FI98266C - A device intended for personal use to monitor life functions - Google Patents

Description

98266

PERSONAL BODY MONITORING DEVICE

The invention relates to a portable or ambulatory device for personal use which monitors and measures the vital functions of its wearer non-invasively. The device mainly measures the oxygen saturation 5 (oxygen saturation) of the wearer's blood and possibly other vital signs. In addition to the measuring sensors, the device is equipped with a memory and a data processing unit. The device may further be provided with a display and / or an alarm.

Many 10 different devices have been developed to monitor human vital functions. Devices used in a hospital environment are usually attached to the patient, providing continuous real-time information about the patient's condition. The second group consists of easily mobile devices, which are used to perform the measurement when necessary.

15 The latter devices can also be used at home and carried with you. An example is a standard thermometer. The advantage of hospital equipment permanently connected to the patient is the long-term collection of data made possible by continuous measurement and the possibility to warn of 20 disorders of vital functions. The disadvantage of hospital devices is that they bind the patient to the bed or at least to the laboratory space in the vicinity of the device.

Devices for outpatient use that continuously register vital signs have also been developed. An example of such is the wrist-connected device described in International Patent Publication WO 93/16636, which comprises sensors e.g. to measure skin temperature and electrical conductivity, heart rate, and hand movements. The device further comprises a radio transmitter 30 connected to a separate receiver. However, this wristband device does not comprise any oximeter, i.e. a device for measuring oxygen saturation. This is an obvious shortcoming because in certain situations, measuring oxygen saturation is more important than, for example, measuring body temperature or pulse 2 98266.

U.S. Patent No. 5,275,159 discloses a portable device for diagnosing sleep apnea for monitoring a patient's heart rate and blood oxygen saturation. The oximeter used here is of the conventional type based on the measurement of light passing through a finger. However, due to the oximeter solution and the solution of other components, this set of devices significantly limits the normal life of a person. Because of this, it cannot be considered as an actual 10 outpatient device that a person could use for an extended period of time without interfering with their normal life.

It is an object of the present invention to obviate the above problems and to provide a new vital signs monitoring device for ambulatory use which does not have the limitations of previously known devices.

The features of the invention appear from claim 1.

Measurement of blood oxygen saturation has been cumbersome with current equipment, and the need for continuous measurement is apparently not fully understood. However, for certain 20 groups of people (e.g., young children and sleep apnea patients), measuring and monitoring oxygen saturation is particularly important in some situations. With the device according to the invention, the above-mentioned drawbacks can be remedied. The device according to the invention is a lightweight integral unit which can be easily carried along and which still continuously measures and stores the vital functions of its wearer. The device according to the invention can be particularly conveniently placed on the wrist, in which case the use of the device does not differ from the use of an ordinary wristwatch. All the sensors of the device, 30 data processing and storage circuits, the power supply and other necessary components are located in a single device.

The device according to the invention can be used for a wide variety of purposes 3 98266 and the main areas of application are presented below:

Sleep apnea syndrome research

Obstructive sleep apnea syndrome (abbreviated as 5 OSAS), or sleep apnea syndrome, has in recent years become one of the main targets of medical sleep research. As research progresses, it has become clear that this is a real public disease. 1-2% of the adult population (up to 3-5% of the working-age male population) and about 5% of 10 children experience some degree of sleep apnea. As severe, the disease involves a significant strain on both the central nervous system, the lungs and the bloodstream, and thus a wide range of immediate and chronic health, safety and social risks. If left untreated, pediatric sleep apnea syndrome 15 can lead to serious consequences, even central nervous system damage.

Sleep apnea syndrome can be studied with a so-called sleep mattress that registers body, heart and lung movements. There is an obvious need to include a measurement of blood oxygen content in Uniap studies. When sleep apnea syndrome is suspected in a child, it would always be good to perform long-term registration of sleep apnea (Matti Erkinjuntti, Markku Partinen & Heikki Lang: "Obstructive sleep apnea syndrome", KIASMA, Turku 1990). The device 25 according to the invention thus provides valuable additional information for sleep apnea research and the device can monitor the situation of sleep apnea patients.

Investigation and prevention of sudden deaths Sudden infant death syndrome (abbreviated as 30 SIDS) is the sudden unexplained death of a child under one year of age. Investigating cache deaths is difficult because the deaths occur imperceptibly, mostly in the morning, when the child is not observed. The device according to the invention may be helpful in determining the causes of cache death, as the device registers the events in memory for later analysis. This allows for a broad-based study at a reasonable cost.

5 Studies in the field (Pertti Rintahaka: "Sudden infant death syndrome in Finland in 1969-80. An Epidemiological Study". Publications of the Finnish Medical Board. Series Studies 3/1985, Helsinki 1985) are suspected to cause respiratory arrest. Since the device according to the invention accurately measures the oxygen saturation of the blood, it is possible to detect even a short respiratory failure. The device is therefore helpful in preventing sudden deaths, as the device can wake up the child and its guardians with an alarm when they notice that breathing is blocked or stopped.

15 Health monitoring

The device according to the invention can continuously collect information on the state of health of the wearer for the safety of the sick or elderly. In the event of a seizure, it can also issue an alarm by phone. The device can provide advance notice of an illness-20 to workers whose illness may cause an accident.

patient monitoring

In a hospital, the device according to the invention can also be used for continuous monitoring of the health status of patients outside the intensive care unit. In addition, the device is suitable for use in temporary and / or poorly equipped hospitals (field hospitals and hospitals in developing countries).

The invention will now be described with reference to the accompanying figures, in which Figure 1 schematically shows the basic functions of the device according to the invention.

Figure 2 shows the basic operation of the oxygen saturation sensor used in the device according to the invention

Figure 3a shows a device according to the invention fitted to a wristband. Figure 3b shows the skin-facing side of the device according to Figure 3a.

Figure 4 shows oxy and deoxyhaemoglobin absorption curves

Figure 5 shows a circuit diagram of the oxygen connection of the oxygen saturation sensor

Figure 6 shows the decrease in oxygen saturation of the subject's blood as a function of time by compression with a compression bandage

Figure 7 shows the decrease in the oxygen saturation of the subject's blood as a function of time by holding the breath 15

Figure 1, which schematically shows the components of the device according to the invention according to an embodiment, shows on the left the oxygen saturation sensor 1 and the temperature sensor 2, as well as other sensors 3 which may be added.

20 The oxygen saturation sensor optically measures the oxygen content of hemoglobin in the blood and the temperature sensor the body temperature. The measurement signals are converted to digital form by an AD converter 4. The signal processing circuit 5 receives, compares and analyzes the measurement data from the sensors, monitors the exceeding of the given alarm limits, and sends a signal to the alarm 6 in chronological order. The data to be stored is encoded and compressed to save memory capacity. The measurement is performed at certain intervals to minimize memory and energy consumption. The timer 8 in the device shortens the measurement interval if necessary, for example when it detects a deviation from normal vital functions. The data in the memory can be decoded for more detailed analysis on a microcomputer via PC interface 9. This allows long-term monitoring of the vital functions of 6,982,66 people. The measurement results and the cause of the alarm can be read on display 10.

Figure 2 shows the basic operation of the oxygen saturation sensor used in the device according to the invention. This oxygen saturation sensor 5 is based on measuring changes in light reflected from subcutaneous tissue 11 and blood vessels 12. In this solution, the light source (s) 13 and the receiver (s) 14 can be located on the skin surface 15 on the same side of the tissue to be measured and in the same plane 10, which makes it easy to implement a portable oximeter. Although such an oximeter based on the measurement of reflected light is known per se, it has not been suggested in the literature that it could be used in ambulatory devices according to the present invention.

Figures 3a and 3b show a device with a display 10 according to the invention fitted to a wristband. The wrist strap closure 16 may also act as a start switch for the device so that the device starts when placed on the skin and locked by the closure. The receivers 14 are located in the bottom of the housing of the device. The light source 13 can be constructed to include the necessary components for transmitting several different wavelengths. When in use, the device monitors the placement of sensors on the surface of the skin, which prevents an error alarm when the sensors are in an inappropriate position.

Measurement of blood oxygen saturation

Oxygen saturation of the blood, i.e. oxygen saturation, means the relative amount of oxygen that the blood contains in the measurement situation 30 in relation to its maximum binding capacity. 98.5% of the oxygen carried by the blood is carried by hemoglobin. Oxygen saturation is measured with an oximeter that optically determines the ratios of oxyhemoglobin to deoxyhemoglobin. Oxygen-bound hemoglobin is called oxy-hemoglobin (HbO2) and oxygen-donating hemoglobin is called deoxyhemoglobin (Hb). Figure 4 shows the absorption curves of oxy-hemoglobin 17 and deoxyhemoglobin 18. The figure shows a clear (approximately eight-fold) difference between the absorption coefficients of oxy-5 hemoglobin and deoxyhemoglobin at 655 nm. The decrease in oxygen saturation increases the absorption of light at the above wavelength.

Calibration of the Oxygen Saturation Measurement 10 The wavelength corresponding to the intersection of the absorption curves can be used to calibrate the instrument. Since the absorption coefficient of oxyhemoglobin and deoxyhemoglobin is the same at the above intersection point, the total wavelength absorption from the quality of the underlying tissue alone. The oxygen saturation sensor can also be calibrated by using a wavelength between 800 nm and 1000 nms as the second wavelength and applying the pulse oximeter principle. By selecting the appropriate transmission wavelengths and monitoring their absorption relative to each other, a blood oxygen saturation value is obtained that is highly accurate independent of the measurement site and the quality of the tissue beneath it. If there are several receivers, a comparison can be made between them to obtain a more reliable measurement result. For example, when using three receivers placed around a light source, the measurement result of one receiver may be found to be erroneous if it differs significantly from the measurement results of the other two receivers and is disregarded when calculating oxygen saturation. Pulse oximeters often have the problem of small signal amplitude due to poor sensor placement. With the implementation of several receivers, the signal can be taken from those receivers from which a sufficiently large amplitude is obtained.

The following describes the experimental measurements of the oxygen saturation sensor.

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Figure 5 shows a circuit diagram of the test circuit of an oxygen saturation sensor with an LED and one photodiode and an amplifier. The measuring equipment was an oxygen saturation sensor and a multimeter used as a voltmeter. Oxygen saturation sensor-5 ri was constructed of three photodiodes and one LED. The wavelength of the LED is 655 nm. Each photodiode has its own amplifier unit, which consists of a general-purpose operational amplifier (μΑ741) and a resistor circuit according to Figure 5. In connection, the -V inputs of the operational amplifiers are 10 connected to the ground conductor and the + V inputs to a voltage of +5 V. The output values of the amplifiers vary between approx. 4.7 V (sensor illuminated with a lamp) and approx. 2.2 V (minimum value when the sensor is against the skin and the LED is on). The resolution of the multimeter used is 1 mV in this voltage range and ± 15% is accurate. As the voltmeter reading decreases, the oxygen saturation of the blood decreases.

Blood oxygen saturation measurements were performed on the subject's wrist. Oxygen saturation was reduced in two ways: by squeezing the arm with a compression bandage and by holding 20 breaths. The measurement results are shown graphically in Figure 6 (by compression with a compression bandage) and in Figure 7 (by holding the breath). The figures show the output voltage of one sensor amplifier on the y-axis, the changes of which correspond to the changes of blood oxygen saturation. In addition, arrows 25 indicate times when compression has stopped or respiration has resumed.

One or more of the following measurements can also be added to the device according to the invention: Temperature measurement 30 The temperature can be measured with a thermistor, the resistance variations of which are converted by means of an amplifier circuit into voltage variations which are further directed to the monitoring circuit.

Pulse measurement 9 98266

Pulse measurement is performed either optically with a pulse oximeter or by measuring variations in the pressure on the skin surface caused by vasodilation. Pressure variations can be measured from a chamber printed on the surface of the skin or by using an electret membrane sensitive to pressure changes. Pulse measurement is performed by taking multiple samples frequently for a moment, e.g., five seconds. Ko. the measurement is performed at certain intervals.

Other measurements 10 The device can be connected to e.g. the following measurements as needed: ECG, skin moisture (measuring the electrical conductivity of the skin), motion detection (accelerometer), blood pressure, amount of carbon dioxide in the blood, body fluid balance, and blood flow rate. In addition, for example, the following external factors can be measured: the concentration of extracorporeal gases, e.g., carbon monoxide, external sounds (e.g., snoring), and external temperature.

Device size and device variations for different uses

The device according to the invention is made sufficiently small by using microcircuits as well as surface mount components. Suitable diodes for the device are about 3 mm or smaller in diameter, so the diameter of the sensor becomes about 1 cm. Suitable power sources are e.g. coin-cell batteries or batteries of the same size used in watches.

25 Different device variations can be implemented with the following basic configuration: adjustable strap, housing with connector for data transfer and power supply charging, display device, acoustic alarm, oxygen saturation and heat sensor, signal processing and alarm circuit and power supply.

30 The child restraint may have the same construction as the basic configuration described above.

10 98266

In addition to the basic configuration, memory, communication routines, pulse measurement and, if necessary, other measurement sensors must be added to the device used in the study.

The elderly safety device and the patient monitoring device suitably comprise the components of the above-mentioned examination device and, if necessary, a radio transmitter which instructs a base station connected to the telephone to forward the alarm to a number pre-selected by the device carrier.

Peripherals and software 10 PC interface and software

The PC connection of the device to be used for research and hospital use can be implemented either via a serial port or a separate I / O card. The measurement results of a standard monitoring device can also be transferred to a home computer, from where they can be further sent by a modem to a doctor for analysis.

Telephone line

The transfer of measurement results to the doctor's computer can also be handled by telephone. For example, in home care for a sick elderly person, the physician may be informed of changes in the patient's health status on a daily basis. For data transmission, a separate data transmission device connected to the telephone line is required, to which an additional device for transmitting the alarm can also be connected.

Central unit for receiving radio signals and amplifier units

In nursing homes and hospitals, residents and patients can use safety devices with a radio transmitter, which send an alarm signal to the central unit if there is something abnormal in the plaintiff's vital functions. Amplifier-30 units are needed in areas that exceed the range of the radio transmitter of the 11 98266 safety device.

Charging the batteries • If the safety device is equipped with batteries instead of batteries, they can be charged at the same time as reading the mit-5 background results. Two of the connection pins in the housing of the device are reserved for charging the batteries. If the measurement data is read on a PC, then a separate I / O card charges the batteries during data transfer. The same principle can be used when measuring results are transmitted by a separate device over the telephone.

It will be apparent to those skilled in the art that various embodiments of the invention may vary within the scope of the claims set forth below.

Claims (7)

98266 An ambulatory device for personal use for monitoring the vital signs of a carrier, comprising one or more sensors suitable for non-invasive monitoring of vital signs, characterized in that the device comprises a 5 oximeter (1), a storage and data processing unit and an independent power supply, all of the above components is housed in the same housing. Device according to claim 1, characterized in that the oximeter is based on measuring the light reflected from the subcutaneous tissue (11). Device according to claim 1 or 2, characterized in that it comprises a timer (8), whereby the measurement or measurements can be performed at certain intervals. Device according to Claim 1, 2 or 3, characterized in that it comprises the necessary components by means of which the device can check and calibrate itself. Device according to one of Claims 1 to 4, characterized in that it is provided with a display (10) and / or one or more alarms (6). Device according to one of Claims 1 to 5, characterized in that it is provided with a data transmission unit. Device according to one of Claims 1 to 6, characterized in that it further comprises one or more sensors for monitoring external factors. : s ll <l Hill l! IM PATENTKRÄV 98266