Automated blood analysis system

• US 3,910,256 A
• Filed: 07/22/1974
• Issued: 10/07/1975
• Est. Priority Date: 12/29/1972
• Status: Expired due to Term

• Current Assignee: Justin S. Clark, Lloyd George Veasy
• Original Assignee: Justin S. Clark, Lloyd George Veasy
• Inventors: Clark, Justin S., Veasy, Lloyd George
• Primary Examiner(s): Medbery, Aldrich F.
• Application Number:
  US05/490,603
• Time in Patent Office: 442 Days
• Field of Search: 128/1,2G,2R,2L,214B,214E 356/39-42 73/64.1
• US Class Current: 600/325
• CPC Class Codes: G01N 35/00594 Quality control, including calibration or testing of components of the analyser
• CPC Class Codes: G01N 35/00693 Calibration

Abstract

A system for automatically withdrawing blood from a patient and testing various parameters of the blood, such as oxygen saturation, hemoglobin, gas content (PO2, PCO2) and pH, includes a withdrawal unit which automatically withdraws a measured volume of blood, and returns all of it to the patient except a small measured quantity which is provided to an analysis unit that measures the gas content and pH. The withdrawal unit includes provision for continuously monitoring patients'"'"''"'"' blood pressure, irrigation from a standard I.V. source between blood withdrawals, or a constant low flush of saline, alternatively, as well as detection of any air in the blood, which results in shutting down the system and activating an air alarm. The withdrawal unit also has provision for automatically withdrawing a small sample of blood, measuring oxygen content, and returning all blood to the patient, all on a programmed basis. The analysis unit includes two-point gas and pH calibration and includes use of calibration fluid for washout. In each complete use cycle, blood from the withdrawal unit is washed into the analysis unit and blood in the analysis unit is moved and washed out using saline, water and calibration fluids. The withdrawal unit may be used alone to acquire blood samples, and the analysis unit may be fed by more than one withdrawal unit or by manually-acquired blood specimens.

Claims

1. A method of timing of blood withdrawal and examination system connected to a patient via a catheter, comprising the steps of:

filling the system with at least one biologically inert fluid;

calibrating the system;

withdrawing blood, upon command, from the patient through the catheter into the system in fluid-to-fluid contact with the inert fluid;

sensing the inert fluid/blood interface at a blood examination site;

automatically and instantaneously discontinuing the withdrawal step when the sensing step occurs;

applying pressure to the inert fluid to push substantially all of the blood out of the system through the catheter and back into the patient.

2. The method of claim 1 wherein the withdrawing and applying steps comprise the step of confining the flow of inert fluid and blood to laminar flow in passageways of uniform cross-sectional area and configuration.

3. The method of claim 1 further comprising the step of terminating the withdrawing step if the sensing step does not occur within a predetermined time.

4. The method of claim 1 further comprising the step of examining at least one blood characteristic at the blood examination site and providing a visual display of the results.

5. The method of claim 4 further comprising the step of initiating additional automated blood withdrawal and examination at other sites when said visually displayed results are abnormal.

6. A method of minimizing Blood loss during blood withdrawal and blood testing, comprising the steps of:

withdrawing blood, upon command, from a patient through a catheter into a blood withdrawal system;

discharging only a predetermined quantity of blood from the withdrawal system into a blood testing system while maintaining a physical separation between the two systems;

creating a fluid/blood interface in the blood testing system;

displacing in unison fluid, blood and the interface into the blood testing system;

sensing the fluid/blood interface at a blood testing site;

automatically discontinuing the displacing step when the sensing step occurs;

testing the blood at said site;

applying pressure to the blood to discharge blood from the blood testing system to waste.

7. The method of claim 6 further comprising the step of terminating the displacing step if the sensing step does not occur within a predetermined time.

8. The method of claim 6 further comprising the step of returning substantially all of the blood in the withdrawal system to the patient through the catheter.

9. A method of calibrating a blood monitoring system comprising the steps of:

providing at least one source of calibration fluid;

displacing calibration fluid from the source through lines of the system to at least one blood monitoring site;

causing a calibration measurement in respect to the calibration fluid to be made at said site;

removing a quantity of blood from the patient through a catheter;

creating an interface between the blood and the calibration fluid;

simultaneously displacing the calibration fluid and the blood within lines of the system so as to distinctly maintain the interface while evacuating fluid from and introducing blood at said site;

causing a blood measurement to be made at said site.

10. The method of claim 9 wherein the removing step precedes the displacing step.

11. The method of claim 9 further comprising the step of flushing blood from the lines of the system following the last-mentioned causing step.

12. The method of claim 9 further comprising the steps of allowing the calibration fluid and the blood respectively to equilibrate at said site before causing said measurements to be made.

13. A method of calibrating a blood monitoring system comprising the steps of:

placing one calibration fluid within lines of the system at one monitoring site and another calibration fluid within lines of the system at a second monitoring site;

causing a calibration measurement to be made at each site in respect to the calibration fluid there disposed;

removing blood from the patient through a catheter into lines of the system;

evacuating calibration fluid from the sites and replacing the calibration fluid with blood;

causing a blood measurement to be made at each said site.

14. The method of claim 13 wherein each causing step comprises two separate measurements each made at a different time.

15. The method of claim 13 wherein said evacuating step comprises removing the two calibration fluids from said sites at different points in time.

16. The method of claim 13 wherein said placing step comprises separate acts each made at a different time.

17. The method of claim 13 wherein said placing, causing and evacuating steps, respectively, occur at essentially the same point in time.