Site coding for medical devices for introduction into a...

Details Site coding for medical devices for introduction into a... Site coding for medical devices for introduction into a...

1999-09-23

2001-07-24

Winakur, Eric F. (Department: 3736)

Surgery

Diagnostic testing

Cardiovascular

C600S486000, C600S394000, C600S381000

Reexamination Certificate

active

06264613

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to medical devices, such as catheters, sensors, transducers, or the like, for introduction into a patient's body, in particular the patient's blood vessel, for measuring one or more physiological parameter(s), and to connectors for connecting the medical devices.
BACKGROUND OF THE INVENTION
Catheters represent the most common medical devices for introduction into a patient's body. A catheter, in general, is a tubular medical device for insertion into canals, vessels, passageways, or body cavities usually to permit injection or withdrawal of fluids or to keep a passage open or to carry sensors. Catheters are often applied for determining blood flow and/or volumetric hemodynamic parameters with thermodilution techniques, or for invasive blood pressure and/or oxygen saturation measurements with embedded fiber optics.
Thermodilution catheters, as typical examples for catheters, are well known in the literature and medical practice for determining blood flow, cardiac blood volumes, or pulmonary blood volumes. Such catheters are typically small diameter catheters for insertion in blood vessels, carrying distal temperature sensing means with more or less additional lumens, to inject the dilution liquid and/or to transmit a blood pressure in a vessel at a distal opening to a proximal opening for pressure sensing means. A common characteristic of the thermodilution measurements is the injection of a cold bolus and to sense the temperature displacement downstream with the temperature sensing means of the catheter. From the magnitude, duration, appearance time, mean transit time, and down slope time of the temperature displacement curve, flow and volume parameters of organs or parts thereof between site of bolus injection and site of temperature sensing are derived by appropriate measurement algorithms of a general purpose processing device. A representative thermodilution catheter is illustrated in U.S. Pat. No. 3,995,623.
FIG. 1
illustrates a conventional thermodilution catheter
2
for insertion by central venous access through the right heart into the pulmonary artery. The catheter
2
comprises a distal tip orifice
1
, communicates through an internal lumen of the catheter
2
, and terminates in a luer fitting
3
. A balloon
4
communicates through an internal lumen of the catheter
2
and terminates in a syringe
5
for the purpose of inflating the balloon. A thermistor
6
is connected by small wires embedded in a wall of catheter
2
to dedicated pins in a catheter connector
7
. An injectate orifice
8
communicates through an internal lumen of the catheter
2
and terminates in a luer fitting
9
.
FIG. 2
illustrates a conventional thermal dilution catheter
2
for insertion by an arterial access into an aortic or near an aortic vessel. The catheter
2
comprises the same characteristics as in
FIG. 1
, however, without the balloon
4
, the syringe
5
including internal lumen, the injectate orifice
8
, and luer fitting
9
including internal lumen.
FIGS. 3A and 3B
illustrate in detail an example of the electrical catheter connector
7
as used e.g. by the Hewlett-Packard HP M1642A Catheter Interface Cable. The lug of the catheter connector
7
in
FIG. 3A
comprises electrical contact pins
10
enclosed by a threaded collar
11
. A corresponding device connector socket
7
A in
FIG. 3B
is adapted to receive the catheter connector plug of FIG.
3
A. In
FIG. 3B
, a device connector
14
includes electrical pin receptors
10
A and a threaded slip collar
15
to secure the connection of the connectors
7
and
14
.
Thermodilution catheters today are used most widely to determine blood flow and pressures in the pulmonary artery. Such catheters are inserted via a central venous access like the right internal jugular vein or left subclavian vein through the right heart and placed with the distal end in the pulmonary artery. The rate of blood flow is computed from the displacement of blood temperature according to the Stewart-Hamilton dilution equation for a thermal indicator as described in U.S. Pat. No. 3,987,788 or in the publication “The thermodilution method for the clinical assessment of cardiac output”, J. R. C. Jansen, Intensive Care Med (1995) 21:691-697. In another application, the transpulmonary thermodilution technique, the thermodilution catheter is located in the arterial side of the vascular system and placed via a femoral, radial or axillary artery access. In addition to the derived blood flow calculation the circulatory filling status can be determined from the appearance time, mean transit time and down slope time of the blood temperature displacement as described in the U.S. Pat. No. 5,526,817.
It has been shown that erroneous applications of catheters, e.g. due to a wrong placement in the intra-vascular system or selection of the measurement parameters, can lead to wrong measurement results and might cause serious harm to the patients, e.g. due to a wrong therapeutic decision based on the wrong results.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to reduce the risk of erroneous catheter measurements. The object is solved by the independent claims. Preferred embodiments are shown by the dependent claims.
It has been found that physiological parameters measured within the patient's body exhibit different characteristics dependent on the respective measuring site, i.e. the spatial location of the measuring device. In particular for applications of thermal dilution catheters (cf. e.g. FIG.
1
), the spatial location of the place of injection of the cold bolus and the place of sensing of the temperature displacement represents a strong influence on the measurement. Coding the application site thus allows a measurement evaluation algorithm to take into consideration the different application sites. In particular, the size-coding allows to automatically set characteristic measurement parameters dependent on the site-coding, so that a correct parameter setting and algorithm selection can be ensured or, in other words, that the risk of erroneous catheter applications can be reduced.
The site coding can be accomplished by any means as known in the art such as electronically, mechanically, optically or combinations thereof.
The site coding, in general, provides the possibility to optimize and/or adapt the measuring behavior on the respective measuring site. Signal modifications due to influences of the respective site of measurement can be automatically corrected. Specific measuring or measurement evaluation modules for providing specific results can be automatically enabled or disabled dependent on the site coding.
The site coding according to the invention allows a precise definition of the measurements the medical device is dedicated for or, in other words, to clearly define which parameters will be processed and displayed with a connected processing unit.
The invention also allows automatically adapting a measurement on the specific conditions and influences of a respective measurement site, e.g. in a way that the measurement results are automatically evaluated in accordance with the setting of the site coding. This renders the possibility, for example, to adapt the measurement results to specific measurements characteristics determined by the respective measurement site e.g. for adapting the sensing resolution to the signal strength at the coded site. Accordingly, marking or “labeling” the measurement with a specific label, e.g. “CVP” for a pressure at central venous access or “ABP” for a blood pressure at arterial access, can thus be achieved.
Additionally, site coding according to the invention allows providing information about possible parameters to be measured in a specific site.
Furthermore, the inventive site coding renders the possibility to automatically provide information about the specific embodiment of the medical device, e.g. information how the medical device is embodied with respect to the specific measuring site.
In addition to the coding of the respe

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