Patient Monitoring System With Bedsheet-mounted Antenna

Abstract

A patient monitoring system in which biological data are sensed by a self-contained unit attached to the patient, the unit containing a very low-powered radio transmitter. A radio receiver is coupled to an antenna which is incorporated in the bed covering in such a manner as to pickup signals from the transmitter regardless of the position of the patient on the bed, the antenna being flexible to avoid discomfort to the patient and to withstand motion of the patient. The metal bedframe acts as a shield against unwanted radio frequency signals. Suitable display and recording apparatus can be connected to the receiver at the bedside or at a remote location.

Description

BACKGROUND OF THE INVENTION

In an intensive care facility, the condition of a patient is often monitored on instruments connected to sensing devices attached to the patient, the instruments being at the bedside or at a remote location. The various sensors are usually connected by electrical wiring to the instruments, the wiring being a nuisance and greatly restricting movement of the patient. Motion of a patient during sleep can pull a sensor loose and cause a loss of data or false data. Biological sensors have been developed which use a radio link to convey data to a monitoring source, such as for monitoring an ambulatory patient or for telemetry of data from a pilot or astronaut in flight. Radio link apparatus of this type must have sufficient power for reasonable transmission range and is subject to interference from other sources of radiation. It is thus desirable to have a wireless monitoring link from a patient to the readout apparatus, which is particularly adapted for bed patients and is not subject to interference.

SUMMARY OF THE INVENTION

The apparatus described herein utilizes a self-contained biological sensor unit attached to a patient and having a very low power radio transmitter with a range on the order of a few feet. Signals are picked up by an antenna incorporated into the bed covering, preferably under the patient, so that the metal bed frame structure acts as a shield against outside radiation. The antenna is flexible to accommodate movement of the patient and avoid discomfort, and has a pattern of conductive elements which ensure signal reception regardless of the position of the patient on the bed. From the antenna, connections are easily made to bedside or remote instrumentation for monitoring.

The primary object of this invention, therefore, is to provide a new and improved patient monitoring system.

Another object of this invention is to provide a new and improved patient monitoring system having a wireless biological sensing and transmitting unit which does not hamper movement of the patient.

A further object of this invention is to provide a new and improved patient monitoring system in which the receiving antenna for the signals is incorporated in the bed covering and is shielded against outside interference by the bed frame.

Other objects and advantages of this invention will become more apparent upon a reading of the following detailed description and an examination of the drawings wherein:

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a block diagram of the sensor and transmitter unit.

FIG. 2 is a block diagram of the antenna and receiver unit.

FIG. 3 is a perspective view showing a typical bed with an antenna and bedside instrumentation.

FIG. 4 is an underside view of a portion of a blanket or the like, incorporating the antenna.

FIG. 5 is an enlarged sectional view taken on line 5-5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The sensor unit 10, shown in FIG. 1, includes a temperature sensor 12, a heart beat pickup 14 and an EKG-sensor 16, as an example. The temperature sensor may be a thermistor or similar quick response thermocouple, the heart beat pickup can be a simple microphone, and the EKG-sensor usually has spaced skin contacting electrodes. Such devices, and others for various biological sensing purposes, are well known and any desired combination may be incorporated in the sensor unit. All the sensors are connected to a radio transmitter 18 of conventional design, having an antenna 20. Since the range involved is measured in inches, or a few feet at the most, the transmitter can be a very low powered type and the antenna need be no more than a terminal or stub. The sensor unit is preferably a single self-contained unit for direct attachment to a patient at a suitable location, such as under an arm. Such units, attached adhesively or strapped on, are known and take a variety of forms, the block diagram being intended only as a typical representation.

The instrumentation unit 22, shown in FIG. 2, includes a radio receiver 24, a display instrument 26 and a recorder 28. Receiver 24 is of conventional type and may be built into or separate from the display instrument. The display includes conventional type readouts for showing the particular biological functions, such as an oscilloscope 30 for the EKG-data and digital or meter type instruments 32 and 34 for temperature and heart beat rate, respectively. Recorder 28 is a conventional tape or strip graph recorder commonly used for biological monitoring. It is assumed that suitable conventional amplifier means is included in the receiver to provide proper signals for the display and recorder.

Signals are received by an antenna 36, shown as a multiple armed dipole connected to receiver 24. The antenna is incorporated in or attached to part of the bed covering, such as a sheet or blanket 38 fitted over the mattress under the patient. The dipole arrangement, with multiple radial arms 40 extending from a common center, ensures adequate reception of signals with the patient in any position on the bed. A total of eight arms is shown, but any convenient number may be used. To avoid discomfort to the patient and prevent damage to the antenna from patient motion, the antenna is made from flexible material such as metallized plastic. Aluminized mylar has been found satisfactory and has good strength characteristics, and may be attached to blanket 38 by adhesion or stitching.

Leadouts 42, also of metallized plastic, extend from the dipoles to an edge of the blanket and are connected to a two-wire conductor 48 for connection to the receiver. A suitable detachable connector may be used at the leadouts to allow cleaning of the blanket by normal techniques. In FIG. 5 the antenna elements are shown with their metal surfaces 44 against the blanket and the plastic backing 46 outside. If necessary, the antenna could be sandwiched between two layers of material for protection.

In the installation shown in FIG. 3, the instrumentation unit 22 is on a bedside table 50, but could be at a remote location, or supplemented by remote instruments. With the antenna 36 in the horizontal plane on top the mattress, the metal bed frame 52 acts as a shield against outside interference which might cause false readings. While the receiver can be made selective to specific frequency and signal characteristics of the transmitter, there are many sources of radiation which can cause spurious signals. In a bed with raised side structure the shielding effect would be greater.

The band of frequencies normally available for such use is from 88 to 100 mHz., at which frequencies the antenna arms 40 would be about 15 inches long for an average one eighth wavelength, precise matching not being critical. This dimension is compatible with the usual size of hospital beds. Due to the very low power involved there would be no interference between similar units used at adjacent beds.

Claims

Having described my invention, I now claim.

1. A patient monitoring system comprising,

a sensor unit for attachment to a patient with sensors that sense certain biological functions and provide output signals in response thereto,

radio transmitter means responsive to said output signals for transmitting signals corresponding to said output signals,

a receiving antenna comprising a flexible bed covering sheet for fitting over a bed and under a patient and having a metallized plastic material secured on portions thereof,

lead out conductors integral with said antenna and of similar material and extending to the edge of the bed covering element,

and readout instrumentation means having a radio receiver connected to said conductor for receiving the transmitted signals.

2. A patient monitoring system as claimed in claim 1 in which,

said metallized plastic material is deposed on said bed covering sheet in the form of a dipole antenna structure with each pole having a plurality of arms extending substantially horizontally on the bed when the flexible bed covering is laid on the bed,

and said arms are substantially radial about a common center between the dipoles.

3. The system of claim 1, wherein at least portions of the bed are of metal and comprise an interference shield for said antenna.