Patent ID: 8858451

Claim:
A blood vessel catheter system, comprising: a catheter tube having a first portion configured for insertion into a blood vessel of a patient, and a second portion configured to remain outside the body of the patient when the first end is inside the blood vessel; a pressure sensor configured for connection outside of the patient's body to the second portion of the catheter tube, wherein the pressure sensor is configured to sense pressure in a liquid inside the catheter tube as an indication of a blood pressure of the patient, wherein the pressure sensor is configured to generate an electric pressure signal indicative of the blood pressure, and wherein the pressure sensor includes an electric interface configured to releasably couple the pressure sensor to a reusable measurement unit; a reservoir of rinsing fluid connected to the second portion of the catheter tube; a stop cock connected to the second portion of the catheter tube and configured for selective placement into at least: a rinsing position in which the stop cock allows a flow of rinsing fluid from the reservoir to the second portion of the catheter tube; a nulling position in which the stop cock establishes the application of a predetermined reference pressure to the pressure sensor, and a sampling position in which the stop cock prevents the flow of rinsing fluid from the reservoir to the second portion of the catheter tube; and a flow control unit positioned between the reservoir and the second portion of the catheter tube, said flow control unit comprising: an upstream end in fluid communication with the reservoir; a downstream end in fluid communication the second portion of the catheter tube; and structure between the upstream end and the downstream end of the flow control unit defining first, second, and third fluid flow paths between the reservoir and the second portion of the catheter tube: wherein said first fluid flow path includes a non-closing rinsing capillary configured to permanently allow fluid communication between the upstream end and the downstream end of the flow control unit, and a controlled flow of fluid between the reservoir and the second portion of the catheter tube when the stop cock is in its rinsing position; wherein said second fluid flow path includes a first check valve configured to open when fluid pressure at the downstream end of the flow control unit exceeds a fluid pressure at the upstream end of the flow control unit by a first predetermined threshold pressure difference; and wherein said third fluid flow path includes a second check valve configured to open when fluid pressure at the upstream end of the flow control unit exceeds fluid pressure at the downstream end of the flow control unit by a second predetermined threshold pressure difference.