Patent GB-1463675-A (GB)
Title: Automated blood analysis system
IPC: G01N33/49
Filed: 1973-12-29
Abstract: 1463675 Automated blood testing HEALTH SERVICES CORP 29 Dec 1973 [29 Dec 1972] 59745/73 Heading A5R In an automated blood testing system comprising a fitting for a catheter and a blood withdrawal unit 22, the latter comprises a fluid passageway in fluid communication with the fittting, one test station disposed at a site on the passageway means for introducing a biologically inert fluid in the passageway and means for displacing said fluid along the passageway in either direction, whereby, in use, an interface may be created between the blood and the fluid so that blood can be withdrawn along the passageway to the testing device and tested, and then returned to the patient. The system permits rapid testing of blood pH, blood gas and oxygen content of blood with automatic washout of the system between tests, and automatic testing of a blood gas tester 234 and a calibration of a pH tester 238 before and after the test. Withdrawal Unit(s), 22 Fig. 2: In fluid valves 62, 90, 120 and 134, and also in a constant volume pump 140, the continuous heavy lines, e.g. 64, 66, indicate fluid paths during the normal (deenergised) state of the valves and the pump, the valves and the pump being energized respectively by electrical signals at terminals 80a, 80b, 160 or 80c, 164 or 80d, and 156 or 154, respectively. The electrical output at terminals 40 of an oximeter 36 provides the oxygen content of the blood whereas the outputs at .terminals 54, 56 of air detectors 48, 50 in response to a signal at 52 operate an OR gate (384) (Fig. 4 not shown) thereby indicating that air bubbles have been detected, and also stopping the withdrawal of blood from the patient. An I.V. solution source and pump 84 may be used for irrigation and or infusion purposes in absence of which an 8PSI saline source 110 is used through a constrictor 104 to flush the catheter constantly so as to avoid blood clotting between blood withdrawal cycles. Saline from a reservoir 170 is used in the withdrawal of blood from, and return of a portion of the blood to, the patient, in supplying some of the withdrawn blood to a blood cup (190, Fig. 3 not shown) for analysis and in flushing the withdrawal unit and an analysis unit 24. Analysis unit (24, Fig. 3 not shown): The blood cup (190) and an outlet tube 124 (Fig. 2) supplying blood for the cup are physically separated from each other, and as a result the need to sterilize the unit (24) is avoided. Buffer stations one and two of known pH are used respectively to calibrate the pH tester (238) before and after the blood test, whereas water from (216) is used to flush out the buffer solutions from the pH tester, and when mixed with CO2 from (312), the aqueous solution along with saline from the withdrawal unit is used to flush the analysis unit. There is a provision for checking the gas leakage of electrodes of the blood gas tester (234). Either of blood detectors (268', 250) provides a signal at (272 or 254) respectively in response to a signal at (270 or 252) respectively when a blood/saline interface is encountered in the respective detector, thereby removing the output signal of a normally operating OR inverter gate (430, Fig. 4 not shown) and eventually terminating the pull stroke of a constant volume pump (294). Timing Unit (26, Fig. 4 not shown): For a complete blood analysis switch START is operated. This sets a latch (376), that operates an OR gate (358) and thereby provides electrical power to an 1/6 RPM motor (346) by closing a normally open switch (348). Various electrical signals at various terminals of the system provided by a sixteen track timer (359) and different operations carried out in the system at various times from the start of the motor and during one complete revolution of the motor, are depicted in Figures 4, 5 (not shown). At the end of one complete cycle, the motor automatically stops. There is a provision in the form of a one track rotary timer (358) for a routine testing of the blood using the oximeter.