WO2010038176A1

WO2010038176A1 - Garment for positioning a plurality of sensors and a sensor carrier

Info

Publication number: WO2010038176A1
Application number: PCT/IB2009/054195
Authority: WO
Inventors: Ralf Schmidt; Harald Reiter
Original assignee: Koninklijke Philips Electronics N.V.; Philips Intellectual Property & Standards Gmbh
Priority date: 2008-10-02
Filing date: 2009-09-25
Publication date: 2010-04-08

Abstract

To detect slowly deteriorating health conditions requires monitoring of physiological signals over a long period of time wherein the change in those physiological signals that are indicative for a health problem is small. To enable the acquisition of data of physiological signals a garment (10) for positioning a plurality of sensors (25) relative to the skin of a wearer is provided in which the position of the sensors relative to each other and the wearer are unaffected over time when the garment is repeatedly put on and off. Said garment comprises a wearable body structure (15) of flexible material and is characterized in that the garment further comprises a bendable and inextensible sensor carrier (20), each of the plurality of sensors being affixed to a predetermined position on a skin facing side (41) of the carrier (20).

Description

Garment for positioning a plurality of sensors and a sensor carrier

TECHNICAL FIELD OF THE INVENTION

The invention relates to a garment for positioning a plurality of sensors relative to the skin of a wearer and a sensor carrier for use in the garment.

BACKGROUND OF THE INVENTION

As the population of the USA, Europe and Japan are ageing an increase in the amount of people suffering from chronic diseases is to be expected. To prevent that the expenses for the treatment of chronic diseases are rising dramatically early detection and prevention of developing diseases becomes important. Especially the early detection of cardiovascular diseases (CVD) is desirable because of their huge incidence and follow-up costs.

By measuring vital parameters in daily life it is possible to observe slowly developing health deteriorations. This allows an intervention at a very early stage of the disease. US6551252 discloses a physiological monitoring apparatus with a monitoring apparel worn by a monitored individual, the apparel having attached sensors for monitoring parameters reflecting cardiac function. The sensors include one or more ECG leads and one or more plethysmographic sensor with conductive loops positioned closely to the individual to monitor at least basic cardiac parameters. When patients at home are doing measurements without supervision the measurement conditions may not be optimal resulting in a loss of accuracy of the obtained data. Because of this inaccuracy slowly developing health deteriorations may remain unnoticed.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a garment that enables more accurate measurement of physiological data indicating slowly developing health deteriorations. The object is achieved with the garment as defined in claim 1. The invention is based on the insight that detection of slowly developing health deteriorations requires regular measurements over a longer period of time wherein the data obtained with consecutive measurements must be compared and therefore a high relative accuracy is required to allow detection of a trend. As the patient is not permanently wearing the garment, but only for example 15 minutes per day, the data of the consecutive measurements originates from potentially changing measurement conditions, that is the patient may not be able to make sure that the sensors in the garment have each time a measurement is done a same relative position to each other and to his body. As a consequence the data of the consecutive measurements cannot be compared with each other despite a high absolute accuracy of each of the measurements. To be able to detect a trend in the data of consecutive measurements the sensor position should each time a measurement is done have a same position relative to each other and to the body. This is achieved with the garment of claim 1 wherein the garment comprises a bendable and inextensible sensor carrier having a skin facing side at which each one of the plurality of sensors is affixed at a predetermined position. Because the carrier is inextensible the position of the sensors relative to each other is not changed even if the carrier is bended and pulled against the skin of the wearer when the garment is put on. The sensor carrier is coupled to a wearable body structure to make sure that each time that the garment is put on and the measurements are done the sensors on the sensor carrier make contact with a same position on the body. As with the garment of claim 1 the sensor position relative to each other and to the body is kept constant the differences in measurement conditions for consecutive measurements are reduced enabling a more accurate measurement of physiological data indicative of slowly developing health deteriorations thereby achieving the object of the invention. A further advantage of the garment of claim 1 is that even medically and technically inexperienced persons are able to use the garment without the need for supervision. The garment may be used daily at home and the measurement data of consecutive measurements may be provided to a caregiver, for example by telephone or the Internet. Based on the data the caregiver may detect a trend in the health condition and give the patient advice to change for example the medication.

In a further embodiment of the garment the sensor carrier is detachable. This has the advantage that the wearable body structure can be easily cleaned. An example of fastening means that may be used are hook and loop fasteners. Hook and loop fasteners provided in the form of strips and patches are well known and commercially available under the Trademark Velcro. It is understood that such mating strips customarily comprise two different forms, one presenting a 'hook' surface, and the other representing a 'loop' surface. Such fasteners may be formed as desired of any suitable form of plastic or other moldable material. The first fastening means (with for example the 'hook' surface) are preferably positioned on and affixed to a non-skin facing side of the carrier, the second fastening means (with for example the 'loop' surface) are preferably affixed to an inner surface of the garment. The carrier is fastened by pushing the first fastening means to the second fastening means and is easily removed by pulling the carrier from the garment thereby separating the first and second fastening means.

Heart Failure is a complication of a plurality of heart diseases such as coronary artery disease and heart attack. With heart failure, blood moves through the heart and body at a slower rate and pressure in the heart increases. As a result the heart cannot pump enough oxygen and nutrients to meet the body's need. The kidneys respond by causing the body to retain fluid (water) and sodium. If fluid builds up in the arms, legs, ankles, feet, lungs or other organs, the body becomes congested. Heart failure is an example of a slowly developing health deterioration that may be detected with consecutive measurements over a period of days. Heart Failure patients tend to accumulate fluid in their limbs. The garment according to the invention may be part of a monitoring system for determining changes in the status of patients with chronic congestive heart failure, with the goal of intervening before the onset of acute congestive heart failure. As most of the fluid is accumulated close to the lungs in a preferred embodiment the garment is arranged to cover with the sensor carrier the chest of the wearer, preferably at a position close to the lungs.

The carrier comprised in the garment is bendable and inextensible. An example of a well known material that is both bendable and inextensible is a sheet of paper. Paper is however a relative fragile material making it unsuitable. Other examples of materials having the features of being both bendable and inextensible are plastic or foam. These materials are relative strong (in comparison with paper) making them suitable for use as carrier. A further advantage is that these materials are easy cleanable, processable and relatively low cost. A further advantage of choosing foam is the commercially availability of bio compatible foam materials (such as for example polyethylene foam or polyurethane foam) which easies approval procedures required for healthcare related products. Therefore in a preferred embodiment the carrier comprises foam or plastic. The sensors that are affixed to the skin facing side of the carrier are made of a flexible and electrically conductive material such as for example conductive textile or conductive silicone. The sensors may be used for sensing of physiological signals at the skin of the wearer or for stimulating by injecting a current in the skin of the wearer. The sensor comprising conductive textile or conductive silicone has the advantage of providing a 'dry contact' with the skin which makes it fit for daily use. A sensor that has to be glued each day to a same position on the body may cause skin irritation.

In a further embodiment of the garment the sensor carrier further comprises a connecting means arranged to detachably couple a monitoring means. The monitoring means comprises electronic circuitry for measuring the physiological signals obtained by each one of the sensors and is therefore electrically coupled to each one of the sensors when it is coupled to the connecting means. After putting the garment on the patient can easily couple the monitoring means to the connecting means after which the daily measurement is started. In the process for monitoring patients with chronic congestive heart failure a high frequency current is passed between electrodes applied to the chest of a patient. The current, voltage and phase angle between a measured current and voltage are determined to enable the calculation of congestive heart failure indicia values. Therefore in a further embodiment of the garment some of the sensors are used to inject the high frequency current in the body of the patient whereas other sensors are used to measure a resulting voltage. In a preferred embodiment the sensor carrier comprises at least 4 sensors that are positioned in a preferably straight line. A current source comprised in the monitoring means is coupled to the two most distant positioned sensors thereby creating a current path through the tissue of the chest. A voltage measurement means comprised in the monitoring means measures the voltage across the sensors that are positioned on the line between the two most distant positioned sensors. When fluid accumulates in the chest of the patient the impedance of the tissue will change resulting in a change of the measured voltage.

In a further embodiment of the garment each one of the sensors is coupled with a conductive cable to the connecting means. To prevent cross talk between the sensors that are used for current injection and the sensors that are used for voltage measurement a preferred cable arrangement is where the conductive cables that are coupled to the current injection sensors are positioned at the non skin facing side of the carrier and the conductive cables arranged for coupling to the measurement sensors are positioned at the skin facing side of the sensor carrier. An advantage of this cable arrangement is that it enables the use of unshielded cables. An advantage of this cable arrangement is that in a simple and low cost way crosstalk is prevented or reduced. A further advantage is that by modifying the thickness of the carrier the crosstalk can be further reduced.

In a further embodiment of the garment the current source provides an AC current with a frequency in a range of 10OkHz - 1 Mhz. The measurement means determines for a plurality of frequencies in said frequency range a voltage across two of the plurality of sensors. By measuring the voltage for a plurality of frequencies the impedance of the tissue for a plurality of frequencies is obtained. The impedance is typically in the range of 20 - 40 Ohm. The monitoring means is arranged to detect changes in the impedance by comparing the impedance value for each one of the plurality of frequencies with a threshold. The threshold may be dependent on the frequency of the current. The threshold may for example be a previously determined impedance value for said frequency of the current. This enables the detection of a decrease in the impedance resulting from fluid accumulation in the body. The invention further relates to the sensor carrier for use in the garment as discussed above. The carrier comprises a strip of a bendable and inextensible material, preferably foam or plastic, and has a plurality of sensors coupled to a skin facing side of the strip. In a further embodiment the non skin facing side comprises fastening means to allow separable fastening to the flexible wearable body structure of the garment.

In a further embodiment the sensor carrier comprises a strip of bendable and inextensible material that is covered with a textile. The sensors comprise a flexible material that is covered with a conductive textile that is stitched to the textile. Due to the flexible material included in the sensor said sensor protrudes with respect to the bendable and inextensible material that is comprised in the sensor carrier. This embodiment has the advantage of providing a sensor carrier that is fit for mass production. A further advantage is that the materials making up the sensor carrier are relatively low cost.

In a further embodiment the sensor carrier further comprises connecting means affixed to the non- skin facing side of the carrier. The connecting means allow the detachably coupling of monitoring means of which the function and features previously have been discussed. The sensor carrier further comprises electrical conductive cables that couple each one of the sensors to the connecting means. The electrical conductive cables may be shielded or unshielded.

Some of the sensors may be used to inject current in the body of the wearer whereas other sensors may be used to measure a voltage resulting from a current path of the injected current through the body. To prevent cross talk between the sensors that are used for current injection and the sensors that are used for voltage measurement a preferred cable arrangement is where the conductive cables that are coupled to the current injection sensors are positioned at the non skin facing side of the carrier and the conductive cables arranged for coupling to the measurement sensors are positioned at the skin facing side of the sensor carrier. An advantage of this cable arrangement is that in a simple and relative low cost way crosstalk is prevented or reduced thereby enabling the use of unshielded cables. A further advantage is that by modifying the thickness of the carrier the crosstalk can be further reduced.

In a further embodiment of the sensor carrier the electrical conductive cables are electrical conductive textile cables, for example a textile band with metallic conductive fibers. A textile cable provides the advantage of being connectable to a textile sensor using commercially available ultrasonic welding techniques. The invention further relates to a method for producing the discussed sensor carrier comprising the steps of ultrasonic welding of a conductive textile cable to a conductive textile comprised in a sensor and coupling the sensor to a strip of bendable and inextensible material.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Fig. 1 illustrates a garment for positioning a plurality of sensors relative to the skin of a wearer;

Fig. 2 illustrates a further garment for positioning a plurality of sensors relative to the skin of a wearer;

Fig. 3 comprising Figs. 3a, 3b and 3c illustrates a sensor carrier for use in a garment; Fig. 4 comprising Figs. 4a, 4b and 4c illustrate an embodiment of a sensor carrier;

Fig. 5 illustrates a further garment for positioning a plurality of sensors relative to the skin of a wearer;

Fig. 6 illustrates a patient wearing the garment; Fig. 7 illustrates a further sensor carrier for use in a garment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 illustrates a garment 10 for positioning a plurality of sensors 25 relative to the skin of a wearer. The plurality of sensors is comprised in a sensor carrier 20. The plurality of sensors is affixed to a material that is bendable and inextensible such as for example foam or plastic. The plurality of sensors are positioned and attached to a skin facing side of the sensor carrier. Because of the material being bendable and inextensible the skin facing side of sensor carrier will follow the contours of the body of the wearer. The garment 10 comprises a wearable body structure 15 which is made of a flexible material and which is arranged to follow closely the contours of the wearers' body thereby providing a force that pulls the sensor carrier against the body resulting in the plurality of sensors making conductive contact with the skin of the wearer. Due to the wearable body structure of the garment and the inextensible feature of the carrier the position of each sensor relative to each other and relative to the skin of the wearer will be the same each time the wearer puts the garment on. This enables the comparison of measurement data obtained with the sensors in consecutive measurements over a long period of time wherein the garment is several times put on and off.

Fig. 2 illustrates a further garment for positioning a plurality of sensors relative to the skin of a wearer wherein the sensor carrier 20 is detachable. The carrier comprises first fastening means 30 positioned on a non-skin facing side of the carrier. Second fastening means are affixed to an inner surface 40 of the garment 10. The first fastening means 30 enable a separable fastening of the sensor carrier to the second fastening means 35. This provides the advantage that the carrier 20 may be easily separated from the body structure 15 to enable cleaning. A further advantage is that the garment shown in Fig. 2 can be more easily put on than a 'sweater model' garment of claim 1, which may be advantageous for elderly patients. A further advantage is that with the use of fastening means 30, 35 such as hook and loop fasteners of the trademark Velcro the coupling of the body structure 15 to the sensor carrier 20 is adjustable to the circumference of the body of the patient.

Fig. 3 comprising Figs. 3a, 3b and 3c illustrates a sensor carrier 20 for use in a garment. Fig 3a shows a sensor carrier with the skin facing side upwards. The sensors 25 comprise a flexible material 23 and conductive textile 24 that is covering the flexible material. The sensor carrier comprises a strip 21 of bendable and inextensible material and textile 22 that is covering the strip. The strip has preferably the shape of a rectangular plane with a predetermined thickness but may have any shape. The conductive textile 24 of the sensors is sewn or stitched to the textile 21 of the carrier 20. The sensor carrier further comprises connecting means 45. Each one of the sensors is electrically coupled 31, 32 with the connecting means 45. The sensors may be used to measure a physiological signal; for example the sensors may be used to measure the ECG of the wearer. Some of the sensors may however also be used to inject an AC current in the body of the wearer, the other sensors being used to measure a resulting voltage caused by a current path through the tissue of the body. For example the two most outward positioned sensors in Fig. 3a may be used to inject an AC current, the other two sensors being used to measure a resulting voltage. To minimize the crosstalk between the cables coupling the 'current injection sensors' to the connecting means and the cables coupling the 'measurement sensors' to the connecting means 45 a cable arrangement is used wherein the (largest portion of the) cables 32 coupling the connecting means 45 to the 'current injection sensors' are positioned at the non skin facing side (indicated with the dashed line). The cables 31 coupling the 'measurement sensors' to the connecting means 45 are positioned at the skin facing side (indicated with a straight line). Fig. 3b shows a side view of the sensor carrier 20 showing the protrusion of the sensors 25 with respect to the strip 21 at the skin facing side 41. Fig. 3c shows the carrier 20 when it is bended and adjusted to the circumference of the body to which it is pulled by the flexible body structure.

Fig. 4 comprising figs 4a, 4b and 4c shows a preferred embodiment of the sensor carrier 20 according to the invention. Fig. 4c shows the sensor carrier 20 in which textile cables 31, 32 are coupled between the connecting means 45 and the sensors 25. The conductive textile cable may for example be a textile band with metallic conductive fibers. Standard textile technology like sewing provides a stable mechanical coupling of the textile cable to the textile sensor but does not give a reliable electrical coupling. Also using a conductive yarn for the sewing doesn't yield a stable electrical coupling of the textile cable to the textile sensor. In the invention it is proposed to use commercially available ultrasonic welding techniques to couple the textile fabric 24 of the sensor 25 and the textile cable 31, 32 in order to achieve a stable and reliable mechanical and electrical coupling. The welding process melts the plastic components in the yarn (e.g. Lycra). Pressure applied in the welding process then gets the non-melting metal fibers of the textile sensor and the textile cable in to contact, see Fig. 4a and 4b. The mechanical and electrical contact is fixed when the plastic hardens again. The resulting sight of the coupling contact of the textile sensor to the textile band indicates the application of ultrasonic welding, see Fig. 4b. The cables are pressed between the textile 22 and the strip 21 resulting in a fixed positioning. An advantage of this embodiment of the sensor carrier is that it uses standard materials that are easy processable making the garment comprising this sensor carrier fit for mass production.

Fig. 5 illustrates a further garment 10 for positioning a plurality of sensors 25 relative to the skin of a wearer. Monitoring means 60 are detachably coupled to the connecting means 45. The monitoring means 60 comprises electronic circuitry for measurement of physiological signals. The obtained data may be transmitted wirelessly to a base station. Fig. 6 illustrates a patient 5 wearing the garment. The shown carrier 20 comprises 4 sensors 25 positioned in a straight line. The sensors may be used to determine the bio-impedance of the tissue of the chest, and may be used to monitor fluid accumulation in the body of the patient. The two outward positioned 26 sensors are coupled to an AC current source comprised in the monitoring means 60. The other two 27 sensors are coupled to voltage measurement means comprised in the monitoring means and are used to measure the voltage resulting from a current path through the tissue of the chest.

Fig. 7 illustrates a further sensor carrier 20 for use in a garment. The monitoring means 60 comprises an AC current source 50 and voltage measurement means 55. The monitoring means is detachably coupled with the connecting means 45 to the carrier 20. The connecting means 45 further facilitate an electrical coupling of the current source 50 with the two outward positioned 26 sensors and an electrical coupling of the other two 27 sensors with the voltage measurement means 55.

Claims

CLAIMS:

1. A garment (10) for positioning a plurality of sensors (25) relative to the skin of a wearer, said garment comprising a wearable body structure (15) of flexible material characterized in that the garment further comprises a bendable and inextensible sensor carrier (20) coupled to the wearable body structure (15), each of the plurality of sensors being affixed to a predetermined position on a skin facing side (41) of the carrier (20).

2. A garment (10) according to claim 1 wherein the sensor carrier (20) is detachable, the carrier comprising first fastening means (30) preferably positioned on a non- skin facing side of the carrier (20), the first fastening means (30) being arranged for separable fastening to a second fastening means (35), the second fastening means being affixed to preferably an inner surface (40) of the wearable body structure (15).

3. A garment (10) according to claim 2 wherein the garment (10) is arranged to cover with the sensor carrier (20) the chest of the wearer (5), preferably at a position close to the lungs.

4. A garment (10) according to any one of claims 1-3 wherein the sensor carrier (20) comprises preferably plastic or foam and each one of the sensors (25) comprises preferably conductive textile or silicone.

5. A garment (10) according to any one of claims 1-4 wherein the sensor carrier (20) further comprises a connecting means (45), each one of the sensors (25) being electrically coupled to the connecting means, the connecting means being arranged for detachable mechanical coupling of a monitoring means (60) to complete an electrical current path between each one of the sensors and the monitoring means (60).

6. A garment (10) according to any one of claims 1-5 wherein the sensor carrier (20) comprises at least 4 sensors (25) being positioned in a preferably straight line, the monitoring means (60) comprising a current source (50) arranged to be coupled to the two most distant positioned sensors (26), the monitoring means further comprising voltage measurement means (50) arranged to be coupled to the sensors not being the two most distant positioned sensors.

7. A garment (10) according to claim 6 wherein each one of the sensors (25) is coupled with a conductive cable to the connecting means (45), the conductive cables arranged for coupling to the two most distant positioned sensors (26) being positioned at the non skin facing side of the carrier, the conductive cables arranged for coupling to the sensors other than the two most distant positioned sensors being positioned at the skin facing side (41) of the sensor carrier (20).

8. A garment (10) according to claim 6 or claim 7 wherein the current source (50) is arranged to provide an AC current with a frequency in a range of 100kHz - 1 Mhz, the measurement means (55) being arranged to determine for a plurality of frequencies in said range a voltage across two of the plurality of sensors (27) not being the most distant positioned sensors, the monitoring means (60) being arranged to compare the determined voltages with a threshold.

9. A sensor carrier (20) for use in a garment according to any one of claims 1 - 8, the carrier comprising a strip (21) of a bendable and inextensible material, preferably foam or plastic, the carrier further comprising a plurality of sensors (25) affixed to a skin facing side (41) of the carrier (20).

10. A sensor carrier (20) according to claim 9 wherein the strip (21) is covered with a textile (22), each one of the sensors (25) comprising a flexible material (23) covered with a conductive textile (24) and being sewn to the textile (22).

11. A sensor carrier (20) according to claim 9 or 10 further comprising connecting means (45) affixed to the non-skin facing side of the carrier, the carrier (20) further comprising electrical conductive cables (31, 32) coupling each one of the sensors (25) to the connecting means, the connecting means being arranged for detachably mechanical coupling of monitoring means (60) to complete an electrical current path between each one of the sensors and the monitoring means (60).

12. A sensor carrier (20) according to claim 11 wherein each electrical conductive cable (31, 32) comprises a textile band having metallic conductive fibers wherein the mechanical and electrical coupling of the electrical conductive cable with the conductive textile covering the sensor (25) is obtained with ultrasonic welding.