Abstract:
Patient monitoring apparatus for use in an environment which includes a plurality of sensors. The apparatus provides collection and display of patient data signals collected from a medical patient using the sensors, including periods when the patient is being transported. The apparatus comprises a portable monitor coupled to a plurality of distinct data acquisition modules, which are coupled to the sensors. The modules includes cartridges, which detachably mount to the portable monitor, and pods which are positioned independent of the monitor. The pods reduce the number of cables extending between the patient&#39;s bed and the portable monitor by combining signals from many sensors into a single output signal. The modules collect patient data in analog form from the sensors and provide digital data signals to the monitor. The portable monitor includes: a display device for displaying the patient data, and storage for the patient data. The portable monitor may be coupled to a docking station. The portable monitor receives power from the docking station, and transfers data to a remote display device by way of the docking station. Patient data is displayed on either one of the portable monitor or the remote display device. A battery pack and a hardcopy output device attach to the case of the portable monitor.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of Ser. No. 07/989,415 filed Dec. 11, 1992 now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to medical systems and in particular to patient monitoring systems for collecting, storing and displaying medical data. 
     BACKGROUND OF THE INVENTION 
     In hospitals and other health care environments, it is often necessary to continually collect and analyze a variety of medical data from a patient. These data may include electrocardiogram signals, body temperature, blood pressure, respiration, pulse and other parameters. 
     Monitoring systems in the related art have typically fallen into one of two general categories: multi-function monitoring, recording and displaying systems which process and collect all of the data desired, but are bulky and difficult to transport; and small, portable systems which are easy to transport, but process and collect fewer types of data and have limited storage capability. Initially (e.g., in an ambulance or an emergency room) a patient is connected to a simple, portable monitor to observe a limited number of medical attributes, such as EKG or non-invasive blood pressure. As the patient moves to higher care facilities (e.g., an intensive care unit or operating room) it is desirable to augment these simple monitors to observe additional parameters. Generally, this is accomplished by disconnecting the patient from the simple monitor and connecting the patient to a monitoring system having more robust capabilities. 
     The need for continuity of data collection and display is most pressing in emergency situations. Hospital personnel want to monitor additional parameters, change the selection of parameters viewed, or retrieve additional data from the patient&#39;s history. At the same time, the patient may have to move to a different care unit. During an emergency, the speed at which a patient is transferred from a bed to an operating room or intensive care unit may substantially impact the patient&#39;s chance of survival. Hospital personnel need to be able to quickly add functionality and go. 
     Two major considerations in the design of monitoring systems have been ease and speed of system reconfiguration. It is particularly undesirable to connect sensors to a patient or disconnect them immediately prior to transportation or administration of critical procedures. U.S. Pat. Nos. 4,715,385 and 4,895,385 to Cudahy et al. discuss a monitoring system which includes a fixed location display unit and a portable display unit. A digital acquisition and processing module (DAPM) receives data from sensors attached to the patient and provides the data to either or both of the fixed and portable display units. Normally, the DAPM is inserted into a bedside display unit located near the patient&#39;s bed. When it is necessary to reconfigure the system for transporting the patient, the DAPM is connected to the portable display and then disconnected from the bedside display. The DAPM remains attached to the patient during this reconfiguration step and during patient transport, eliminating the need to reconnect the patient to intrusive devices. Once the DAPM is disconnected from the bedside display, a transportable monitoring system is formed, comprising the portable display and DAPM. 
     Besides the time delays which may be encountered when adding sensors to the monitor configuration, systems in the prior art also leave much to be desired with respect to cable management. A large number of cables extend between the patient and the monitor. In the past, there has been at least one cable added for each parameter monitored. For example, there may be five cables for EKG, two for cardiac output, two for temperature, plus four hoses for measuring blood pressure using invasive sensors. This array of cables and hoses interferes with the movement of personnel around the patient&#39;s bed. The greater the number of cables and hoses, the greater the risk that someone will accidentally disrupt one of them. This has been a common problem in previous systems from several vendors. 
     Furthermore, the digital acquisition and processing module of the Cudahy et al. system has a fixed parameter configuration, and if the parameter requirements change due to a change in condition of the patient, the digital acquisition and processing module must be disconnected and a different module including the new parameters which are required to be monitored must be connected. This process is not only time consuming, due to the reconnection of the sensors and cables between the patient and the module, but also destructive of data since patient data acquired in the first processing module is lost when it is disconnected and is not transferred to the subsequent processing module. Furthermore, the processing module of Cudahy et al. is extremely bulky and difficult to position near a patient. In order to use the fixed display to observe data from the DAPM, the DAPM must be inserted into the fixed display. And furthermore, the processing module of Cudahy et al. requires extensive cabling to the different patient sensors, which further adds to the complexity and setup time of the system. 
     Additional simplification of the steps performed to reconfigure the system is also desirable in order to reduce the time to prepare the patient and monitoring system for transportation to an operating room or intensive care unit. 
     SUMMARY OF THE INVENTION 
     The present invention is embodied in patient monitoring apparatus for display on a display device of patient data. The apparatus is adapted for use in a system which includes a plurality of sensors. The patient data are collected from a medical patient using the plurality of sensors. 
     The apparatus includes a data acquisition cartridge which selectively communicates with the plurality of sensors. The data acquisition cartridge collects patient data from a selected sensor and transmits conditioned data signals produced from the patient data to a portable monitor. 
     The apparatus also includes an independently positionable, self contained data acquisition pod. The data acquisition pod selectively communicates with the plurality of sensors. The data acquisition pod is adapted to collect further patient data from a further selected sensor. The data acquisition pod transmits the further conditioned data signals produced from the patient data to the portable monitor. 
     The portable monitor detachably couples to the data acquisition cartridge and the data acquisition pod. The portable monitor receives and stores the conditioned data and the further conditioned data. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  is a block diagram of an exemplary patient monitoring system in accordance with the invention. 
     FIG. 1 b  is an isometric view of the patient monitoring system shown in FIG. 1 a.    
     FIG. 2 is a block diagram of a printed circuit board within the patient monitoring system shown in FIG. 1 a.    
     FIG. 3 is a block diagram of a printed circuit board within the patient monitoring system shown in FIG. 1 a.    
     FIG. 4 is a block diagram of a data acquisition pod shown in FIG. 1 a.    
     FIG. 5 is an isometric view of a cartridge shown in FIG. 1 a.    
     FIG. 6 is an isometric view of the docking station shown in FIG. 1 a.    
     FIG. 7 is a flow diagram of the memory update process used in the system shown in FIG. 1 a.    
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENT 
     Overview 
     An exemplary portable monitor assembly  100  in accordance with the present invention is shown in FIG. 1 a . A portable monitor  102  is detachably coupled to and acquires physiological data signals from a plurality of data acquisition modules. The data acquisition modules include data acquisition pods  150 ,  152 ,  154 ,  155 ,  156  and  158  and data acquisition cartridges  160  and  162 . The pod basically combines the patient data into a single output signal, whereas the cartridges combine patient data and may also include signal processing and sensor support devices. The pods  150 - 158  are advantageously small, and may be placed in a variety of locations, providing a high degree of flexibility to medical personnel. The pods  150 - 158  provide cable management capability because each pod is connected to monitor  102  by, at most, one cable, regardless of how many sensors are coupled to the pod. The pods  150 - 158  and cartridges  160  and  162  may be attached to both invasive and non-invasive sensors (not shown) for collecting physiological data from a patient. As used herein, the detachable coupling of the data acquisition modules, and in particular for pods  150 - 156 , is intended to include any manner of communicating the acquired data signals to monitor  102 , such as a wireless communication link. 
     Many prior art systems required insertion of the cartridges (modules) into a bulky box or into a display. The data acquisition pods in the present invention are standalone (self-contained) devices. In addition, they connect directly to the case  103  of the portable monitor  102 . There is no need to insert the pods into a bulky box, or into a display unit, to display data. As a result the monitor-pod configuration need not be changed to transport the patient. No additional connections need be established between the monitor and the pods, and no connections need be detached. 
     Pods  150 - 158  and cartridges  160  and  162  may be connected to portable monitor  102  independently of one another. To add function to the monitoring system for a higher level of care, an additional pod  150 - 158  or cartridge  160  or  162  may be added without affecting any other modules that are already coupled to monitor  102 . There is no need to reconfigure the entire system to add a module. 
     Pods  150 - 158  are independently positionable, both from one another, and from monitor  102 . In accordance with the present invention, pods  150 - 158  may be placed in any convenient location close to the patient. Each pod may be placed at a different location if desired, to minimize the lengths of the cables and hoses connecting the patient to the respective pods. Alternatively, the pods may be collocated, so that all of the cables and hoses are confined to a single region. Either method enhances cable management. 
     The portable monitor  102  displays the physiological data and includes means for detachably mounting data acquisition cartridges, which may include a Non-Invasive Blood Pressure (NIBP) cartridge  160  and/or an end-tidal cartridge  162  (for measuring airway carbon dioxide). A three channel recorder  164 , and a battery pack  166  may also be detachably connected to portable monitor  102 . Each device  160 - 166  is configured to provide both electrical and mechanical couplings when the device is mounted on the monitor  102 . Each cartridge  160  and  162  and recorder  166  provide their own return circuits with 5000 volts isolation from the portable monitor ground, to prevent current flow from the patient to earth ground by way of the cartridge and monitor  102 . The portable monitor  102  has a user-accessible slot for one random access memory card (or RAM card)  106  which allows easy removal and storage of patient data, such as demographic and physiological trend data. The memory card may also be used to transfer replacement software instructions to the portable monitor. 
     Each pod  150 - 158  receives analog data signals from a plurality of sensors, and combines the data from the plurality of sensors into a combined analog data signal. The combined analog data signal is then converted to a digital output channel which is coupled to portable monitor  102 . By channeling patient data signals from many sensors into a single cable for transfer to monitor  102 , the desired cable management is achieved. For example, if pod  150  is located at or on the bed, the number of cables between the bed and monitor  102  is reduced from eight to one. 
     A base EKG pod  150  provides connections for a five electrode (7 lead) EKG, one connection for a pulse oximetry (SpO 2 ) sensor, and two multifunction receptacles for measuring temperature, impedance respiration and/or cardiac output. 
     In the exemplary embodiment, two special purpose pods are available as alternatives to pod  150 . A diagnostic pod  156  accepts data from the same sensors as base pod  150 , and also has five extra leads which may be used for EEG or for a 12 lead EKG. A neonatal pod  158  has input terminals for the same types of data as diagnostic pod  156 , plus an additional terminal for a transcutaneous oxygen or carbon dioxide sensor. Pod  152  includes channels for mounting four pressure transducers and two additional temperature sensors. Alternatively, Pod  154  may be used to collect data from two pressure transducers. Catheter Pod  155  provides oximetry data (SvO 2 ). Further pods performing different functions may optionally be added and would be understood by those skilled in the art. 
     In accordance with one aspect of the invention, portable monitor  102  is detachably coupled to a docking station  110  which may be positioned near the patient&#39;s bed (e.g., on the bed, a bed rail, a wall, an intravenous pole or a shelf). In accordance with another aspect of the invention, portable monitor  102  and docking station  110  provide complementary services. Monitoring devices which attach to the patient&#39;s body or are transported with the patient are coupled to the portable monitor  102 ; whereas devices and services which are fixed in the room or are to be made continuously available in the room are coupled to the docking station. 
     The docking station  110  provides portable monitor  102  with a full suite of power and communications services. These services allow portable monitor  102  to perform functions previously performed primarily through the use of large, fixed monitoring systems. At the same time, the simple connection between the docking station  110  and monitor  102  allows rapid disconnection of monitor  102  for transporting the patient. The user merely picks up monitor  102  from docking station  110  to prepare monitor  102  for transport. Docking station  110  recharges the battery of monitor  102  while the monitor is in the docking station, so that in most instances, it is not even necessary to install a battery pack to transport the patient. 
     Docking station  110  provides mechanical support for mounting the portable monitor  102 , as well as electrical couplings to a remote display device  120  (typically a bedside display), power  114 , large display  122 , and television display  124 . Remote display device  120  may be a fully functioning monitor including processing and display functions, or just a slave display receiving signals from the docking station for display. Docking Station  110  can also communicate with several local area networks (LANs). Docking station  110  provides a simple mechanism to connect portable monitor  102  with several devices and networks without the need to connect individual cables. Data and power connectors on docking station  110  and on the case  103  of portable monitor  102  allow physical and electrical connections to be established concurrently. Although docking station  110  may be coupled to networks and remote stations outside of the patient&#39;s room, docking station need not mount on the wall to connect to these networks and stations. Docking station  110  may be connected to a wallbox  140  to provide the additional communications links. 
     Although the portable monitor  102  as described in the exemplary embodiment performs the functions of a multi-function bedside monitor when attached to docking station  110 , it may be desirable to use the portable monitor  102  in conjunction with an additional remote display  120 . For example, in the operating room, the remote display  120  may be a slave display so as to provide a larger or more easily readable display. The remote display  120  may be a conventional, fully functioning bedside patient monitoring unit which receives, stores, displays and transmits medical data. Alternately, the remote display  120  may be an intelligent workstation with a VGA display and conventional disk storage. The portable monitor  102  also includes a port  127  for optionally connecting the portable monitor directly to a remote display  120  when the portable monitor is not in docking station  110 . 
     Upon establishment of a connection between portable monitor  102  and docking station  110 , assembly  102  determines whether the most recent physiological data for the patient is stored in the assembly or in a remote display  120  coupled to docking station  110 . The more recent data are then copied to the device (display monitor  102  or remote display  120 ) having the less recent data (assuming that the remote display  120  has processing capability). A conventional memory card  106  (shown in FIG.  2 ), is used to transfer data between the portable monitor  102  and the remote display  120 . It is understood by those skilled in the art that, as an alternative to using a memory card for data transfers, the data may be directly transferred by a communications link. 
     Once the portable monitor  102  is coupled to the remote display  120 , and the data in the two monitors are synchronized by the memory card  106  transfer discussed above, all patient data received by the portable monitor  102  are transferred to the remote display  120 . In this manner, patient data are stored redundantly in remote display  120  and portable monitor  102 . The patient can be switched from one portable monitor  102  to another  102 ′ (not shown) by transferring the memory card to the second portable monitor  102 ′, and from one remote display  120  to another  120 ′ (not shown) without any loss of data, or any break in the continuity of the data. 
     According to another aspect of the invention, display setup data are stored in portable monitor  102 . The setup data are used to define which waveforms and which parameters appear in the available screen areas. Unlike the systems in the prior art, the setup data in monitor  102  are independent of which sensors are furnishing data, or which display is used (Whereas in the prior art, the setup data were typically stored in the display and were entered by the user each time a new display was attached to the monitor). The setup data are applied when the display is coupled to monitor  102  and turned on. If the display is configured to display the waveform being monitored, portable monitor  102  places the data in the appropriate areas of the display. If the display is not configured to display the waveform, then it is not displayed until the user selects the waveform on the display. 
     FIG. 1 b  shows the physical configuration of the monitor assembly  100  of FIG. 1 a . Porizable monitor  102  is mounted on docking station  110 , providing physical support, power, and communications. Monitor  102  acquires physiological data signals from data acquisition pods  150  for EKG data and  152  for pressure data. The non-invasive blood pressure cartridge  160 , the end tidal CO 2  cartridge  162 , a hardcopy output device such as recorder  164  and the battery back  166  are individually attached to portable monitor  102  for purposes of illustration. 
     DETAILED DESCRIPTION 
     Portable Monitor 
     As shown in FIGS. 1 a  and  1   b , portable monitor  102  is the core of a modular patient monitoring system  100 . Portable monitor  102  includes an integrated liquid crystal display (LCD)  104 . Peripheral devices may be coupled to the portable monitor  102 , including input devices (e.g., pods  150 ,  152 ,  154 ,  155 ,  156 ,  158  and cartridges  160  and  162 ) and output devices (e.g., recorder  164  and cathode ray tube (CRT) display  120  and LCD  122 ). A possible minimum configuration of the exemplary embodiment includes portable monitor  102 , an EKG pod ( 150 ,  156  or  158 ) and the battery pack  166 . Additional pods ( 152 ,  154  and/or  155 ) and cartridges ( 160 ,  162 ) may be substituted or added, depending on the types of trend data desired for each specific patient. Portable monitor  102  may be directly connected to additional external displays  120  and  122  through analog output ports  172 . Alternatively, portable monitor  102  may be detachably mounted on a docking station, such as docking station  110 , which can provide couplings to both power and communications networks. Portable monitor  102  receives power from docking station  110  through a connector  125 . 
     FIG. 2 is a block diagram showing the interaction of the components of portable monitor  102 . Portable monitor  102  includes two printed circuit boards (PCBs): a processor PCB  200  and a peripheral PCB  220 . Processor PCB  200  provides processing and storage resources for algorithm computation and for controlling system operations. In conjunction with peripheral printed circuit board (PCB)  220 , Processor PCOB  200  controls the acquisition of data from the pods and cartridges, the processing of patient data, display of parameters and waveforms, alarms and Ethernet™ and multi-vendor connectivity. 
     Processor  202  may be a Motorola 68EC040 or comparable processor. It controls the operation of portable monitor  102  and performs the non-numerically intensive arithmetic computations. Some numerically intensive computations are performed by components on peripheral PCB  220 , and are discussed below. A 32 bit processor bus, which may be Multibus II, provides the processor  202  access to the other devices on the processor PCB  200 . 
     Three memory systems are located on the processor PCB  200 . A boot erasable programmable read only memory (EPROM)  230  provides the initial program startup, system console support, and the method to erase and download software into the flash EPROM (FPROM)  232 . The EPROM may include 27C1024, 27C2048 or 27C4096 devices, which allow two wait state operation for the processor  202 . The EPROM has a total memory size of 256 KB to 1 MB, with 32 bit access. 
     Flash EPROM  232  contains the executable code. Flash EPROM  232  is programmed on processor PCB  200  under the control of processor  202 . Flash EPROM  232  may include AMD/NEC 28F020 or 28F040 devices, which allow two wait state operation. Flash EPROM has a total memory size of 2 to 4 MB of memory, with 32 bit access. Flash EPROM  232  supports a line burst fill mode of operation. 
     A dynamic random access memory (DRAM)  208  provides program data space. The system may also be set to a development mode, in which executable code is placed in DRAM  208 . DRAM  208  may include NEC D424190 or HM514280 devices, which allow 2 wait state operation. The DRAM  208  has a total memory size of 1 MB of memory. The memory is organized as 32 data bits and 4 parity bits. 
     Processor PCB  200  includes support circuitry  203  for processor  202 . Circuitry  203  includes: DRAM parity generation and checking  236 ; two interval timers  240  and  242 ; a watchdog timer  238 , an interrupt handler  244 , a serial diagnostic port  234 , memory mode selection  248 , bus error time-out  246  and PC memory common interface adaptor control  247 . In the exemplary embodiment, support circuitry  203  is implemented in application specific integrated circuits (ASIC). 
     Parity circuit  236  generates odd parity on memory writes and checks for errors on memory reads. If an error is detected, a parity error flag is set on a byte basis. 
     Two interval timers  240  and  242  are provided for time measurement. The first timer  240  has a range of 0.1 to 12.7 milliseconds (msec). The second timer  242  has a range of 1 to 127 msec. The user selects the interval for each timer. If either timer is enabled and counts to the specified interval, an interrupt flag is set. 
     Watchdog timer  238  allows selection of a timeout interval between 0.01 and 1.27 seconds. The user selects the interval. During system startup, watchdog timer  238  is disabled. If timer  238  is enabled and counts to the specified value during execution of any process, an interrupt flag is set. If the interrupt is not serviced within predetermined interval, a processor reset is generated. 
     Interrupt handler  244  prioritizes the various interrupt sources into seven levels for the processor. The interrupts may be generated by watchdog timer  238 , parity checker  236 , timer  240 , peripheral PCB  220 , timer  242 , graphics controller  254 , or diagnostic port  234 . 
     Diagnostic serial port  234  provides a receive and transmit communications channel at 1.2, 9.6, or 19.2 Kbits per second, with 8 data bits, no parity, and 1 stop bit. The choice of the data rate is determined by a programmable parameter value. Data transfers are supported by polled status and interrupt control. Internal loopback may be programmed. 
     Memory mode selection  248  controls the allocation of normal program execution space to the three physical memory devices: boot EPROM  230 , flash PROM  232  and DRAM  208 . During system startup, the execution space is allocated on boot EPROM  230 . 
     The bus error time-out function  246  activates a 10 microsecond timer when a bus cycle starts. The bus error is activated if a data acknowledge signal is not received within the 10 microsecond time period. 
     Bus master circuit  206  on processor PCB  200  maps a 16 Mbyte peripheral space into the address space of CPU  202 . In the exemplary embodiment, CPU  202  has a 32 bit data bus  212  and peripheral bus  328  (as shown in FIG. 3) includes a 16 bit data bus. In order to accommodate the different bus data paths, bus master  206  includes a circuit to split each 32 bit word received from CPU  202  into two 16 bit words which peripheral bus  328  can accept. Each pair of 16 bit words is transmitted over two peripheral bus cycles. 
     A conventional random access memory card  106  is used for information storage and transfer. The memory card interface is controlled by the PC memory common interface adaptor control function  247  of ASIC  203 . Memory card  106  is a credit card sized encapsulated circuit board containing static RAM and a small battery. The information stored in the memory card  106  includes setup data (e.g., alarm limits), patient specific demographic and physiological trend data, and software. 
     Typically, memory card  106  will be used when transferring patient data between two different portable monitors  102 . Such transfers typically occur when a patient moves from one care unit (e.g., intensive care unit, operating room, or recovery room) to another. When used for storing software, memory card  106  provides a convenient mechanism for downloading software upgrades to portable monitor  102 , which are then stored in a flash EPROM  232 , shown in FIG.  3 . When used for these purposes, memory card  106  may be removed from portable monitor  102 , except when in use for data or software transfers. 
     Another possible use of memory card  106  may be to associate a respective card with each patient from admission to checkout, providing rapid access to the patient&#39;s history at any time during his or her stay in the hospital. When used for this purpose, memory card  106  may remain in portable monitor  102  at all times between patient admission and discharge, except when the card is transferred between two portable monitors. All patient trend data would be stored, in a particular memory card and continuously upgraded at appropriate intervals. 
     Still another use for the memory card is for software maintenance and upgrades. A new (second) set of instructions may be downloaded to the Flash EPROM  232  from the memory card  106  to replace the existing (first) set of instructions. 
     FIG. 3 is a block diagram of peripheral PCB  220  shown in FIG.  2 . Peripheral PCB  220  manages the interfaces between portable monitor  102  and all external devices and networks to which it may be connected. Peripheral PCB  220  is coupled to a port  327  of processor PCB  200 . A peripheral bus  328 , which may use conventional Intel Multibus format, couples processor  202  and the devices on the peripheral PCB  220 . Peripheral bus  328  includes a 16-bit data path and a 24-bit address space, and has a bandwidth of at least 8 Mbytes/second. 
     Multiple bus masters can access peripheral bus  328 , under the control of an arbiter  361 , described below. The bus masters include: host bus master  206  for processor  202 ; two digital signal processors (DSPs)  330   a  and  330   b  for preprocessing the data acquisition samples; a carrier sense multiple access/collision detection (CSMA/CD) controller direct memory access (DMA) channel  362 ; two DMA channels  344   a  and  344   b  for transmitting commands to pods  150 - 158  and cartridges  160 ,  162  and for receiving sample data from the pods and cartridges; and a DMA channel for transmitting data to thermal recorder  164 . When one of these bus masters (which may be either  206 ,  334 ,  362 ,  344   a ,  344   b  or  358 ) uses bus  328 , processor  202  gives permission and releases control of address, data and strobe lines (not shown) in the bus  328 . The bus master  206 ,  334 ,  344   a ,  344   b ,  358  or  362  then places memory addresses on bus  328 , directing DMA data transfers to send or receive data. 
     The DSP DMA control is implemented in a bus master application specific integrated circuit (ASIC)  334 . Bus master circuit  334  connected to the DSPs  330   a  and  330   b  allows the DSPs to access the entire memory space  322  via peripheral bus  328 . DSPs  330   a  and  330   b  access bus  328  by an indirect method. The DSP first writes to an address register  334   a  in bus master  334 . This address points to the desired address on peripheral bus  328 . After loading the address, the DSP may write to locations on bus  328 . After each word is written, the lower sixteen address lines (not shown) will automatically increment, allowing efficient moves of block data. 
     Bus Master  334  may also operate in slave mode, allowing the CPU  202  to arbitrate DSPs&#39;  330   a  and  330   b  communications with peripheral bus  328 . In this mode, CPU  202  can write directly into the DSPs&#39; static random access memories (SRAM)  332   a  and  332   b . This capability is used during initial download of the DSP code from CPU flash programmable read only memory (FPROM)  232  as shown in FIG.  2 . CPU  202  may also use this capability to deposit variables to and retrieve variables from DSPs  330   a  and  330   b . All other bus masters (DMA channels  344   a ,  344   b ,  358  and  362 ) are prevented from accessing the DSPs&#39; SPEM  332   a  and  332   b  in this manner, to ensure the integrity of the DSP code. 
     DMA channels  344   a ,  344   b ,  358  and  362  use peripheral bus  328  to read and write shared SRAM memory  322  and peripherals  150 ,  152 ,  154 ,  155 ,  156 ,  158 ,  160 ,  162 , and  164 . Channels  344   a  and  344   b  are used for data acquisition from pods  150 ,  152 ,  154 ,  155 ,  156 ,  158  and/or cartridges  160 ,  162 . Channels  344   a ,  344   b  send commands and timing information to the pods and cartridges, and receive data and status from them. 
     When receiving data, channels  344   a ,  344   b  write the received data to respective buffers every two milliseconds (msec). After five consecutive two msec cycles, the data in the buffers are written over with new data. To ensure transfer of the data to the shared memory  322  for storage, two different types of interrupts are generated within channels  344   a  and  344   b . The first interrupt is generated every two msec when data are placed in the buffer. The second interrupt is generated each time five blocks of data are received, i.e., every ten msec. 
     DMA channel  358  is a special purpose thermal head driver for recorder  164 . This channel combines data from three different locations in shared memory  322  to overlay grid, text and waveform data. Channel  358  also chains together print pages of varying length for outputting the data to recorder  164 . The output signal from channel  358  is sent over a serial link  386  to recorder  164 . 
     DMA channel  362  is a conventional single chip CSMA/CD controller for twisted pair cable. This channel is used for communications to LANs when portable monitor  102  is placed in a docking station  110 . Channel  362  is not operated when portable monitor  102  is removed from docking station  110 . 
     Data are received from the pods and cartridges by way of two cross point switches  346   a  and  346   b . All pod connections are through switch  346   b , which provides a 5000 volt isolation between the sensor return circuits and portable monitor  102  ground to guard against ground loops, which could endanger patient safety and introduce noise into the measured data. In the exemplary embodiment, crosspoint switch  346   a  does not provide this isolation, so cartridges  160 ,  162  provide their own 5000 volt isolation between cartridge return circuits and the portable monitor  102  ground. Otherwise the two crosspoint switches  346   a  and  346   b  are functionally and logically identical. 
     The crosspoint switches  346   a ,  346   b  receive patient data signals from the pods and cartridges and multiplex the data signals before passing them on to channels  344   a  and  344   b . Each switch  346   a  and  346   b  can communicate with either channel  344   a  or  344   b  via separate 1.6 Mhz links  348   a ,  348   b ,  350   a , and  350   b.    
     The two DMA channels  344   a  and  344   b  are synchronous and are run in a master/slave configuration. Every 15.6 microseconds, there are transfers between the pods/cartridges and shared memory  322 . These transfers include two reads (one per channel  344   a  and  344   b ) and two writes (one per channel  344   a  and  344   b ) to a shared memory  322 . Shared memory  322  includes an extra two byte word for channels  344   a  and  344   b  that is fetched during each 15 microsecond transfer to configure the crosspoint switches  346   a  and  346   b . The low byte is used to control the crosspoint switch of slave DMA channel  344   b  and the high byte is used to control master DMA channel  344   a . For each respective pod port  364 ,  366 ,  368 ,  370  and cartridge port  372 ,  374 , one respective bit in the control word is used to enable power to the pod, and another respective bit is used to enable transmission of a sync signal to the pod. Thus a total of five words are transferred during each 15 msec cycle. The data samples are interleaved between the two DMA channels  344   a  and  344   b.    
     To allow modifications to the configuration of pods and cartridges, CPU  202  issues a request for identification to the pods and cartridges by way of their respective ports  364 ,  366 ,  368 ,  370 ,  372  and  374 . The pod or cartridge responds with a unique identification signal. 
     When commanding the pods and cartridges, the channels  344   a  and  344   b  fetch 24 bit words from shared memory  322 . Each 24 bit word includes an 8-bit DMA control word and a 16-bit front end command. The 8-bit DMA control word includes a 3-bit slot address identifying the port  364 ,  366 ,  368 ,  370 ,  372  and  374  to which the command is routed and a 2-bit DSP redirection control to identify the routing of the data returned by the pod or cartridge. The 16-bit command is transferred to the pods/cartridges. 
     The DMA channels  344   a  and  344   b  also communicate with DSPs  330   a  and  330   b  by way of a serial interface  338 . All of the data received by channels  344   a  and  344   b  is routed to the DSPs in addition to shared memory  322 . The DSP is sent a frame sync signal from master DMA channel  344   a  every 2 msec. 
     A bus arbiter  352  controls access to bus master  334  and DMA channels  344   a  and  344   b . Bus master circuit  334  provides both round robin and prioritized arbitration. Since DMA channels  344   a  and  344   b  could lose data if denied access to bus  328  for an extended period, a round robin element is included in the arbitration scheme. Within the timing constraints that prevent loss of data, bus arbiter  352  also allows burst mode operation, allowing multiple words to be written without entering additional wait states. Bus arbiter  352  also allows burst mode operation during read cycles. 
     In addition to the bus masters, there are also slave devices coupled to bus  328  by universal asynchronous receiver/transmitters (UARTs)  354 . These include two multi-vendor ports  380  and  382  (MVP1, MVP2 respectively), and a battery port  378 . 
     The two DSPs  330   a  and  330   b  may be conventional processors such as Analog Devices ADSP  2101  or  2105  DSP chips. These are 16-bit processors with an instruction set which includes normalization and exponent derivation by barrel shifting. Since many of the operations performed in the EKG algorithms are common signal processing functions, most of the computationally intensive and simply defined processing stages may be performed in the DSPs. These stages may include finite impulse response (FIR) and infinite impulse response (IIR) filtering, cross-correlation, power spectrum estimation and others. Matrix algorithms and other numerical processing may also be performed in the DSPs. 
     In addition to performing signal processing tasks, DSPs  330   a  and  330   b  distribute data to all of the output devices coupled to portable monitor  102 , including local display devices and network devices. The DSPs perform appropriate sample rate conversion, data scaling, and offsetting to the raw sample data collected by monitor  102 . 
     Monitor  102  includes a small internal battery (not shown). If external battery  166  (shown in FIG. 1 b ) is at a low charge level, the internal battery provides power for a time period (e.g., 1 minute) which is sufficient to remove battery  166  and install another external battery. 
     Data Acquisition Pods 
     FIG. 4 shows a block diagram of an exemplary data acquisition pod  150 . Pod  150  is self-contained. That is, Pod  150  includes all of the electronics required to acquire a signal from a sensor, condition the signal and transmit the signal to portable monitor  102 , without inserting pod  150  in the monitor  102 , or in a box (Pod  150  is unlike prior art data acquisition cartridges which must be mechanically inserted into a separate box to couple with the monitoring system). The use of a self-contained, standalone pod  150  simplifies preparing the patient for transportation. There is no need to remove pod  150  from a box, or to reconnect any cables between the pod  150  and monitor  102 . 
     Pod  150  receives patient data from a plurality of sensors  410   a - 410   n  via terminals  411   a - 411   n  (or terminals  16  and  17  as shown in FIG.  1 ). These sensors may measure EKG, blood pressure, pulse, temperature, EEG or other physiological parameters. Each input data stream is amplified and filtered by circuits  418   a - 418   n  to remove noise and any undesirable signals which the sensors may acquire. The amplified and filtered output signals  420   a - 420   d  are combined to form a single signal  415  by a combiner which may be a time division multiplexer  414 . The combined signal  415  is then converted from analog form to digital form by A/D converter  412 . Pod  150  includes a single coupling  150   a  to portable monitor  102 . Signals are transmitted to coupling  150   a  by way of a communications ASIC,  416 . Pod  150  may also optionally include a memory  432  for storing calibration data and alarm limits. Pods  152 ,  154 ,  155 ,  156  and  158  are similar insofar as the functions shown in FIG. 4 are concerned. 
     The main function of the pods  150 - 158  is data acquisition. The filtering and amplification are performed to ensure that the data furnished to monitor  102  accurately represent the parameters sensed by sensors  410   a - 410   n . The application of mathematical algorithms to these data to process the signals is performed inside portable monitor  102 . This division of services between pods  150 - 158  and monitor  102  reduces the size of the pods  150 - 158  relative to typical prior art data acquisition cartridges. Pods  150 - 158  are small enough to be positioned conveniently in a variety of positions, including: on a shelf, on a bed, on a bed rail or headboard, under a pillow, or on an intravenous pole. 
     An exemplary patient monitoring system in accordance with the invention (shown in FIG. 1 a ) may include any one of a basic, diagnostic or neonatal pod. A base EKG pod  150  acquires real-time EKG and respiration waveforms as input data, which are processed by QRS, arrhythmia and S-T segment analysis algorithms in DSP&#39;s  330   a  and  330   b . The sensors (not shown) in pod  150  are five electrodes with leads I, II, III, IV (AVR, AVL and AVF leads) and V (chest). From this data, portable monitor  102  can determine impedance respiration as well as heart rate. 
     Base pod  150  also accepts input data from two temperature sensors which may be used for measuring nasal respiration and cardiac output (C.O.). A nasal respiration thermistor (not shown) may be used to detect respiration by sensing the changes in nasal passage temperature due to the difference in temperature between inhaled and exhaled air. C.O. data are acquired by using the thermodilution method. An Edwards type catheter (not shown) can be used to inject either cooled or room temperature water into the coronary artery. Downstream blood temperature and injectate temperatures are then measured. 
     Lastly, pod  150  receives data representative of pulse and oximetry. Oximetry data representing the saturation, or fraction of oxyhemoglobin to functional hemoglobin (SPO 2  in %O 2 ) are collected using absorption spectrophotometry. 
     As shown in FIG. 1 b , pod  150  includes two proximately located switches  13  and  15 . Switch  13  is coupled to a circuit which transmits a signal to monitor  102  causing monitor  102  to condition itself to start the cardiac output procedure (e.g., perform range and alarm limit adjustments). The operator actuates switch  13  at the same time that he or she injects the injectate into the patient for cardiac output measurement. The DSPs  330   a  and  330   b  in monitor  102  calculate the waveform of the temperature gradient between thermistors for the cardiac output procedure. Similarly, switch  15  is coupled to a circuit which transmits a signal to monitor  102  causing monitor  102  to configure itself to start the wedge procedure and/or switch the display to wedge mode. (The wedge procedure is executed during a measurement of the pulmonary artery wedge pressure). The operator actuates switch  15  at the same time that he or she inflates a balloon inside the patient&#39;s pulmonary artery for pulmonary artery wedge pressure measurement. Switches  13  and  15  are conveniently co-located on pod  150  (near the sensors on the patient). This facilitates concurrent actuation of switch  13  while starting the cardiac output measurement, and facilitates concurrent actuation of switch  15  while starting the wedge procedure. 
     Systems in the prior art typically featured the cardiac output switch  13  and wedge switch  15  on the monitor  102 . It is more convenient to locate switches  13  and  15  close to the patient (as in the present invention) than on monitor  102  (as done in the prior art), because the operator is close to the patient while injecting liquid (for measuring cardiac output) or inflating a balloon in the patient&#39;s artery (for a pulmonary artery wedge pressure measurement). Because pod  150  is small and is easily located close to the patient, pod  150  is an advantageous device on which to locate switches  13  and  15 . In some hospital room configurations, it may be desirable to place monitor  102  too far away to conveniently access monitor  102  while starting the procedures, making the switch location on pod  150  advantageous. Furthermore, safety is enhanced, because the operator does not have to walk around the lines (e.g., lines  18  and  34 ) connected to monitor  102 . 
     Diagnostic pod  156  includes input terminals to receive data from sensors similar to those used in conjunction with base pod  150 . In addition, the diagnostic pod accepts five further leads for receiving EKG data from additional electrodes which may be placed on the patient&#39;s chest. Alternatively, additional terminals may be used to receive EEG data. 
     Neonatal pod  158  includes input terminals similar to diagnostic pod  156 . In addition, neonatal pod  158  includes terminals for receiving long-term, non-invasive, transcutaneous data for monitoring the partial pressures of oxygen and carbon dioxide. In addition to transcutaneous monitoring, a general gas bench for blood gas analysis may be included. 
     In addition to one of the above EKG pods  150 ,  156  or  158 , an exemplary patient monitoring system in accordance with the invention may include a pressure pod  152  (or  154 ) and/or an oximetry catheter pod  155 . Pressure pod  152  accepts data from 4 invasive pressure sensors, which are fluidly coupled to strain gage transducers, and accepts data from 2 temperature sensors. 
     Referring again to FIG. 1 b , the pressure pod  152  has a zero switch  42  conveniently located on pod  152 , where it is easily actuated while calibrating sensors (not shown) by exposing them to atmospheric pressure. Actuating the zero switch causes pod  152  to transmit a zero signal to monitor  102 , causing monitor  102  to reset the value of its waveform to zero in response to the voltage currently detected across the sensor. A second switch  44  located on pod  152  sends a further signal to monitor  102 , causing monitor  102  to condition itself to begin a wedge procedure. The response of monitor  102  to this further signal is the same as described above with respect to actuation of switch  15  on pod  150 . As described above with respect to pod  150 , the location of the control switches on the pod (near the patient) simplifies operations. 
     Pressure/Temperature pod  154  accepts data from two transducers. The catheter pod  155  receives data from a catheter inserted into the patients artery. 
     It is understood by one skilled in the art that many different embodiments of the data acquisition pod may be developed to meet different data acquisition requirements. Both the types of sensors used and the number of sensors of each type may be varied. 
     Data Acquisition Cartridges 
     FIG. 5 shows the mechanical configuration of an exemplary non-invasive blood pressure cartridge  160 . In contrast to pods  150 - 158 , cartridge  160  is not independently positionable, but mounts on monitor  102 . 
     Cartridge  160  accepts data via line  19  for oscillometric measurement of systolic, diastolic, and mean arterial pressures from a cuff transducer (not shown). Cartridge  160  performs functions similar to the pod functions shown in FIG.  4 . In addition, the cartridge provides a separate 5000 volt isolation between the cartridge return circuit and the portable monitor ground for safety and to reduce undesirable noise. 
     As shown in FIG. 5, cartridge  160  includes a suitable mechanism to attach itself to portable monitor  102 . This may be in the form of a guide piece  160   a  with a latch  160   c . Guide piece  160   a  slides into a mating guide (not shown) on portable monitor  102 , engaging connector  160   b  with a mating connector  129  (shown in FIG. 1 a ) on the monitor, and engaging the latch  160   c  with a mating catch (not shown) on the monitor in a single operation. Many variations in the shape of guide piece  160   a  and latch  160   c  may be used to provide the mechanical coupling at the same time that connector  160   b  is engaged to provide electrical coupling. Mounting cartridge  160  directly to monitor  102  is convenient and uses space efficiently; a bulky box is not needed to house the cartridge. 
     The end-tidal CO 2  Cartridge  162 , recorder  164  and battery pack  166  each use a similar coupling technique, to facilitate reconfiguration of the portable monitor  102 . The end-tidal CO 2  Cartridge  162  receives data representing inhaled and exhaled carbon dioxide partial pressures from an airway adapter (not shown) via line  21 , and engages connector  131  (shown in FIG.  1 ). The recorder  164  is a conventional three channel thermal printer. The battery pack  166  includes a conventional nickel-cadmium battery. 
     As with the data acquisition pods, the data acquisition cartridge may be practiced in a number of alternative embodiments. Both the types of sensors used and the number of sensors of each type may be varied. Preferably, data acquisition modules which are bulky, heavy, or consume large amounts of power are implemented as cartridges, while small, lightweight low power data acquisition modules are implemented as pods. For example, pressure cartridge  160  includes a motor and pneumatic devices, in addition to the filters, amplifiers, multiplexer and A/D converter. In considering whether a new type of sensor should be added to a pod or a cartridge, isolation requirements may be a factor, since each cartridge provides its own isolation. 
     Docking Station 
     FIG. 6 shows docking station  110  to which portable monitor  102  may be attached. A connector  110   a  provides data communications couplings to the portable monitor. A guide  110   b , which may be integral with connector  110   a  as shown in FIG. 6, facilitates proper positioning of monitor  102  on docking station  110 , and assists in maintaining monitor  102  in position while monitor  102  is on docking station  110 . A separate connector  110   g  provides power. Respective connectors  110   c  and  110   d  provide power and data communications links from portable monitor  102  to external power sources, devices and networks, when monitor  102  is on docking station  110 . Connector  102   d  may be a conventional connector to interface directly to an Ethernet™ LAN  118  (shown in FIG.  1 A). Additionally, the data may be output to a remote display  120  or  122 , or to an intelligent workstation, for display in VGA format. 
     An optional clamp  110   e  may be used to mount a docking station on an intravenous pole (not shown). Alternatively, clamp  110   e  may be omitted and backplate  110   f  may be fastened directly to a wall or bed. 
     Many variations of the docking station mechanical configuration are possible. For example, connector  110   a  and guide  110   b  may be separate from one another. There may be multiple connectors  110   a  and/or multiple connectors  110   d . Additional mechanical fasteners may be added to improve the stability of the detachable mounting. 
     Connector  110   d  may alternatively connect to a smart wallbox  140 , as indicated in FIG. 1 a . The wallbox converts the twisted pair CSMA/CD signal from line  136  (shown in FIG. 1 a ) to 10 Mbits/second Thinnet, which uses the IEEE 802.3 Type 10-Base-2 standard. This connection provides a LAN connection between portable monitor  102  and remote stations which may be patient monitoring systems or computers. A separate connection  138  provides 1 Mbit/second communications with an input/output device LAN, which may include keyboards, pointing devices, voice input, bar code readers and label printers. Eight additional multi-vendor ports (MVP)  130  are provided. Four analog output ports provide waveform data for transmission to external devices (e.g., monitors, recorders). Wall box  140  assigns ID numbers to devices which connect to it. This allows the portable monitor to automatically identify any changes to the configuration devices connected to the wall box  140 . 
     Data Transfers During Connection 
     FIG. 7 is a flow diagram showing steps which are performed automatically to update the patient data in portable monitor  102  memory (the portable monitor data storing means), or the data in remote display  120  memory (assuming that remote display  120  has storage), so that both are kept current. At step  750 , portable monitor  102  is inserted in docking station  110 , and the connection to the remote display  120  is established. At step  752 , memory in the remote display  120  is checked for data. If there are no data then patient physiological data stored in the portable monitor  102  is downloaded to remote display  120  memory at step  754 . If there are data in remote display  120 , at step  756 , a determination is made whether the data in remote display  120  and the data in portable monitor  102  are associated with the same patient. A double comparison is made; both patient name and patient identification are compared. If either the name or the ID do not match, or if either the name or ID is blank, then the data in the portable monitor  102  and remote display  120  are considered to be associated with two different patients. 
     If the data are from two different patients, at step  758  remote display  120  will prompt the operator to choose either the data in remote display  120  or the data in portable monitor  102 . Once the operator has selected one of the sets of data, at step  760  the data are copied from remote display  120  to the portable monitor  102  if remote display  120  is selected, or from portable monitor  102  to remote display  120  if portable monitor  102  is selected. 
     If it is determined at step  756  that the data in remote display  120  and portable monitor  102  are associated with the same patient, then at step  762 , a determination is made whether the data in remote display  120  are newer than the data in portable monitor  102 . If the portable monitor data are newer, then at step  764  the portable monitor data are copied to remote display  120 . If the remote display data are newer, then at step  766 , the remote display data are copied to portable monitor  102 . 
     The same sequence of steps is performed when memory card  106  is inserted into monitor  102 , except that monitor  102  exchanges data with memory card  106  instead of remote display  120 . It is understood that replacing display  120  with memory card  106  in steps  750  through  766  above, the data in monitor  102  and memory card  106  are kept current. 
     It is understood by one skilled in the art that many variations of the embodiments described herein are contemplated. While the invention has been described in terms of exemplary embodiments, it is contemplated that it may be practiced as outlined above with modifications within the spirit and scope of the appended claims.