Surgery – Diagnostic testing – Cardiovascular
Patent
1997-10-10
1999-12-21
Nasser, Robert L.
Surgery
Diagnostic testing
Cardiovascular
600526, A61B 500
Patent
active
060042753
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an apparatus for the continuous measurement of the cardiac output without indicator using a flow directed thermodilution catheter comprising of: adapted for measuring the pressure in the arteria pulmonalis; catheter and which is adapted for measuring the pressure of the right atrium; catheter and which is adapted for measuring the pressure of the right ventricle; end of catheter; the balloon is inflated, through lumen; filled with sterilized fluid; which are adapted for measuring the pressure based on the Wheatstone bridge principles in order to continuously measure: time intervals, at the moment the balloon is inflated.
The most important application of this invention will be found in Intensive Care, Operation Room, Heart catheterisation laboratories, Emergency Room and hospital units where the cardiac activity of very ill patients must be continuously followed with the help of hemodynamic monitoring.
Flow-directed catheters of the so called Swan-Ganz type are described in document EP-A-0363117. The flow directed catheter has a balloon which is inflated during the insertion of the catheter into the patient in order to lead the catheter through the heart valves into the arteria pulmonis. The balloon also makes it possible to measure the wedge pressure when inflated at the PA position, without displacement of the catheter. This type of catheter has several lumina, in order to measure the intracardiac pressures and intermittently the cardiac output by means of bolus thermodilution and in order to take bloodsamples.
This total set-up makes it possible to diagnose the patient's health condition. However measuring Cardiac Output continuously is not possible, as this measurement is restricted because of the limitation of the total amount of blouses (normal single bolus volume is 10 cc) which can be injected into the patient to measure the bolus thermodilution cardiac output.
The thermodilution cardiac output measurement is an accepted, well known technique to measure the cardiac output of a patient. To execute this technique a so called Swan-Ganz catheter is introduced into the patient in a large vein, e.g. vena jugularis, vena subclavia or vena femoralis. The catheter is then placed with its tip (distal end) in the pulmonary artery. Through an opening at about 30 cm of the distal end, a bolus of 10 cc physiologic fluid solution of NaCl 0.9% with a known temperature is injected into the right atrium. A temperature senor in the pulmonary artery (approx. 26 cm distal of the injection site and about 4 cm from the distal end of the catheter) measure the temperature change and the temperature difference compared to the injected bolus temperature.
With a catheter placed in a vein or an artery the blood pressure can be measured directly. The catheter is connected to a so called pressure set, which is also filled up with fluid and which is connected to a pressure transducer. The pressure transducer is connected to an electronics device, also called hemodynamic monitor, which computers the pressure values and displays them on a screen, together with the dynamic pressure wave signal.
Also known is the measurement of contractility of the heart whereby a series of catheters of the so called Swan-Ganz type using pressure sensitive tip transducers are lead into several cavities of the heart, in order to measure various intracardial pressures. This measurement is executed in the left heart more precisely in the left atrium, the left ventricle and aorta, which gives information about overall and regional ventricle functions. Registration of the blood pressures is included in this method.
In a later stage volume-sensitive transducers have been used during the catheterisation to obtain the total pressure-volume curve. Doing so, the pressure-volume curve is registered over one heart cycle, with the end diastolic pressure value defined as one point within the curve.
To obtain the total curve, the measurement is repeated with several pre- and afterload conditions, e.g. by vena cava inferior clamping.
The pro
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