Capillary filtration and collection method for long-term monitoring of blood constituents

• US 4,777,953 A
• Filed: 02/25/1987
• Issued: 10/18/1988
• Est. Priority Date: 02/25/1987
• Status: Expired due to Term

• Current Assignee: Ash Access Technology, Inc.
• Original Assignee: ASH Medical Systems Incorporated
• Inventors: Ash, Stephen R., Janle-Swain, Elsa M.
• Primary Examiner(s): HINDENBURG, MAX F
• Application Number:
  US07/018,616
• Time in Patent Office: 601 Days
• Field of Search: 128/632, 128/635, 128/768, 128/769, 604/4, 604/29, 604/50, 604/66
• US Class Current: 600/347
• CPC Class Codes: A61B 2010/008 Interstitial fluid
• CPC Class Codes: A61B 5/14528 invasively
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• CPC Class Codes: A61B 5/415 the glands, e.g. tonsils, adenoids or thymus
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: B01D 2313/06 External membrane module supporting or fixing means
• CPC Class Codes: B01D 61/18 Apparatus therefor
• CPC Class Codes: B01D 63/024 with a single potted end

Abstract

A method and device for long term monitoring of the blood level of various blood constituents. The monitoring is accomplished by capillary filtration and collection of an ultrafiltrate of blood. Filtration of the ultrafiltrate occurs through a filter composed of hollow fibers which are implanted within an interstitial body space in fluid communication with blood capillaries. The ultrafiltrate is drawn through the filter and into an ultrafiltrate collector which extends externally of the body. The collector provides a vacuum for withdrawing the ultrafiltrate and holds discrete liquid samples of the ultrafiltrate. The method and device is particularly suited for long term monitoring of blood glucose levels in diabetic patients or other blood chemical constituents in other patients.

Claims

1. A method for continuous long term monitoring of the blood level of a physiological constituent of blood, comprising the steps of:

implanting a porous membrane filter within an interstitial body space in fluid communication with blood capillaries;

filtering an ultrafiltrate of blood from the capillaries by exerting a negative pressure withdrawal force on the porous membrane filter so as to cause the ultrafiltrate to flow from the capillaries through the filter at a desired flow rate;

collecting the ultrafiltrate in a reservoir located externally of the body; and

assaying the ultrafiltrate to measure a desired physiological constituent thereof.

2. The method of claim 1 wherein said assaying step includes measuring the level of glucose in the ultrafiltrate.

3. The method of claim 1 wherein said filtering and collecting steps include filtering the ultrafiltrate along with a gas and collecting the ultrafiltrate inside said reservoir in distinct liquid boluses separated by the gas.

4. The method of claim 3 wherein said collecting step includes collecting the ultrafiltrate inside said reservoir in distinct liquid boluses separated by the gas in a volume ratio of gas to ultrafiltrate of about ten to one.

5. The method of claim 1 wherein said filtering step is accomplished at a flow rate in a range from about 20 to 500 microliters per hour.