Sensor adapter cable

[0001] The present application is a continuation of U.S. application Ser. No. 13/100,287, filed May 3, 2011, titled Sensor Adapter Cable, which claims priority benefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 61/330,586, filed May 3, 2010, titled Sensor Adapter Cable; the above-cited provisional patent application is hereby incorporated by reference herein.

[0002] Pulse oximetry systems for measuring constituents of circulating blood have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care and neonatal units, general wards, home care, physical training, and virtually all types of monitoring scenarios. A pulse oximetry system generally includes an optical sensor applied to a patient, a monitor for processing sensor signals and displaying results and a patient cable electrically interconnecting the sensor and the monitor. The monitor may be specific to pulse oximetry or may be a multi-parameter monitor that has a pulse oximetry plug-in. A pulse oximetry sensor has light emitting diodes (LEDs), typically one emitting a red wavelength and one emitting an infrared (IR) wavelength, and a photodiode detector. The emitters and detector are typically attached to a finger, and the patient cable transmits drive signals to these emitters from the monitor. The emitters respond to the drive signals to transmit light into the fleshy fingertip tissue. The detector generates a signal responsive to the emitted light after attenuation by pulsatile blood flow within the fingertip. The patient cable transmits the detector signal to the monitor, which processes the signal to provide a numerical readout of pulse oximetry parameters such as oxygen saturation (SpO₂) and pulse rate.

[0003] A sensor adapter cable provides medical personnel with the convenience of utilizing otherwise incompatible sensors with multiple SpO₂ monitors or monitor plug-ins. For example, each monitor plug-in may have a keyed connector that mechanically locks-out incompatible sensors. Further, each sensor may have sensor identification (ID) components that can be read by a pulse oximetry monitor or monitor plug-in so as to electrically lock-out incompatible sensors. The sensor adapter cable advantageously allows the interconnection of these otherwise incompatible devices. In an embodiment, a sensor adapter cable allows the use of any of a Masimo sensor with a ProCal ID, a Masimo sensor with an EEPROM ID and a Nellcor/Philips sensor with an R-cal ID with either of a Masimo SET plug-in or a Philips FAST-SpO2 plug-in to a Philips IntelliVue™ monitor, all available from Philips Medical Systems, Andover, Mass.

[0004] A sensor adapter cable has both a mechanical and an electrical interface to a monitor plug-in so as to provide multiple sensor compatibility. In an embodiment, a dual key 8-pin D-shape connector (D8) at one end of an adapter cable provides mechanical compatibility with two-types of plug-in input connectors, as described in U.S. patent application Ser. No. 11/238,634 (Pub No. US2006/0073719 A1) titled Multiple Key Position Plug filed Sep. 29, 2005 and incorporated by reference herein. Further, a family of sensor adapter cables has sensor connector configurations that include MC8, M15 and DB9 connectors, as shown and described below.

[0005] The limited pins available on a D8 connector require sharing of pins to accommodate various sensor ID components. For example, an EEPROM sensor ID and a R-cal resistor sensor ID may need to share the same D8 pin. Such an approach, however, creates the potential for the EEPROM to effect the R-cal measurement in Philips FAST equipped devices and for the R-cal voltage drop to effect the ability of Masimo SET equipped devices to read the EEPROM.

[0006] An 8-pin dual-key cable which is capable of working correctly with any combination of Philips or Masimo SET equipped SpO2 plug-ins requires the connection of the proper ID component(s) to the SpO2 plug-ins while at the same time electrically disconnecting components that are not used or that could potentially interfere with the connected SpO2 technology. Further, this solution cannot impact the ability of each of the SpO2 technologies to operate correctly across its entire range of sensors and accessories.

[0007] One aspect of a sensor adapter cable provides medical personnel with the convenience of utilizing otherwise incompatible optical sensors with multiple blood parameter plug-ins to a physiological monitor. The plug-ins each have keyed connectors that mechanically lock-out incompatible sensors in addition to readers that poll sensor identification components in each sensor so as to electrically lock-out incompatible sensors. The sensor adapter cable has a sensor connector, a plug-in connector, an interconnection cable and a pod. The sensor connector mechanically connects to a predetermined sensor and electrically communicates with sensor electrical elements within the predetermined sensor. The plug-in connector mechanically connects to a predetermined plug-in and electrically communicates with lug-in electrical elements within the predetermined plug-in. An interconnection cable mechanically attaches between and provides electrical communications between the sensor connector and the plug-in connector. A pod is incorporated within the interconnecting cable that electrically interfaces the sensor connector to the plug-in connector.

[0008] In various embodiments, the pod has a cut in the interconnection cable that exposes cable wire ends. A circuit board is spliced to the cable wires end. A pre-mold encapsulates the cut, the circuit board, and the cable wire end, and an over-mold envelopes the pre-mode so as to define the pod. The circuit board comprises a first switch that, when closed, connects a resistor ID on the circuit board to the plug-in connector so as to enable a first plug-in attached to the plug-in connector to communicate with a sensor attached to the sensor connector. The circuit board also comprises a second switch that, when closed, connects an EEPROM ID on the circuit board to the plug-in connector so as to enable a second plug-in attached to the plug-in connector to communicate with a sensor attached to the sensor connector. The sensor adapter cable disconnects the resistor ID and the EEPROM ID when the first switch and the second switch are both open. The first switch may incorporate an n-channel MOSFET that turns on in response to a positive control signal from the first plug-in so as to switch in the resistor ID. The second switch may incorporate a p-channel MOSFET that turns on in response to a negative control signal from the second plug-in so as to switch in the EEPROM ID.

[0009] Another aspect of a sensor adapter cable is a method of interfacing any of multiple physiological monitor plug-ins to any of multiple optical sensors. An interface cable has a sensor connector on a first end and a plug-in connector on a second end. Resistive and memory IDs are incorporated within the cable. A sensor ID read signal is asserted at the plug-in connector. A particular one of the IDs is presented to the plug-in connector in response to the read signal. In various embodiments, unselected IDs are isolated from the plug-in connector and the selected ID. Switches are integrated with the IDs and are responsive to the read signal so as to connect the selected ID and disconnect the remaining IDs. A first switch is closed and a second switch is opened so as to select either a resistive ID or a memory ID. Both the first switch and the second switch are opened so that the sensor adapter cable functions as a patient cable. A circuit board with the switches and IDs is spliced between a portion of the interface cable conductors. The circuit board is encapsulated into a calibration pod portion of the interface cable.

[0010] A further aspect of a sensor adapter cable is a plug-in connector means for connecting to a plug-in module for a physiological monitor. A sensor connector means connects to an optical sensor. An interface cable mechanically and electrically interconnects the plug-in connector means and the sensor connector means. A pod means is integrated with the interface cable for allowing sensors to connected to and be recognized by the plug-in module. In various embodiments, the pod means comprises a circuit board means for splicing sensor IDs into the interface cable. A switching means selectively activates and isolates the sensor IDs so that only a single sensor ID is presented to the plug-in connector. A control means is in communications with the plug-in connector means for making the switching means responsive to a ID read signal from the plug-in module. The pod means further comprises an encapsulation means for enclosing the circuit board means within the pod means, where an encapsulations means embodiment comprises a premold of at least one of an epoxy, HDPE and PVC and an overmold of medical grade PVC.

[0024] FIG. 1 illustrates a physiological parameter monitoring system 100 that incorporates a sensor adapter cable 120 or a family of sensor adapter cables so as to interconnect various sensors 110 with parameter processing plug-ins 130 to a physiological monitor 140. The sensors 110 include various types and configurations of optical devices as described above. Sensors typically have ID components that identify the sensor to a plug-in 130 so as to insure compatibility. Examples of ID components include an active component ID 114, such as a memory, or a passive component ID 112, such as one or more resistors having a specified range of values. In a particular embodiment, an active component ID 114 includes an EEPROM and a passive component ID 112 includes a ProCal resistor (Masimo) or an R-cal resistor (Philips/Nellcor).

[0025] Also shown in FIG. 1, a sensor adapter cable 120 has a sensor connector 122, a plug-in connector 124, a pod 900 and an interconnecting cable 128. The sensor connector 122 mechanically and electrically interfaces to one or more sensors 112, 114. The plug-in connector 124 interfaces to one or more plug-ins 130. The plug-ins 130, in turn, mechanically and electrically connect with a physiological monitor 140. The sensors 110 provide sensor signals to the plug-ins, which are used to calculate oxygen saturation (SpO2) and pulse rate among other parameters. The monitor 140 controls the plug-in operating modes and displays the parameter calculations accordingly. In an embodiment, the plug-ins are any of Masimo® SET® modules (Masimo Corporation, Irvine, Calif.) or Philips FAST-SpO2 modules, all available from Philips Medical Systems, Andover, Mass. In an embodiment, the physiological monitor is any of various IntelliVue™ monitors also available from Philips. The sensor connector and/or the plug-in connector can be any of various D8, M15, MC8 and DB9 connectors to name a few.

[0026] FIGS. 2A-B illustrate a sensor adapter cable embodiment 200 employing a M15 sensor connector 210 and a D8 plug-in connector 10. A cable 20 interconnects the sensor connector 210 and the plug-in connector 10. A pod 900 integrated with the cable 20 contains a sensor adapter circuit 400 (FIG. 4) that insures electrical compatibility between a passive and an active ID 110 (FIG. 1) and a particular plug-in 130 (FIG. 1).

[0027] FIGS. 3A-C further illustrate a sensor adapter cable embodiment 200, showing the respective pinouts of the M15 connector 210 and the D8 connector 10. Also shown are the corresponding cable 20 color-coded wires, inner shield and outer shield. Further shown is a sensor adapter circuit 400 and its connections relative to the connectors 10, 210 and cable 20 wires.

[0028] FIG. 4 illustrates the sensor adapter circuit 400 having plug-in connections 410 and sensor connections 420. The plug-in connections 410 (J1, J2, J3) connect to the plug-in connector 10 (FIGS. 2-3, 5-6, 7-8). The sensor connections 420 (J4, J5) connect to the sensor connector 210 (FIGS. 2-3); 510 (FIG. 5-6) or 710 (FIGS. 7-8). Table 1 below defines the signal names and associated connections to the plug-in connector pins.

[0029]

TABLE 1
Adapter Circuit and Plug-in Connector Pinouts
		Reference	Plug-in
	Signal Name	Designation	Connector Pin #
	R-TYPE/EEPROM	J2	3
	RCAL/CONTROL	J1	4
	OUTER SHIELD	J3	7

[0030] The switch components 430, 440 used in this design (Si2312 and Si2351 or equivalents) are high impedance MOSFET devices that have no impact on R-cal and R-TYPE resistor measurements due to the fact that the MOSFET gates do not require current to activate. When the cable is connected to a Philips FAST equipped device, the RCAL/CONTROL signal will be a positive voltage. The RCAL/CONTROL voltage is 2.9V without a sensor connected and can be as low as 1.1V with the minimum value RCAL resistor of 6.04KΩ. This is understood to represent the entire range for the RCAL/CONTROL voltage. When the cable is connected to a Masimo XCal capable SpO2 module, a negative voltage will be applied to RCAL/CONTROL signal. This will turn on Q2 and turn off Q1 which will allow the Masimo system to read the EEPROM contents. Table 2, below, describes how the switches (Q1, Q2) operate.

[0031]

TABLE 2
Adapter Circuit Switch Truth Table
	RCAL/
SpO2	Control	Switch	Switch
Module	Signal	Q1	Q2	Comments
Philips	Positive	Closed	Open	Philips FAST
FAST	voltage			module can
				measure RCAL and
				R-TYPE resistors
Masimo	Open (No	Open	Open	Same as patient
ProCal	driving	(Don't	(Don't	cable
Technology	voltage)	care)	care)
Masimo	Negative	Open	Closed	Masimo board will
XCal	voltage			read EEPROM;
Technology				negative voltage
				will be supplied
				by the Masimo board

[0032] The n-channel transistor (Q1) 430 was chosen with a very low turn-on threshold (0.85V max) so that it is guaranteed to turn on and switch in the R-TYPE resistor even at the lowest RCAL/CONTROL voltage of 1.1V. The on-resistance of the FET is so low (less than 100 mΩ) that it will not affect the measured R-TYPE resistor value. At the same time, the p-channel FET (Q2) 440 will be turned off since the gate-to-source voltage (Vgs) will be positive. Even in the worst possible case, the Vgs will be −0.3V which is not low enough to turn-on the p-channel device. The minimum turn-on threshold for the p-channel is −0.6V. The purpose of resistors R1 and R2 and ESD protection diodes D1 and D2 are to protect the MOSFET devices. This sensor adapter embodiment ensures proper operation and ample margin in all possible combinations of sensor and device types and therefore meets the design requirements necessary to allow Masimo SET or Philips FAST systems to work correctly with a dual key D8 connector capable of plugging into either type of system.

[0033] FIGS. 5A-B illustrate a sensor adapter cable embodiment 500 employing a MC8 sensor connector 510 and a D8 plug-in connector 10. A cable 20 interconnects the sensor connector 510 and the plug-in connector 10. A pod 900 integrated with the cable 20 contains a sensor adapter circuit 400 (FIG. 4) that insures electrical compatibility between a passive and an active ID 110 (FIG. 1) and a particular plug-in 130 (FIG. 1).

[0034] FIGS. 6A-C further illustrate a sensor adapter cable embodiment 500, showing the respective pinouts of the MC8 connector 510 and the D8 connector 10. Also shown are the corresponding cable 20 color-coded wires, inner shield and outer shield. Further shown are the sensor adapter circuit 400 connections relative to the connectors 10, 510 and cable 20 wires.

[0035] FIGS. 7A-B illustrate a sensor adapter cable embodiment 700 employing a DB9 sensor connector 710 and a D8 plug-in connector 10. A cable 20 interconnects the sensor connector 710 and the plug-in connector 10. A pod 900 integrated with the cable 20 contains a sensor adapter circuit 400 (FIG. 4) that insures electrical compatibility between a passive and an active ID 110 (FIG. 1) and a particular plug-in 130 (FIG. 1).

[0036] FIGS. 8A-C further illustrate a sensor adapter cable embodiment 700, showing the respective pinouts of the DB9 connector 710 and the D8 connector 10. Also shown are the corresponding cable 20 color-coded wires, inner shield and outer shield. Further shown are the sensor adapter circuit 400 connections relative to the connectors 10, 710 and cable 20 wires.

[0037] FIGS. 9A-B illustrate a pod 900 that splices the sensor adapter circuit 400 (FIG. 4) into the sensor adapter cable 20. The pod 900 has a overmold 910, a premold 920, a copper foil shield 930, a circuit board 940 and heat-shrink tubing 950. The circuit board 940 provides the sensor adapter circuit 400 (FIG. 4) described above. The board 940 is mounted to the cable 20 and electrically interconnected to the cable wires and outer shield, as described with respect to FIG. 4, above. The premold 920 is manufactured to envelop the circuit board 940 and spliced cable portion. The copper foil shield 930, if used, envelops the premold 920, and the overmold 910 envelops all of the pod 900 components.

[0038] FIGS. 10A-D illustrate attachment of the circuit board 940 to the adapter cable 20. Shown is cable preparation (FIG. 10D) for splicing with the circuit board 940 (FIG. 100). Also shown are preparation of the cable wires (FIG. 10B) and mounting of the circuit board 940 to the cable wires. FIGS. 11A-C further illustrates the assembled pod 900.

[0039] A sensor adapter cable has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to be construed as limiting the scope of this disclosure. One of ordinary skill in the art will appreciate many variations and modifications.