Invented by Sean Farrell, Joseph Michael Fallon, Kulwinder S. Plahey, Michael James Beiriger, Fresenius Medical Care Holdings Inc
The Fresenius Medical Care Holdings Inc invention works as followsThis disclosure is about medical fluid cassettes, and systems and methods related to them. A medical fluid cassette may include a base with a region on top and another region below, a membrane covering the first area of the base and a membrane covering the second area of the base. The second membrane can bounce away from the base after a force is released to push the second membrane towards the base.
Background for Medical fluid cassettes, related systems and Methods
Dialysis is used to treat a patient who has insufficient kidney function. “The two main dialysis methods include peritoneal and hemodialysis.
During hemodialysis, (?HD?) the patient’s blood is passed through a dialyzer of a dialysis machine while also passing dilution solution or dialysate through the dialyzer. Dialysis machines pass the patient’s dialysis solution through the dialyzer while the blood is also passed. Dialyzers have a semi-permeable dialysate membrane that separates blood from dialysate. This membrane allows for diffusion and osmosis to occur between the dialysate, and blood. The exchanges that occur across the membrane remove waste products from the blood, such as urea, creatinine and other solutes. These exchanges regulate other substances in the blood, like sodium and water. The dialysis machine works as a kidney to cleanse the blood.
During peritoneal dialysate (?PD? Dialysis solution is periodically infused into the peritoneal cavity of a patient. The peritoneal membrane acts as a semi-permeable natural membrane, allowing diffusion and osmosis to occur between the solution in the patient’s bloodstream. The exchanges that take place across the patient’s membrane, similar to the exchanges that occur across the dialyzer during HD, remove waste products from the blood such as urea, creatinine and other solutes. They also regulate the level of sodium and water in the blood.
Many PD machines are designed for automatic infusion, dwell and drainage dialysate into and out of the patient’s peritoneal cavities. The treatment usually lasts several hours and begins with a drain cycle that empties the peritoneal cavities of dialysate. The sequence continues through successive phases of fill, dwell and drain. “Each phase is called a ‘cycle.’
In one aspect, the invention includes a fluid pumping device that has a cassette enclosure with a piston that can be moved. The system also includes a medical cassette that is designed to be placed within the cassette enclosure. The medical fluid cassette consists of a base with a first and second region. A first membrane is placed over the first region of base and a secondary membrane is placed over the second region. The first membrane forms at least one fluid path with the first area of the base, and the second membrane defines a fluid pumping chamber with the second area of the base. The second membrane has a greater resilience than the first. The cassette can be positioned within the cassette enclosure to allow the second membrane to be moved towards the base to decrease the volume of a fluid pump chamber. Upon retraction of a piston, the second can bounce back to increase the volume.
In another aspect, a medical liquid cassette comprises a base with a first and second region. A first membrane covers the first region of base and a secondary membrane covers the second region. The first membrane forms at least one fluid path with the base’s first region, and the second membrane defines a fluid pumping chamber with the second base region. The second membrane has a higher resilience than the first and is designed to bounce away from the base after releasing the force that was used to push the second membrane towards the base.
The invention also includes a method of medical fluid delivery that involves expelling medical fluids from a fluid chamber defined by a membrane and an recessed area of the base of a cassette of medical fluids by pressing the membrane into the recess, then drawing the medical fluid back into the fluid chamber by retracting a piston and allowing it to rebound towards the retracting piston head, due to the resiliency and flexibility of the membrane.
The invention also includes a housing which at least partially defines an enclosure for a medical cassette, and a piston that can be moved relative to the housing. The cassette has a fluid chamber between a membrane, and a base. The piston also includes a piston with a circumferential area that can move inward when pressed against a membrane on the cassette.
Implementations can include any or all of the following features.
In some implementations, a receded region is used for the second area of the base.
In certain implementations, a first region of a base is a substantially flat region from which a plurality raised ridges extend.
In some implementations, a second membrane is thicker than a first membrane.
In certain implementations, the thickness of the first membrane is between 0.004 inches and 0.006 inches, while the thickness of the second membrane ranges from 0.05 to 0.12 inches.
In some cases, the first membrane and second membrane are made of different materials.
In certain implementations, a second membrane made of elastomer is used.
In some implementations, a second region is recessed in the base. The second membrane is then sized so that it covers a portion of base surrounding the recessed area.
In certain implementations, the peripheral region of the membrane is sealed between the base and the second membrane.
In some cases, the second membrane has a dome shaped section.
In certain implementations, a medical fluid cassette also includes a ring attached to the second layer and that presses the second layer against the base.
In some cases, the first ring may be attached to the base.
In certain implementations, a second ring can be positioned on the side of the base that is opposite to the second membrane. The second ring must then be secured to the first one in such a way as to force the first to press the second membrane into the base.Click here to view the patent on Google Patents.