Disposable oximetry sensor

Details Disposable oximetry sensor Disposable oximetry sensor

2002-08-21

2004-06-01

Winakur, Eric F. (Department: 3736)

Surgery

Diagnostic testing

Measuring or detecting nonradioactive constituent of body...

C600S323000

Reexamination Certificate

active

06745061

ABSTRACT:

FIELD OF THE INVENTION
The present invention is generally directed to photoplethysmographic measurement instruments, and more specifically to disposable pulse oximetry sensors.
BACKGROUND
A common technique used to monitor blood oxygen levels is pulse oximetry. In this regard, it is known that the light transmissivity and color of blood is a function of the oxygen saturation of the heme in the blood's hemoglobin. For example, heme that is saturated with oxygen appears bright red because saturated heme is relatively permeable to red light. In contrast, heme that is deoxygenated appears dark and bluish as it is less permeable to red light. A pulse oximeter system measures the oxygen content of arterial blood by utilizing a pulse oximetry sensor to first illuminate the blood with, for example, red and infrared radiation and determine the corresponding amounts of red and infrared radiation that are absorbed by the heme in the blood. In turn, such light absorption amounts may be employed by a pulse oximetry monitor in conjunction with known calibration information to determine blood oxygen levels.
Pulse oximetry sensors generally include one or more light emitters, a detector(s), and a means for holding these components relative to a patient's tissue. These sensors may generally be classified as reusable or disposable. Reusable sensors typically are more intricate and designed for multiple uses on multiple patients. In this regard, reusable sensors generally must be cleaned between use on different patients. Disposable sensors are typically simplified sensors that are used for a predetermined period on a single patient and discarded. Accordingly, disposable sensors may in some instances be more desirable than their reusable counterparts.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a disposable pulse oximetry sensor that has a reduced part count and it therefore easily produced.
Another objective of the present invention is to provide a pulse oximetry sensor that lends itself to production through an automated process.
A further objective of the present invention is to provide a disposable sensor that is economical to manufacture and use while providing required sensor performance.
The inventors of the present invention have recognized the increased need for the use of disposable medical sensors and in particular disposable pulse oximetry sensors. This increased need arises due to, inter alia, concerns in properly cleaning medical instruments between uses of communicable diseases, such as AIDS and Hepatitis B. In this regard, patients as well as hospitals may prefer using new medical instruments, that is, medical instruments that have not been used previously. Additionally, the inventors have recognized that although reusable pulse oximetry sensors tend to initially be more expensive, their ability to be reused may lower their per-use cost below that of disposable pulse oximetry sensors currently existing, leaving hospitals and patients torn between their preferences and the financial realities of the health care system. Accordingly, the inventors have devised a reduced part count pulse oximetry sensor that is easily produced resulting in a disposable pulse oximetry sensor that is cost effective on a per-use basis in comparison with reusable pulse oximetry sensors.
One or more of the above objectives and additional advantages are indeed realized by the present invention where, in one aspect, a pulse oximetry sensor having an integrally formed connector is provided. The sensor includes a substantially clear flexible substrate that may be conformed about a portion of a patient's tissue, such as a finger. This flexible clear substrate may be formed from any material that provides the desired flexibility and is substantially transparent, allowing for emitting and detecting light signals through this clear substrate. A particularly apt substrate may be made from a polymer thick film (PTF) such as polyester. Mounted on a top surface of the clear flexible substrate is at least one active pulse oximetry component. That is, at least one light emitter, such as a light emitting diode, and/or a light detector, such as a photodiode. Particularly, these active components are mounted on the top surface of the clear substrate such that they emit/detect light through the clear substrate and its bottom surface. In this regard, the clear substrate acts as a lens covering the active surfaces of the light emitter and/or light detector and reducing the overall part count required for the pulse oximetry sensor. Further, as noted, the sensor has an integrally formed connector that allows the flexible substrate to be interconnected to, for example, an electrical pin connector connected to a pulse oximetry monitor.
Various refinements exist of the features noted in relation to the subject first aspect of the present invention. Further features may also be incorporated into the subject first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. For example, the bottom surface of the clear flexible substrate (i.e., the patient side of the sensor) may contain an adhesive and/or a release liner covering the adhesive for selectively securing the sensor to a patient's tissue. Additionally, a compressible material layer may be disposed on the patient side surface of the flexible sensor for increased patient comfort. Preferably, any compressible material layer utilized will contain apertures aligned with each light emitter and/or light detector mounted on the top side of the clear flexible substrate, allowing light to be emitted and/or detected through these apertures free from interference. Further, the flexible sensor may contain a light blocking layer applied to the top surface of the clear flexible substrate to minimize the effect of ambient light sources upon the sensor. This light blocking layer may include a separate substrate interconnected to the clear flexible substrate or some sort of opaque coating applied to the top surface of the clear flexible substrate.
Regardless of which additional features the sensor utilizes, in a one embodiment, all materials applied to the bottom surface (i.e., patient side) of the clear flexible substrate contain a substantially clear portion aligned with the active pulse oximetry components. As will be appreciated, this provides for increased light transfer between a light emitter and/or detector upon application to an appendage as well as allowing for the utilization of light (e.g., ultra violet (UV) light or high intensity visible light) to cure various light-curable adhesives that may be used to mount one or more of the components to the clear flexible substrate during manufacture. For example, the light emitter and/or detector may be encapsulated on top of the clear substrate using a light-curable clear adhesive to stabilize the emitter/detector as well as provide increased focusing of light into or from the clear substrate. Light may be applied through these layers and the bottom surface of the clear substrate to cure the adhesive(s). In a further embodiment, all the materials applied to the bottom surface of the clear substrate will be at least partially transparent materials to allow light curable adhesives to be utilized in laminating the various materials together. In addition, or alternatively, thermal and/or mechanical pressure may be utilized to initiate or complete the cure of adhesives as well as thermally bond (i.e., laminate) one or more of the various material layers together.
In a second aspect of the present invention, a pulse oximetry sensor is provided comprising a substantially clear flexible substrate that may be conformed about a patient's tissue having, mounted on its top surface, at least one active pulse oximetry component. Again these active components (i.e., light emitter and/or light detector) are mounted on the clear substrate's top surface such that they emit/detect light through the clear substra

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