CPR FEEDBACK DEVICE

Abstract

A medical device for lay rescuers and first aiders as part of “survival chain” in cardiac arrest scenario. The device gives audible feedback to its user regarding the adequate chest compression depth, based on American Heart Association (AHA) guidelines. In addition, it raises user's sense of capability and confidence in cases of cardiac emergencies.

Claims

1. A portable medical device for lay rescuers and first aiders as part of “survival chain” in cardiac arrest scenario built to fit between user's palm and patient chest to be applied on middle of patient's chest, returning audible feedback with every correct chest compression provided, comprising: an upper part made of soft material to ergonomically fit human palm, glued to a solid upper cover; and a picture or a schematic drawing placed on its upper part indicating the correct place on patient chest where device is to be placed; and An upper lid located under the soft layer made of solid material capable of enduring high pressure, connected to the other parts of the device by a rotatory closing system; and a lower lid made of solid material; and A printed electronic circuit (PCB) located on the solid lower lid comprising a comparator comparing one analogue voltage level with another analogue voltage level or some preset reference voltage producing an output signal based on voltage comparison; Printed circuit and Sensors; and electronic components assembled on top of the printed electronic circuit; and a Force-sensitive resistor (FSR) sensor comprising three layers attached to the rear side of lower lid in a niche and whereas one layer comprises active element dots; and A cushion made of soft concave material having a circular curved elevation made of same material located in lower part of the device being in contact with patient's chest.

2. A portable device according to claim 1 wherein the solid upper lid may be manufactured by plastic injection into a three-dimensional printer.

3. A portable device according to claim 1 wherein the curved cushion's inner part having no contact with patient's chest, is located about a millimeter away from sensor and when causing pressure on patient's chest the curved cushion is compressed gradually touching sensor and activating the electric circuit.

4. A portable device according to claim 1 wherein FSR has a variable resistance as function of applied pressure.

5. A small portable device according to claim 4 wherein FSR is made of two layers separated by a spacer.

6. A portable device according to claim 4 wherein the layer of the FSR is the active area having active element dots, solid spacer has air vent and layer is made of a conductive film and a flexible substrate.

7. FSR according to claim 4 wherein the more one presses, the more of the active element dots touch the semiconductor reducing resistance.

8. FSR according to claim 4 wherein with no pressure, the sensor looks like an infinite resistor (open circuit) and as pressure increases, resistance reduces.

9. A portable device according to claim 1 wherein comparator compares magnitudes of two voltage inputs and resistors' predetermined reference voltage is connected to negative entrance of compactor.

10. A comparator according to claim 9 wherein when circuit is stable, the output is 0 volt and buzzer is on “off” position and when sensor is pressed, voltage in positive entrance of comparator changes and the higher the pressure gets, so does the voltage in positive entrance of comparator; and when voltage in positive entrance of comparator passed the predetermined reference voltage, comparators' outlet changes from 0 to 3 volts and buzzer is turned on.

11. A comparator according to claim 9 wherein predetermined pressure for FSR to close circuit is 50 kg.

12. A portable device according to claim 1 having a suitable silicone adapter wherein the upper part of the adapter is flat, and its bottom part contains a hollow opening for the portable device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0081] FIG. 1—External view of the device.

[0082] FIGS. 2a-2f—Layout of device's parts.

[0083] FIG. 3—Location of FSR sensor

[0084] FIGS. 4a-4c—Internal view of device in open cut.

[0085] FIGS. 5a-5b—Lower silicone cushion inner.

[0086] FIG. 6—Schematic print of circuit board (PCB).

[0087] FIG. 7—electrical components.

[0088] FIG. 8—FSR sensor description.

[0089] FIG. 9—FSR sensor diagram

[0090] FIG. 10—Sensor Characteristics

[0091] FIG. 10—Spatial structural change of circular concave elevation

[0092] FIG. 11—Silicone adapter

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0093] The device is a small portable device, (approximately D: 50 mm; thickness 24 mm; height 57 mm), built to fit between user's palm and patient chest (FIG. 1). A bystander who carries the device applies it on the middle of patient's chest as shown in picture/schematic drawing 101. The user receives audible feedback with every correct chest compression provided; otherwise, the device stays silent.

[0094] Device's upper part, soft upper pad 104, (FIG. 1) is made of soft material, (like, for example, rubber), to ergonomically fit user's palm. The soft upper pad 104 is glued to solid upper cover 100. Picture/schematic drawing 101 which is placed on upper pad 104 describes the correct place on patient chest where the device is to be placed.

[0095] A solid upper lid 100 is located under upper pad 104. That lid may be manufactured by plastic injection into a pre-designed mold. The material of the lid has to be of a solid material capable of enduring the high pressure inflected on the device when performing the CPR.

[0096] Upper lid 100 connects to the other parts of the device by a single screw and by a rotatory closing system 110 (FIG. 4c).

[0097] A printed electronic circuit 105 (PCB) (FIG. 2c) is located under plastic lid 100 (FIGS. 2b and 2c). On top of which electronic components are assembled (FIG. 2c). The circuit connects to a hard-lower lid 103 by two screws 112 (FIG. 4a).

[0098] Hard lower lid 103 is made of solid material similar to the material of solid upper lid 100 and may also be manufactured by plastic injection into a pre-designed mold. Electronic circuit 105 is printed on lower lid 103 (FIG. 2d).

[0099] FSR sensor 106 (FIG. 2e) is attached to the rear side of hard lower lid 103. Sensor 106 is inserted into a niche of about 0.5 millimeter 103A on the rear side of hard lower lid 103 (FIG. 3), in order to isolate sensor 106 from any contact with cushion 107 to avoid electric current to save buttery 108 (FIG. 4a).

[0100] Cushion 107 (FIG. 2f) which is made of soft concave material is located in lower part of the device and is in contact with patient's chest. The inner part of cushion 107, which has no contact with patient's chest, is located about 0.5 mm away from sensor 106. When causing the pressure on patient's chest, cushion 107 is compressed and touches FSR sensor 106. The contact with the sensor activates the electric circuit.

PCB 105 has 3 parts (FIG. 4a): [0101] (1) Comparator 109 compares one analogue voltage level with another analogue voltage level or some preset reference voltage, VREF and produces an output signal based on this voltage comparison. In other words, the op-amp voltage comparator compares the magnitudes of two voltage inputs and determines which is the larger of the two (FIG. 6). [0102] (2) Printed circuit 113 (FIG. 7). [0103] (3) Force-sensitive resistor (FSR) sensors 106 (FIG. 8).

[0104] FSR 106 has a variable resistance as a function of applied pressure. The FSR is made of 2 layers 106a & 106d separated by spacer 106b. Layer 106a is the active area having Active Elements dots, plastic spacer 106b has air vent 106c. Layer 106d is made of a conductive film and a flexible substrate. The more one presses the device, more of those Active Element dots on 106a touch the semiconductor decreasing the resistance. When there is no pressure, the sensor looks like an infinite resistor (open circuit), as the pressure increases, the resistance decreases (circuit closes) (see FIG. 9).

[0105] As explained above, comparator 109 (FIG. 4b) compares the magnitudes of two voltage inputs. Resistors' predetermined reference voltage is connected to negative entrance of compactor 109.

[0106] When circuit is stable, the output is 0 volt and buzzer is on “off” position. When sensor is pressed, voltage in positive entrance of comparator 109 changes. The higher the pressure gets, so does the voltage in positive entrance of comparator 109. When voltage in positive entrance of comparator 109 passed the predetermined reference voltage, comparator 109 outlets changes from 0 to 3 volts (battery 108 voltage) and buzzer 111 is turned on (FIG. 4b). (See table 1 that refers to FIG. 6)

TABLE-US-00001 TABLE 1 Item Value Description FSR High Force Sensing Resistors resistance R1  50 Kohm Used to tune the sensitive of the system R2 2.2 Kohm Reference Voltage R3 2.2 Kohm Reference Voltage IC1 LMV321 Comparator Buzzer HS-123B The buzzer will be active when the comparator output will be ‘ON’. Battery CR2032 Battery 3 Volts

[0107] The predetermined pressure for FSR 106 to close circuit as explained above is 50 kg, based on numerous researches detailed above. It was proved that, in order to effectively reach, patients' chest pressure of 50 kg., user shall have to get as deep as 51 mm in over 50% of tested patients. See tables 2 & 3:

[0108] With the aim of saving lives and increasing the survival rates following a cardiac arrest, the device has to be widely distributed and used. With this in mind, the device was designed to be easy to use, small dimensional and affordable.

[0109] As mentioned above, a change (decrease) in the FSR resistance is achieved with increasing force applied on it. As seen in FIG. 10 (Sensor Characteristics) the sensor's ‘Pressure Sensitivity Range’ (highlighted in yellow) is 1 to 125 PSI (0.07 kg/cm.sup.2-8.78 kg/cm.sup.2). Yet, a thorough examination of the FSR resistance-pressure curve (FIG. 8) shows that the actual sensitivity range is even lower: 1-80 PSI (0.07 kg/cm.sup.2-5.62 kg/cm.sup.2) as at values above 80 PSI the curve is near constant.

[0110] The ranges of the FSR are much lower than needed according to CPR guidelines for effective chest compressions (50 kg).

[0111] Choosing FSR that would endure higher weights (50 kg as needed) will make the whole device not affordable to the end user.

[0112] A special mechanic structure combined with specific material's specifications as used in our device (silicon hardness level and compression capability) causes partial absorption of applied pressure as well as gradual distribution of the remaining pressure on the FSR. This allows the FSR in question to work under applied pressure of 50 kg.

[0113] As may be observed in FIG. 11, when compression is made by the user, the silicon cushion which comes in direct contact with patient's chest, absorbs certain amount of the pressure due to its compressibility. At a certain point, a circular curved elevation (made of same compressible silicon material) in inner part of cushion 107 (FIG. 5) meets the FSR and is being compressed against it. The more pressure is applied, the more it changes its spatial structure (becoming flat) and comes in more contact with FSR 106 (gradual pressure) allowing the use of FSR 106 under applied pressure of 50 kg. Using an FSR with higher ‘Pressure Sensitivity Range’ is not cost-effective and will not allow its wide spread among the general population thus increasing the chance of using it in real time (see FIG. 10)

[0114] If the elevation in inner silicon cushion 114 is flat (not curved), the pressure would have to be applied overall FSR surface at one time rather than gradually, thus preventing the buildup of a pressure equivalent to 50 kg.

[0115] A Silicone adapter 115 of about 7.2 cm diameter is provided with each device and may be used at user's choice and preference (FIG. 12).

[0116] Adapter 115 is made of soft silicone material. The upper part of adapter 115 is flat while it's bottom part 116 contains a hollow opening for the insertion of the original small device. Due to a larger surface area, adapter 115 increases user's comfort when prolonged CPR is required (rural areas, medical teams etc.)

[0117] Silicone adapter 115 enables the use of the device in hospital where prolonged CPR is required, maintaining the principles of the simplicity and cost-effectiveness of original device.