This invention relates to an improved automated peritoneal dialysis (APD) system for use in medical treatment involving administration of parenteral fluids as in peritoneal dialysis.
It is known that patients experiencing partial or complete renal failure are often helped by peritoneal dialysis regimens. Two types of peritoneal dialysis are commonly available. Manual peritoneal dialysis allows a dialysate fluid from a bag to be gravity fed through a tube into an indwelling catheter extending into a patient's peritoneal cavity. Automated peritoneal dialysis may be carried out as set forth in U.S. Pat. No. 5,350,357 to Kamen et al. The Kamen et al. automated peritoneal dialysis system is an attractive system for home use in that it provides a small footprint system while allowing a patient to dialyze himself or herself several times in the course of a night with fresh dialysate contained in multiple bags. That automated system includes a heater for raising the temperature of the dialysate from ambient to body temperature and includes a disposable liquid delivery set for mating with a cycler which causes pneumatic force to be supplied to selected portions of the delivery set to pump dialysate through the delivery set from the dialysate bags to the heater bag, from the heater bag to the patient and from the patient to a drain. Fresh peritoneal dialysis solution is infused into the patient's peritoneal cavity wherein by osmotic exchange wastes such as solutes of sodium and chloride ions, urea, creatinine and water are transferred to the dialysate solution in the peritoneal cavity and are then removed from the peritoneal cavity. The Kamen et al. system proceeds through a succession of fill, dwell, and drain phases that follow one after another and one of the advantages of the system is provided by the fact that the system can emulate either fixed height or different head height conditions regardless of the actual head height. The system is able to switch rapidly during a given peritoneal dialysis procedure between a relatively low pressure mode and a high pressure mode, with the low pressure being used during patient infusion and drain procedures and the high pressure mode being used to move dialysate through circuits not directly connected to the patient. Unfortunately, the system requires a number of high pressure and low pressure reservoirs therein for supply of pneumatic force to a pneumatic interface, which in turn requires a large number of valves associated with reservoirs. The multiple reservoirs and numerous valves result in a relatively large system in which there is only a limited choice of pneumatic pressure levels available for actuating the dialysate pumps, and there is no capability to obtain selectable pressure versus time profiles, e.g., to ramp up or to ramp down the pneumatic pressure as quickly or as slowly as may be desirable for a given dialysis regimen.
The Kamen et al. system operates at unmodulated pneumatic supply pressure levels which may prove to be disadvantageous in certain patient regimens.
Thus, it is desirable to be able to provide an automated peritoneal dialysis system having a cycler capable of delivering a wide range of pneumatic pressures and pressure profiles to a cassette of a disposable dialysate through a liquid delivery set which the dialysate solution may be moved to and from the patient.