Abstract:
An antenna is integrated into the handle of a portable patient monitor or other portable medical diagnostic instrument to enable wireless communication with a central station. The handle is made of a rugged plastic material, e.g., polycarbonate, which protects the antennae against damage. In addition, the plastic material used in the handle does not negatively impact RF transmissions to and from the antenna. The antenna is supported in a pair of slots formed in respective ribs of a molded piece forming a part of the handle.

Description:
FIELD OF THE INVENTION 
     This invention generally relates to portable medical diagnostic equipment. In particular, the invention relates to equipment used to monitor patients at a remote location or during transport in a hospital or other patient care setting. 
     BACKGROUND OF THE INVENTION 
     When providing medical care to patients, it is frequently necessary to monitor the patient using medical monitoring instruments. One type of instrument, the patient monitor, is capable of monitoring the patient to acquire electrocardiogram data, cardiac output data, respiration data, pulse oximetry data, blood pressure data, temperature data and other parameter data. In particular, lightweight portable monitors exist which can be moved with the patient, allowing continuous monitoring during patient transport. Also these portable monitors can be used at locations remote from a central station in a hospital facility or other patient care setting. 
     To facilitate monitoring at remote locations or during patient transport, modern portable patient monitors are powered by rechargeable batteries. Extended-use batteries, with quick recharge times, help maximize monitor availability. Advanced monitors have a smart battery management system which maximizes battery life, reducing maintenance and replacement. These patient monitors can also be plugged into any conventional electrical power system for use, e.g., at the patient&#39;s bedside, before and/or after the patient is transported. At the bedside, advanced patient monitors can be hardwired to a central station via a local area network (LAN) for enhanced patient surveillance efficiency. In addition, the most advanced patient monitors have a built-in wireless option which enables the monitor to go mobile without sacrificing connectivity. Such monitors also support importation of demographic and laboratory data from a hospital information system for increased efficiency. 
     Portable patient monitors with integral battery power supply are commercially available in a compact, ergonomic package which allows easy handling. Typically such monitors have a drop-tested rugged design which allows them to withstand the punishment of the demanding intra-hospital transport applications. Mounting options make these monitors ideally suited for headboard/footboard, siderail, rollstand and IV pole use. The compact design is achieved in part through the use of flat display panels. The color or monochrome screen accommodates all numerics and multiple waveforms. 
     In addition to displaying waveforms and numerics representing the data being acquired, advanced patient monitors have a central processing system which stores and analyzes the acquired data. In particular, the central processing system is programmed with algorithms for analyzing the acquired data. The central processing system controls the transfer of data to the display panel for display and to the LAN via either a hardwired or wireless connection. 
     Known patient monitors incorporate an optional radiofrequency local area network (RF LAN) feature that utilizes antenna diversity technology. Antenna diversity technology uses the stronger signal from two antennae to reduce multipath RF interference and provide redundancy. To maximize transmissions, the antennae should be mounted a minimum distance of one-quarter wavelength apart on the top surface of the monitor. An antenna mounted on a portable device is exposed to the risk of damage during monitor movement. Damage to the antenna could result in a non-functional RF LAN subsystem in the monitor. Thus, there is a need for a portable wireless instrument in which the antennae are not inherently susceptible to damage. 
     SUMMARY OF THE INVENTION 
     The present invention mitigates potential damage to an antenna of a portable wireless instrument, such as a patient monitor, by incorporating the antenna inside the instrument handle. The handle is made of material which does not negatively impact RF transmissions and which is sufficiently rugged to protect the antennae against damage when the instrument is subjected to impacts. The preferred material is a plastic such as polycarbonate. 
     In accordance with the preferred embodiment of the invention, a pair of antennae are integrated into the handle of a portable patient monitor to enable wireless communication with a central station. The handle comprises front and rear molded pieces which are fastened together, the antennae being mounted to one of the molded pieces. Each antenna is securely supported in a respective pair of slots formed in respective ribs of the molded piece. In the assembled state, the front and rear molded pieces of the handle protect the antennae against impacts. 
     The invention is not limited in application to handles designed to house two or more antennae. The construction technique disclosed herein can be employed in portable instruments having a single antenna. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a drawing showing a generally frontal view of a portable patient monitor in accordance with the preferred embodiment of the invention. 
     FIG. 2 is a block diagram showing a patient monitor with an antenna integrated into the handle in accordance with the preferred embodiment of the invention. 
     FIG. 3 is a drawing showing an exploded view of the monitor handle with integrated antennae in accordance with one preferred embodiment of the invention. 
     FIG. 4 is a drawing showing an elevational rear view of the assembled handle in accordance with the preferred embodiment, with the rear handle piece being removed. 
     FIG. 5 is a drawing showing an elevational end view of the assembled handle in accordance with the preferred embodiment, with the front and rear handle pieces being outlined in dashed lines. 
     FIG. 6 is a drawing showing an elevational rear view of the front piece of the handle shown in FIG.  3 . 
     FIGS. 7 and 8 are drawings showing sectional views of two ribs forming part of the front handle piece, the sections being respectively taken along lines  7 — 7  and  8 — 8  indicated in FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A portable patient monitor, depicted in FIG. 1, comprises a housing  2  and a handle  4  connected to the top of the housing. Reference numeral  56  identifies a lens of an alarm light assembly, which will be described in more detail later. The monitor further comprises a flat display panel  6  secured in a generally rectangular window formed in the front face of the housing  2 . An operator interface comprises a plurality of keys, forming a keypad  8 , and a so-called “trim” knob  10 , which allows the user to select and focus on a particular menu. The display panel  6  displays waveforms and numerical data. The status of a pair of batteries A and B is indicated in the lower right-hand corner of the display panel. A “soft” operator-actuated menu key  11 , appearing in the lower left-hand corner, can be used to call up additional menus. 
     In accordance with the preferred embodiment of the invention, a pair of antennae  14  are integrated into the monitor handle  4 , as generally represented in the block diagram of FIG.  2 . For the sake of completeness, FIG. 2 also shows the basic internal structure of the portable patient monitor depicted in FIG.  1 . Although FIG. 2 (as well as FIGS. 3,  7  and  8 ) also shows an alarm light  12  integrated into the handle, this is the subject of a copending patent application. 
     The preferred embodiment shown in FIG. 2 comprises a processor/power management subassembly  16 , a display subassembly  18  and a data acquisition system module  20 , each of which will be described below. 
     The processor/power management subassembly  16  comprises a processor board  22  powered by an ac mains power supply via a power supply board  24 . Alternatively, the processor board  22  can be powered by rechargeable batteries  26  when the patient monitor is disconnected from the mains power supply, e.g., during patient transport. The processor/power management subassembly  16  further comprises a peripheral expansion connector  28 , which allows the processor to communicate with peripheral processors added as the result of future expansion of the system. 
     The display subassembly  18  comprises a liquid-crystal display (LCD) flat panel  6 , a backlight inverter  30  for powering the fluorescent tubes of the flat display panel and a keypad  8  for operator inputs. The flat display panel  6 , the backlight inverter  30  and the keypad  8  are electrically coupled to the processor board  22  via a display flexible printed circuit board (flex)  32 . 
     The data acquisition system (DAS) module  20  comprises a plurality of ports for patient connections and a DAS board  34 . The patient connection for acquiring noninvasive blood pressure (NBP) data is coupled to the DAS board  34  via an NBP flex  36 . The leads for acquiring electrocardiogram (ECG), respiratory and other cardiovascular data are coupled to the DAS board  34  via a patient connector flex  38 . The ECG leads connect to electrodes attached to the patient&#39;s chest. The acquired data is sent to the processor board  22  for signal processing and analysis via the display flex  32 . The processor board  22  controls the display panel  6  to display the desired waveforms and numerical data based on the acquired data received from the DAS board  34 . 
     In addition to displaying acquired data, the patient monitor depicted in FIG. 2 also has the capability of automatically activating audible and visual alarms in response to acquired data exceeding a preset alarm threshold. The alarm thresholds are user-selectable via keypad entries. The visual alarm indicator is an alarm light  12  built into the monitor handle  4  which flashes when activated; the audible indicator is an audio speaker  40  which emits alarm tones when activated. The alarm light  14  and audio speaker  40  are controlled by the processor board  22  via a writer flex  42 . The processor board also controls a writing device  44 , e.g., a thermal recorder, via the writer flex  42 . The writer  44  serves to create a written record of selected data readings. 
     The patient monitor shown in FIG. 2 also has the ability to communicate with a LAN (not shown) via a hardwired Ethernet connection  46 , with a defibrillator (not shown) via connection  48  and with an auxiliary piece of equipment (not shown), e.g., a ventilator or a remote control device, via connection  50 . The processor board provides synchronization signals to the defibrillator via connection  48 . Also the patient monitor can communicate wirelessly with the LAN using a pair of antennae  14 , which are also preferably integrated into the monitor handle  4 . The processor board  22  sends signals to and receives signals from the antennae  14  via a PC card interface  52  which interfaces with a RF LAN card  54 . The PC card interface  52  plugs into a socket which resides on the processor board  22 . The RF LAN card comprises digital-to-analog converters for converting digital signals from the processor into RF signals, a transmitter for pulsing the antennae  14  to transmit the RF signals, a receiver for receiving RF signals from the antennae  14 , and analog-to-digital converters for converting received RF signals into digital signals in a format acceptable to the processor. The RF LAN feature utilizes antenna diversity technology. The antenna diversity technique uses the stronger of the two signals respectively received via the antennae  14  to reduce multipath RF interference and provide redundancy. 
     A handle incorporating antennae in accordance with the preferred embodiment is shown in FIG.  3 . The handle  4  comprises two molded pieces made of opaque plastic material: a front handle part  60  and a rear handle part  62 . Both parts are designed with cutouts  64  which, when the two parts of the handle are fastened together by screws  66 , form an opening in which an alarm light assembly, comprising a lens  56  and a printed circuit board  58 , is securely installed. Through holes  86  are molded in the front handle part  60  and threaded holes (not visible in FIG. 3) are molded in the rear handle part  62  for receiving the screws  66 . The handle  4  is preferably mounted at an inclined angle relative to the monitor housing, as seen in FIG.  1 . In the preferred embodiment, the assembled handle is attached to the monitor housing by screws (not shown in FIG.  3 ). For this purpose, one pair of throughholes  88  are provided in the front handle part  60 . Another pair of throughholes (not visible in FIG. 3) are provided in the rear handle part  62 . The screws for attaching the handle have threaded ends which threadably engage threaded holes (not shown) in the monitor housing. 
     Referring to FIG. 4, the preferred embodiment of the invention comprises a pair of antennae  14 . Each antenna  14  comprises a thin metal core  72 , a brass outer tube  74  and a coaxial cable  76 . In conventional fashion, the thin metal core  72  is connected to a central conductor of the coaxial cable  76 , while the brass outer tube  74  is connected to an outer tube in the coaxial cable  76 . The exposed core  72  may optionally be coated with an insulating material. 
     FIG. 4 shows the handle with the rear handle piece removed. The front handle piece comprises two sets of stiffening ribs  78  and  80  molded into the concave legs of the front handle piece. Each set of ribs  78  and  80  supports one antenna  14 . Preferably the ribs are generally mutually parallel. Rib  78  supports a portion of the brass metal tube  74 , while rib  80  supports a portion of the coaxial cable  76 . Although not shown, the rear handle piece is also provided with two sets of stiffening ribs molded into its concave legs. 
     As best seen in FIG. 7, each rib  78  has a pair of slots  82  and  90 . As best seen in FIG. 8, each rib  80  has a pair of slots  84  and  92 . The centerlines of slots  82  and  84  are generally coplanar, the plane of the centerlines in turn being generally perpendicular to the generally mutually parallel ribs. This alignment of the slots  82  and  84  is best seen in FIG. 7, which shows a rear view of the front handle piece  60  with the antennae removed. The alarm light cable (not shown) is installed in slots  90  and  92 . Each slot has a semicircular termination and a draft (i.e., degree of taper) of a few degrees (e.g., 2°) to facilitate removal of the molded front handle piece from the mold. The diameter of the semicircular end of slot  82  in rib  78  is greater than the diameter of the semi-circular end of slot  84  in rib  80  to accommodate the diameter of the brass metal tube, which is larger than the diameter of the coaxial cable. The antennae are held in place by a small amount of adhesive during assembly. 
     Referring to FIGS. 4 and 5, the alarm light is an assembly comprising a curved lens  56  made of molded plastic material and a printed circuit board  58  attached to a stake  98  integrally connected to the underside of lens  56 . The printed circuit board  58  carries four light-emitting diodes (LEDs)  94  in a 2×2 layout, two red LEDs and two yellow LEDs. The LEDs  94  are connected to the processor board ( 22  in FIG. 3) by means of a connector  96 , which is also mounted on the printed circuit board  58 , and an alarm light cable, not shown. A groove  68  is formed along the periphery of lens  56 . When the handle is assembled, the edges of cutouts  64  (best seen in FIG. 3) engage the peripheral groove  68 , thereby securely holding the alarm light assembly in place. The LEDs are activated when the processor determines from the acquired data that an alarm state exists. 
     While the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the essential scope thereof. In particular, the person skilled in the art will readily appreciate that the number of antennae need not be two. For example, a single antenna can be used in portable instruments which do not use antenna diversity technology. Any number of antennae incorporated within the handle of a portable instrument is within the scope of the invention. Therefore it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.