Patent Application
20090310123
1. Field of Invention
The present invention relates to the non-invasive, optical detection of blood in translucent fluids. In particular, this invention relates to a system of interrelated optical devices, lenses and electronic circuit designed and deployed to detect the intrusion of blood in intravenous tubing for extracorporeal medical devices. More particularly, this invention relates to the detection of blood concentrates within the fluid More particularly yet, this invention relates to improved blood leak detector technology manifesting in increased reliability and accuracy These improvements include; liquid lens technology, proportional light energy absorption properties, electronic circuit stability as well as a means of self-monitoring proper installation of tubing and fluid flow.
2. Prior Art
Early model blood leak detectors used invasive optical means whereby they redirect the flow of dialysate (and blood) pass sensor(s) embedded in the intravenous tubing; ref U.S. Pat. Nos. 4,085,047; 4,017,190; 3,832,067. Because the solution and blood came in contact with the apparatus, it caused serious hygiene concerns, plus created ample work and costs in the cleansing process between patients. Shortly thereafter non-invasive optical detectors were employed that used the ‘angle of incidence’ theory for their mode of operation; whereby they tried to detect the change in angle of reflectance of dialysate vs. blood; ref U.S. Pat. No. 4,166,961. These devices could not detect small concentrates of blood particles within the dialysate solution. Still other blood leak detectors tried to detect the introduction of blood in dialysate solution by use of variance in reflectance properties of different wavelengths of light; ref U.S. Pat. No. 5,734,464. These were prone to drift, required frequent calibration and are susceptible to ambient light and electrical noise. Still other blood leak detectors attempted a similar procedure by using long and short wavelengths, then to electronically balance the two and “look” for a change in state of one of them; ref U.S. Pat. No. 4,181,610. These fell to the same short comings as above e.g. drift, frequent calibration, ambient light and electrical noise. Still others tried to overcome these shortcomings by damping their effects by comparing the signal outputs, from multiple samples, to know references stored in a software program; ref U.S. Pat. No. 5,670,050. Such software and hardware created significant cost to the device, plus was only masking the inherent shortcoming. Others employed single beam optics in the near infrared range, e.g. 800 to 930 nm wavelengths, that pass a narrow beam of light, e.g. 0.03 to 0.06 inch diameter, through intravenous tubing, whereby they need to squash the tubing in order for the light to penetrate the tube; ref. U.S. Pat. No. 7,230,687. Although an improvement over previous devices from the stand point of overcoming the shortcomings of drift, frequent calibrations and ambient conditions, these devices utilize a narrow field of view e.g. 0.03 to 0.06 inch beam width; thus fail to sample a significant portion of the dialysate to determine low concentrates of blood. Plus these devices employ light in the near infrared range that utilizes a contrast measurement—not a blood absorption measurement, of which this light range is susceptible to like contrast measurements from other contaminants; such as bubbles and micro bubbles. In addition, these devices require the use of a pop-up vane, which is an opaque material that blocks the light beam when the intravenous tubing is removed. This would indicate, to one skilled in the art, that the sensor can not detect the difference between the absence of the tube and a tube without fluid and/or a tube with clear fluid being present. The pop-up vane, being a mechanical device, is inherently subjected to failure; due to wear and clogging of its actuating mechanism, e.g. spring, rocker, etc. Plus, given the sticky nature of intravenous fluids and their tendency to leak, would require meticulous cleaning after each application. Still others have attempted utilizing laser light beam sources. These create an even tighter light beam path, which narrows the sampling of fluid being viewed, plus the laser light creates heat that can alter the characteristics the solution.
The present device overcomes the problems described above by creating a non-invasive detection means, whereby the sensor housing forms the translucent tubing and fluid into a biconvex lens to disperse a light beam across the majority of the fluid then to collect the dispersed light energy to a single point on the opposing side; thus being able to calculate the light absorption over a much wider viewing area than the projected beam path; typically 0.03 to 0.06 inch diameter. The sensor housing also shields the detector from the effects of ambient light, overcoming the problem of previous devices. The present invention also overcomes the problems associated with frequent calibrations, drift and electrical noise by way of achieving a strong signal to noise ratio. This is accomplished through the use of light that is the most susceptible to absorption by blood e g light in the visible spectrum—400 to 800 nm wavelength; in combination with dispersing this light energy over the majority of fluid within the tube, therefore allowing for the maximum level of energy absorption by the blood present. The use of light in the visible spectrum also overcomes the light scattering effects caused by bubbles within the fluid e.g. light in longer wavelengths is more susceptible to scattering by air bubbles. By achieving a high signal to noise ratio, the present device can reliable detect the states of:
By utilizing visible light produced from light emitting diodes (LEDs), creates little to no heat, thus alterations in the characteristics of the solution is avoided unlike blood leak detectors that employ laser or incandescent light.
Recent developments in international medical equipment standards has required multiple detection levels of blood percentage within intravenous tubing for extracorporeal treatment systems; whereby the equipment is to react differently to differing concentrates of blood such as: indicate, annunciate, shut down. It is envisioned that the requirements will be further refined as the blood detection technology is further developed. In addition to having a blood concentrate detector determine the percentage of blood in solution over as wide a range as possible, it is also desirable to minimize adverse effects upon the sensor do to their environment; such as contact with solution/blood, leakage of solution/blood into mechanical parts, electrical noise interference, ambient light interference, etc. Plus the sensor should be designed in such a manner to avoid the need for calibration and should be easily cleaned without damage. The blood concentrate detector described here is believed to satisfy these requirements and to overcome the shortcomings of prior blood leak detectors.
In a first embodiment, the invention is a blood concentrate detector comprising a light source emitting light, in a wavelength range of 400 to 800 nm, to an opposing photo-detector with amplification circuitry, housed in an enclosure that can accept an intravenous tube.
A second embodiment of the invention is a blood concentrate detector comprising a housing having a slotted opening for insertion of the intravenous tube, wherein the slot opening is smaller than the nesting position of the tube, where as the housing acts to secure the tube in place and at the desired optical path between the light emitter and photo-detector receiver.
A third embodiment of the invention is a blood concentrate detector comprising a housing having a nesting position that forms, and/or allows the tube to form, a biconvex lens when filled with translucent fluid.
A forth embodiment of the invention is a blood concentrate detector comprising a housing having embedded optical filters for the light to traverse through the inner wall of the nesting area and through the opposing inner wall of the nesting area to the receiver.
A fifth embodiment of the invention is a blood concentrate detector comprising an analog circuit that can accurately measure the light intensity of: absence of tubing, presence of translucent tubing, presence of translucent tubing with the presence of translucent fluid, presence of small concentrates of blood within fluid, presence of higher concentrates of blood within fluid, and the presence of all blood within tubing.
As the light beam passes through the aperture 114 it traverses in a conical pattern across the tube cavity 106 with a percentage of the light beam entering the photo-detector orifice 116 and traveling to the photo-detector 102. The conical expansion of the light beam over the entire space of the tube cavity 108 is a function of the tube being absent
While the above descriptions contain much specificity, these should not be construed as limitations on the scope, but rather as an exemplification of several preferred embodiments thereof Many other variations are possible. For example, it is envisioned that; multiple light emitters and photo-detectors could be employed for redundancy, blood flow rate measuring, etc. or signal manipulation could be done extraneous to the sensor(s) or modification to the tube nesting area could be achieved or analog signal measurements could be converted to digital signals or embedded optical filters could be attached to the optical elements in lieu of the housing or fewer or more increments in signal levels could be disclosed, etc.
Accordingly, the scope should be determined not by the embodiment(s) illustrated, but by the appended claims and their legal equivalents.
