1. The Field of the Invention
This invention relates to systems, devices, and methods for enabling the acquisition from outside the body of a patient of data pertaining to medical devices implanted therein. More particularly, the present invention relates to a system in which an implanted medical device, such as an infusion port or a prosthetic implant, may be identified or otherwise characterized by data obtained from outside the body of a patient using a hand-held medical device characterization probe.
2. Background Art
The medical use of implantable devices in human patients is steadily increasing. In addition, due to technological advances in implantable medical devices, the implanted duration of the residency of such devices is also lengthening.
Examples of such implantable medical devices include artificial heart valves, prosthetic joints, vascular grafts, artificial ligaments and tendons, urinary and gastrointestinal tract sphincters, vena cava blood filters, penal implants and other tissue expanders, fistula and hernia repair devices, implantable infusion ports with associated long term catheters, defibrillator catheters, demand pacer heart leads, as well as nonpassive implantable devices, such as artificial hearts, pacemakers, and medicament pumps.
As the use of this wide variety of implanted devices becomes more common and frequent, certain associated problems can be anticipated. That to which the present invention is directed relates to ascertaining the identity of such devices after the implantation thereof, or to obtaining other characterizing data about the implanted devices. Reasons for needing such an identification or such data will be discussed below, along with some of the constraints imposed by medical practices on the process of doing so.
The very reason for the installation of an implantable medical devices is to provide for a repeated function that is required by the body of the patient on the long term basis. Thus, medical devices are implanted, so that the accomplishment of such functions does not require excessively frequent therapy procedures. In some cases, such as with a prosthetic implant or a demand pacer heart lead, the medical device installed provides a function required on a continuous basis.
The implantation of any such devices, however, causes significant trauma to the patient. Thus, once implanted, there is a accordingly an incentive to avoid reaccessing such devices through any surgical reopening of the body of the patient.
Some implanted medical devices, such as implantable access ports and the long term catheters associated therewith, are nevertheless accessed to a very limited degree on a regular and repeated basis using specialized access tools that penetrate the skin of the patient to the access port. These are specifically adapted for correct interaction with each respective type of access port. Such access tools include needles and semi-rigid catheters, each in varying sizes adapted to a specific access port. The access tools penetrate the skin of the patient at the implantation site and then are used, respectively, to infuse fluids into or to withdraw fluids from the access port.
Palpation may be used to locate some implanted devices, and patient memory and the medical records, if available, can provide further information relative thereto. Nevertheless, to date, a marked lack is apparent in the field of implantable medical device technology of systems, devices, and methods that successfully enable the acquisition of data from outside the body of the patient, where that data pertains to medical devices implanted therein.
For example, different implantable devices are recommended for installation at the same implant location in the body of a patient. Thus, regardless of the use to which a device may be applied, the discovery of the implant location of that device, which is typically achieved by palpation of the body of the patient, is inadequate to identify that device or otherwise to supply characterizing data relative thereto. Such information is, however, essential to medical personnel providing post-implantation therapy that involves the device. Only with accurate and complete information about an implanted device can medical personnel adopt appropriate procedures, administer correct medicaments, and use proper, complementary access tools. A case in point will serve to illustrate.
The access ports associated with several types of infusion systems are frequently placed in the chest of the patient. Nevertheless, the catheter associated with such an access port may extend through the cardiovascular system to the vena cava, to the body cavity for peritoneal therapy, or alternatively to numerous other possible sites. As palpation can locate only the access port, and not the catheter associated therewith, the identity or purpose of an access port implanted in the chest of a patient is not immediately apparent, even when the implant site has been located.
If radiographic equipment is available at the site of any therapy associated with the access port, radiographic viewing of the patient can sometimes be of assistance. Radiographic view systems are disadvantageously large, rendering impossible the use of such systems to derive information about an implanted medical device, when the patient in whose body that device is implanted is not at or cannot be readily brought to a site at which radiographic viewing equipment is available.
Also, radiographic viewing of the implantable access port itself is usually incapable of providing any detailed information about the access port or the catheter attached thereto. If the profile of the port is not distinctive, then only if the implanted catheter is radio-opaque, can radiographic viewing assist medical personnel in identifying or otherwise deriving characterizing data relative to the infusion system.
Two risks are associated with post-implantation therapy utilizing an implanted access port, where the full nature of the implanted system is unknown. First, such access ports require use of a correct corresponding access tool: a needle or a semi-rigid catheter, each of various sizes or constructions. The use of an improper type of access tool with an access port, can result in damage to the access port or to the catheter attached thereto. At the very least, the use of an improper access tool rapidly accelerates the aging of the implanted access port.
Even if an appropriate type of access tool is utilized to penetrate the tissue of the patient and interact with the access port, the location of the distal tip of the catheter associated therewith will determine the proper type of any infusate to be injected into the port. Catheters extending through the cardiovascular system to the venae cavae are most frequently utilized for chemotherapy, so that a chemotherapeutic medicament should be injected into the access port associated therewith. On the other hand, if the catheter associated with such an implantable infusion port extends into the epidural space, for the purpose of providing periodic anesthesia there, the accidental injection of chemotherapeutic medicaments would certainly have disastrous consequences. Implantable ports with attached catheters extending into the body cavity for peritoneal therapy may need to be injected with antibiotics or other solutions, but never anesthesia or chemotherapeutic medicaments of the vesicant variety.
Clearly, the discovery of an implanted medical device in the body of a patient does not adequately identify or otherwise characterize that port, so as to enable medical personnel to practice post-implantation therapy without disastrous risks to the patient.
It might be presumed that the knowledge of a patient of the nature of the implant medical devices in the body thereof could be used to guide medical personnel. Nevertheless, this is not actually the case.
While a patient may know a substantial amount of information about a medical device implanted in the body thereof, frequently that information is not of the detail required to enable medical personnel to conduct post-implantation therapy procedures with correct access tools and correct dosages of medicaments.
The medical environment in which implants are prescribed and installed are unfamiliar surroundings in which many patients are ill at ease. Often the circumstances requiring the implants accompany severe disease or the discovery of such in the body of the patient. Under these stressful circumstances a clear and accurate understanding of the nature of an implant is often lost on the very recipient thereof.
Even if a patient is fully aware of the location, identity, and technical specification of a medical device implanted in the body thereof, that patient may be unable to communicate such information to medical personnel at a post-implantation therapy institution due to language or cultural barriers.
It is not uncommon that patients with implanted medical devices do not even retain a clear memory of the purpose of the implanted device. In extreme cases, a patient may be mentally incapable, either due to age, drug use, or other psycho-physical condition. Patients involved in accidents or severely ill patients may lack any consciousness whatsoever. Nevertheless, under all such conditions, the existence of an implanted medical device in the body of a patient suggests a need for possibly immediate, but certainly regular, therapy activities.
The increasingly long duration of some medical implants raises other concerns.
First, a patient, particularly an elderly patient, is likely to carry in the body thereof a plurality of implanted medical devices located at a corresponding plurality of implant sites. When such a patient is treated by any medical personnel, it is important initially an to ascertain the identity of or secure other characterizing data about each and every such implanted medical device.
Not only as discussed above is it necessary to have a relatively high level of certainty as to the appropriate procedures, medications, and access tools to be used with each, but it is possible that the timing of post-implantation therapy procedures for one such implanted device must be adjusted for the timing of such procedures associated with another implanted medical device. Otherwise, disastrous consequences, such as, adverse drug interactions are possible. Where such a patient is either mentally impaired, unconscious, or even just not completely informed as to the specification of each implanted medical device, the task of inventorying these devices and selecting appropriate sets of procedures at compatible times is increasingly demanding.
As a patent carrying an implanted device moves from one location to another, a device implanted at one institute will later be involved in post-implantation therapy at another institution.
Reliance on the memory of the patient to identify implanted devices is not always wise or feasible. Other sources of information about the implanted devices must be accessed before post-implantation therapy can safely ensue. It would appear that such a source of information might be locatable in the medical files of the patient.
Nevertheless, medical files for any given patient may not be current, or may not have travelled with the patient from one medical therapy institution to another.
While adequate information about implanted medical devices may in due course become available to medical personnel, many post-implantation therapeutic activities cannot be postponed until the convenient time that medical records have been located and then transferred between medical institutions. Those institutions may be situated in remote cities or countries, and obtaining the cooperation of such remote institutions may be quite difficult. Often business hours in distant time zones may not even overlap. In the meantime, a patient with an implanted medical device may be forgoing urgent post-implantation therapy procedures.
Inadequate medical records and poor patient memory are pronounced among the uneducated, the indigent, the homeless, the drug-addicted, and the criminal elements of society. These patients accordingly present accentuated risks of medical malpractice on the part of medical personnel who engage in post-implantation therapy procedures without adequate information about the implanted medical devices of such patients or even refrain from therapy procedures when such information is unavailable.
Accordingly, a need exists for identifying or otherwise deriving data characterizing an implantable medical device independently of medical records or of the memory of the patient in the body of which that device is implanted. Ideally, this should be able to be accomplished without directly accessing the medical device or prematurely exposing it to the environment exterior to the body of the patient.
Product liability implications of implantable medical devices also suggest a need to be able to identify such devices after their installation in the body of a patient or to derive other characterizing data relative thereof.
It has been suggested by the United States Food and Drug Administration that the manufacturers of implantable medical devices track those devices in order to be able to assist in recalling any that are discovered after the implantation thereof to be defective or to have dangerous effects. Recent publicity related to the failure of artificial breast implants provides but one example of the type of situation lending impetus to some form of medical implant identification and characterization system.
While efforts can be made to track the locations of implanted medical devices through the pooling of information by doctors and medical institutions, this approach can not be expected to be fully effective. Pooled medical information will not identify the physical location of each and every implant recipient. Such individuals will frequently move from one location to another without notifying medical institutions, or treating doctors.
Accordingly, as an additional safety net in this regard it would be desirable to provide all implanted medical devices with some form of identification or characterization data that travels with the patient, is not dependent upon the memory or communication capacities thereof, and can be obtained or accessed nonintrusively at any medical institution from outside the body of the patient.
Nevertheless, to date implants about which characterizing data can be derived after the implantation thereof in a body of a patient are limited to nonpassive implanted devices, which include a self-contained source of electric power. Many of the implantable devices requiring identification or other characterizing data are, however, are too small or inexpensive to warrant the inclusion of active electronic components and self-contained power sources therefor. In addition, the implantation of any such power source in the body of a patient is cause for a heightened regulatory concern relative thereto. This in turn requires substantial time for regulatory approval before the associated device can be put to human use. This in turn causes the device to be more costly then would otherwise be necessary.