WO2010103390A1

WO2010103390A1 - Vital signs monitoring system and components thereof

Info

Publication number: WO2010103390A1
Application number: PCT/IB2010/000523
Authority: WO
Inventors: Cornelius Scheffer; Michiel Mayne Blanckenberg; Gunter Winkler; Johan François COETZEE; Andre Rademeyer
Original assignee: Stellenbosch University
Priority date: 2009-03-12
Filing date: 2010-03-12
Publication date: 2010-09-16

Abstract

A vital signs monitoring system is provided in which a monitoring station [1] having wireless communication means [4, 5 and 6] associated with it is operatively in communication with a first sensor unit [2] for attachment to the body of a subject. The first sensor unit has a housing [7] and internal electronic circuitry to enable wireless communication with the monitoring station. The first sensor unit has a set of ECG contacts [9] on the outer surface thereof with each contact being adapted to have attached directly thereto an ECG electrode [10] so as to provide on the outer surface of the housing, a set of ECG electrodes in fixed spaced relationship relative to each other and orientated for cotemporaneous contact with a subject's body. The ECG contacts are preferably of conventional configuration with releasable sprung fastening means. The first sensor unit is generally adapted to be attached to the dorsal region of a person's body with the arrangement of the ECG contacts being a reversed image of that conventionally used on the chest in order to obtain a default ECG (PQRST) rhythm graph.

Description

VITAL SIGNS MONITORING SYSTEM AND COMPONENTS THEREOF

FIELD OF THE INVENTION

This invention relates to a vital signs monitoring system in which a monitoring station is located remotely from sensor units that may be attached to a subject being monitored, typically a patient, and wireless communication is employed between a remote sensor unit and the monitoring station for transmitting data containing information as to the vital signs of the subject. The invention also relates to sensor units that are suitable for inclusion in such a system.

The vital signs with which this invention is concerned include any one or more of an electrocardiogram (ECG) evidencing the heart's function, oxygen saturation, pulse rate, blood pressure, respiratory rate, movement, body temperature and heart and respiratory sounds.

BACKGROUND TO THE INVENTION

There are numerous instances in which it is desirable for medical personnel to be alerted to the fact that one or more vital signs of a patient have deviated outside of a predetermined range. Monitoring systems have accordingly being employed in the past and sensor arrangements have been devised whereby information as to the vital signs can be transmitted by wireless communication to a central monitoring station. As far as applicant is aware, all of such sensor arrangements employ a substantially conventional arrangement of, for example, electrodes attached to the chest in the instance of an electrocardiogram (ECG) derivation and a finger clip oximeter to determine the blood oxygen level. In the instance of conventional patients, although the sensors may be strapped or otherwise attached to the patient's body, the patient will generally accept their presence and behave in a manner appropriate to their being allowed to remain in situ so that they can perform their proper function. This is in spite of any inconvenience or restriction in mobility that is occasioned by the presence of the sensors on the body.

However, in particular instances, the presence of such items on the body of a patient may not be accepted by the patient. In particular, and simply by way of example, the attachment of such sensors to the body of a psychotic patient in a hospital may not be accepted by the patient. In the event that the patient is sedated, secluded or restrained, the patient is at risk of possible adverse events (including death) if not monitored at least over a particular period of time. As a consequence of this risk, patients are currently monitored clinically by staff visiting the patient, as well as by video monitoring.

If the patient is sleeping or sedated, the clinician has no knowledge of whether or not the patient's vital signs are stable and within predetermined ranges. When a patient is sedated, the following adverse events may occur: changes in blood pressure, pulse rate, respiration and body temperature.

Still further in the instance of psychotic patients, there is always the danger that any sensors attached to the body can be ripped off and possibly used to inflict injury on the patient, medical personnel or someone else in the vicinity.

OBJECT OF THE INVENTION

It is an object of this invention to provide a vital signs monitoring system in which at least one sensor is to be attached to a subject's body and the sensor or sensors exhibit one or more advantages over prior art arrangements. SUMMARY OF THE INVENTION

In accordance with one aspect of this invention there is provided a vital signs monitoring system comprising a monitoring station and at least a first sensor unit for attachment to the body of a subject wherein the first sensor unit has a housing and internal electronic circuitry and wherein wireless communication means are associated with the monitoring station and first sensor unit to enable wireless communication therebetween, the system being characterised in that the first sensor unit has a set of ECG contacts on the outer surface thereof with each contact being adapted to have attached directly thereto an ECG electrode so as to provide on the outer surface of the housing, a set of ECG electrodes in fixed spaced relationship relative to each other and orientated for cotemporaneous contact with a subject's body.

Further features of this aspect of the invention provide for the ECG contacts to be of conventional configuration with releasable sprung fastening means (similar to that of a press stud) in which instance the ECG electrodes have cooperant fastening means; for the first sensor unit to be adapted to be attached to the dorsal region of a person's body, preferably between the left and right scapulas, in which instance the arrangement of the ECG contacts is preferably a reversed image of that conventionally used on the chest in order to obtain a default ECG (PQRST) rhythm graph; and for the first sensor unit to include one or more of a microphone responsive in use to respiratory sounds of a patient, a temperature module responsive in use to body temperature, a pulse/heartbeat monitor and an accelerometer responsive in use to body movements.

It is a particular feature of this invention that the vital signs monitoring system include an optional second sensor unit adapted to be worn on the hand and wrist of a patient with the components thereof being operatively sheathed within a glove that can preferably be secured against unauthorized removal and wherein the second sensor unit includes a blood oxygen monitor (or, as they are often termed, oximeter) and wireless communication means for communicating data containing information as to blood oxygen level either to the first sensor unit and then onwards to the monitoring station or directly to the monitoring station. The second sensor unit may include an accelerometer arranged to register time periods of low physical activity during which blood oxygen readings can effectively be made and, also, a pulse/heartbeat monitor in which instance it will not be included in the first sensor unit.

The invention also provides, as separate items of merchandise, first and second sensor units as defined above separately and apart from each other and separately and apart from the monitoring station.

The invention further provides a method of monitoring the vital signs of a patient, the method comprising applying to the patient at least a first sensor unit as defined above and monitoring signals emitted by the first sensor unit remotely utilizing a monitoring station as defined above.

Further features of the method provided by this invention provides for the first sensor unit to be applied to the dorsal region of a patient's body; and for a second sensor unit to be applied to the hands and wrists region of the patient.

In order that the invention may be more fully understood one embodiment thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:-

Figure 1 is a schematic block diagram of one form of system according to the invention; Figure 2 is a schematic diagram illustrating a person's chest and the normal placement of ECG electrodes thereon;

Figure 3 is a schematic diagram illustrating a person's dorsal region and the general placement of ECG electrodes carried by a first sensor unit according to the invention;

Figure 4 is an underneath isometric view of a first sensor unit according to the invention;

Figure 5 is a plan view thereof;

Figure 6 is a partly broken away perspective schematic illustration of a second sensor unit according to the invention that is associated with a glove; and,

Figure 7 is a schematic illustration of an example of the appearance of the graphic user interface of a monitor screen of a monitoring station.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In the embodiment of the invention illustrated in the drawings a vital signs monitoring system comprises a monitoring station (1), a first sensor unit (2) that is specially designed for attachment to the dorsal region of a person's body between the left and right scapulas, and a second sensor unit (3) adapted to be worn on the hand and wrist of a person's body. The arrangement is such that the sensor units will generally be worn by a person who is remote from the monitoring station and communication between the sensor units and monitoring station is wireless. In this the embodiment of the invention the arrangement is such that the first sensor unit has wireless transmitter means (4), typically of Bluetooth quality, for communicating with the remote monitoring station and information from the second sensor unit is transmitted by short-range wireless transmission from a transmitter (5) in the second sensor unit to a cooperant receiver (6) the first sensor unit.

In this manner all data recorded by either of the sensor units is transmitted via a single wireless communication channel to the monitoring station. It is, of course, possible for the second sensor unit to transmit its data directly to the monitoring station although it is envisaged that this arrangement would be less cost-effective and somewhat more complex.

The first sensor unit, illustrated particularly in Figures 4 and 5, has a housing (7) in which its electronic circuitry and wireless communication means are housed including an ECG processing circuit (8). The housing is somewhat squat having a major inner surface in the peripheral confines of which is a set of ECG contacts (9) that operatively receive a set of generally conventional

ECG electrodes (10) by way of conventional releasable sprung press stud type fastening means (not shown).

The arrangement of the ECG contacts/electrodes on the first sensor unit is approximately a reverse image (see Figure 3) of that conventionally used on the chest (see Figure 2) in order to obtain the same electrical vector across the heart and to generate a default ECG (PQRST) rhythm graph. The ECG contacts/electrodes are appreciably closer together than they would be in the instance if they were located at the ends of flexible leads and attached to the chest so that the entire housing and ECG electrode assembly can be dorsal mounted between the scapulas of a subject with the ECG electrodes attached to the housing. It is important that the electrodes be placed underneath the device to ensure that a patient cannot gain access to them. The whole dorsal mounted device is, of course, chamfered so that no sharp corners exist.

The distance between the positive (9a, 10a) and negative (9b, 10b) ECG contacts/electrodes correlates to the amplitude of the measured ECG waveform. The further they are from each other the larger the signal. The distance between these two electrodes should be great enough to ensure that the SNR of the small ECG waveform measured on the back of the patient is good enough to recognize the PQRST rhythm. Digital filters may be used to filter out most of any unnecessary noise present.

Applicant's investigations have revealed that an average person's distance between their left and right scapulas when pushing back their shoulders is about 100mm. Therefore the distance between the top two electrodes that are to be placed to the left and right of the vertebral column has been designed to be 70 mm. The maximum length between the positive ECG electrode (bottom) and the diagonally opposite negative ECG electrode (top) has been designed to be 125mm. This distance of 125 mm is large enough to measure a good quality SNR ECG waveform when signal processing is done on the measured ECG signals. In use, to ensure that the device stays in place and to reduce movement of the electrodes on the skin, a very strong adhesive plaster is used to cover the device and keep it attached to the skin between the left and right scapulas.

The first sensor unit also has a microphone (11) positioned on the inner surface of the housing that is responsive in use to respiratory sounds of a patient. The sounds picked up on the back of a patient are preferably amplified and external sounds (noise) kept to a minimum. To ensure that this is accomplished the small microphone is fitted in an integral sleeve to accommodate the movement of the diaphragm. The air-coupled microphone unit is also preferably carried on a spring system (not shown) to ensure that the microphone is, in use, pressed against the skin of the patient to provide an air chamber that is sealed when the first sensor unit moves away from the skin by a small distance.

The first sensor unit also has a temperature module (12) responsive in use to body temperature. The contact of the module is an ECG type electrode (13).

Finally, the first sensor unit is fitted with an accelerometer (14) designed to measure the amount of movement of a subject fitted with the unit. When the patient moves excessively, transmission of the ECG and acoustic sound data is suspended to ensure that false readings or not transmitted. When this occurs a warning message may be displayed on the screen at the monitoring station. A clinician on duty should then visit the patient to establish if there is a medical emergency.

The first sensor unit includes just one microcontroller (15) to sample all the different analogue sensors' channels and send this data using a developed serial protocol to the monitoring station using a dedicated Bluetooth connection.

Turning now to the second sensor unit (3), the main component thereof is an oximeter (16) contained in a wrist mounted housing (17) and fed from a finger clip probe (16a) that is to be fitted to the index finger of a subject, in use. The second sensor unit includes an accelerometer (18) to monitor movement of the wrist in consequence of the fact that movement influences the measurement of oxygen saturation. The second sensor unit also includes a pulse monitor (19).

The second sensor unit includes a protective glove (20) to be securely installed over the wrist mounted housing, finger clip and connecting wires in order to secure these components from interference by a patient. This sensor unit is selected to measure the usual two PPG's (plethysmograph) and calculate the oxygen saturation ratio value from the two PPG signals (red and infrared light). The oximeter probe uses two LED's (light emitting diodes) on one side of the finger at wavelengths of 660 nm (red spectrum) and 905nm (infrared spectrum) respectively and a photodiode on the other side of the finger. The optical sensors are susceptive to motion artefacts and, as psychotic patients will not always be still during measurements, remaining still for an extended period is necessary for accurate measurements and the accelerometer is thus used to determine the time periods in which readings can be reliably taken.

To ensure that the device is as small as possible, one microcontroller is used to sample the red and infrared channels and send the red PPG signal together with the calculated ratio value using a developed serial protocol to the first sensor unit.

In use, it will be understood that the first sensor unit is attached by means of suitable adhesive plaster to the dorsal region of a subject with the relevant electrodes on opposite sides of the spine as will be apparent from the aforegoing. The second sensor unit is attached to the subject's wrist and hand and the covering glove secured in position suitably in a manner in which it is impossible for the subject to remove it. The sensor units are mechanically robust and tamper-proof and rechargeable batteries are typically used to power the devices.

One or more patients can then be monitored from the remote monitoring station and various graphical outputs displayed on a screen. These outputs could, simply by way of example, and as illustrated in Figure 7, be a display of the ECG waveform (21), typically for the last 20 seconds; a graph (22) displaying the calculated HRV graph for the 20 seconds (this can help a clinician detect sudden uneven heart rate); a bar graph (23) displaying the level of movement on the basis of the amount of g forces that the patient generates by movement (this will give a clinician a good indication if the patient is resting or moving at an uncontrolled rate); and two graphs (24, 25) displaying the filtered lung sound graph and respiration of the patient for the last 20 seconds.

At the top of the screen the calculated heart rate (26), temperature (27), respiratory rate (28) and SaO2 (29) are displayed and updated every 20 seconds. A further window (30) is provided to convey any immediate alarm conditions that may develop.

A vital signs monitoring system described above enables one clinician to monitor several patients from a central monitoring station and if any of the vital sign data transmitted to, or calculated at, the central station deviates outside of the selected margins an alarm will be activated to ensure that a clinician on duty can attend to that patient as quickly as possible.

It will be understood that numerous variations may be made to the embodiment of the invention described above without departing from the scope hereof.

The invention therefore provides a vital signs monitoring system in which the various sensors that are operatively attached to a patient cannot be easily removed by the patient; they do not impede blood flow; and cannot be used for the destructive or aggressive purposes by the patient.

Claims

CLAIMS:

1. A vital signs monitoring system comprising a monitoring station [1] and at least a first sensor unit [2] for attachment to the body of a subject wherein the first sensor unit has a housing [7] and internal electronic circuitry and wherein wireless communication means [4, 5 and 6] are associated with the monitoring station and first sensor unit to enable wireless communication therebetween, the system being characterised in that the first sensor unit has a set of ECG contacts [9] on the outer surface thereof with each contact being adapted to have attached directly thereto an ECG electrode [10] so as to provide on the outer surface of the housing, a set of ECG electrodes in fixed spaced relationship relative to each other and orientated for cotemporaneous contact with a subject's body.

2. A vital signs monitoring system as claimed in claim 1 in which the ECG contacts are of conventional configuration with releasable sprung fastening means in which instance the ECG electrodes have cooperant fastening means.

3. A vital signs monitoring system as claimed in either one of claims 1 or 2 in which the first sensor unit is adapted to be attached to the dorsal region of a person's body.

4. A vital signs monitoring system as claimed in claim 3 in which the arrangement of the ECG contacts is a reversed image of that conventionally used on the chest in order to obtain a default ECG (PQRST) rhythm graph.

5. A vital signs monitoring system as claimed in any one of the preceding claims in which the first sensor unit includes one or more of a microphone [11] responsive in use to respiratory sounds of a patient, a temperature module [12] responsive in use to body temperature, a pulse/heartbeat monitor and an accelerometer [14] responsive in use to body movements.

6. A vital signs monitoring system as claimed in any one of the preceding claims in which a second sensor unit [3] is included, the second sensor unit being adapted to be worn on the hand and wrist of a patient with the components thereof being operatively sheathed within a glove [20] and wherein the second sensor unit includes a blood oxygen monitor [16] and wireless communication means for communicating data containing information as to blood oxygen level either to the first sensor unit and then onwards to the monitoring station or directly to the monitoring station.

7. A vital signs monitoring system as claimed in claim 6 in which the second sensor unit includes at least one of an accelerometer [18] arranged to register time periods of low physical activity during which blood oxygen readings can effectively be made and, a pulse/heartbeat monitor [19].

8. First sensor units particularly adapted for use in a vital signs monitoring system as claimed in any one of claims 1 to 7.

9. Second sensor units particularly adapted for use in a vital signs monitoring system as claimed in any one of claims 1 to 7.

10. A method of monitoring the vital signs of a patient, the method comprising applying to the patient at least a first sensor unit of a vital signs monitoring system as claimed in any one of the preceding claims and monitoring signals emitted by the first sensor unit remotely utilizing the associated monitoring station.

11. A method as claimed in claim 10 in which the first sensor unit is applied to the dorsal region of a patient's body.