Process and devices for determining the instant of injection and the duration of injection in thermodilution measurements

Abstract

The present invention relates to a process and devices for determining the instant of injection and the duration of injection in thermodilution measurements in which an injectate fluid at a temperature deviating from the temperature of the blood of a patient is injected at a specific injection site into a blood vessel of the patient and the temperature of the blood is measured at a measuring site downstream of the injection site, the injectate fluid being used at approximately room temperature and, before entry into the blood vessel, passed via a temperature sensor which, before the measurement, has a temperature deviating from room temperature, the temperature determined by the temperature sensor being sensed continuously, the instant of the beginning of injection being determined from a change occurring in the sensed temperature and the instant of the end of injection being determined from a subsequently occurring change in direction of the temperature profile.

What is claimed is:  
     
         1 . A central vein catheter for the injection of an injectate fluid having a temperature deviating from the temperature of the blood of a patient into the central vein of the patient or carrying out thermodilution measurements in which the temperature of the blood is measured at a measuring side downstream of the central vein by a separate device, the catheter comprising: 
 an elongate catheter body, having at least one injection lumen, with a distal end and a proximal end;    at least one connection device at the proximal end for connecting at lest one injectate source to the injection lumen for introducing the injectate fluid;    at least one port of the injection lumen in the vicinity of the distal end of the catheter body for introducing the injectate fluid into the central vein of the patient;    at least one temperature sensor, which is arranged inside the catheter body proximally with respect to the port of the injection lumen; and    at least one evaluation circuit, connected to the temperature sensor for receiving and evaluating the temperature profile determined by the temperature sensor for determining the instant of injection and the duration of injection.    
     
     
         2 . The catheter as claimed in    claim 1   , wherein the temperature sensor is arranged laterally adjacent to the injection lumen.  
     
     
         3 . The catheter as claimed in    claim 1   , wherein there is provided at least one further lumen, which is designed as a sensor lumen and in which the temperature sensor is arranged.  
     
     
         4 . The catheter as claimed in    claim 3   , wherein the sensor lumen is arranged centrally inside the catheter body.  
     
     
         5 . The catheter as claimed in    claim 3   , wherein the sensor lumen ends in the vicinity of the distal end of the catheter body.  
     
     
         6 . The catheter as claimed in    claim 1   , further comprising a heat conductive separating wall between the injection lumen and the temperature sensor.  
     
     
         7 . The catheter as claimed in    claim 1   , wherein at least one clearance is provided between the injection lumen and the temperature sensor.  
     
     
         8 . The catheter as claimed in    claim 1   , wherein at least one further lumen is provided inside the catheter body.  
     
     
         9 . A device for determining the instant of injection and the duration of injection in thermodilution measurements in which an injectate fluid at a temperature deviating from the temperature of the blood of a patient is injected at a specific injection side into a blood vessel of the patient and the temperature of the blood is measured at a measuring side downstream of the injection site, which has: 
 an extacorporeal sensor housing which has at least one input connection, which can be connected to at least one injectate source, and at least one output connection, which can be connected to a blood vessel catheter;    at least one temperature sensor which is arranged in the sensor housing, continuously senses the temperature in a region between the input connection and the output connection and can be connected via at least one line to at least one measuring computer; and    at least one heat contact plate of skin-compatible, heat-conducting material for fastening the sensor housing on the skin of the patient.    
     
     
         10 . The device as claimed in    claim 9   , wherein the sensor housing is provided in its regions facing away from the skin of the patient at least partially with a heat-insulating layer.  
     
     
         11 . The device as claimed in    claim 9   , wherein the heat contact plate is designed as an adhesive plate.  
     
     
         12 . The device as claimed in    claim 9   , wherein the input connection and the output connection of the sensor housing are designed as a female Luer lock connection and as a male Luer lock connection, respectively.  
     
     
         13 . The device as claimed in    claim 9   , further comprising means for heating or cooling the sensor housing.