Blood dialyzing method and apparatus

• US 4,647,378 A
• Filed: 04/03/1984
• Issued: 03/03/1987
• Est. Priority Date: 03/23/1983
• Status: Expired due to Term

• Current Assignee: Nihon Medical Engineering Company Limited
• Original Assignee: Nihon Medical Engineering Company Limited
• Inventors: Minami, Hiromichi
• Primary Examiner(s): Spear, Frank
• Application Number:
  US06/596,264
• Time in Patent Office: 1,064 Days
• Field of Search: 210/646, 210/321.3, 210/90
• US Class Current: 210/646
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/3403 Regulation parameters
• CPC Class Codes: A61M 1/3639 Blood pressure control, pressure transducers specially adapted therefor
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/3344 Measuring or controlling pressure at the body treatment site
• CPC Class Codes: A61M 2205/3351 Controlling upstream pump pressure

Abstract

A blood dialyzing apparatus having a dialyzer with blood and dialysate chambers defined therein comprises a blood pump for pumping the blood from a cannula, pierced in the patient'"'"'s A-V fistula, back to the patient'"'"'s A-V fistula through the blood chamber of the dialyzer, and a fluid circuit for the supply of a dialyzing solution past the dialysate chamber. The fluid circuit includes first and second shut-off valves disposed adjacent the inlet and outlet of the dialysate chamber, respectively, while a pressure sensor is provided to detect the pressure of the blood flowing upstream of the blood pump and also upstream of the blood chamber. When the pressure of the blood so detected attains a value equal to or lower than a predetermined value, the first and second shut-off valves are closed on the one hand and the ultrafiltration pressure in the dialyzer becomes substantially zero.

Claims

1. A method of dialyzing the blood by use of a dialyzer having a semipermeable membrane dividing the interior of the dialyzer into a blood chamber and dialysate chamber, which method comprises the steps of:

measuring the pressure of the blood during the interruption of blood circulation by the use of a pressure sensor disposed on the upstream side of a blood pump while the operation of said blood pump is stopped;

measuring the pressure of the blood during blood circulation by the use of said pressure sensor while the blood pump is in operation;

obtaining a value by subtracting the measured value of the pressure during interruption of the blood circulation which in turn is multiplied by a coefficient less than one from the measured value of the blood pressure during the circulation of the blood;

setting said value as a predetermined value at a setting means;

reducing a ultrafiltration pressure to substantially zero from the normal pressure, if said pressure sensor detects a value of pressure that is equal to or less than the predetermined value while the blood pump is in operation; and

bringing the ultrafiltration pressure back to normal pressure when said pressure sensor no longer detects a value of pressure that is equal to or below the predetermined value.

2. An apparatus for dialyzing the blood by the use of a dialyzer having a semipermeable membrane functioning to divide the interior of the dialyzer into a blood chamber and a dialysate chamber, which apparatus comprises;

a blood pump for feeding the blood into the blood chamber;

a pressure sensor for detecting the pressure of the blood, that is provided at a midway point of a tubing disposed on the upstream side of the said blood pump;

a means for obtaining a value by subtracting a value of the pressure during interruption of the blood circulation which is multiplied by a coefficient less than one from a value of the blood pressure that is detected by the use of said pressure sensor in the initial stage of dialysis while the blood is in circulation;

a setting means for setting said value as a predetermined value; and

a control means for reducing an ultrafiltration pressure in the dialyzer to substantially zero without halting the operation of the blood pump if the pressure sensor detects a pressure with a value that is equal to or less than the predetermined value.

3. An apparatus as claimed in claim 2, further comprising means for generating the ultrafiltration pressure in the dialyzer, and first and second shut-off valves disposed in a supply passage for the supply of a dialzing solution from a source thereof towards the dialysate chamber and a discharge passage for the discharge of the dialyzing solution, which has passed through the dialysate chamber, from the dialysate chamber to the outside, respectively, said first and second shut-off valves being adapted to be closed in the event that the pressure of the blood so detected attains the value equal to or lower than the predetermined value.

4. An apparatus as claimed in claim 3, wherein said ultrafiltration pressure generating means comprises a positive pressure regulator for adjustably clamping a tubing, fluid-coupled to a blood outlet of the blood chamber, to control the effective cross sectional area thereof.

5. An apparatus as claimed in claim 4, wherein said positive pressure regulator comprises a presser element supported for movement between retracted and clamping postions, a stationary block for the support of the tubing when the tubing is clamped to reduce the effective cross sectional area thereof by the presser element then moved from the retracted position to the clamping position, and means for adjusting the position of the stationary block relative to the presser element.

6. An apparatus as claimed in claim 5, wherein said adjusting means comprises an adjustment screw having one end operatively coupled with the stationary block.

7. An apparatus as claimed in claim 3, wherein said ultrafiltration pressure generating means comprises a throttling means disposed on the supply passage and a discharge pump disposed on the discharge passage at a location downstream of the second shut-off valve with respect to the direction of flow towards the outside.

8. An apparatus as claimed in claim 3, wherein said first and second shut-off valves are opened for a predetermined short time at intervals of a predetermined time during the closure thereof as a result of the pressure of the blood having attained the value equal to or lower than the predetermined value.