Patent Publication Number: US-2015080750-A1

Title: Disposable Sensor Device and Monitoring System

Description:
The present invention relates to disposable sensor devices for patient monitoring such as an arterial blood pressure sensor device, a pulse contour cardiac output device and the like. The present invention is further related to monitoring systems for such disposable sensor devices. 
     In patient monitoring there are situations wherein multiple monitoring devices are needed which are dealing with the same parameter. For example, there may be some need to receive the respective signal by a bedside monitor and by a portable device in parallel wherein both should be able to read the parameter of interest. So far, each monitoring device, e.g. the bedside monitoring device and the portable measurement device, uses a separate sensor device. The multiple sensor devices may be closely spaced to detect the same or at least similar results, as e.g. described in US 2006/0009699. 
     Mostly, the sensor device needs some kind of excitation voltage, i.e. a supply DC or AC voltage. Then, the sensor device delivers a detector signal which depends on the excitation voltage and the parameter which is to be analyzed in the monitoring system. 
     To provide two sensor devices of the same kind for being read out by two different monitoring devices leads to a bulky shape on the sensor&#39;s side. Furthermore, the increased space volume may cause a worse frequency response in case an AC excitation voltage is used. Even if the two sensor devices are closely spaced they are not located at the same heart level such that in case of pressure sensor devices different arterial pressure values would be obtained. 
     It is therefore an object of the present invention to provide a disposable sensor device and a monitoring system which allows to monitor a measured parameter of patient by two or more monitoring devices thereby avoiding the drawbacks of the prior art. 
     This object has been achieved by the disposable sensor devices according to claims  1  and  7  and the monitoring systems according to further independent claims. 
     Further embodiments of the present invention are indicated in the depending subclaims. 
     According to one aspect a disposable sensor device for patient monitoring is provided. The disposable sensor device comprises a sensor for providing an electric quantity based on a quantity to be detected, a first signal terminal for providing a tap for the electric quantity, a first supply terminal for supplying the sensor with an electrical supply quantity, and a first connector for accommodating the first signal terminal and the first supply terminal. A second signal terminal for providing a further tap for the electric quantity and a second connector for accommodating at least the second signal terminal are provided. 
     Furthermore, the sensor may be provided as a bridge circuit or any other analogue electric measurement circuit. The bridge circuit could be a Wheatstone full or half bridge e.g. with resistors. 
     Moreover, the second connector further may include a second supply terminal for tapping the supply quantity provided via the first connector. 
     According to another aspect, a monitoring system for patient monitoring is provided. The monitoring system comprises the above disposable sensor device, a first monitoring device connectable to the first connector for tapping the electric quantity via the first signal terminal and for supplying the electrical supply quantity via the first supply terminal. 
     A second monitoring device may be connectable to the second connector for tapping the electric quantity via the second signal terminal. 
     Furthermore, it may be provided a monitoring system comprising the above disposable sensor device, a first monitoring device connectable to the first connector for tapping the electric quantity via the first signal terminal and for supplying the electrical supply quantity via the first supply terminal, and a second monitoring device connectable to the second connector for tapping the electric quantity via the second signal terminal, wherein the second monitoring device is further adapted to tap the electrical supply quantity supplied by the first monitoring device via the second supply terminal, wherein the second monitoring device includes an excitation sensing circuit adapted to sense whether or not an electrical supply quantity is applied on the second supply terminal and to further supply an electrical supply quantity via the second supply terminal to the disposable sensor device in case no electrical supply quantity can be sensed. 
     According to a further aspect a disposable sensor device for patient monitoring is provided. The sensor device comprises a sensor for providing an electric quantity based on a quantity to be detected, a first signal terminal for providing a tap for the electric quantity, and a first connector for accommodating the first signal terminal. The first connector is provided with a trimming element which simulates the influence of a selectively attachable first monitoring device on a measuring of the electric quantity, wherein the trimming element is electrically effective depending on a connector structure of a corresponding further connector to be coupled with the first connector. 
     Moreover, the electric quantity may be applied between the first and a second signal terminals of the first connector, wherein the trimming element is applied between the first and a third signal terminals of the first connector, wherein depending on the connector structure of the corresponding further connector, either the first and second signal terminals are tapped and the third signal terminal remains untapped or the first and a shortcut second and third signal terminals of the first connector are tapped. 
     Moreover, the sensor may comprise a Wheatstone-Bridge circuit or any other analogue electric measurement circuit. 
     According to an embodiment the sensor has a pressure sensor for measuring an arterial pressure of a patient. 
     A first excitation terminal may be provided in the first connector to apply an excitation voltage to the sensor. The excitation voltage may be applied between the first and a second excitation terminals of the first connector, wherein a further trimming element is applied between the first and a third excitation terminal of the first connector, wherein depending on the connector structure of the corresponding further connector, either the first and second excitation terminals are connected with an excitation voltage and the third excitation terminal remains unconnected or the first and a shortcut second and third excitation terminals are connected with the excitation voltage. 
     According to a further aspect a monitoring system for patient monitoring is provided. The monitoring system comprises a disposable sensor device as mentioned above and a first monitoring device for tapping the electric quantity, having a second connector to match with the first connector, wherein the second connector has a connector structure depending on which the trimming element of the first connector is electrically effective. 
     Furthermore, the electric quantity may be applied between the first and a second signal terminal of the first connector, wherein the trimming element is applied between the first and a third signal terminals of the first connector, wherein the second connector has a terminal contact to shortcut the second and third signal terminals of the first connector in a plugged condition such that the trimming element is electrically effective. 
     Moreover, an excitation voltage may be applied between first and second excitation terminals of the first connector, wherein a further trimming element is applied between the first and a third excitation terminal of the first connector, wherein the second connector has an excitation terminal contact which is adapted to provide the excitation voltage from the first monitoring device and to shortcut the second and third excitation terminal to both connect them with the excitation voltage in a plugged condition. 
     According to a further aspect a monitoring system for patient monitoring is provided. The monitoring system comprises a disposable sensor device as mentioned above, and a second monitoring device for tapping the electric quantity, having a third intermediate connector to match with the first connector, wherein the third connector has a connector structure such that, when the first and second connectors are in a plugged condition, the trimming element of the first connector is electrically ineffective. 
     The electric quantity may be applied between the first and a second signal terminal of the first connector, wherein the trimming element is applied between the first and a third signal terminal of the first connector, wherein the third connector has a terminal contact to only contact the second signal terminal but not the third signal terminal of the first connector in the plugged condition such that the trimming element is electrically ineffective. 
     An excitation voltage may be further applicable between first and second excitation terminals of the first connector, wherein a further trimming element is applied between the first and a third excitation terminal of the first connector, wherein the third connector has an excitation terminal contact which is adapted to provide the excitation voltage from the second monitoring device and to only contact the second excitation terminal but not the third excitation terminal of the first connector in the plugged condition such that the further trimming element is electrically ineffective. 
     According to a further aspect a monitoring system for patient monitoring is provided. The monitoring system comprises a disposable sensor device as mentioned above, a first monitoring device for tapping the electric quantity, having a second connector to match with the first connector, wherein the second connector has a connector structure such that, when the first and second connectors are in a plugged condition, the trimming element of the first connector is electrically effective, and a second monitoring device for tapping the electric quantity, having a third intermediate connector having two outlets to respectively match with the first and the second connector, wherein the second connector has a connector structure such that, when the first and second connectors are in a plugged condition, the trimming element of the first connector is electrically ineffective, wherein the third connector has a connector structure such that when the second and third connectors are in a plugged condition, the second monitoring device receives the electrical quantity passed through the third connector. 
     Furthermore, the electric quantity may be applied between the first and a second signal terminal of the first connector, wherein the trimming element is applied between the first and a third signal terminal of the first connector, wherein the second connector has a terminal contact which is adapted to shortcut the second and third signal terminals of the first connector in the plugged condition of the first and second connectors such that the trimming element is electrically effective, wherein the third connector has a terminal contact which is adapted to only contact the second signal terminal but not the third signal terminal of the first connector in the plugged condition of the first and third connector such that the trimming element is electrically ineffective. 
     An excitation voltage may be applicable between first and second excitation terminals of the first connector, wherein a further trimming element is applied between the first and a third excitation terminal of the first connector, wherein the second connector has an excitation terminal contact which is adapted to shortcut the second and third excitation terminals to both connect them with the excitation voltage in a plugged condition, wherein the third connector has an excitation terminal contact which is adapted to only contact the second excitation terminal but not the third excitation terminal of the first connector in the plugged condition of the first and the third connector such that the further trimming element is electrically ineffective, wherein the third connector further has a connector structure such that when the first, second and third connectors are in a plugged condition, the second monitoring device is adapted to supply the excitation voltage to the sensor via the third connector. 
     An excitation supply unit may be provided in the second monitoring unit which is adapted to detect, when the first and third connector are in the connected condition, an appliance of an excitation voltage on the first and second excitation terminals of the first connector, and in case that no excitation voltage is applied on the first and second excitation terminals of the first connector the excitation supply unit supplies an excitation voltage via the third connector to the first connector otherwise the excitation supply unit does not supply any excitation voltage. 
     Moreover, the second monitoring device may be adapted to monitor the quantity to be detected for the case the trimming element is electrically effective. 
    
    
     
       Preferred embodiments of the present invention are described in detail in conjunction with the accompanying drawings, in which same reference signs indicated elements having the same or similar functionality and in which: 
         FIG. 1  shows schematically a configuration of a monitoring system according to an embodiment of the present invention; 
         FIG. 2  shows schematically the electrical interconnections between the bedside monitor and the disposable pressure transducer; 
         FIG. 3  shows schematically a further configuration of a monitoring system according to the embodiment of  FIG. 1 ; 
         FIG. 4  shows schematically the electrical interconnections between the bedside monitor, the portable measurement device, and the disposable pressure transducer; 
         FIG. 5  schematically illustrates the terminals of the transducer plug A; 
         FIG. 6  schematically illustrates the terminals of the intermediate plug B; 
         FIG. 7  schematically illustrates the terminals of the BSM plug C; 
         FIG. 8  shows the BSM plug c, the intermediate plug B and the transducer plug A in a connected condition; 
         FIG. 9  shows the BSM plug C and the transducer plug A in a connected condition; and 
         FIG. 10  shows a disposable sensor device and a monitoring system according to a further embodiment. 
     
    
    
     In  FIG. 1  a possible configuration of a monitoring system in a first configuration is disclosed. The monitoring system includes as a first monitoring device a bedside monitor (BSM)  1  for receiving, storing and/or visualizing patient-related data of a patient P. In the illustrated example, the bedside monitor  1  is directly coupled with an arterial pressure module  2  which receives a sensor signal from a disposable pressure transducer (DPT)  7  as a sensor via a cable connection. The arterial pressure module  2  receives the sensor signals and provides a communication of pressure information obtained with the sensor signal to the bedside monitor  1 . 
     An arterial catheter  9  is placed inside the patient P and is coupled with a reservoir  11  via a respective tubing  5 . The tubing  5  is configured to supply an infusion liquid from the reservoir  11  to the patient&#39;s body. The tubing  5  is lead through an organizer plate  8  which is preferably located at mid-chest level of the patient. A stop cock  17  for disconnecting the reservoir  11  from the catheter  9  is placed on the organizer plate  8 . In proximity to the stop cock  17  at the mid-chest level a pressure transducer  7  as a sensor device is placed at the tubing  5  to detect the pressure of the infusion liquid within the tubing  5 . The infusion liquid in the tubing  5  transmits the blood pressure in the patient&#39;s arterial vessels to the pressure transducer  7  at the organizer plate  8 . 
     The cable connection between the bedside monitor  1  and the pressure transducer  7  includes a connection cable  3  which is connected or connectable to the bedside monitor  1  and which is provided with a third connector C, further referenced as BSM plug C. The pressure transducer  7  is provided with a pressure transducer cable  6  and provided with a first connector A further referred to as transducer plug A. Transducer plug A and BSM plug C can be coupled to provide electrical connections between the bedside monitor  1  and the pressure transducer  7 . 
     In  FIG. 2  it is schematically shown the electrical interconnections between the bedside monitor  1  and the disposable pressure transducer  7  as well as a structure of an exemplary pressure transducer. In the given example, the disposable pressure transducer  7  has a number of four pressure detecting elements  12  which are coupled to form a Wheatstone bridge as it is well-known in the art, to increase detection sensitivity. The Wheatstone bridge receives an excitation voltage via excitation lines E+, E− which may be a DC voltage in case of resistive detecting elements  12  and which may be an AC voltage having a predefined oscillation frequency and magnitude in case the detecting elements  12  are capacitive or inductive detecting elements. From the output nodes of the Wheatstone bridge sensor signals S+, S− are tapped via signal lines by the bedside monitor  1 . The sensor signals S+, S− depend on the pressure to be detected according to the states of the detecting elements  12  as well as on the excitation voltage. Instead of pressure transducer any kind of sensors which provide a detectable sensor signal can be applied with each embodiment of the present invention. 
     In cases of a situation wherein in patient monitoring multiple measurement devices are needed to e.g. detect the blood pressure of the patient P the monitoring system proposes a way to further use the pressure transducer  7  as the sensor device for a portable measurement device  4  which is to be further connected with the pressure transducer  7 .  FIG. 3  shows schematically a second configuration of the monitoring system wherein the portable measuring device  4  is connected with the pressure transducer  7 . 
     The portable measurement device  4  is provided via a measurement cable with an intermediate connector B further referred to as intermediate plug B. The measurement cable includes as described above excitation lines and signal lines to supply the pressure transducer  7  and to receive the sensor signal from the pressure transducer  7 , respectively. The intermediate plug B is adapted to couple the portable measurement device  4  with the cable connection between the bedside monitor  1  and the pressure transducer  7 . The intermediate plug B is coupled in between the BSM plug C and the transducer plug A. 
       FIG. 4  schematically shows the electrical coupling of the pressure transducer  7  with both the bedside monitor  1  and the portable measurement device  4 . To avoid the case that both the bedside monitor  1  and the portable measurement device  4  provides an excitation voltage for the pressure transducer  7  preferably at least the portable measurement device  4  can include a excitation sensing circuit  16  which detects via the excitation lines whether an excitation voltage is already supplied to the pressure transducer  7  and if an excitation voltage is already supplied to the pressure transducer  7  no excitation voltage is supplied by the portable measurement device  4 . Otherwise the portable measurement device  4  supplies an excitation voltage to the pressure transducer  7  via excitation lines. 
     In general, each of the monitoring devices  1 ,  4  connected to the pressure transducer  7  may be configured to deliver an excitation voltage to the pressure transducer  7  if it is not present. In this configuration all monitoring devices to be coupled to the detector device could be built up equally and the monitoring device which provides the excitation to the detector device is defined on the fly. 
     As mentioned above, the pressure transducer  7  has to function with both configurations either connected to a bedside monitor  1  only or connected simultaneously to the bedside monitor  1  and the portable measuring device  4  in parallel. 
     The connection of the pressure transducer  7  to the bedside monitor  1  may be mandatory. Then, the pressure transducer  7  gets its excitation voltage from the bedside monitor  1 . The portable measurement device  4  detects the excitation voltage and measures the sensor signal. However, the pressure reading on the bedside monitor  1  may under no circumstances be influenced by a parallel connection of the portable measurement device  4 . As the portable measurement device  4  includes an input resistance the sensor signal is influenced by the input resistance of the sensing ports of the portable measurement device  4  if the portable measurement device  4  is connected to the cable connection. By providing the pressure transducer  7  with a Wheatstone bridge the sensitivity with regard to input resistances of portable measurement device  4  and/or the bedside monitor  1  are already substantially decreased. Furthermore, according to the present embodiment the connectors, i.e. the transducer plug A, the BSM plug C and the intermediate plug B of the portable measurement device  4  are provided with a structure which allows the bedside monitor  1  to detect the sensor signal from the pressure transducer  7  under the same conditions either with the portable measurement device  4  connected or not. 
     In  FIG. 5  the terminals of the transducer plug A are schematically shown. The terminals for the provision of the excitation voltages to the pressure transducer  7  are referred to as first and second excitation terminals  20  and  21 ,  25  respectively, the signal terminals for reading the sensor signals from the pressure transducer  7  are indicated as first and second signal terminals  22  and  23 , respectively. The transducer plug A includes a first trimming resistance R 1  and a second trimming resistance R 2 . The first trimming resistant is coupled between the first excitation terminal  20  and a third excitation voltage terminal  24 . The second trimming resistance R 2  is coupled between the first signal terminal  22  and a third signal terminal  25 . The third excitation terminal  24  and the third signal terminal  25  are open that means they are not contacted in a non-contacting condition of the transducer plug A. Furthermore, the second excitation terminal  21  and the third excitation terminal  24  as well as the second signal terminal  23  and the third signal terminal  25  are fully isolated from each other. 
     The first and the second trimming resistances R 1 , R 2  (impedances) have respective values that simulate the resistances (impedances) of the portable measurement device  4  if connected to the BSM plug A. Therefore, the value of the first trimming resistance R 1  is selected to correspond to the internal resistance between the excitation terminal contacts of the portable measurement device  4 . The value of the second trimming resistance R 2  is selected to correspond to the internal input resistance of detection signal contacts of the portable measurement device  4  for receiving the sensor signal. 
     In  FIG. 6  the internal structure of the intermediate plug B is shown. The intermediate plug B provides interconnection wiring  33  for each of the excitation voltages E+, E− and each of the sensor signals S+, S− which are further branched to the portable measurement device  4  such that the portable measurement device  4  can provide an excitation voltage, receive an excitation voltage and may tap the sensor signal from the pressure transducer  7  via the transducer plug A. For coupling with the transducer plug A, the intermediate plug B has first contacts  34  of a first outlet  31 . For coupling with the BSM plug C, the intermediate plug B has second contacts  35  of a second outlet  32 . The first outlet  31  is structurally adapted to be only connectable to the transducer plug A wherein the second outlet  32  of the intermediate plug B is structurally adapted to be only connectable with the BSM plug C. Thereby, faulty interconnections between the devices can be avoided. 
       FIG. 7  illustrates the structure of the BSM plug C. The respective excitation lines E+, E− and sensor signal lines S+, S− connected with the bedside monitor  1  are coupled to respective contacts  41 . 
     The BSM plug C can be connected with the second outlet  32  of the intermediate plug B such that the interconnection wiring are in contact with the respective excitation lines E+, E− and the signal lines S+, S− of the BSM cable. The contacts  41  of the BSM plug C can be provided as long contact pads which are able to simultaneously contact, in a plugged condition with plug A, the second and third excitation terminal  21 ,  24  as well as the second and third signal terminals  23  and  25 ,  15  respectively. 
     As shown in  FIG. 8 , the BSM plug C, the intermediate plug B and the transducer plug A are connected with each other. An electrical interconnection of the excitation lines and signal lines between the transducer plug A and the BSM plug C is provided by the interconnection wiring  33  in the intermediate plug B. Furthermore the intermediate plug B provides the electrical connection of the interconnection wiring  33  with the portable measurement device  4  such that the portable measurement device  4  receives the excitation voltage as well as the sensor signals provided by the pressure transducer  7 . When coupling the first outlet  31  of the intermediate plug B to the transducer plug A the first contacts  34  of the intermediate plug B do only connect the first and second excitation terminals  20 ,  21  and the first and second signal  30  terminals  22 ,  23  of the transducer plug A, respectively. The third excitation terminal  24  and the third signal terminal  25  are not electrically contacted. One reason therefore is that between the first and second excitation terminals  20  and  21  of the transducer plug A a value of the first trimming resistance R 1  is provided as the input resistance of the portable measurement device  4 . Therefore the first trimming resistance R 1  should not be electrically effective within the transducer plug A. The same is for the second trimming resistor R 2  which also is electrically ineffective as the portable measurement device  4  is in electrical connection with the first and second signal terminals  22  and  23 . To summarize, the trimming resistors (impedances) R 1 , R 2  provided within the transducer plug A are made electrically ineffective as they are not necessary to simulate the internal resistances of the portable measurement device  4  as it is already connected. 
     However, as shown in the configuration of  FIG. 9  the BSM plug C is configured to be also connected with the transducer plug A. In such a configuration contacts of the BSM plug C contacts the second excitation voltage terminal  21  and the second signal terminal  23  in the manner described with regard to the connection with the intermediate plug B. However, the BSM plug C further provides an interconnection (shortcut) between the second excitation terminal  21  and the third excitation voltage terminal  24  as well as between the second signal terminal  23  and the third signal terminal  25 . The shortcut make the first and second trimming resistors R 1  and R 2  electrically effective such that between the first and second excitation terminals  20 ,  21  as well as it been the first and second signal terminals  22  and  23  the trimming resistances (impedances) R 1 , R 2  are applied which simulate the state of a connection of the portable measurement device  4  although it is not connected to the monitoring system in this configuration. As there is no portable measurement device  4  connected the trimming resistors R 1 , R 2  are electrically effective. 
     The plugs A, B, C can be provided with terminals and contacts configured as simple contact pads, pins and the like which can be contacted with corresponding terminals and contacts which may be adapted like flexible contact beams, spring-like contacts and the like. 
     In general, features for connectors A, B, and C should fulfill following requirements:
         the transducer connector can be connected either with a first outlet of the intermediate connector B or with an monitoring device connector each for connecting the detector device with a respective monitoring device;   a second outlet of the intermediate connector is only connectable with a monitoring device connector but not with the transducer connector;   in case the transducer connector is directly connected with a monitoring device connector, trimming resistances are made electrically effective and coupled with at least one of excitation terminals and signal terminals of the transducer connector;   in case the intermediate connector is connected with the transducer connector the trimming resistances R 1 , R 2  are not made electrically effective.       

     The embodiments of the present invention provide at least one or more of the following advantages:
         an arterial blood pressure waveform can be measured by two or more monitoring devices in parallel using only one sensor   known disadvantages of curve-damping by using two sensors which would result in a larger dead space within one pressure sensor are ruled out;   the pressure of exactly the same heart level can be recorded by two monitoring devices;   the pressure transducer can be trimmed to correct impedance conditions independently from whether it is connected to the bedside monitor alone or to both the bedside monitor and the portable measurement device in parallel;   the pressure transducer is only provided with one transducer plug which only has one outlet so safety requirements during defibrillation are fulfilled. In other words no open connection exists.       

     The principle of the present invention can be used for any passive analogue sensor like e.g. a thermostat for temperature measurement, a conductivity sensor or an electrical impedance sensor as long the additional measurement device has an adapted interface and its inner resistance (impedance) is known as constant. 
     Further to the embodiment of the monitoring system of  FIGS. 1 and 3  the pressure transducer  7  can also be applied close to the catheter  9 . Moreover, further connectors can be provided within the connection cables of all monitoring devices and the sensor device. 
     In the above-mentioned embodiment preferably both the bedside monitor  1  and the portable measurement device  4  are provided with a source for an excitation voltage. Both devices may be provided with excitation sensing circuits to decouple the excitation voltage if an excitation voltage is already present on the excitation lines in the cable connection between the respective measurement device and the pressure transducer  7 . However, as portable measurement devices usually are battery powered it is preferred that the portable measurement device is the device which decouples the excitation voltage from the transducer in case the bedside monitor  1  may provide the excitation voltage. In other words, it can be provided that the provision of the excitation voltage by the bedside monitor  1  has priority to the provision of the excitation voltage by the portable measurement device  4 . 
     Another embodiment is shown in  FIG. 10 , wherein another structure of a disposable sensor device in a monitoring system is depicted. The monitoring system  50  of  FIG. 10  includes a disposable sensor device  51  having a transducer  52  and a connector  55  having a first connector port to accommodate two first signal terminals  54  and two first supply terminals  53  as known from the embodiments described above. Preferably, the transducer  52  and the connector  55  may be integrally formed, however, they can also be connected together via a suitable cable. The circuitry of the transducer  52  (e.g. Wheatstone Bridge) may be similar or the same as of the above embodiments. Instead of a Wheatstone bridge a simple voltage divider comprising a series connection of two pressure sensors or of one pressure sensor and one or more resistors. A tap between the pressure sensors or between the pressure sensor and the resistors provides a single sensor signal based on the detected pressure. 
     The connector  55  is further provided with a second connector port accommodating second signal terminals  56  and, as an optional feature, second supply terminals  57 , wherein each of the first supply terminals  53  is electrically interconnected with a respective second supply terminal  57  (if existing) and each of the first signal terminals  54  is electrically interconnected with a respective second signal terminal  56 . 
     To the first connector port a first plug  63  may be connected to electrically connect a first monitoring device  60  to the disposable sensor device  51  via the first supply lines  61  and the first signal lines  62 . Normally, the first monitoring device  60  provides an excitation voltage via the first supply lines to the disposable sensor device  51 . The excitation voltage can be set as already explained with respect to the above embodiments. 
     The first monitoring device  60  receives a sensor signal via the first signal lines  62  from the disposable sensor device  51  to detect the quantity to be measured, such as the blood pressure of the patient, as already described above. 
     To the second connector port a second plug  73  may be connected to connect a second monitoring device  70  to the disposable sensor device  51  via the second supply lines  71  and the second signal lines  72 . The second monitoring device  70  preferably merely receives a sensor signal via the second 20 signal lines  62  from the disposable sensor device  51  to detect the quantity to be measured, but without supplying any supply to the disposable pressure device. In that case no supply lines need to be provided between the second plug  73  and the second monitoring device  70 . Thereby, the second monitoring device  70  can be provided without a supply source for driving the sensor device  51  and the design effort for the second monitoring device  70  can be reduced. 
     According to another embodiment, the second monitoring device  70  may be provided with an excitation sensing circuit  74  which can be connected via second supply lines with the second supply terminals in the connector  55  of the disposable sensor device  51 . The excitation sensing circuit  74  is adapted to detect whether or not an excitation is provided from the first monitoring device  60  via the first supply terminals  53  and supplies an excitation voltage by its own in case no excitation voltage can be detected via the second supply lines  71 . 
     In case the transducer merely includes a voltage divider or another circuit instead of a Wheatstone bridge only one or more than two first and second signal lines  62 ,  72  as well as 10 the respective connectors may be provided. 
     REFERENCE NUMERALS 
       1  Bedside monitor 
       2  Arterial pressure module 
       3  Cable 
       4  Portable measurement device 
       5  Tubing 
       6  Pressure transducer cable 
       7  Pressure transducer 
       8  Organizer plate 
       9  Catheter 
       11  Reservoir 
       12  Pressure detecting elements 
       16  Excitation sensing circuit 
       17  Stop cock 
       20  First excitation terminals 
       21  Second excitation terminals 
       22  First detection signal 
       23  Second detection signal 
       24  Third excitation terminals 
       25  Third detection signal 
       31  First outlet 
       32  Second outlet 
       33  Interconnection wiring 
       34  First contacts 
       35  Second contacts 
       41  Contacts 
       51  Disposable sensor device 
       52  Sensor 
       53  First supply terminal 
       54  First signal terminal 
       55  Connector 
       56  Second signal terminal 
       57  Second supply terminal 
       60  First monitoring device 
       61  First supply lines 
       62  First signal lines 
       63  First plug 
       70  Second monitoring device 
       71  First supply lines 
       72  First signal lines 
       73  Second plug 
       74  Excitation detection circuit