Pumps – Miscellaneous
Reexamination Certificate
2001-08-09
2004-02-03
Tyler, Cheryl J. (Department: 3746)
Pumps
Miscellaneous
C604S891100
Reexamination Certificate
active
06685452
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to medical devices, and more specifically, to human body implantable drug delivery pumps.
PAIN
Briefly, the brain, not the point of an injury, registers any sensation of pain. When pain is felt, it is a reaction to signals that are transmitted throughout the body. These signals are sent from the pain source, through the nerves in the spinal cord, to the brain, where they are perceived as pain. Pain can be controlled by preventing the pain signals from reaching the brain.
The origin of some pain is neuropathic, while other pain is nociceptive. Neuropathic pain is pain that is caused by damage to nerve tissue. Nociceptive pain means pain caused by an injury or disease outside the nervous system.
Acute pain (such as spraining an ankle) acts as a warning to signal harm or possible damage to tissues in the body. It prevents additional damage by alerting you to react and remove the source of pain. However, when pain lasts a long time (over six months) and is not relieved by standard medical management, it is called “chronic” pain. In chronic pain, the pain signal no longer helps, but hinders the body. Pain is recognized as a major public health problem. In the United States, it is estimated that chronic pain affects 15% to 33% of the U.S. population, or as many as 70 million people. In fact, chronic pain disables more people than cancer or heart disease and costs the American people more than both combined. Pain costs an estimated $70 billion a year in medical costs, lost working days, and workers' compensation.
ADVANCED PAIN THERAPIES
APT™ Neurostimulation (“Advanced Pain Therapy Neurostimulation”) is available from Medtronic, Inc., and commonly used for neuropathic pain. APT™ Intrathecal treatment, also available from Medtronic, Inc., is commonly used for nociceptive pain.
APT™ Neurostimulation (including both spinal cord stimulation and peripheral nerve stimulation) uses a small neurostimulation system that is surgically placed under the skin to send mild electrical impulses to the spinal cord. The electrical impulses are delivered through a lead (a special medical wire) that is also surgically placed. These electrical impulses block the signal of pain from reaching the brain. Peripheral nerve stimulation works in the same way, but the lead is placed on the specific nerve that is causing pain rather than the spinal cord.
APT™ Intrathecal uses a small pump that is surgically placed under the skin of the abdomen to deliver medication directly into the intrathecal space (where fluid flows around the spinal cord). The medication is delivered through a small tube called a catheter that is also surgically placed. The spinal cord is like a highway for pain signals on their way to the brain, where the feeling of pain is experienced by the body. Because the medication goes directly to the site of action in the spinal cord, where pain signals travel, APT™ Intrathecal offers many people significant pain control with much lower doses of medication than would be required by oral medications (pills). This helps minimize the side effects that often accompany other treatments.
A doctor can do a screening test to see if APT™ Intrathecal will relieve pain, before the patient commits to the therapy. In addition, APT™ Intrathecal is non-destructive and reversible. Typically, people who have success with APT™ Intrathecal experience greater than 50% reduction in their pain and improved ability to go about activities of daily living.
The SynchroMed® Infusion System is a fully implantable, programmable APT™ Intrathecal system available from Medtronic. The SynchroMed® Infusion System has two parts that are both placed in the body during a surgical procedure: the catheter and the pump. The catheter is a small, soft tube. One end is connected to the catheter port of the pump, and the other end is placed in the intrathecal space (where fluid flows around the spinal cord). The pump is a round metal device that stores and releases prescribed amounts of medication directly into the intrathecal space. It is about one inch (2.5 cm) thick, three inches (8.5 cm) in diameter, and weighs about six ounces (205 g). It is made of titanium, a lightweight, medical-grade metal. The reservoir is the space inside the pump that holds the medication. The fill port is a raised center portion of the pump through which the pump is refilled. The doctor or a nurse inserts a needle through the patient's skin and through the fill port to fill the pump. Some pumps have a side catheter access port that allows the doctor to inject other medications or sterile solutions directly into the catheter, bypassing the pump.
The SynchroMed® pump automatically delivers a controlled amount of medication through the catheter to the intrathecal space around the spinal cord, where it is most effective. The exact dosage, rate and timing prescribed by the doctor are entered in the pump using a programmer, an external computer-like device that controls the pump's memory. Information about the patient's prescription is stored in the pump's memory. The doctor can easily review this information by using the programmer. The programmer communicates with the pump by radio signals that allow the doctor to tell how the pump is operating at any given time. The doctor also can use the programmer to change your medication dosage.
CURRENT TECHNIQUE FOR HUMIDITY PROTECTION
As indicated, an APT™ Intrathecal pump is a sophisticated electromechanical device. In addition to its reservoir, fill port, and other mechanical components, the device includes microelectronics in an electronic chamber. Implantation of an APT™ Intrathecal pump is also a significant life event. Given the electronics in the units and the significance of implantation, long-term excellence in the performance of the units is highly desirable. Unfortunately, one common failure mode (way things fail) for implantable device electronics is corrosion of conduction pathways, or short circuiting of the pathways, caused by the presence of water vapor and salts. The short circuiting of the pathways often occurs from dendrites which form between circuits which are at different voltage potentials, when in the presence of ionic vapors. Plastic components in the electronics (e.g., chip carriers), absorb trace amounts of water vapor in normal air, and these vapors can leave the plastics after implantation, risking corrosion.
Consistently, the electronics of the devices are protected. They are protected against liquids, and against humidity. Liquid protection, by surrounding the electronics in a hermetic enclosure, prevents entry of fluids from the human body or drugs from the drug pathway. Humidity protection provides for a dry environment for the internal electronic components. A dry interior promotes long life and accuracy in the performance of the electronic components.
In current device manufacture, a last or near-last step of manufacture is the humidity protection step. The device is fully assembled, with only a pinhole called a “tig” hole remaining as an opening to the interior. The unit is then “baked” by bringing it to a temperature of about 100 degrees Fahrenheit (37 degrees C.) while a vacuum is created in the heating chamber or “oven”. The air inside the unit is pulled by the vacuum through the tig hole, bringing internal moisture, including moisture previously absorbed in plastic components, out with it. Typically, the tig hole is so small that the time necessary to pull the air from the unit is a day to two days. The external vacuum is then reduced and in a short time, the baked unit is “backfilled” with helium, meaning the vacuum inside the unit is filled with helium, also through the tig hole. Within the short time available, the tig hole is then welded closed.
This vacuum bake time can be a significant time constraint for assembling the implantable pump.
SUMMARY OF THE INVENTION
A primary object of the invention is to substantially advance the construction of human body implantable drug delivery pumps.
Another primary obje
Christiansen Chris C.
Olsen James M.
Christiansen Chris C.
Tyler Cheryl J.
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