Surgery – Diagnostic testing – Measuring fluid pressure in body
Reexamination Certificate
2001-10-26
2003-07-22
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Measuring fluid pressure in body
C600S300000, C600S549000, C600S555000, C600S587000
Reexamination Certificate
active
06595930
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a probe for physiological tonometry or pressure measurement in a human or animal body, the probe comprising a probe head, a line such as a catheter, and a pressure transducer in the probe head. For measuring pressure in the body, the probe head with the pressure transducer is disposed at the measuring site, with the probe head being adapted to be connected to an analyzer and display unit via the line.
BACKGROUND OF THE INVENTION
Probes of this kind have been known for a long time and are employed particularly for intra-cranial pressure measurement. There, the probe consists of a probe head including an electric pressure transducer. For tonometric measurement, the probe head with the pressure transducer is arranged on the measuring site. The probe head is then connected via a catheter including electric connecting leads to an analyzer and display unit by means of a coupler such as a connector. The pressure measured by the probe or detected by the pressure transducer included in the probe head is then displayed in the display unit.
Such probes may be used mainly to measure the epidural pressure—in this case the probe is located between the cranial bones and the Dura mater—the subdural pressure—here the probe is located between the Dura mater and the brain substance—the parenchymatous pressure—for this measurement the probe is located in the brain substance—or the ventricular pressure—in which case the probe is located in a ventricle. All of these measurements are consistently measurements of a relative pressure, which means that the pressure is measured relative to the environment.
The pressure transducer consists, for instance, of a piezo crystal mounted on the distal end of the catheter in the probe head. The catheter may comprise a silicon tube or a tube made of another biologically compatible material, for example, and includes electric leads disposed inside. The catheter is adapted for connection via a coupler to the analyzer and display unit.
Resistance strain gauges or capacitive pressure transducers may also be employed as an alternative to the piezo crystal. The electric pressure transducer is designed as a bridge circuit, e.g. in the form of a Wheatstone bridge, in order to increase the sensitivity. A current or voltage source outside the probe is provided for supplying the bridge circuit or the pressure transducer with electric power. The leads are connected to a voltage source and the pressure transducer.
For tonometric application, the probe is guided to the measuring site in the body. Then the catheter is connected to the analyzer and display unit that serves equally as power or voltage source, i.e. a source of energy, for the probe. The energy and equally the electric signals are transmitted via the electric leads contained in the catheter tube. The measurement of a relative pressure requires the storage of the electric value of the bridge voltage at zero pressure. To this end, null balancing must be carried out.
The crucial point in the known probes resides, however, in the aspect that these probes are only able to perform a certain number of pressure measurements and must then be recalibrated. As a result of the necessary sterilization cycles, the users are therefore required to record a log of the number of the operating applications of the probe. When a predetermined number of operating applications of the probe—i.e. of pressure measurements—is reached, the probe must be returned to the manufacturer for recalibration.
This method of recording the performed operating applications is, however, extremely expensive and, as a rule, does not function in an optimum manner in practical application. As result, probe failure occurs again and again because the probes are used even though the specified number of operating applications has been exceeded. In the everyday routine in a hospital it is impossible to keep records of the number of operating applications. The reliability and safety in operation is then no longer ensured and failure occurs in the implanted condition, which exposes the clinically monitored patient to a substantial risk.
SUMMARY OF THE INVENTION
The present invention is therefore based on the problem of improving a probe for physiological pressure measurement in the human or animal body in such a way that a facilitated recording of the operating applications will become possible while the aforementioned disadvantages are avoided.
This problem is solved by providing a counter means which records the number of performed operational applications of the probe.
This problem can also be solved by a controller means, which records a transducer offset value after each autoclaving or sterilization operation performed to sterilize the probe after each use and detects an error condition by detecting abnormal offset values or abnormal offset value changes since a previous autoclaving or sterilization operation.
The invention is based on the finding that counter or controller means are available of such a small size that they can be incorporated into probes so that the probe can record and report its operating applications automatically.
In accordance with the present invention, the probe therefore comprises a counter or controller means recording the operating applications of the probe. In this simple manner it is ensured that each tonometric application will be recorded. Now a record kept by hand is no longer required. Moreover, this provision improves the safety with respect to manipulations of the specified number of operating applications and hence the documentability of possibly asserted warranty claims.
In a preferred embodiment at least one additional counter for counting overload conditions of the pressure transducer is integrated in the unit. It can be set to count overload conditions all the time during autoclaving or sterilization or only during regular operation.
In another preferred embodiment an additional counter for counting autoclaving or sterilization operation is provided. These autoclaving or sterilization operations may be detected by a rise in temperature or pressure.
Another preferred embodiment of the invention comprises an additional timer for measuring operational hours.
The counter means is preferably disposed in that part of the coupler that is connected to the line.
In order to prevent specifically any use of the probe in excess of the specified number of operational uses and hence false measuring results or the failure of the probe during measurement, the counter means renders the pressure transducer and hence the probe inoperative as soon as the specified number of operating applications is reached.
The number of the operating applications and/or the number of applications remaining until the end of service of the probe can be displayed via a display means so that the user can inform himself at any time about the remaining number of operational applications and the number of completed operational uses of the probe. To this end, the display means is integrated, in particular, into that part of the coupler that is connected to the line so that the user can obtain this information from the probe directly.
According to one embodiment of the invention, the probe comprises an electric pressure transducer and an electric counter means. The counter means is configured with temperature-resistant electric components. The counter means triggers a counting operation only when voltage is applied to the probe throughout a defined period. This provision is intended to prevent that the counting operation is triggered when a voltage is applied only briefly. This may be the case, for instance, when the connection with the probe is to be tested. What is to be counted is only the occurrence of an actual application in operation, i.e. when the voltage is applied, for instance, for half an hour at minimum.
To prevent a further use of the probe when the specified number of operating applications has already been reached, the counter means operates a switch that disconnects the power supply of the pressure
Mallari Patricia
MIPM Mannendorfer Institut fur Physik und Medizin GmbH
Nasser Robert L.
St. Onge Steward Johnston & Reens LLC
LandOfFree
Probe for physiological pressure measurement in the human or... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Probe for physiological pressure measurement in the human or..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Probe for physiological pressure measurement in the human or... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3029446