Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-10-23
2002-11-26
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S485000, C600S486000, C600S561000, C600S576000, C600S578000, C600S579000
Reexamination Certificate
active
06485428
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
Central-venous catheters, that is to say catheters which are inserted into large veins near to the heart, are used for the measurement of given haemodynamic parameters and for the continuous or discontinuous application of medicaments or infusion solutions and are an important component of patient monitoring and (intensive) medical care. The puncturing or aspiration of veins which are near to the heart presupposes skill, experience and knowledge of the anatomical factors involved. Besides the variability of the position of veins near to the heart in particular difficult puncturing conditions repeatedly result in incorrect puncturing of arteries which are in adjacent relationship.
Arterial puncturings or aspirations with thick cannulae as are used for the insertion of guide wires or catheters can result in massive bleedings under pressure into the surrounding tissue for example nerves, and then necessitate operative rectifying intervention. Incorrect arterial puncturing can represent a considerable risk to a patient who must undergo an operative procedure using a heart-and-lung machine and whose blood is made non-coagulatable for that purpose. Puncturing a vessel wall which has been arteriosclerotically altered can result in the mobilisation of plaques which are entrained with the blood flow into smaller arteries and can clog same. For that reason incorrect arterial puncturing in the region of the vessels in the neck which also supply the brain (arteria carotes) can result in a stroke and possibly disability of a patient. Those complications, even if rare, which however are tragic in the individual situation in which they occur and which involve high consequential costs have resulted in the recommendation of firstly finding veins which are close to the heart, by means of a thin needle (pre-puncturing cannula or also referred to as a “finder-needle”) in order then to puncture the vessel with the thicker cannula, in the direction of puncturing of the finder-needle.
In the arteries of the circulatory system of the body a mean pressure of 70-100 mm Hg with an amplitude between systolic and diastolic pressure of about 40-60 mm Hg is physiological, whereas in the veins which are close to the hear of the circulatory system a mean pressure of 7-10 mm Hg with an amplitude of only a few mm Hg is physiological. Under pathological conditions the pressure difference between arteries and veins and also the pressure amplitude in the vessels can become both greater and also smaller.
If an artery is punctured with a cannula having a large lumen, that can generally be recognised by virtue of the spraying and pulsating discharge of blood from the cannula. In contrast after a vein is punctured the blood will flow away from the cannula under a low pressure and fairly continuously Irrespective of whether an artery or a vein has been punctured however the high through-flow resistance of cannulae with a small lumen results in a uniform discharge of blood from the cannula, which at most pulsates discretely and never sprays out. Accordingly recourse must be had to other criteria in order to identify an artery or a vein. The colour of the blood is therefore a poor criterion.
By virtue of the higher oxygen content arterial blood is normally lighter than venous blood. Lung or heart diseases however can have the result that arterial blood also appears comparatively dark: in contrast venous blood is also really light when the patient is breathing with pure oxygen, for example in the context of initiating anaesthesia.
A reliable possible way of distinguishing arterial and venous blood is blood gas analysis in which the oxygen and carbon dioxide partial pressures are measured. That is time-intensive and labour-intensive and thus expensive.
The blood pressure in the punctured vessel can also be measured directly by means of a riser line. When the blood is allowed to flow back into the line the transfer of several milliliters of blood into the line requires some time, depending on the through-flow resistance of the cannula. If in contrast operation is conducted with a riser line which is filled with liquid, for example filled with common salt solution preparation of the riser line is a comparatively time-consuming procedure. At any event an assistant is required in order to hold the riser line.
A pressure-converter system, which is referred to as a transducer system, again detects not only the mean blood pressure as with a riser line but also the blood pressure amplitude in the punctured vessel. As the insertion of catheters presupposes sterile operating conditions, this procedure necessarily means that the transducer system must firstly be prepared in a sterile condition, that is highly time-consuming and also requires a “third hand” to which the cable connection for connection to the monitor can be handed over.
In view of the level of expenditure and complication and the difficulties involved in identifying a vein which is close to the heart without any doubt by means of a feeder-needle clinical practice often involves foregoing the pre-puncturing procedure. Unintentional arterial puncturings are then only detected after insertion of the catheter by means of intravasal pressure measurement or by virtue of blood rising in the infusion system and/or by an X-ray of the thorax.
The risk of HIV- (AIDS-) or hepatitis infection by virtue of contact with the blood of infected patients has resulted in “closed” cannula or syringe systems being offered not only for taking blood but also for the insertion of central-venous or arterial catheters. A closed system for example for the pressure-controlled handling of a fluid is known from the present applicant's DE 195 03 230.
So-called side-port cannulae are in turn available on the market for the low-contamination insertion of central-venous catheters. They have an additional duct which is disposed laterally and which is closed by a valve mechanism and by way of which a guide wire can be introduced after puncturing of the vessel, by way of which wire the catheter is then pushed into the vessel: the so-called “Seldinger procedure”. Furthermore, a syringe is also known from U.S. Pat. No. 4,813,938, referred to hereinafter as the “Raulerson syringe”, with a through duct in the plunger, which is closed by a valve mechanism and through which a guide wire can be introduced into the punctured vessel without the syringe having to be disconnected.
Both systems effectively prevent the escape of blood even after unintentional puncturing of an artery with a cannula having a large lumen, and accordingly give a false sense of security. As the syringe and the cannula do not have to be disconnected, as in the conventional procedure, incorrect arterial puncturing is usually recognised only after insertion of the catheter and thus maximum trauma for the vessel wall.
The object of the present invention is to provide a compact apparatus which is simple to operate and which can measure the pressure in a cavity, and which in particular permits a precise reliable distinction to be drawn between veins and arteries by means of a cannula, wherein the apparatus permits controlled insertion of a catheter or the like, in such a way as to avoid unnecessary injuries, in particular with the exclusion of blood contamination of the person operating the apparatus.
A first configuration of the invention is a one-person-operable, sterilisable, medical pressure measuring apparatus or manometer which has at least one cannula connection, a measuring duct and an entry, and wherein the measuring duct opens into a closed container with rigid wells in which there is a compressible medium.
Therefore, a liquid does not rise against the force of gravity, as in the case of the known construction, in an open container, for example a riser line, but penetrates into a closed container of a given volume and with non-elastic walls, which is for example filled with air, and in so doing successively compresses the air.
The pressure resulting in a closed container of that n
Greenberg Laurence A.
Locher Ralph E.
Mallari Patricia C.
Nasser Robert L.
Stemer Werner H.
LandOfFree
Apparatus for and method of intravasal pressure measurement... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for and method of intravasal pressure measurement..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for and method of intravasal pressure measurement... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2983068