Patent Application
20090155770
Nosocomial or hospital acquired infections (HAI) have been estimated by the World Health Organization (WHO) to kill between 1.5 and 3 million people every year worldwide. Though commonly referred to as hospital acquired infections, nosocomial infections result from treatment in any healthcare service unit, and are generally defined as infections that are secondary to the patient's original condition. In the United States, HAIs are estimated to occur in 5 percent of all acute care hospitalizations, resulting in more than $4.5 billion in excess health care costs. According to a survey of U.S. hospitals by the Centers for Disease Control and Prevention (CDC), HAIs accounted for about 1.7 million infections and about 99,000 associated deaths in 2002. The CDC reported that “[t]he number of HAIs exceeded the number of cases of any currently notifiable disease, and deaths associated with HAIs in hospitals exceeded the number attributable to several of the top ten leading causes of death in U.S. vital statistics” (Centers for Disease Control and Prevention, “Estimates of Healthcare Associated Diseases,” May 30, 2007).
HAIs, including surgical site infections (SSIs), catheter related blood stream infections (CRBSIs), urinary tract infections (UTIs), ventilator associated pneumonia (VAP), and others, may be caused by bacteria, viruses, fungi, or parasites. For instance, bacterial organisms, such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa are common causes as are yeasts such as Candida albicans and Candida glabrata, fungi such as those of the genus Aspergillus and those of the genus Saccharomyces, and viruses such as parainfluenza and norovirus.
Ongoing efforts are being made to prevent HAI through, for instance, improved hand washing and gloving materials and techniques, but such efforts have met with limited success. In an effort to better understand and curb HAIs, government regulations have increased pressure on hospitals and care-givers to monitor and report these types of infections. However, these measures are further complicated due to the prevalence of outpatient services, a result of which being that many HAIs do not become evident until after the patient has returned home. As such, infection may proceed undiagnosed for some time, complicating treatment and recovery.
A need currently exists for improved methods for diagnosing HAI, including SSI. Moreover, methods that could monitor a patient, for instance a patient's surgical site, in an outpatient setting, would be of great benefit.
In accordance with one embodiment, disclosed is a method for detecting the presence or amount of a pathogen that is a source of a hospital acquired infection. For example, a method may include locating a portion of an implantable device in an in vivo environment. A method may also include transmitting an optically detectable signal that is directly or indirectly emitted from the pathogen through a fiber optic cable to a detector. For instance, bacterial pathogens may autofluoresce in response to an excitation signal and directly produce the optically detectable signal. The presence or amount of the pathogen may then be determined.
According to another embodiment, a portable device for detecting the presence or amount of a pathogen that is a source of a hospital acquired infection is disclosed. A device may include, for instance, an implantable device and a portable enclosure containing a power source, an optical detector, a signal processor, and a signaling device for emitting a signal upon detection of the pathogen in an environment. The device may also include a connecting device, for instance for attaching the enclosure to the clothing or body of a wearer. In addition, the device may include the fiber optic cable that is affixed to the implantable device and that may be in optical communication with the detector and may extend from the enclosure, so as to be inserted into the environment of interest. Accordingly, disclosed devices may provide for improved monitoring of potential infection sites with little or no additional burden on health care workers.
Other features and aspects of the present disclosure are discussed in greater detail below.
A full and enabling disclosure of the subject matter, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the appended figures in which:
Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements.
Reference now will be made in detail to various embodiments of the disclosed subject matter, one or more examples of which are set forth below. Each example is provided by way of explanation, not limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present disclosure without departing from the scope or spirit of the subject matter. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.
The present disclosure is generally directed to methods for detection of HAI. In one particular embodiment, disclosed methods may be utilized for continuous monitoring of a potential infection site and may be utilized to alert patients and/or health care providers to the presence of pathogens at an early stage of infection, thereby providing for earlier intervention and improved recovery rates from infection.
Any source of HAI may be detected according to disclosed methods. In one particular embodiment, common bacterial sources such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa may be detected. However, it should be understood that disclosed methods are not limited to either these bacteria or bacterial pathogens in general. Other common sources of HAI that may be detected according to disclosed methods include, without limitation, other bacterial sources such as coagulase-negative staphylococci, Enterococcus spp., Enterobacter spp., Klebsiella pneumoniae, Proteus mirablis, Streptococcus spp., and so forth, as well as yeast, fungal, viral, and parasitic sources, as previously mentioned.
Presently disclosed methods and devices utilize a fiber optic-based sensor to examine a potential infection site or fluid obtained there from for the presence of HAI pathogens. More specifically, disclosed sensors include a fiber optic cable for transmitting an optically detectable signal from a site of inquiry that is provided in conjunction with an implantable medical device. The optically detectable signal may carry information regarding the presence or amount of a pathogen at the site that is a cause of an HAI.
An optically detectable signal that may signify the presence of a pathogen may be generated according to any methodology. For instance, in one particular embodiment, an optically detectable signal may be directly generated by a pathogen, e.g., a pathogenic bacterium upon autofluorescence of the pathogen. According to this embodiment, when in the presence of an excitation signal, a pathogen may autofluoresce with a unique spectral signature. An excitation signal may be provided via the same fiber optic cable that transmits the optically detectable signal from the site or may be provided from a different source, as desired. Analysis of the characteristics of the emission signal produced in response to the excitation signal may be used to determine the presence or concentration of pathogens at the site of inquiry and provide a route for early detection of a nosocomial infection.
It should be understood, however, that the method of generating the optically detectable signal is not critical to the disclosed subject matter, and disclosed devices may be utilized to detect any optically detectable signal produced either directly or indirectly due to the presence of the pathogen in the local environment. For instance, in another embodiment, disclosed devices may be utilized in conjunction with a fluorescent dye including a material that may specifically bind a targeted pathogen. Such fluorescent dyes are known in the art and may be utilized in conjunction with a sensor device as disclosed herein. For instance, U.S. Pat. No. 5,545,535 to Roth, et al., U.S. Pat. No. 5,573,909 to Singer, et al., U.S. Pat. No. 6,051,395 to Rocco, and U.S. Patent Application Publication No. 2007/0086949 to Prasad, et al. disclose fluorescent materials that may exhibit specific binding to a targeted material, for instance a targeted surface receptor of a bacterium. In the presence of the targeted bacteria, the fluorescent dyes may bind the bacteria and emit an optically detectable signal. Thus, the pathogen may indirectly produce the detectable signal.
Irrespective of the manner of generation of the optically detectable signal, upon generation of the signal, a sensor device as disclosed herein, including a fiber optic cable in conjunction with an implantable medical device, may detect and transmit the signal. Beneficially, disclosed sensing devices may incorporate any implantable medical device in conjunction with a fiber optic cable. For instance, a sensing device may include a fiber optic cable in conjunction with an implantable catheter. As utilized herein, the term ‘implantable catheter’ generally refers to an elongated structure that may be either flexible or rigid for insertion into a body cavity, duct, or vessel to allow the passage of fluids either into or out of the body or to distend a passageway. In addition, an implantable catheter may define one or more lumens therein.
Referring to
An end portion of device 10 is illustrated in more detail in
At least one end of fiber optic cable 40 may terminate at outer surface 26 of catheter 22. Accordingly, light may pass into and/or out of fiber optic cable 40 at the terminus of fiber optic cable 40. The other end of fiber optic cable 40 is at a monitor 100, which is described in more detail below.
Optical fibers and cables may have a variety of physical characteristics, depending upon the specific requirements of a sensing system and site of inquiry.
Optical fibers for use as disclosed herein may generally include multi-mode fibers having a core diameter greater than about 10 micrometers (μm). The preferred core diameter in any particular embodiment may depend upon the characteristics of a signal that is expected to travel through the fiber, among other system parameters. For instance, in those embodiments in which a laser excitation source is used to deliver an excitation signal through an optical fiber, a core diameter may be between about 50 μm and about 100 μm, or about 80 μm in one embodiment. In other embodiments, for instance in those embodiments in which an excitation light source produces less coherent radiation, such as a multi-wavelength light emitting diode (LED), for example, it may be preferable to utilize an optical fiber for carrying the excitation signal that defines a somewhat larger core diameter, for instance between about 90 μm and about 400 μm.
The core/clad boundary of a fiber may be abrupt, as in a step-index fiber, or may be gradual, as in a graded-index fiber. A graded-index fiber may be preferred in some embodiments, as graded index fibers may reduce dispersion of multiple modes traveling through the fiber. This is not a requirement however, and step-index fibers may alternatively be utilized, particularly in those embodiments in which an optical fiber is of a length such that dispersion will not be of great concern.
An optical fiber may be formed of sterilizable, biocompatible materials that may be safely placed and held at a potential infection site, and in one particular embodiment, at a surgical site. For example, an optical fiber formed of any suitable type of glass may be used, including, without limitation, silica glass, fluorozirconate glass, fluoroaluminate glass, any chalcogenide glass, or so forth may form the core and/or the clad.
Polymer optical fibers (POF) are also encompassed by the present disclosure. For instance, an optical fiber formed of suitable acrylate core/clad combinations, e.g., polymethyl methacrylates, may be utilized. It may be preferred in some embodiments to utilize a multi-core POF so as to lower losses common to POF due to bending of the fiber. For instance, this may be preferred in those embodiments in which an optical fiber may be located at an in vivo site of inquiry in a non-linear conformation.
The end of a fiber may be shaped as desired. For instance, and as illustrated in
An optical fiber may be formed so as to detect an emission signal at locations along the length of the fiber, in addition to at the terminal end of the fiber. For instance, at locations along the length of the fiber the clad may be etched, generally with a predetermined angle, such that excitation light may exit the fiber and/or detectable signals emitted from a pathogen may enter the optical fiber at these locations. For example, the clad of a fiber may be bent or otherwise notched at a predetermined angle to form a ‘window’ in the fiber. Thus, a single optical fiber may detect signals from transformed bacterial over a larger area.
A fiber optic-based sensor for use as described herein may include a fiber optic cable comprised of a single optical fiber or a plurality of individual fibers, depending upon the specific design of the sensor. For instance, a plurality of optical fibers may be joined to form a single fiber cable of a size to be combined with an implantable device and located at an in vivo site of interest. For instance, a multi-fiber fiber optic cable may have a diameter of less than about 1.5 mm. Moreover, when considering utilization of a multi-fiber fiber optic cable, it may be beneficial to utilize a portion of the optical fibers of the cable to deliver an excitation signal to an area, while other optical fibers of the cable may be utilized to carry emission signals from the area back to a detection device.
When utilizing a plurality of optical fibers in a fiber bundle or cable, individual fibers may be formed and arranged in relation to one another so as to provide a wider field of detection. For instance,
In the embodiment illustrated in
Of course, combinations of such designs, as well as other fiber design for improving the collection of a signal area, including methods as discussed above as well as methods as are generally known to those in the art, may be utilized as well.
A sensor may be located at a site according to any suitable method. For instance, in the embodiment illustrated in
Reservoir 42 may be of any suitable size and material as is known in the art. For instance, reservoir 42 may be formed of the same materials as catheter 22. In one embodiment, reservoir 42 may be formed of an opaque material, so as to limit excessive background light during the detection regime.
Fluid may pass through catheter 22 and into reservoir 42 and be held in reservoir 42 for a period of time. During that time, an optically detectable signal from a pathogen contained in the fluid held in reservoir 42 may be detected through utilization of a sensing device as disclosed herein. For example, one or more excitation signals may be transmitted from fiber optic cable 40 to illuminate fluid held in reservoir 42. The excitation signal(s) may be predetermined so as to induce targeted pathogens in the fluid to autofluoresce. Reflection and any emission signals generated due to the presence of pathogens in the fluid may than be transmitted via fiber optic cable 40 from reservoir 42 to a detection device and analyzed for unique spectral signatures indicative of HAI-causing pathogens. A system such as that illustrated in
Another embodiment of a detection system as disclosed herein is illustrated in
Barrier 44 may be, for instance, a semi-permeable porous membrane having a porosity to allow materials less than about 0.2 μm across the membrane, with a preferred pore size generally depending upon the size of pathogens that are targeted for detection. By way of example, semi-permeable membrane 44 may be derived from a water insoluble, water wettable cellulose derivative, such as cellophane, cellulose acetate, cellulose propionate, carboxyethyl cellulose, and so forth; insolubilized gelatin; partially hydrolized polyvinyl acetate; or polyionic film forming compositions such as polysulfonated anionic polymers or ionically linked polycationic polymers, such as marketed by Amicon Company. Barrier 44 may be attached to a wall of reservoir 42 or optionally may be attached to another component of a sensing system. Fiber optic cable 40 may terminate at a location with portion 48 of reservoir 42 so as to examine the fluid for the presence of HAI-causing pathogens.
Referring to
In one preferred embodiment, enclosure 20 may be portable. For example, enclosure 20 may be a molded plastic enclosure of a size so as to be easily carried by or attached to a wearer. For instance, enclosure 20 may include clips, loops, or so forth so as to be attachable to a patient's clothing or body. In one embodiment, enclosure 20 may include an adhesive surface, and may be adhered directly to a patient's skin. In general, enclosure 20 may be relatively small, for instance less than about 10 cm by about 8 cm by about 5 cm, so as to be inconspicuously carried by a patient and so as to avoid impedance of a patient's motion. Enclosure 20 may completely enclose the components contained therein, or may partially enclose the components contained therein. For example, enclosure 20 may include an access port (not shown) that may provide access to the interior of enclosure 20. In one embodiment, an access port may be covered with a removable cover, as is known in the art.
A first component as may be held within enclosure 20 is power supply 2 that may be configured in one embodiment to supply power to an excitation source 4 as well as other of the operational components as will be later described. In an exemplary configuration, power supply 2 may correspond to a battery, however those of ordinary skill in the art will appreciate that other power supplies may be used including those that may be coupled to an external alternating current (AC) supply so that the enclosed power supply may include those components necessary to convert such external supply to a suitable source for the remaining components requiring a power source.
As previously noted, power supply 2 may be configured to supply power to excitation source 4. In the illustrated exemplary configuration, excitation source 4 may correspond to a light emitting diode (LED), however, again, such source may vary and may include, but is not limited to, laser diodes and incandescent light sources. Excitation source 4 may correspond to a white light source, a non-white multi-wavelength source, or a single wavelength source, as desired or required. In a preferred exemplary configuration, an LED may be selected due to the low power consumption of such sources. The wavelength of the excitation energy supplied by excitation source 4 may be of any suitable wavelength, from infrared (IR) to ultraviolet (UV). In general, the preferred excitation energy wavelength may depend upon any specific pathogens for which the device is designed to detect. For instance, in those embodiments in which a specific bacteria or genera is being detected, the excitation wavelength may be specific for that target. In other embodiments, however, for instance when a plurality of different pathogens are being detected, and the different pathogens respond to different excitation wavelengths, an excitation source may provide multiple wavelengths, either through combination of signals from a plurality of single wavelength sources or through a single, incoherent source, as desired.
Excitation energy source 4 is optically coupled to a fiber optic cable 40 as illustrated. Fiber optic cable 40 is configured to extend externally from enclosure 20 to the field of inquiry, e.g., within a surgical site or other wound, and so forth. It should be appreciated that although the monitor 100 of
Moreover, as discussed previously, plural excitation energy sources may be used. In such a configuration, each excitation source may be optically coupled to one or more optical fibers and or fiber optic cables such that multiple excitation wavelengths may be delivered to the field of enquiry.
Housed within enclosure 20 is an optical detector 8 coupled to fiber optic cable 40. Optical detector 8 may correspond to a photodiode, a photoresistor, or so forth. Optical detector 8 may include optical filters, beam splitters, and so forth that may remove background light and reduce the total input optical signal at the detector 8 to one or more diagnostically relevant emission peaks. An input signal at detector 8 may be examined and analyzed for emission peaks of interest according to any suitable method. For instance, optical detector 8 may comprise a plurality of notch filters, each of which may be tuned to the spectral signature of a different autofluorescent pathogen. In one particular embodiment, the total input optical signal to detector 8 may be deconvoluted and analyzed according to a principal components analysis (PCA) regime as is known in the art.
For instance, input data to detector 8 may be reduced to relevant emission peaks based on maximum variations between the input spectra. In those embodiments in which a device is designed to examine a site for a plurality of different pathogens, the total input optical signal at the detector 8 may include a plurality of diagnostically relevant emission peaks. Accordingly, detector 8 may generate an output signal representing one or more emission peaks of interest. In addition, detector 8 may provide information with regard to the strength of each signal, for instance the pulses of light emitted over a particular time having a particular spectral signature, and this information may be correlated to the concentration of the detected pathogen.
In one particular embodiment, the signal from detector 8 may be transmitted to signal processor 12 for further analysis according to a PCA method. A PCA regime may utilize information regarding a library of spectra derived from pathogens, e.g., bacteria, of a reference sample to create a reference set, wherein each of the spectra are acquired under identical conditions. Data analysis techniques that may be carried out may include spectral data compression and linear regression. Using a linear combination of factors or principal components, a reconstructed spectrum may be derived. This reconstructed spectrum may then be compared with the spectra of known specimens which serve as the basis for determination of the presence or concentration of bacteria at the site of inquiry.
U.S. Pat. Nos. 7,110,886 to Ito, et al., 6,961,599 to Lambert, et al. and 6,662,621 to Cohenford, et al., all of which are incorporated herein by reference thereto, describe PCA regimes as may be utilized in analysis of an emission signal. In addition, a number of computer programs are available which carry out these statistical methods, including PCR-32™ (Bio-Rad, Cambridge, Mass., USA) and PLS-PLUS™ and DISCRIMINATE™ (Galactic Industries, Salem, N.H., USA). Discussions of the underlying theory and calculations of suitable methods may be found in, for example, Haaland, et al., Anal. Chem. 60:1193-1202 (1988); Cahn, et al., Applied Spectroscopy, 42:865-872 (1988); and Martens, et al., Multivariate Calibration, John Wiley and Sons, New York, N.Y. (1989).
Signal processor 12 may include a microprocessor configured to evaluate the strength or other characteristics of the output signal received over line 10 to, e.g., detect which specific bacteria is present in the field of enquiry and to produce a detection signal that may be coupled to line 14 for passage to a signaling device 16. Accordingly, if the detection signal reaches a predetermined threshold value, corresponding to a positive determination of the target pathogen, a detectable signal may be initiated at signaling device 16. For example, a detectable signal may be initiated at a signaling device 16 upon detection of any pathogen, i.e., any detection of a targeted pathogen at all may trigger initiation of a signal at signaling device 16. Optionally, if the detection signal at signal processor 12 indicates a pathogen concentration greater than a threshold amount, which may be correlated to the strength of the input signal to signal processor, signaling device 16 may be triggered to initiate a signal. For instance, signaling device 16 may be preset to initiate a detectable signal when the strength of the emitted signal correlates to a bacterial concentration greater than about 105 CFU/mL (colony forming units/milliliter), in one embodiment.
In an exemplary configuration, a detectable signal may initiate a visible or audible signal that may be detected by the wearer within or at the surface of the enclosure 20 by way of signaling device 16. For instance, a visible signal may optionally include utilization of a liquid crystal diode (LCD) device, or an equivalent thereof, that may provide the signal as a readable output. For example, a visual signal may be provided at a surface of the device as an instruction such as, for instance, “CALL YOUR DOCTOR”, “VISIT HOSPITAL,” or so forth.
In addition to or alternative to a visual and/or audible signal at the enclosure 20 itself, signaling device 16 may include a transmitter portion that, upon initiation of the detectable signal, may transmit an electromagnetic signal to receiver 18. Receiver 18 may be remote from the signaling device 16. For instance, receiver 18 may be on the wearer's body at a distance from the signaling device 16, at a location apart from the wearer's body that may be conveniently chosen by the wearer, e.g., within the wearer's home, office, or so forth, or may be at a monitoring facility, for instance at a medical facility, such that appropriate medical personal may be quickly informed of the change in status of the patient's site of inquiry. In alternative embodiments, the detectable signal may be transmitted to multiple receivers, so as to inform both the wearer and others (e.g., medical personnel) of the change in status of a site. Transmission of a signal to a remote site may be carried out with a radio frequency transmission scheme or with any other wireless-type transmission scheme, as is generally known in the art. For instance, a wireless telephone or internet communications scheme could be utilized to transmit a signal to a remote location according to known methods.
Wireless transmission systems as may be utilized in conjunction with disclosed devices and methods may include, for example, components and systems as disclosed in U.S. Pat. Nos. 6,289,238 to Besson, et al., 6,441,747 to Khair, et al., 6,802,811 to Slepian, 6,659,947 to Carter, et al., and 7,294,105 to Islam, all of which are incorporated in their entirety by reference.
As previously mentioned, sensors as described herein are not limited to devices for use in drainage of a surgical or wound site. Another embodiment of a sensing device as disclosed herein is illustrated in
An intravenous catheter 922 may be formed fairly flexible, so as to be easily inserted into and pass through the venous architecture without damaging the vessel walls. For example, a venous catheter 922 may be formed of soft, flexible polyurethane such as Tecoflex® or Pellethane®.
Intravenous catheter 922 is a multi-lumen catheter including lumen 923, through which a fluid may flow, for instance for delivery into an artery or vein, and also including lumen 921, within which fiber optic cable 40 may be affixed, for instance with an adhesive or through any other suitable bonding methodology. Following insertion, an optically detectable signal emitted by a pathogen may be transmitted by fiber optic cable 40 to a monitor, as described above. For instance, in one embodiment, fiber optic cable 40 may deliver an excitation signal to the site that may excite an optically detectable emission signal by targeted pathogenic bacteria in the field of inquiry. The autofluorescent emission signal may then be transmitted back to a monitor via fiber optic cable 40.
Of course, an intravenous catheter as described herein does not require a multi-lumen catheter, as is illustrated in
In another embodiment, a sensor may include a fiber optic cable in conjunction for a Foley catheter or a ureteral catheter, for instance in conjunction with bladder and/or kidney drainage in detection of a hospital acquired urinary tract infection.
In yet another embodiment, a sensor may include a fiber optic cable in conjunction with an endotracheal tube 1122, as illustrated in
Referring to
In yet another embodiment, a sensor may include a fiber optic cable in conjunction with a catheter utilized for delivery of pain medication, for instance directly to a surgery site.
While the subject matter has been described in detail with respect to the specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. Accordingly, the scope of the present disclosure should be assessed as that of the appended claims and any equivalents thereto.
