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Blood gas parameter measuring system

  • US 5,184,618 A
  • Filed: 01/23/1991
  • Issued: 02/09/1993
  • Est. Priority Date: 04/25/1990
  • Status: Expired due to Fees
First Claim
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1. A system for invasive measurement of blood gas parameters, including pH, pO2 or pCO2, or for measuring other parameters influencing the time constant of an excited state of a fluorescent dye, comprising:

  • (a) a light generation device including(a1) a generator having an outer signal (2),(a2) a controllable delay device (4) having at least two delay states and(a3) a light source means (6) coupled to said generator (2) via said delay device (4) for producing excitation light of a first wavelength;

    (b) a fluorescent measuring probe (1) provided with(b1) a fluorescent dye that is positionable in ion exchange connection with blood;

    (b2) said fluorescent dye adapted to be brought to an excited state by means of light of a first wavelength and returning, while emitting light of a second wavelength, from the excited state to a ground state with a time constant depending on the blood gas parameter to be measured,(c) a light reception device (16) for converting light of said first and second wavelengths into a received signal;

    (d) a switchable light guide means (7)(d1) having at least two states and optically coupled between said light source (6);

    said light reception means (16) and said fluorescent measuring probe (1), for coupling, in a first switched state, light of the first wavelength from the light source (6) to the fluorescent measuring probe (1) and light of the second wavelength from the fluorescent measuring probe (1) to the light reception means (16), and(d2) for guiding light of the first wavelength from the light source means (6) to the light reception means (16) in a second switched state;

    (e) a phase metering means (17 to 20, 23 to

         27), coupled to said generator (2) and said light reception means (16)(e1) for producing a phase reference signal phaselocked to the output signal of the generator (2) and responsive to the received signal from the light reception means (16),(e2) to produce a phase metering signal indicative of the phase difference between said output and receive signals;

    (f) an evaluation means (28) connected to said phase metering means,(f1) and responsive to phase metering signals in the at least two delay states of said controllable delay device (4), when said switchable light guide means (7) is(f2) in the second switched state, for determining the transfer characteristic of the blood gas parameter measuring system, and(f3) which, in the first switched state of the light guide device (7), determines a value of the blood gas parameter on the basis of the transfer characteristic, the phase metering signal and a correlation between the respective values of the blood gas parameter and dependent values of said time constant, said correlation being predetermined for the fluorescent measuring probe (1).

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