrics, using spectrophotometric or other techniques. Furthermore, the monitor 12 may be a multi-purpose monitor suitable for performing pulse oximetry and measurement of tissue water fraction, or other combinations of physiological and/or biochemical monitoring processes, using data acquired via the sensor 10. Furthermore, to upgrade conventional monitoring functions provided by the monitor 12 to provide additional functions, the
patient monitor 12 may be coupled to a multi-parameter patient monitor 16 via a cable 18 connected to a sensor input port and/or via a cable 20 connected to a digital communication port.
The sensor 10, in the example depicted in FIG. 1, is a 5 reusable sensor that is covered to provide a unitary or enclosed assembly. The sensor 10 includes an emitter 22 and a detector 24 which may be of any suitable type. For example, the emitter 22 may be one or more light emitting diodes adapted to transmit one or more wavelengths of light, such as l o in the red to infrared range, and the detector 24 may be a photodetector, such as a silicon photodiode package, selected to receive light in the range emitted from the emitter 22. In the depicted embodiment, the sensor 10 is coupled to a cable 14 that is responsible for transmitting electrical and/or optical 15 signals to and from the emitter 22 and detector 24 of the sensor 10. The cable 14 may be permanently coupled to the sensor 10, or it may be removably coupled to the sensor 10—the latter alternative being more useful and cost efficient in situations where the sensor 10 is disposable. 20
The sensor 10 described above is generally configured for use as a "transmission type" sensor for use in spectrophotometric applications, though in some embodiments it may instead be configured for use as a "reflectance type sensor." Transmission type sensors include an emitter and detector 25 that are typically placed on opposing sides of the sensor site. If the sensor site is a fingertip, for example, the sensor 10 is positioned over the patient's fingertip such that the emitter and detector lie on either side of the patient's nail bed. For example, the sensor 10 is positioned so that the emitter is 30 located on the patient's fingernail and the detector is located opposite the emitter on the patient's finger pad. During operation, the emitter shines one or more wavelengths of light through the patient's fingertip, or other tissue, and the light received by the detector is processed to determine various 35 physiological characteristics of the patient.
Reflectance type sensors generally operate under the same general principles as transmittance type sensors. However, reflectance type sensors include an emitter and detector that are typically placed on the same side of the sensor site. For 40 example, a reflectance type sensor may be placed on a patient's fingertip such that the emitter and detector are positioned side-by-side. Reflectance type sensors detect light photons that are scattered back to the detector.
For pulse oximetry applications using either transmission 45 or reflectance type sensors the oxygen saturation of the patient's arterial blood may be determined using two or more wavelengths of light, most commonly red and near infrared wavelengths. Similarly, in other applications a tissue water fraction (or other body fluid related metric) or a concentration 50 of one or more biochemical components in an aqueous environment may be measured using two or more wavelengths of light, most commonly near infrared wavelengths between about 1,000 nm to about 2,500 nm. It should be understood that, as used herein, the term "light" may refer to one or more 55 of infrared, visible, ultraviolet, or even X-ray electromagnetic radiation, and may also include any wavelength within the infrared, visible, ultraviolet, or X-ray spectra.
Pulse oximetry and other spectrophotometric sensors, whether transmission-type or reflectance-type, are typically 60 placed on a patient in a location conducive to measurement of the desired physiological parameters. For example, pulse oximetry sensors are typically placed on a patient in a location that is normally perfused with arterial blood to facilitate measurement of the desired blood characteristics, such as arterial 65 oxygen saturation measurement (Sa02). Common pulse oximetry sensor sites include a patient's fingertips, toes, fore
head, or earlobes. Regardless of the placement of the sensor 10, the reliability of the pulse oximetry measurement is related to the accurate detection of transmitted light that has passed through the perfused tissue and has not been inappropriately supplemented by outside light sources or modulated by subdermal anatomic structures. Such inappropriate supplementation and/or modulation of the light transmitted by the sensor can cause variability in the resulting pulse oximetry measurements.
As noted above, the sensor 10 discussed herein may be configured for either transmission or reflectance type sensing. For simplicity, the exemplary embodiment of the sensor 10 described herein is adapted for use as a transmission-type sensor. As will be appreciated by those of ordinary skill in the art, however, such discussion is merely exemplary and is not intended to limit the scope of the present technique.
Referring now to FIGS. 2A and 2B, a first embodiment of the sensor 10 is depicted which includes a frame 50 covered with a covering material 52 in both an open and a closed configuration respectively. The frame 50 houses an emitter 22 and detector 24 within respective optical component housings. In the depicted embodiment, the emitter 22 and detector 24 are not covered by the covering material 52 and/or optically communicate through respective windows 54 that are substantially transparent to the wavelengths of interest and that are provided in the covering material 52.
In the depicted embodiment, the emitter 22 and detector 24 are provided substantially flush with the patient facing surfaces of the sensor 10, as may be suitable for pulse oximetry applications. For other physiological monitoring applications, such as applications measuring tissue water fraction or other body fluid related metrics, other configurations may be desirable. For example, in such fluid measurement applications it may be desirable to provide one or both of the emitter 22 and detector 24 recessed relative to the patient facing surfaces of the sensor 10. Such modifications may be accomplished by proper configuration or design of a mold or die used in overmolding the frame 50, as discussed below, and/or by proper design of the respective emitter housing and/or detector housing of the frame 50.
The frame 50 may be solid or skeletal (i.e., a framework of spaced apart beams and struts) depending on the rigidity and solidity desired of the frame 50. In addition the frame 50 may include different structures or regions composed of different materials or which have different physical properties, such as rigidity, elasticity, and so forth. The frame 50 generally defines the shape of the sensor 10 when coated, though, in some embodiments, portions of the sensor 10 may be formed from the covering material 52 without corresponding underlying frame structures. Alternatively, in other embodiments, portions of the frame 50 may not be covered and may form part of the exposed surface of the sensor 10. Indeed, though the sensor 10 is depicted in an exemplary covered embodiment, in other embodiments, the frame 50 may not be covered but may instead primarily constitute the sensor body.
In certain embodiments, the frame 50 may be constructed, in whole or in part, from polymeric materials, such as thermoplastics, capable of providing a suitable rigidity or semirigidity for the different portions of the frame 50. Examples of such suitable materials include polyurethane, polypropylene and nylon, though other polymeric materials may also be suitable. In other embodiments, the frame 50 is constructed, in whole or in part, from other suitably rigid or semi-rigid materials, such as stainless steel, aluminum, magnesium, graphite, fiberglass, or other metals, alloys, or compositions that are sufficiently ductile and/or strong. For example, metals, alloys, or compositions that are suitable for diecasting,