GB1569140A - Body surface contour deformation sensor and method - Google Patents

Description

(54) BODY SURFACE CONTOUR DEF ORMATION SENSOR AND METHOD (71) 1, LOREN WILLIAM LEONARD, a citizen of the United States of America, of 162 Plantation, Houston, Texas 77024, U.S.A., do hereby declare the invention, for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following state ment: This invention relates to a method and a device for detecting body swelling.

Attempts have been made in the past to detect swelling or edema in a patient, for example swelling caused by improper operation of a needle or catheter, as evidenced by U.S. Patent No. 3,853,118. Devices of this sort are limited in their capability and, in particular, point out some of the medical problems associated with intravenous infusions into the human body.

Customarily, intravenous (Br) infusions are achieved by inserting a needle or catheter of the proper gage cannula typically just under the skin and into a subcutaneous vein. Two or three problems typically occur. At the time of insertion of the cannula, the medical personnel may believe that it was inserted without lateral movement into a presumably straight vein when in fact the point was laterally misaligned or otherwise contacted against the vein wall thereby forming tears or scratches on interior vein walls which are undesirable. The cannula may be too large for the vein. Further, the venipuncture site may not.seal around the cannula. On insertion through the layers of subsurface skin (dermis and epidermis) including the wall of vein leakage (extravasation) may occur back along the cannula. Even if the cannula is perfectly placed in the vein with no problems, subsequent patient movement can inadvertently force the cannula through a vein to infuse the IV fluid into body tissue (otherwise known as infiltration). This leakage between layers of the skin sometimes is very harmful because the IV solution is delivered to the wrong part of the body of the patient typically causing phlebitis or thrombophiebitis. A further problem is enlargement of the small openings formed by the cannula and resultant chemical or hydraulic action of the IV solution.

That is to say, the cannula is correctly inserted but after it has been in place for a period of time, extravasation along the pinhole sized openings formed in the path of the cannula may occur and thereby cause swelling to be formed in the near vicinity.

Most of the problems which arise with difficulty in IV infusions are evidenced with a slight early swelling in the immediate area. The swelling is very slight and difficult to observe in the beginning. However, it is at this juncture that remedial steps are most effective.

The present invention provides in one aspect a device for detecting edema or body swelling comprising a sensor head formed from inflexible material and having a recess therein and a flat skirt portion wholly surrounding the periphery of the recess whereby the sensor head can be placed against a selected area of a patients skin with the recess nearest the skin to form a chamber whose volume is varied by deformations in the skin, and with the skirt flat against the skin, adhesive means being provided for securing the sensor head against the skin without the deformation or compression of the skin and a tube communicating with the inside of said recess being connected to pressure sensing means arranged to detect changes in pressure within the chamber whereby deformations of the skin causing such pressure changes are detected by the pressure sensing means.

By "inflexible'', we mean that the material of the sensor head is sufficiently rigid not to be distorted by changes in pressure in the recess.

In another aspect the invention provides a method for detecting edema or body swelling using a device as defined above wherein the recess in the sensor head of the device is placed against the skin of a patient and adhesively secured thereto and wherein changes in pressure within the chamber due to localised swelling under the skin covered by the recess are detected by the said pressure sensing means.

With the foregoing edema problems in view, the present apparatus is a device which can detect swelling in the near vicinity of the site of an IV infusion or some other source of edema. It is sensitive and therefore able to provide a prompt and early indication of swelling so that remedial steps can be taken quickly to avoid aggravated problems. The signal is provided sufficiently promptly to enable removal of the needle or aleviation of the source of edema so that the problem is not aggravated by continued swelling and accumulation of IV fluids at an unintended location. If the infusible is not delivered to the intended location, the medication may be lost and the planned program of treatment will be delayed and recovery will be delayed. More importantly, this apparatus is able to be attached at any point of the body where a needle is inserted into the human body. It can be attached close to an incision or fracture beneath a bandage or cast. Typically, needles are inserted in the veins of the arms or legs but the am paratus is not limited to those locations.

It is able to be attached without the use of a tourniquet or pressure cuff extending around the limb or trunk of the body.

Moreover, it can be left unattended and yet forms a signal which sounds through an appropriate alarm device an alarm to nursing personnel. As a result of the use of the present device, localized trauma and edema in the vicinity of the site of an IV infusion or other edema is thereby avoided and the problems associated with a localized injury are thereby either reduced or avoided.

The device preferably has a thin flexible membrane affixed across the recess. This layer may have a skin contact adhesive on its outer side so that it attaches to the body and takes the form or shape of the body and secures the sensor head in position. The adhesive layer closes over the chamber. The chamber formed in the outer body captures a certain volume of air. As swelling occurs, the thin adhesive membrane deflects into the chamber thereby changing air pressure in the chamber.

The chamber is communicated by a small passage into a tubing which is connected to a pressure transducer which forms a signal indicative of a change in pressure.

Other geometric shapes of chamber may be used.

In an alternative embodiment, the device is constructed with an outer rigid body member defining a chamber which is open on one face and the adhesive means attaches the surrounding skirt to the skin of the patient. When the skirt is adhesively attached to the skin, the suspected area of swelling is free to protrude into the chamber formed by the recess. The adhesive closes the chamber.

Figure 1 is a perspective view of the IV swelling detector of the present disclosure showing a flexible pneumatic tube extending to a signal transducer; Figure 2 is a section plan view of the sensor head of the device of Fig. 1 showing details of construction.

Figure 3 is a lengthwise sectional view along the center line of the sensor head showing the thin membrane which attaches across the recess for communicating swelling of a patient which is converted into a pressure signal in a conduit extending from the chamber on the left hand side of the Figure, and showing the open recess alternative embodiment with no membrane attached where the area of swelling protrudes into the chamber as seen on the right hand side of the Figure; and Figure 4 is a transverse sectional view through the sensor head showing additional details of construction of the recess.

Attention is first directed to Figure 1 of the drawings where the IV swelling detector of the present invention has a sensor head identified generally by the numeral 10. The edema detector will be described for detection of swelling in the specified example and other examples of its use will be set forth later. It is connected by way of a small flexible hollow tube 12 to an alarm device 14. The apparatus operates, and will be described, by forming small pressure signals in the tubing 12 which are communicated to the alarm device 14.

The alarm device itself is resnonsive to a small change in pressure, and if the change is of specified size, it forms an alarm signal such as the sounding of a bell.

Going to Figures 2 to 4 of the drawings, the numeral 16 identifies a surrounding flat skirt which is generally rectangular except that a notch 18 is removed from one end.

The surrounding skirt defines a generally flat surface as illustrated in the drawings.

A needle or catheter which typically will measure from about three to ten centimeters in length extending from a fitting is inserted at the appropriate location into a patient. The rectangular skirt is positioned immediately adjacent to the needle with the actual point of insertion located at the notch 18 The skirt serves as an anchor or relatively fixed platform for the device.

The need'e can be inserted approximately parallel and located along a center line af the apparatus, and hence, it is positioned just beneath an internal approximately rectangular recess 20 centered in the surrounding skirt. The notch 18 enables the recess 20 to be positioned in an overlying relationship above the catheter adjacent to the point of insertion. In other words, the full length of the needle which is inserted into the body of the patient is located just beneath the recess 20. Swelling normally occurs in the near vicinity of the recess 20 and accordingly, the surrounding skirt is notched to enable the chamber to be located as close as possible to the full length of the needle. The apparatus connected to the catheter or cannula normally lays against the body, often aided by the use of adhesive tape to fix it in location. This limits movement of the needle or catheter and the possibility of traumatic injury as a result of the unwanted movement. Moreover, the apparatus is able to be used at any point where a needle or catheter is inserted. This is particularly helpful in that it is not limited to attachment to the limbs of a person through the use of a surrounding pressure cuff or other strap mechanism.

The sensor head 10 is formed with an outer body portion 24. The portion 24 incorporates the surrounding skirt and, at the central portions thereof, a raised shoulder defines an upstanding wall portion 26 Which captures a certain air volume therewithin to define the recess 20. The sensor head 10 is preferably formed of a fairly rigid plastics material about 10 times or more stiffer than the diaphragm described below.

The recess itself is in the forni of a generally rectangular space. The sidewall 26 which defines the surrounding edge of the chamber is preferably formed at an angle to enable ease of removal from an injection molding machine. This enables easy removal by the incorporation of a suitable draft angle at the sidewall 26. The chamber itself measures up to about 10 centimeters in length, and typically is in the range of two or three centimeters in width.

While it can be larger, it is not necessary that a larger recess be formed. The recess is up to about one centimeter in depth.

The chamber itself is thus defined on five sides by the outer body portion 24 and is closed over by a thin diaphragm 30 made of flexible plastic material of about three mil thickness. Tn an alternative embodiment, the recess 20 is onen in the last side or face. A suitable adhesive is placed on the outer skirt or lip of the body portion 24.

The adhesive attaches the open body portion 24 to the patient's body and seals the recess 20 directly against the skin of the patient.

The diaphragm 30 is adhesively joined to the surrounding skirt 16. It is stretched tight over the chamber. and upon closing against the outer body 24, thus defines the chamber. The diaphragm 30 is formed of relatively thin material, and typically is up to about 10 mils in thickness and has a tensile strength sufficient to flex with the skin of the patient, and elasticity to deflect with swelling. Thinner material can be used although material in the range of one or two mils are perhaps a bit on the fragile side. A suitable thin adhesive is placed on the outer surface of the diaphragm 30.

The adhesive fixes the diaphragm to the patients body.

The adhesive selected in either of the above described embodiments is preferably a type which is non-toxic, non-allergenic, and non-pyrogenic. Preferably, the adhesive is placed on the dipahragm 30 or skirt 16 at the time of manufcature. The tacky surface is then covered with a disposable wrapper which protects the adhesive during manufacture, shipment and storage.

The wrapper is easily removed at the time of installation. This exposes the tacky surface which then enables the sensor head 10 to be quickly and temporarily attached to the body of a patient. To this end, the outer wrapper is peeled from the diaphragm 30 or skirt 16 and the apparatus is then ready for installation. The adhesive also functions as a sealant preventing leaks of air from beneath the skirt.

The outer body 24 is formed with a hollow fitting 36 at one end. The fitting 36 extends through the sidewall 26. An axial passage from the recess 20 to the exterior is thus defined. The fitting 36 is sized to receive the pneumatic tube 12 which is inserted into it. The tube 12 is preferably joined to the fitting 36 in a leak proof connection. This enables the tube 12 to transfer elsewhere a pneumatic signal formed by the change of volume in the chamber formed by recess 20. Pressure changes of 0 04 psi and smaller caused by edema have been detected. It is best to consider the operation of the device to enhance the explanation. The device is packaged as described above with a disposable wrapper which is peeled from the diaphragm 30 or skirt 16. At the time of installation, the needle is first inserted in the patient. The needle serves as a marker limiting the location of the sensor head 10. The needle thus defines the center line position, and the diaphragm face or skirt is placed over the point of insertion and the immediate vicinity. The wrapper is peeled from the diaphragm 30 or skirt 16, and the sensor head 10 is gently but firmly adhesively joined to the body of the patient. At this juncture, substantially the entire length of the needle is located so that any edema associated with the use of the needle is detectab1e by deformation or deflection of the diaphragm or in the alternative embodiment where no diaphragm is used by direct tissue swelling into the chamber as seen in the right hand portion of Figure 3. The tubing 12 is connected to the alarm device 14. The sensor is relatively rigid but can be bent sufficiently to be wrapped around the arm of a small person (e.g. a baby) in which case of course the diaphragm is deformed accordingly. This does not detract from use of the device; rather, it enables the sensor head to be affixed to the patient even though the arm or leg is extremely small. Sensitivity is increased by bending the head.

After attachment, the IV infusion proceeds with the passage of time. In the event that swelling occurs for any reason, the swelling is manifested at the site of the needle by localized swelling. The swelling is very slight at first as might occur by the accumulation of only a small portion of the injectable subcutaneously in the patient. The device is sensitive to edema having a volumetric displacement of a very small drop, or about 65 microliters change.

Should a less sensitive device be desired, the alarm device can be calibrated to sound on larger pneumatic changes. This slight and localized swelling is nevertheless sufficient to deform the diaphragm 30. When the diaphragm is deformed, it is forced into the chamber 20 to compress air. This reduces the volume of the chamber 20.

In the alternative embodiment, as seen in the right hand portion of Figure 3, where diaphragm 30 is omitted and recess 20 is open, the localized swelling directly protrudes into chamber to reduce the volume of the chamber. As the volume is reduced, an air pressure change is forced from it through the tubing 12. The pressure change forced into the tubing 12 thus becomes a pneumatic signal communicated through the tubing to an alarm device 14.

An alarm is sounded. This quickly brings nursing personnel to attend the patient and particularly to inspect the area surrounding the site of the IV needle. Speed of detection is many fold over the other techniques.

The apparatus is advantageous in that it furnishes an early warning of swelling and trauma.

Separate and apart from the foregoing, the edema detector can be used to detect swelling from other sources. As an example consider a cast applied to the upper leg. The swelling detector can be slipped under the cast and adhesively joined to the patients skin and left there. The skirt around the chamber is sized to extend beyond the area of expected swelling and thus serves as a type of reference. This will enable the device to extend beyond the localized swelling. This avoids swelling which lifts the entire detector.

WHAT I CLAIM IS: - 1. A device for detecting edema or body swelling comprising a sensor head formed from inflexible material and having a recess therein and a flat skirt portion wholly surrounding the periphery of the recess whereby the sensor head can be placed against a selected area of a patients skin with the recess nearest the skin to form a chamber whose volume is varied by deformations in the skin, and with the skirt flat against the skin, adhesive means being provided for securing the sensor head against the skin without the deformation or compression of the skin and a tube communicating with the inside of said recess being connected to pressure sensing means arranged to detect changes in pressure within the chamber whereby deformations of the skin causing such pressure changes are detected by the pressure sensing means.

2. A device according to claim 1 wherein a membrane of relatively flexible material is stretched across the said recess and thereby overlies, and conforms to the shape of, the skin facing the recess.

3. A device according to claim 2 wherein the adhesive means comprises a skin contact adhesive on the outer surface of the membrane.

4. A device according to claim 2 or claim 3 wherein the membrane has a thickness of from 1 to 10 mm.

5. A device according to any one of claims 2 to 4 wherein the membrane extends over the entire area of the side of the skirt which abuts the skin.

6. A device according to any preceding claim wherein the recess is of generally rectangular shape.

7. A device according to any preceding claim wherein the skirt has a notched for tion thereof to allow the sensor head to be positioned over the end of a needle or catheter projecting through the skin.

8. A device for detecting body swelling or edema substantially as herein described with reference to, or as illustrated in, the accompanying drawings.

9. A method for detecting edema or body swelling using a device according to any preceding claim wherein the recess in the sensor head of the device is placed against the skin of a patient and adhesively secured thereto and wherein changes in pressure within the chamber due to loca

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. in the right hand portion of Figure 3. The tubing 12 is connected to the alarm device 14. The sensor is relatively rigid but can be bent sufficiently to be wrapped around the arm of a small person (e.g. a baby) in which case of course the diaphragm is deformed accordingly. This does not detract from use of the device; rather, it enables the sensor head to be affixed to the patient even though the arm or leg is extremely small. Sensitivity is increased by bending the head. After attachment, the IV infusion proceeds with the passage of time. In the event that swelling occurs for any reason, the swelling is manifested at the site of the needle by localized swelling. The swelling is very slight at first as might occur by the accumulation of only a small portion of the injectable subcutaneously in the patient. The device is sensitive to edema having a volumetric displacement of a very small drop, or about 65 microliters change. Should a less sensitive device be desired, the alarm device can be calibrated to sound on larger pneumatic changes. This slight and localized swelling is nevertheless sufficient to deform the diaphragm 30. When the diaphragm is deformed, it is forced into the chamber 20 to compress air. This reduces the volume of the chamber 20. In the alternative embodiment, as seen in the right hand portion of Figure 3, where diaphragm 30 is omitted and recess 20 is open, the localized swelling directly protrudes into chamber to reduce the volume of the chamber. As the volume is reduced, an air pressure change is forced from it through the tubing 12. The pressure change forced into the tubing 12 thus becomes a pneumatic signal communicated through the tubing to an alarm device 14. An alarm is sounded. This quickly brings nursing personnel to attend the patient and particularly to inspect the area surrounding the site of the IV needle. Speed of detection is many fold over the other techniques. The apparatus is advantageous in that it furnishes an early warning of swelling and trauma. Separate and apart from the foregoing, the edema detector can be used to detect swelling from other sources. As an example consider a cast applied to the upper leg. The swelling detector can be slipped under the cast and adhesively joined to the patients skin and left there. The skirt around the chamber is sized to extend beyond the area of expected swelling and thus serves as a type of reference. This will enable the device to extend beyond the localized swelling. This avoids swelling which lifts the entire detector. WHAT I CLAIM IS: -

1. A device for detecting edema or body swelling comprising a sensor head formed from inflexible material and having a recess therein and a flat skirt portion wholly surrounding the periphery of the recess whereby the sensor head can be placed against a selected area of a patients skin with the recess nearest the skin to form a chamber whose volume is varied by deformations in the skin, and with the skirt flat against the skin, adhesive means being provided for securing the sensor head against the skin without the deformation or compression of the skin and a tube communicating with the inside of said recess being connected to pressure sensing means arranged to detect changes in pressure within the chamber whereby deformations of the skin causing such pressure changes are detected by the pressure sensing means.

2. A device according to claim 1 wherein a membrane of relatively flexible material is stretched across the said recess and thereby overlies, and conforms to the shape of, the skin facing the recess.

3. A device according to claim 2 wherein the adhesive means comprises a skin contact adhesive on the outer surface of the membrane.

4. A device according to claim 2 or claim 3 wherein the membrane has a thickness of from 1 to 10 mm.

5. A device according to any one of claims 2 to 4 wherein the membrane extends over the entire area of the side of the skirt which abuts the skin.

6. A device according to any preceding claim wherein the recess is of generally rectangular shape.

7. A device according to any preceding claim wherein the skirt has a notched for tion thereof to allow the sensor head to be positioned over the end of a needle or catheter projecting through the skin.

8. A device for detecting body swelling or edema substantially as herein described with reference to, or as illustrated in, the accompanying drawings.

9. A method for detecting edema or body swelling using a device according to any preceding claim wherein the recess in the sensor head of the device is placed against the skin of a patient and adhesively secured thereto and wherein changes in pressure within the chamber due to loca

lised swelling under the skin covered by the recess are detected by the said pressure sensing means.

10. A method according to claim 10 substantially as herein described with reference to the accompanying drawings.