Patent Application
20080147147
This invention relates generally to vein locating or vein visualization devices, and more specifically to devices that use near-infrared (NIR) or ultrasound energy to locate or visualize venous structures in patients.
Intravenous (IV) access is problematic in many patients due to difficulty in finding and locating veins that are suitable. Many patients have veins that are not visible with the naked eye, or are beneath the surface of the skin so that they cannot be felt or seen. Patients with dark skin, and excess of subcutaneous fat, or with small or deep veins often fall into this category.
As reported by InfraRed Imaging Systems, Inc. of Columbus, Ohio, vascular access procedures rank as the most commonly performed, invasive, medical procedure in the U.S., with over 1.4 billion procedures performed annually (c 2005). These procedures also rank as the top patient complaint among clinical procedures. The overwhelming majority of vascular access procedures are performed without the aid of any visualization device and rely on what is observed through the patient's skin and by the clinician's ability to feel the vessel. Medical literature reports the following statistics: (1) a 28% first attempt IV failure rate in normal adults; (2) a 44% first attempt IV failure rate in pediatrics; (3) 43% of pediatric IVs require three or more insertion attempts; (4) a 23% to 28% incidence of extravasation/infiltration; (5) a 12% outright failure rate in cancer patients; and (6) 25% of hospital in-patients beyond three days experience difficult vascular access. See Brown P., “An I.V. Specialty team can mean savings for hospital and patient,” Journal of the National Intravenous Therapy Association, 17(5):387-388 (1984); Frey A M., “Success rates for peripheral IV insertion in a children's hospital,” Journal of Intravenous Nursing, 21(3):160-165 (1998); Palefski S. et al., “The infusion nurse and patient complication rates of peripheral short catheters: A prospective evaluation,” Journal of Intravenous Nursing, 24(2):113-123 (2001); Lininger R., “Pediatric peripheral IV insertion success rates,” Pediatric Nursing, 29(5):351-254 (2003); and Barton A. et al., “Improving patient outcomes through CQI: Vascular access planning,” Journal of Nursing Care Quality. 13(2):77-85 (1998), the contents of which are incorporated herein by reference.
A number of products for locating veins are known or currently available. These include products utilizing (1) ultrasound imaging, such as the Bard Site-Rite® 5 Ultrasound System marketed by Bard Access Systems, Inc. of Salt Lake City, Utah, (2) near-infrared (NIR) imaging, such as the IRIS Vascular Viewer marketed by InfraRed Imaging Systems, Inc. and the Vein Viewer Imaging System marketed by Luminetx Corporation of Memphis, Tenn., (3) liquid crystal thermal surface temperature measurement patches, such as the K-4000 Vena-Vue® Thermographic Vein Evaluator manufactured by Biosynergy, Inc. of Elk Grove Village, Ill., and (4) visible light illumination, such as the Venoscope® II Transilluminator/Vein Finder and the Neonatal Transilluminator marketed by Venoscope, L.L.C. of Lafayette, La., and the Veinlite®, Veinlite LED™, Veinlite EMS™ and Veinlite PEDI™ manufactured by TransLite, LLC of Sugar Land, Tex.
Others have performed experiments using optical light fibers that are moved over the skin to generate vessel maps based on spatially resolved reflectance at the skin surface. See Fridolin et al., “Optical Non-Invasive Techniques for Vessel Imaging: I. Experimental Results,” Phys. Med. Biol. 45, 3765-3778 (2000) and Fridolin et al., “Optical Non-Invasive Techniques for Vessel Imaging: II. A Simplified Photo Diffusion Analysis,” Phys. Med. Biol. 45, 3779-3792 (2000), the contents of which are incorporated herein by reference.
The currently-available vein-locating products often include imaging equipment and displays. In addition, imaging equipment, though portable, often must reside on a cart or stand, making transport difficult. Liquid crystal surface temperature patches work in some cases; however, they are difficult to use and may not work on patients that have poor limb circulation, small veins, or that have a greater than average subcutaneous fat layer near the IV access site.
The inadequacies of current vascular access practices significantly compromise patient care and contribute to rising healthcare costs. Multiple access attempts and outright failures delay patient treatment, frustrate healthcare professionals, and increase the likelihood of downstream complications and expense.
The invention provides an improved vein-locating or vein-visualization device that is intended for use during intravenous access medical procedures. The vein-locating or vein-visualization device of the present invention is, in one aspect, a device that is used in a similar manner to a construction stud finder to identify regions under the skin where there is a change in light absorption or blood flow.
In another aspect, the invention utilizes near-infrared (NIR) energy or ultrasound energy to “see” various to various depths, such as several cm, within tissue. Veins contain de-oxygenated hemoglobin, which has a near infrared absorption peak at around 760 nm and a lesser, more broad absorption plateau over the range of 800 to 950 nm. There is a window of wavelengths in the near infrared region between 650 and 900 nm in which photons are able to penetrate tissue far enough to illuminate deeper structures beyond depths of 1 cm. In a preferred embodiment, the invention utilizes near-infrared wavelengths of approximately 880 to 890 nm for imaging subcutaneous veins in tissue.
In yet another aspect, the invention provides a self-contained, small, low-cost, and portable vein-locating or vein-visualization device for clinical use. In various embodiments, the present invention may include (1) a single infrared source and detector pair, (2) a single source and an array of detectors, or (3) an array of sources and an array of detectors.
In a further aspect, the present invention provides a device for detecting a surface or subsurface venous or vascular structure in a patient. The device includes an optical source for transmitting optical energy into the tissue of the patient, an optical detector for detecting at least a portion of the optical energy that is transmitted into and reflected and scattered by the tissue, and an indicator operably associated with the optical source and the optical detector. The indicator is adapted to indicate relative changes in the detected reflection of the optical energy transmitted into the tissue of the patient.
In still another aspect, the present invention provides a device for detecting a venous structure in a patient. The device includes an optical source for transmitting optical energy into the tissue of the patient, an optical detector for detecting at least a portion of the optical energy that is transmitted into and reflected by the tissue, and a removable coupler operably associated with the optical source and the optical detector.
In yet another aspect, the present invention provides a device for detecting a venous structure in a patient. The devices includes an optical source for transmitting optical energy into the tissue of the patient, an optical detector for detecting at least a portion of the optical energy that is transmitted into and reflected by the tissue, and indicator operably associated with the optical source and the optical detector. The indicator is adapted to indicate relative changes in the detected reflection of the optical energy transmitted into the tissue of the patient.
Further, the device includes a removable coupler operably associated with the optical source and the optical detector, one or more visible light illuminating sources adapted to be positioned near the skin surface of the patient to improve the ability to detect near-surface veins in the tissue, an amplifier operably associated with the optical detector, a modulator operably associated with the optical source and the amplifier, and a marking device to mark the location of the venous structure. The device may also provide for a guide for needle access.
By performing a simple reflectance measurement from the skin surface, it is possible to detect the location of a vein at depths of 4 mm or more below the skin surface. In a preferred aspect, the source and detector elements are incorporated within a hand held, battery operated, portable device that clinicians can use as a tool to help locate veins and thereby assist with IV access.
The present invention, and its presently preferred and alternate embodiments, will be better understood by way of reference to the detailed description herebelow and to the accompanying drawings, wherein:
a illustrates an alternate embodiment of the source and detector embodiment of
b illustrates another alternate embodiment of the source and detector embodiment of
c illustrates a histogram display for the source and detector embodiment of
In one embodiment, as shown in
The housing 12 includes a sensor retaining assembly 13 and an optical collimator assembly 15 for retaining the optical source 14 and the optical detector 16. The housing 12 is held together with suitable fasteners, such as screws 17. The housing 12 further includes low-pass or band-pass filters 19, as explained further below.
The optical source 14 and the optical detector 16 are preferably oriented such that they are perpendicular to the surface 18 of the patient's skin and separated by several mm distance. When the optical source 14 (such as a NIR source) is activated, infrared photons travel through the patient's skin and tissue and are scattered and diffused. The detector 16 picks up some of this reflected and scattered light. When the source 14 is placed over a vein 20, the vein tissue absorbs some of the infrared light and the detector 16 picks up less reflected energy at those wavelengths. This causes a detectable signal change, which indicates the presence of the vein 20. Best results occur when the source 14 and detector 16 line up over the vein 20 (i.e., are in parallel with the direction of the vein 20), since this creates the longest absorption path. Variations in signal change due to a vessel or vein being located beneath the source-detector pair 14, 16 decrease logarithmically with distance. For a source and detector pair 14, 16, each having an aperture of about 1 mm, the optimal separation distance is approximately 5-6 mm. This will typically provide an imaging depth of at least 3-4 mm below the skin surface 18 of a patient.
In another embodiment, as shown in
Further, the housing 112 of the device 110 may also include one or more visible light illuminating sources 134, such as LEDs, which are disposed to be near the surface 118 of the skin, so that visual detection of near-surface veins is facilitated and/or improved. This also has the added benefit of serving as a power-on indication to the operator, since the NIR energy transmitted by the source 114 is not visible to the naked eye.
If, as shown in
In the embodiment shown in
For example, as shown in
For increased sensitivity and depth, as shown in
A key component of the vein finding device 10, 110, 210 is a per-patient sterile disposable coupler/needle guide 350, as shown in
The coupler 350 or, alternatively, the source 14, 114, 214 and detector 16, 116, 216 may contain focusing elements or polarizing filters 360 to polarize the transmitted and received light. A linear polarizing filter 362 is placed on the source 14, 114, 214 and another linear polarizing filter 364 that is optically orthogonal to the first 362 is placed on the detector 16, 116, 216. The polarization of light is preserved in specular reflections and for certain geometries in single scattering events. Multiple Rayleigh-scattering events in tissue diffuse and depolarize the source. (Specular reflection is the perfect, mirror-like reflection of light (or sometimes other kinds of wave) from a surface, in which light from a single incoming direction is reflected into a single outgoing direction. Such behavior is described by the law of reflection, which states that the direction of outgoing reflected light and the direction of incoming light make the same angle with respect to the surface normal; this is commonly stated as θi=θr. This is in contrast to diffuse reflection, where incoming light is reflected in a broad range of directions.)
The polarizers 360 attenuate the light from specular reflections and near-field scattering events. The only light returning from the subject that can pass through the polarization filters 360 results from multiple scattering events occurring relatively deep (about 10 times the single scattering length) within the tissue. This scattered, depolarized light can be thought of as a virtual source that effectively back-illuminates any absorbing material in the foreground. This is linked to photon migration studies. The use of crossed polarizers gates photons by their migration path. Photons that have a longer diffusion path are more likely to pass through the filters and be received by the detector. This allows the device 10, 110, 210 to “see” more deeply into tissue. Also, the received signal will be more attenuated, so a more powerful source 14, 214, 216, such as a laser diode, may be used to obtain sufficient signal power/illumination.
To use the device 10, 110, 210, the operator first installs a disposable coupler 350. Next, they turn on the device, which activates the infrared source(s) 14, 114, 214, detector(s) 16, 116, 216 and any signal processing. Once the device has been activated, it is placed on the patient's skin, so that the disposable coupler 350 is in contact with the skin surface. An optical coupling gel may be used to obtain better optical signal match to the patient's tissue.
The device 10, 110, 210 may be placed on the patient's forearm or in the bend of the elbow (antecubital fascia), which are common places on the body for peripheral IV access, or the device is placed on another part of the patient's body. Next, the operator scans the device across the skin in the direction perpendicular to the expected longitudinal direction of the veins. By monitoring the indicator or display 130 for peaks in absorption, the operator locates a target region for IV insertion. The peaks of the indicator/display 130 represent the depth and size of the vessel below the source-detector arrangement. Next the operator rotates the device to establish vein direction. For a single source-detector configuration, the greatest absorption occurs when the source and detector are oriented in a line that is parallel and over the vein below. For a single source-multiple detector configuration, the vein direction is determined by the widest spatial spread of absorption, which indicates that the detectors are oriented in a line that is parallel and over the vein below. Once the vein location and direction are established, the operator may either mark the IV access site with a marking device or pen 370 (which may be provided by or incorporated in the device, as shown in
The device may also be connected to an image display such that the information from the device is presented on the display to present a map as the device is scanned over a region of interest within the tissue. For accurate display, the position and or scanning rate of the device must be captured in at least two dimensions.
The device may also project a line of visible light onto the surface of the skin over the region where the detected vessel is located, and aligned with the longitudinal direction of the vessel to identify vessel location.
For ease of use, the device 10, 110, 210 is preferably hand held, and may be designed so that during use it rests across the surface of the arm or area to be scanned. This way, the device must only be held down against the surface of the skin and is supported by the surface of the patient when the operator inserts the vascular access device.
As shown in
In another embodiment, the device projects a line of visible light onto the surface of the skin, in the longitudinal direction of the vessel, when the vessel is detected.
In another embodiment, the device may use a an optical Doppler technique where the optical reflection is detected with a sensor, then signal processing is used to identify the portion of the reflection that is due to moving blood cells within the vessel. A similar technique is sometimes used for tissue perfusion measurements, however, it may also be possible to use measurement changes based on Doppler velocimetry to determine the location of larger near-surface vessels based on the relative measurements of blood cell flux as the cells move through tissue. Flux measured in larger veins will be greater than in surrounding tissue capillary flow. For this approach, a single coherent frequency stable optical source such as a laser is used. The optical source is then directed into the tissue, and the reflected signal is monitored with two or more sensors, where the interference between the two is used to provide a Doppler beat frequency which is then used to determine the velocity of particles moving beneath the surface. The beat frequency can be measured by a standard laser Doppler signal processor, a commercial digital photon correlator, or a fast digital correlator. See Tong P. et al., “Two-fiber-optic method of laser Doppler velocimetry,” NASA Tech Briefs (May 2002), the contents of which are incorporated herein by reference.
Electronic schematics for an IR emitter, an IR receiver and a Power Supply for another preferred embodiment of the invention are shown in
Although the present invention has been described in detail in connection with the above embodiments and/or examples, it is to be understood that such detail is solely for that purpose and that variations can be made by those skilled in the art without departing from the invention. The components and features of the various embodiments of the invention can be assorted or combined as appropriate for the application. The scope of the invention is indicated by the following claims rather than by the foregoing description. All changes and variations which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
