WO2017178694A1

WO2017178694A1 - Monitoring respiratory air flow via trachea

Info

Publication number: WO2017178694A1
Application number: PCT/FI2017/050171
Authority: WO
Inventors: Tuukka VISURI; Timo NIINIKOSKI; Eero Karhunen; Toni Leinonen; Sami MELKONIEMI
Original assignee: Nukute Oy
Priority date: 2016-04-12
Filing date: 2017-03-15
Publication date: 2017-10-19
Also published as: FI20165311A

Abstract

Reliable and comfortable manner of measuring respiratory air flow of the subject is provided by a collar for wearing around a neck of a subject and a system for determining a sleep apnea event using the collar. The collar comprises two ends suspended apart by an intermediate portion connecting the two ends, and at least one piezoelectric microphone arranged in at least one of the two ends of the collar. The intermediate portion forms a neck-piece, which when worn by the subject extends around the posterior side of the neck between the lateral sides of the neck such that the piezoelectric microphone is pressed to the skin of the subject for determining a condition of the subject.

Description

MONITORING RESPIRATORY AIR FLOW VIA TRACHEA

FIELD

The present invention relates to determining an event in a condition of the subject and more particularly to monitoring respiratory air flow via trachea. BACKGROUND

The Apnea-Hypopnea Index or Apnea-Hypopnea Index (AHI) is an index used to indicate the severity of sleep apnea. It is represented by the number of apnea and hypopnea events per hour of sleep. The apneas (pauses in breathing) must last for at least 10 seconds and be associated with a decrease in blood oxygenation. Combining AHI and oxygen desaturation gives an overall sleep apnea severity score that evaluates both the number of sleep disruptions and the degree of oxygen desaturation (low oxygen level in the blood).

Sleep apnea is a medical condition characterized by pauses in breathing or instances of shallow or infrequent breathing during sleep. There are two main types of sleep apnea: Obstructive sleep apnea (OSA), the more common form that occurs when throat muscles relax and breathing is interrupted by an airway obstruction at the palate, tongue and epiglottis despite respiratory effort. Central sleep apnea (CSA), which occurs when your brain doesn't send proper signals to the muscles that control breathing. Each pause in breathing, called an apnea, can last for several seconds to several minutes, and may occur from 5 to more than 60 times an hour. Frequent use of the following classification: AHI <5: No OSA / Health; 5 <AHI <15: mild OSA; 15 <AHI <30: moderate OSA; 30 <AHI severe OSA. The most common form of sleep apnea is obstructive sleep apnea (84% of those affected), where Sleep apnea increases risk of other health problems such as type 2 diabetes, high blood pressure, heart problems and stroke. Sleep apnea also causes problems with memory and concentration, and can cause clinical depression.

Conventional systems for measuring sleep apnea have many sensors and in various units which are connected to each other by wires. Thus, the systems are complex and expensive. The units are positioned to a person's face, legs and fingers, which makes the measurement uncomfortable. Moreover, the wiring can be easily disconnected during the sleep which makes it difficult to obtain sufficient information for diagnosis and treatment. BRIEF DESCRIPTION

The present invention seeks to provide an improved system to determine sleep apnea.

According to an aspect of the present invention, there is provided a system as specified in claim 1.

According to another aspect of the present invention, there is provided a system as specified in claim 20.

LIST OF DRAWINGS

In the following the invention will be described in greater detail by means of example embodiments with reference to the accompanying drawings, in which

Figure 1 illustrates an example embodiment of collar for wearing around a neck of a subject;

Figure 2 illustrates an example embodiment of collar worn by a subject seen from a lateral side; and

Figures 3a and 3b illustrate an example embodiment of an adjustable collar;

Figure 4 illustrates an example embodiment of an arrangement the units in a collar;

Figure 5 illustrates an example embodiment of a method for determining a condition and/or an event in a condition of the subject using a collar;

Figure 6 illustrates an example embodiment of a method for determining an end of an event in a condition of the subject using a collar;

Figure 7 illustrates example embodiments of locations for sensor and/or conditioning units in the subject;

Figure 8 illustrates an example embodiment of a method for conditioning of a subject;

Figure 9 illustrates interference suppression in an audio signal obtained by a collar according to an example embodiment;

Figure 10 illustrates an example embodiment of a system for conditioning of subject;

Figure 11 illustrates an example embodiment of a tracheal microphone;

Figure 12 illustrates an example embodiment of method for determining obstructive sleep apnea (OSA) and central sleep apnea (CSA);

Figure 13 illustrates an example embodiment of method for ascertaining a condition of a subject; and

Figures 14, 15 and 16 illustrate further example embodiments related to OSA and CSA determination.

DESCRIPTION OF EMBODIMENTS

Figure 1 illustrates a collar 100 for wearing around a neck of a subject, according to an embodiment. The collar comprises two ends 104, 106 suspended apart by an intermediate portion 102 connecting the two ends. The suspension provides that the ends may be pressed against the neck with a sufficient force for maintaining the collar in a fixed position. At least one piezoelectric microphone 108 is arranged in at least one of the two ends of the collar. The intermediate portion may form a neck-piece, which when worn by the subject extends around the posterior side of the neck between the lateral sides of the neck such that the piezoelectric microphone is pressed to the skin of the subject for determining a condition of the subject.

In an embodiment, the piezoelectric microphone is capable of monitoring the respiratory air flow via the trachea. The respiratory air flow causes vibration of the skin which may be transformed by the piezoelectric microphone into an audio signal.

The suspension of the collar may allow the ends to be bent apart for installing the collar around the neck and for removal of the collar. The material of the collar may flexible. Preferably the collar is flat such that when worn by the subject the sits smoothly on the neck.

The collar provides that the air flow of the subject may be monitored for determining a condition and/or an event in a condition, for example sleep apnea and/or a sleep apnea event, in a manner that is reliable and comfortable for the subject. Particularly, since the intermediate portion between the ends extends around the posterior side of the neck, the collar does not cause pressure on the throat, e.g. the laryngeal prominence. Moreover, when the subject is resting on his/her back, the intermediate portion may be maintained in its position by a pillow that presses the intermediate portion against the posterior side of the neck. In this way the ends of the collar may be maintained fixed in their position for monitoring the air flow via the trachea.

The piezoelectric microphone may facilitate obtaining data, e.g. audio signals, representing an amount of airflow via the trachea, whereby the respiratory air flow via the trachea maybe monitored on the basis of the audio signals. A high volume of air flow may be observed as an audio signal having a high level, whereas a low volume of air flow may be observed as an audio signal having a low level. The data obtained by the piezoelectric microphone may be processed by signal processing methods and/or components that provide, analog- to-digital conversion, sampling, analysis.

When the collar is worn by the subject, a sensor surface of the piezoelectric microphone may be in contact with the skin of the subject. In this way the piezoelectric microphone may transform vibrations of the skin caused by the respiratory air flow into an audio signal for monitoring the respiratory air flow via the trachea. One or more conditions of the subject may be determined on the basis of the level of the audio signal. Examples of the conditions comprise Sleep apnea, Snoring, Bruxism. The conditions may further comprise species for example obstructive sleep apnea and central sleep apnea.

Figure 2 illustrates an example of collar 200 worn by a subject seen from a lateral side, according to an embodiment. The collar may be the collar in Figure 1 and have an intermediate portion that may form a neck-piece. The ends of the collar are positioned below the chin 202 of the subject and around the laryngeal prominence 204, where by the ends do not cause uncomfortable pressure to the throat of the subject. When the collar is worn by the subject, the intermediate portion extends around the posterior side of the neck between the lateral sides of the neck such that the piezoelectric microphone is pressed to the skin of the subject for monitoring the respiratory air flow via the trachea.

In an embodiment, the width w2 of the intermediate portion of the collar may be narrower than the width wl of the ends 104, 106. Particularly, since the ends are pressed to the skin of the subject, the small width wl of the ends provides that the pressure on the neck, although needed for keeping the piezoelectric microphone in touch with the skin, may be kept small. On the other hand the width w2 of the intermediate portion provides that less skin covered by the collar than in the ends. In this way effects such as sweating, abrasion and/or dents may be prevented.

Figures 3a and 3b illustrate an adjustable collar, according to an embodiment. The collar may have ends 304, 306 and an intermediate portion 302 which correspond with the ends and intermediate portion in the collar described with reference to Figure 1. The movability of the ends is illustrated by arrows in the Figures 3a and 3b. As a difference, the intermediate portion 302 may be adjustable between a minimum length, min, and a maximum length, max, wherein the minimum length of the intermediate portion provides that the piezoelectric microphone is pressed to the skin of the subject, when the circumference of the neck is small and the maximum length of the intermediate portion provides that the piezoelectric microphone is pressed to the skin of the subject, when the circumference of the neck is large. In this way the piezoelectric microphone may be pressed against the skin even when the collar is worn by subjects having different circumferences of necks.

In an embodiment, a collar may have ends 304, 306 that may be separated laterally by a distance da, db for allowing the laryngeal prominence of the subject to be located between the ends, when the collar is worn by the subject. In this way pressure form the collar to the laryngeal prominence may be prevented, when the collar is worn by the subject. Preferably, the suspension of the collar may allow the ends to be manually bent apart to a distance da for installing the collar around the neck and for removal of the collar. When the collar is worn by the subject, the ends may be pressed to the skin of the neck and separated by a smaller distance db.

In an embodiment, ends 304, 306 of the collar may be pressed to the skin symmetrically on opposite sides of the trachea. In this way the contact to the skin on one side by one of the ends may be supported by the other end on the other side of the neck, whereby the piezoelectric microphone may be maintained pressed to the skin.

In one example the ends 304, 306 may be connected to the intermediate portion 302 such that the ends and the intermediate portion may be on one another. The intermediate portion may have a groove, where the ends are attached such that the ends may be sled towards each other and away from each other for adjusting the length of the intermediate portion.

In an embodiment, both of the ends 304, 306 may have a piezoelectric microphone 308. In this way audio signals obtained by both the piezoelectric microphones may be processed in monitoring the respiratory air flow via the trachea for obtaining more accurate results than if only one microphone was used.

In an embodiment, an ambient microphone may be arranged in the same end of the collar with the piezoelectric microphone. The ambient microphone may provide obtaining data, e.g. audio signals, representing sounds that are external to the body of the subject. The data obtained by the ambient microphone may be processed together with the data obtained by the piezoelectric microphone for reducing ambient sounds from the audio signals obtained from the piezoelectric microphone. In this way the measurement of the respiratory air flow by the piezoelectric microphone may be improved. When both ends have piezoelectric microphones, the collar may have an ambient microphone in both of the ends such that the ambient sounds received on both sides of the neck may be reduced from the audio signals obtained by the piezoelectric microphones.

Figure 4 illustrates an example arrangement of units in a collar according to an embodiment. In Figure 4, the arrangement is described with reference to the units illustrated in the collar 100 of Figure 1. The collar 100 may comprise a wireless radio transceiver 404 arranged to a different end 106 in the collar than the piezoelectric microphone 108, and an intermediate portion 102 may serve for transferring data and/or electrical power between the units. The intermediate portion may comprise one or more electrical conduits for transferring data and/electrical power between the units, e.g. the transceiver and the piezoelectric microphone, arranged in different ends of the collar. The arrangement of the wireless radio transceiver and the piezoelectric microphone into different ends of the collar facilitates achieving a weight balance between the ends such that the collar may be worn in a fixed position around the neck of the subject.

In an embodiment one or more units in a collar may be arranged in different ends of the collar 100 whereby data and/or electrical power may be transferred between the units via the electrical conduits in the intermediate portion 102. The arrangement of the units into different ends of the collar facilitates achieving a weight balance between the ends such that the collar may be worn in a fixed position around the neck of the subject. Examples of the units comprise: a wireless transceiver 404, a microphone for internal body sounds 108, 408, an ambient microphone 406a, 406b, a battery 410 and a processing unit 402. The microphones for internal body sounds in the ends of the collar may be the same, e.g. piezoelectric microphones. On the other hand the other microphone for internal body sounds may be a tracheal microphone. The piezoelectric microphone may be preferred if there are a lot of disturbing sounds in the same space, i.e. in a high noise environment, with the collar. Examples of high noise environments comprise a hospital. The tracheal microphone may be preferred if there is a low amount of disturbing sounds in the same space, i.e. in a low noise environment, with the collar. Examples of low noise environments comprise a home.

In one example, one end 104 of the collar may comprise the piezoelectric microphone 108, an ambient microphone 406a, a sensor 412 for determining movement of the subject and a battery. The other 106 end may comprise a processing unit 402, a wireless radio transceiver 404, a microphone for internal body sounds 408 and an ambient microphone 406b. The microphone may be a piezoelectric microphone or a tracheal microphone. The intermediate portion 102 may serve for transferring data and/or electrical power between the units. The intermediate portion may comprise one or more electrical conduits for transferring data and/or electrical power between the units arranged in different ends of the collar. The data transferred between the units in different ends of the collar may be e.g. audio signals obtained by the microphone for internal body sounds and the ambient microphone.

In one example, the electrical conduits in the in the intermediate portion may be arranged on a thin film serving as a circuit board. In this way the units in both ends of the collar may practically be located on the same circuit board, while the weights of the ends may be balanced for additional comfort in wearing the collar.

In an example, the wireless transceiver 404 may be a short-range wireless transceiver capable of low power radio transmissions. Preferably the radio frequencies in the Industrial Scientific and Medical frequency bands are used for the wireless communications. Typical ISM frequency bands are in the 2.450 GHz and 5.800 GHz frequency bands. Examples of the suitable wireless transceivers comprise Bluetooth (BT) transceivers. The Bluetooth low energy (BTLE) transceivers may be preferred for low power consumption. Also other short range wireless communications transceivers may be used such as ANT and ANT+ designed and marketed by ANT Alliance organized by Dynastream Innovations Inc.

In an embodiment, at least one of the ends 104, 106 may comprise a sensor 412 for determining movement of the subject. Examples of the sensors comprise a 3D-accelerometer, a gyroscope and a gyroscope provided with a magnetometer or gravitymeter. The 3D-accelerometer may obtain information for indicating movement of the subject. The 3D-accelerometer is capable of producing acceleration information in three dimensions, for example in X-, Y-, and Z- axes. The gyroscope is capable measuring or maintaining orientation, usually by measuring angular rate of turn in relation to a defined axis. The gyroscope may be provided with a magnetometer or gravitymeter. The gyroscope may be connected to or incorporate the magnetometer or gravitymeter to provide absolute angular measurements relative to the Earth's magnetic field. The absolute angular measurements facilitate detecting the position of the subject, e.g. when the subject is in the supine position.

In various embodiments, the collar may have a battery 410 arranged in one of the ends. The battery may be used to power various units and operations performed by the units.

Connections between units of the collar may be arranged by electrical connections arranged by electrical conductors capable of carrying data and/or power. Wireless connections may be employed for data connections between the collar and an external system for example a computer, a smart phone or a tablet computer. In one example, the connections between the units may be arranged on a circuit board formed at least partially on a thin film in the intermediate portion 102.

Figure 5 illustrates a method for determining a condition and/or an event in a condition of the subject using a collar according to an embodiment. The method is now described with reference to a condition of sleep apnea and an event in sleep apnea i.e. a sleep apnea event, in the subject. The method may start 502, when the collar is installed to a neck of the subject for monitoring the respiratory air flow of the subject. The collar may have one or more microphones for internal body sounds, e.g. piezoelectric microphones or tracheal microphones, for obtaining 504 audio signals representing an amount of air flow via the trachea. Preferably the collar may have at least one piezoelectric microphone. The collar may further have a sensor, e.g. 3D-accelerometer, gyroscope or gyroscope provided with a magnetometer or gravitymeter , for determining movement of the subject for obtaining 504 information indicating changes in the positon of the subject. Data from the sensor for determining movement of the subject may be used in determining a change of the position of the subject from an upright position to a supine position. Once the subject has been determined to be in the supine position, the start of sleep may be determined 506 on the basis of the audio signals from the microphones for internal body sounds and the method may continue to monitoring the sleep in steps 508, 510 and 512. Otherwise, further data may be obtained 504 from the microphones for internal body sounds and the sensor for determining movement of the subject. The start of the sleep may be determined on the basis of one or more or a combination of a respiratory rate and a pulse of the subject. The audio signals may be processed for extracting the pulse and the respiratory rate of the subject. The time of the start of sleep may be registered.

In an embodiment, start of sleep may be determined 506 after the audio signal indicating a respiratory air flow is below a level for starting the monitoring and the sensor for determining movement of the subject indicates that the subject has been stabile for a time threshold for starting the monitoring.

The end of the sleep may be determined on the basis of the data from the sensor for determining movement of the subject indicating a change of the position of the subject from the supine, prone or lateral position to the upright position. Also the respiratory rate and/or pulse may be used in determining the end of the sleep. The time of the end of sleep may be registered.

During the start and end of the sleep the respiratory air flow of the subject is monitored on the basis of the audio signals obtained from the microphones for internal body sounds in the collar. The monitoring is based on measuring the audio signal and time the audio signal is below a threshold level. The level of the audio signal being less than the threshold may indicate that the respiratory air flow is reduced or there is no respiratory air flow. Accordingly, the monitoring may comprise:

determining 508 a time period during which a level of the audio signal is below a threshold level for the audio signal, and

determining 512 a sleep apnea event, when 510 the time period is greater or corresponds to a threshold. The determined sleep apnea event may indicate that the subject has sleep apnea.

If 510 the threshold for the time period is not met, the monitoring may be continued 508. The monitoring may be continued 510 until the sleep ends. If 514 the end of sleep is determined, the method may end 516.

The level of the audio signal may be compared to a threshold level that may be preset to a default level or determined by a calibration cycle preceding the determining the condition of the subject. The threshold for the time period may be preset for example to 10 min.

In an embodiment, during the sleep, changes of the sleeping positions are detected on the basis of the sensor for determining movement of the subject during the sleep of the subject. The sensor may be a 3D-accelerometer, a gyroscope or a gyroscope provided with a magnetometeror gravitymeter.

In an embodiment an apnea-hypopnea index may be determined. In a method for determining a condition of the subject, a counter may be incremented by each of the determined sleep apnea events. The counter value may be divided by the hours of sleep for obtaining an apnea-hypopnea index. The hours of sleep may be determined by registering the times of start of sleep and the end of sleep which may be determined as described in the method of Figure 5.

Figure 6 illustrates a method for determining an end of an event in a condition of the subject using a collar according to an embodiment. The method is now described with reference to a condition of sleep apnea and an event in sleep apnea i.e. a sleep apnea event, in the subject. The method may be performed during the sleep of the subject, for example after the sleep has started after the step 506 until the sleep ends in step 514 in the Figure 5. During the sleep, the respiratory air flow of the subject may be monitored for example as described in steps 508, 510 and 512 in Figure 5.

In the method of Figure 6, respiratory air flow information may be obtained 602. The respiratory air flow information may be obtained by the collar installed to a neck of the subject for monitoring the respiratory air flow of the subject. The respiratory air flow information may comprise audio signals representing an amount of air flow via the trachea. The respiratory air flow information may indicate a sleep apnea event. Conventionally a sleep apnea event may last 10 seconds or even up to 1 minute. During this time the airways of the subject are blocked and the respiratory air flow is very small or does not exist. The respiratory air flow information may comprise information indicating a time period the audio signal is below a threshold level for the audio signal, described e.g. in step 508 in Figure 5. In this way the blocking of the respiratory airways may be determined. The respiratory air flow information may also comprise a level of the audio signal.

An end of the sleep apnea event may be determined 604. The end of the sleep apnea event may be determined on the basis of the level of the audio signal exceeding a threshold level after the sleep apnea event is determined. It should be appreciated that different threshold levels may be applied for determining time of the audio signal below a threshold level and for determining the event of the audio signal increasing above a threshold level.

Movement information may be obtained 608 from a sensor for determining movement of the subject. The sensors may be arranged in a collar e.g. as described in Figure 4. However, the sensor may be arranged to the subject also to other locations comprising for example the arm or the leg of the subject. Sensors arranged in the arm or the leg may be connected wirelessly, e.g. by a short-range wireless transceiver capable of low power radio transmissions, to the collar, where the information from the sensor may be processed.

The information obtained from the movement sensor may be used to ascertain 606 the end of the sleep apnea. The end of sleep apnea 610 event may be ascertained positively when the end of the sleep apnea is determined and the obtained movement information indicates that a movement of the subject. Preferably the movement of the subject and the end of the sleep apnea event are substantially simultaneous in time. The movement of the subject may comprise changing a position of the subject from one position to another. Examples of the subject's positions are prone, supine and lateral positions. The method may end 612 after the end of sleep apnea has been ascertained positively. The end of sleep apnea may be ascertained 606 negatively, when the obtained movement information fails to indicate a movement of the subject and the method may end.

In an embodiment, the result of ascertaining 606 the end of sleep apnea on the basis of the movement of the subject may be used to determine a level of the sleep apnea. For example, the level of sleep apnea may be considered more severe, when the movement of the subject is not detected in 606. On the other hand the level of sleep apnea may be determined less severe, when the end of the sleep apnea 610 even is ascertained by the movement of the subject.

Figure 7 illustrates locations for sensor and/or conditioning units in the subject. Units positioned in the locations may be connected wirelessly, e.g. by a short-range wireless transceiver capable of low power radio transmissions, to the collar, where the information from the units may be processed.

The locations comprise a location 704 in the leg, a location 706 in the arm, a location 701 in the chest, a location 702 in the thoracic diaphragm and a location 700 in the neck. A unit positioned in the neck may be arranged in the collar. Units in the other locations may be attached to the subject by attachment means comprising for example Velcro straps and adhesives.

The locations in Figure 7 may be used in various embodiments for installing one or more sensors or a conditioning unit on the subject. Examples of the sensors comprise a sensor for determining movement of the subject.

Figure 8 illustrates a method for conditioning of a subject according to an embodiment. The method may start 802, when conditioning may be performed by a conditioning unit that is positioned to one of the locations illustrated in Figure 7. The conditioning unit may be connected wirelessly, e.g. by a short-range wireless transceiver capable of low power radio transmissions, to the collar. In this way the acoustics signals and/or movement sensor information provided by the collar may be used to cause conditioning the subject.

Audio signals representing air flow via the trachea may be obtained 804. Additionally movement sensor information may be obtained from a sensor for determining movement of the subject.

The obtained 804 information may be matched to a condition of the subject. The obtained information may indicate an event that is specific to a condition, where by the condition may be specified. In an example the obtained information may indicate snoring of the subject. The snoring may be specific to sleep apnea, whereby the snoring may indicate that the subject has sleep apnea.

The subject may be conditioned 808 to perform an action for avoiding an event in a condition of the subject. The conditioning may be performed by a conditioning unit. The event to be avoided may be the determined 806 event. Exampels of the events comprise snoring. On the other hand the condition of the subject may comprise more than one event, whereby the conditioning may be used to avoid an event typically following the determined condition. In an example, in the condition of sleep apnea, snoring may be followed by blocking of the respiratory airways. Thereby, the conditioning may serve for preventing the blocking of the respiratory airways after the snoring, sleep apnea, bruxism or a sleeping position has been determined 806. The action may comprise that the subject changes his position to another position. Examples of the positions comprise supine, prone and lateral position.

The conditioning may comprise generating by a conditioning unit one or more impulses in the nervous system of the subject. Preferably the impulses are generated in the autonomic nervous system of the subject.

In an embodiment, the conditioning may comprise generating impulses until a desired response from the subject is measured. The desired response may be measured by a collar and/or a sensor, for example the sensor for determining movement of the subject. Examples of the desired responses comprise an increased respiratory air flow, movement of the subject and/or a changed sleeping position of the subject. The responses may be determined on the basis of at least one of the level of audio signal, and position or movement information from the sensor for determining movement of the subject. The impulses may be have variable or fixed intervals and/or variable power. Preferably the interval between impulses and/or power of the impulses is increased until a desired response is measured.

Examples of the impulses for conditioning the subject comprise a low power electrical signal. The electrical signal may have a signal form that causes conditioning of the subject.

After the subject has been conditioned, the method may end 810. It should be appreciated that all or some of the steps of the method may be repeated one, two or any number of times for conditioning the subject.

Figure 9 illustrates interference suppression in an audio signal obtained by a collar according to an embodiment. The interference suppression is illustrated by functional blocks that may be implemented by a processing unit and a memory comprising computer program code executable by the processing unit, wherein the execution of the computer program code may cause the functionality of the blocks. In one example, the interference suppression may be implemented in the collar of Figure 4.

Referring to Figure 9, microphones for internal body sounds in each end of the collar may generate audio signals 902, 904. One of the audio signals 902 is generated by the microphone on the left lateral side of the subject and one of the audio signals 904 is generated by the microphone on the right lateral side of the subject. The audio signals on each side may further comprise audio signals generated by ambient microphones.

A phase difference 906 of the audio signal generated by the ambient microphones may be determined. The phase difference may be input to a filter and gain control unit 908. The filter and gain control unit may match signals of the ambient microphones on the basis of the phase difference such that interference that is present only on the left or right lateral side audio signal may be determined. In one example left and right side audio signals may be shifted in time on the basis of the phase difference after which the values of the audio signals may be compared for finding the interference that is present only on the left or right lateral side. After the interference that is present only on the left or right lateral side has been determined, the interference may be suppressed from the audio signal of the ambient microphones. In this way peak-suppressed audio signal may be obtained. After suppression of the peaks, gains may be determined for the audio signals obtained from the microphones for internal body sounds, e.g. the piezoelectric microphones and the tracheal microphones. The gains may be determined on the basis of the levels of the peak-suppressed audio signals and the audio signals of the audio signals to the microphones for internal body sounds.

In an embodiment, ambient sounds may be reduced from the audio signals obtained from the piezoelectric microphone using the audio signals from the ambient microphone.

Figure 10 illustrates an example of system for conditioning of subject. The system may comprise at least a collar 1002 and a conditioning unit 1004. The collar may be a collar described in an embodiment herein. The collar and the conditioning unit may be connected wirelessly or over a wired connection. The connection between the collar and the conditioning unit is capable of communicating information for causing the conditioning unit to generate one or more impulses in the nervous system of the subject. In this way the subject may be conditioned to perform an action for avoiding an event in a condition of the subject. The conditioning unit may be battery powered. If the conditioning unit is connected to the collar over a wired connection, the wired connection may be used for power transfer from the collar to the conditioning unit.

Figure 11 illustrates an example of a tracheal microphone 1100. The tracheal microphone may be used in various embodiments described herein. The tracheal microphone comprises a diaphragm 1102 that is movable by sound waves. The tracheal microphone comprises a microphone element 1104 capable of sensing pressure variations and transforming the pressure variations into a digital audio signal. A sound chamber 1106 is arranged between the microphone element and the diaphragm. The sound chamber may be formed by a shell 1108 and the diaphragm such that the microphone element and the diaphragm are arranged on opposite sides of the sound chamber. When the diaphragm is in contact with the subject, sound waves originating from the subject may cause movement of the diaphragm. The movement of the diaphragm may cause pressure variations within the sound chamber. The pressure variations may be sensed by the microphone element and transformed into a digital audio signal. The sound chamber may be filled with gas such as air for communicating the movement of the diaphragm to the microphone element.

Figure 12 illustrates an example of method for determining obstructive sleep apnea (OSA) and central sleep apnea (CSA). The method may be performed during the sleep of the subject and/or in connection with determining a sleep apnea event in various embodiments described herein. In an example the method may be performed after or partly overlapping with determining a sleep apnea event, for example in 512 in Figure 5.

In the method, the OSA and CSA may be determined on the basis of movement data and an audio signal indicating respiratory flow. The audio signal may be obtained by a microphone, e.g. a piezoelectric microphone, provided in a collar according to an embodiment. The method may start 1200 when one or more sensors for determining movement are installed to the subject. Figure 7 illustrates examples of the positions, where the sensors may be installed. The movement data may be obtained 1202 from at least one of the sensors for determining movement of the subject. The sensors may be included in the collar according to an embodiment or the sensors may be connected wirelessly to the collar for supplying movement data to the collar. The collar may monitor the respiratory air flow via the trachea and utilize measurements of the respiratory air flow and the movement data in determining the CSA and the OSA. The measurement of the respiratory air flow may be performed using the microphone(s), e.g. the piezoelectric microphone, of the collar as described in the monitoring of the respiratory air flow in step 508 of Figure 5, where monitoring is based on measuring the audio signal and time the audio signal is below a threshold level. The wireless connections may be provided as described for sensor units in connection with Figure 7.

The movement data may comprise data generated by sensors for determining movement of the subject. Examples of the sensors for determining movement of the subject comprise a 3D-accelerometer, a gyroscope, and a gyroscope provided with a magnetometer or gravitymeter.

The obtained 1202 movement data may indicate breathing, e.g. paradoxical breathing of the subject. When the subject is breathing, the thoracic diaphragm and the chest are moved. In paradoxical breathing the chest of the subject moves in on inspiration and out on expiration, in reverse of the normal movements of the chest.

In one example, the movement of the chest of the subject may be determined on the basis of the obtained data by a sensor included in the collar. The sensor may be capable of indirectly determining the movement of the chest that is remote from the sensors position, i.e. in the neck, in the subject. The indirect determining of the movement may be achieved by filtering the data generated by the sensor. A filter suitable for processing the data may be configured to extract lower body movements, and particularly the chest movements, from the data produced by the sensor.

In one example, the movement of the chest of the subject may be determined by a sensor located in the chest of the subject. The sensor may be connected wirelessly to the collar for supplying data generated by the sensor to the collar for processing. The sensor in the chest provides that the movement of the chest may be determined directly by the sensor. In this way accurate movement data may be provided with reduced need for data processing, e.g. filtering, compared to determining the movement of the chest indirectly with measuring air flow signal.

In one example, the movement of the thoracic diaphragm of the subject may be determined by a sensor included in the collar. The sensor may be capable of indirectly determining the movement of the thoracic diaphragm that is remote from the sensors position, i.e. in the neck, in the subject. The indirect determining of the movement or air flow signal from the neck may be achieved by filtering the data generated by the sensor. A filter suitable for processing the data may be configured to extract lower body movements, and particularly the thoracic diaphragm movements, from the data produced by the sensor.

In one example, the movement of the thoracic diaphragm of the subject may be determined by a sensor located at the thoracic diaphragm of the subject. The sensor may be connected wirelessly to the collar for supplying data generated by the sensor to the collar for processing. The sensor in the thoracic diaphragm provides that the movement of the chest may be determined directly by the sensor. In this way accurate movement data may be provided with reduced need for data processing, e.g. filtering, compared to determining the movement of the chest indirectly.

CSA may be determined 1208, when 1204, 1206 movement of the thoracic diaphragm the chest are not determined and the audio signal indicates that the respiratory air flow of the subject is reduced or there is no respiratory air flow.

OSA may be determined 1210, when 1204, 1206 the thoracic diaphragm moves and the chest does not move and the audio signal indicates that the respiratory air flow of the subject is reduced or there is no respiratory air flow.

If 1204, 1206 the chest of the subject moves and the thoracic diaphragm moves, it may be determined that the subject does not have 1212 OSA or CSA. The method ends after the movement data has been utilized in determining that the subject does not have 1212 OSA or CSA, or that the subject has 1210 OSA or the subject has 1208 CSA. Figure 13 illustrates an example of method for evaluating certainty of determined condition or an event in the condition of a subject. The condition may be Sleep apnea for example OSA and CSA. In the method the certainty of the determined condition may be evaluated on the basis of movement data.

The method may start 1300 when one or more sensors for determining movement are installed to the subject. Figure 7 illustrates examples of the positions, where the sensor may be installed. When the condition or event is determined during the sleep of the subject, the subject may be asleep, i.e. the sleep has started, for example in 508 in Figure 5. The sensors may generate movement data for determining movement of the subject. The sensors may be included in a collar according to an embodiment or the sensors may be connected wirelessly to the collar for supplying data to the collar. The wireless connections may be provided as described for sensor units in connection with Figure 7.

The movement data may be obtained 1302 from at least one of the sensors for determining movement of the subject. The movement data may comprise data generated by sensors for determining movement of the subject. Examples of the sensors for determining movement of the subject comprise a 3D- accelerometer, a gyroscope, and a gyroscope provided with a magnetometer or gravitymeter.

The movement data may indicate movement of the legs. The movement of the legs may be caused by Restless Legs Syndrome (RLS). RLS is a neurological disorder characterized by an irresistible urge to move one's body to stop uncomfortable or odd sensations.

In one example, the movement of the legs of the subject may be determined on the basis of the obtained data by a sensor included in the collar. The sensor may be capable of indirectly determining the movement of the legs that is remote from the sensors position, i.e. in the neck, in the subject. The indirect determining of the movement may be achieved by filtering the data generated by the sensor. A filter suitable for processing the data may be configured to extract lower body movements, and particularly the body movements below the waist of the subject, from the data produced by the sensor.

In one example, the movement of the legs of the subject may be determined by sensors located at the legs of the subject. The sensors may be connected wirelessly to the collar for supplying data generated by the sensor to the collar for processing. The sensors in the legs provide that the movement of the legs may be determined directly by the sensors. It should be appreciated that both of the legs or only one of the legs may be provided with sensors. In this way accurate movement data may be provided with reduced need for data processing, e.g. filtering, compared to determining the movement of the legs indirectly.

After a condition or an event in the condition of the subject is determined 1304, the movement data from the sensors may be caused to ascertain 1308 or unascertained 1310 the determined condition or event. The ascertaining may follow the step 512 in Figure 5, the step 610 in Figure 6 or step 806 in Figure 8, for example.

When 1306 the movement data from the sensors indicates that the legs are moving or have been moving during the determined condition or event in the condition, the determined event may be treated 1310 as an unascertained condition or event. The unascertained condition or event may be stored with information indicating the uncertainty related to the determined condition or event.

On the other hand, when 1306 the movement data from the sensors indicates that the legs are not moving or have not been moving during the determined condition or event in the condition, the determined event may be treated as an ascertained 1308 condition or event. The ascertained condition or event may be stored with information indicating the certainty that the movement of the legs was not determined in association with the determined condition or event.

The method may end 1312 after the certainty of the determined condition or event has been evaluated and the determined condition or event has been ascertained or unascertained.

An embodiment concerns a system for determining a condition of the subject. The condition may be bruxism. The system may comprise one or more piezoelectric microphones. The system may comprise a processing unit and a memory comprising computer program code executable by the processing unit, wherein the execution of the computer program code causes determining bruxism, when an audio signal indicating a sound pattern that matches to an event in bruxism is obtained. The event may be movement of teeth against each other. A sound pattern matching to the event in bruxism may be frequencies and/or amplitudes that form an envelope for signals in a frequency domain or time domain. The audio signal may be determined to indicate the event in bruxism, when the audio signal fits into the sound pattern. The sound pattern may be generated on the basis of sound samples of gnashing of teeth. Some or all parts of the system may be provided in a collar according to an embodiment.

An embodiment concerns a system comprising a collar according to an embodiment. The system may have a processing unit and a memory storing a computer program comprising computer program code for execution on the processing unit, wherein the execution of the computer program code causes a method or one or more steps of a method according to an embodiment. The memory may be a computer -readable storage medium. The computer -readable storage medium may be a computer program distribution medium readable by a computer or a processor. The computer -readable storage medium may be, for example but not limited to, a record medium, computer memory and read-only memory, for example. The processing unit may be a processor, a combination of a processor and a memory or a computer.

Implementation of the system may vary. In one example, the system may essentially comprise the collar without any external systems or devices. In this example the collar houses the memory and the processing unit. In another implementation the system may comprise an external system for example a computer, a smart phone or a tablet computer, which is capable of communicating with the collar. In this implementation one or more of the method steps may be performed in the external system. Therefore, the functionalities described for the collar herein may be implemented in the external system.

It should be appreciated that units such as piezoelectric microphones, ambient microphones, tracheal microphones and sensors for determining movement of the subject are capable of performing measurements for the purposes of determining a condition of the subject. The measurements performed by a piezoelectric microphone, a tracheal microphone and the ambient microphone may generate audio signals that indicate measured decibel levels. The audio signals may be digital audio signals. Examples of the sensors for determining movement of the subject comprise a 3D-accelerometer, a gyroscope, and a gyroscope provided with a magnetometer or gravitymeter. The measurements performed by a 3D-accelerometer may generate signals indicating proper acceleration, which is the acceleration it experiences relative to freefall and is the acceleration felt by people and objects. The gyroscope may generate signals indicating orientation. When the gyroscope is provided with a magnetometer or gravitymeter, signals indicating absolute angular measurements relative to the Earth's magnetic field may be generated.

Various embodiments described herein may be applied to various conditions and events in said conditions. The events may refer to physical events in a subject, i.e. person, which may be observed by the means described herein. An example of a condition is sleep apnea. The events of sleep apnea may comprise, snoring, blocking of respiratory airways and continuation of respiration.

In an example embodiment, a system 1410 to determine a sleep apnea comprises a microphone 1412 configured to obtain audio signals representing an amount of respiratory air flow via a trachea of a subject; and a processing unit 1414 and a memory 1418 comprising computer program code 1416 executable by the processing unit 1414.

The execution of the computer program code 1416 causes: determining inhales I and exhales E from the audio signals based on an analysis of frequencies F of the audio signals. As shown in Figure 14, the inhales 1400 are marked with an "I" and the exhales are marked with an "E". In an example embodiment, the inhales 1400 contain higher frequencies than the exhales 1402.

In Figure 14, the inhales I and the exhales E follow each other regularly, and it may be determined that the subject has normal breathing, i.e., the subject does not have a sleep apnea.

In Figure 15, a time period 1504 between successive exhale 1500 and inhale 1502 exceeds a predetermined time threshold, based on which it may be determined 1510 a central sleep apnea for the subject.

In Figure 16, a time period 1604 between successive exhale 1600 and inhale 1602 includes one or more partial inhale attempts 1606, 1608, based on which it may be determined 1610 an obstructive sleep apnea for the subject.

The predetermined time threshold and the recognition of the partial inhale attempt 1606, 1608 may be determined and calibrated for the subject experimentally, and also based on research. These parameters may also vary depending on sex and age of the subject, for example.

In an example embodiment, the microphone 1412 is placeable in a proximity of the trached of the subject in order to capture the audio signals.

In an example embodiment, the microphone 1412 is a piezoelectric microphone. In an example embodiment, the microphone 1412 is an arrangement comprising a contact microphone for capturing audio signals from the trachea of the subject and also an ambient microphone for capturing other sounds caused by respiratory and/or noise that may be filtered out from the audio signal captured with the contact microphone.

In an example embodiment, the microphone 1412 is placed in the collar 100. In an alternative embodiment, the microphone 1412 is placeable by the subject.

In an example embodiment, the system 1410 comprises two separate parts: the microphone 1412, and the processing entity (1414, 1416, 1418). The processing entity 1414, 1416, 1418 may be implemented as an independent apparatus (smartphone, smarthwatch, laptop, computer, any other portable/stationary data processing device) or in a server or in a computing cloud. In an alternative embodiment, the system 1410 is implemented within a single apparatus, which may be portable.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A system to determine a sleep apnea, comprising:

a collar (100) for wearing around a neck of a subject, said collar comprising:

two ends (104, 106) suspended apart by an intermediate portion (102) connecting the two ends;

at least one microphone (108) for obtaining audio signals representing an amount of air flow via a trachea of the subject arranged in at least one of the two ends of the collar, wherein the intermediate portion forms a neck-piece, which when worn by the subject extends around the posterior side of the neck between the lateral sides of the neck such that the microphone is pressed to the skin of the subject for determining a condition of the subject; and a sensor (412) arranged to obtain information indicating movement of the subject; and

a processing unit (402) and a memory comprising computer program code executable by the processing unit, wherein the execution of the computer program code causes:

obtaining an audio signal indicating respiratory flow by the microphone;

determining a time period during which a level of the audio signal is below a threshold level for the audio signal; and

determining an event in a condition of the subject, when the time period is greater or corresponds to a threshold for the time period, characterized in that movement data of the chest and thoracic diaphragm is determined directly or indirectly by the sensor for determining movement of the subject, and the movement data of the chest and the thoracic diaphragm and the audio signal indicating the respiratory flow are used to determine a central sleep apnea or an obstructive sleep apnea for the subject.

2. The system of claim 1, wherein the microphone (108) is capable of monitoring the respiratory air flow via the trachea.

3. The system of any preceding claim, wherein the two ends (104, 106) are pressed to the skin symmetrically on opposite sides of the trachea.

4. The system of any preceding claim, wherein the intermediate portion (102) is adjustable between a minimum length and a maximum length, wherein the minimum length of the intermediate portion provides that the microphone is pressed to the skin of the subject and matches the minimum length, when the circumference of the neck is small and the maximum length of the intermediate portion provides that the microphone is pressed to the skin of the subject, when the circumference of the neck is large and matches the maximum length.

5. The system of any preceding claim, wherein both of the ends (104,

106) have a microphone for internal body sounds, for example a piezoelectric microphone and/or a tracheal microphone.

6. The system of any preceding claim 1 to 4, wherein the collar (100) comprises wireless radio transceiver (404) arranged to a different end than the microphone, and the intermediate portion may comprise one or more electrical conduits for transferring data between units arranged in different ends of the collar.

7. The system of claim 6, wherein the wireless radio transceiver (404) is a Bluetooth radio transceiver.

8. The system of any preceding claim, wherein at least one of the ends

(104, 106) comprise at least one of a gyroscope, a gyroscope provided with a magnetometer or gravitymeter, a 3D-accelerometer, a battery (410) and an ambient microphone (406a).

9. The system of any preceding claim, wherein the ends (104, 106) are separated laterally by a distance for allowing the laryngeal prominence of the subject to be located between the ends, when the collar is worn by the subject.

10. The system of any preceding claim, wherein the event is a sleep apnea event, and the execution of the computer program code causes:

incrementing a counter by each of the determined sleep apnea events; and

dividing the counter value by the hours of sleep for obtaining an apnea-hypopnea index.

11. The system of any preceding claim, wherein the event is a sleep apnea event, and

a sleep start time is determined after the audio signal indicating respiratory air flow is below a level for starting the monitoring and a sensor for determining movement of the subject indicates that the subject has been stabile for a time threshold for starting the monitoring.

12. The system of any preceding claim, wherein the event is a sleep apnea event and changes of the sleeping positions are detected on the basis of the sensor for determining movement of the subject during the sleep of the subject.

13. The system of any preceding claim, wherein the event is a sleep apnea event and an end of the sleep apnea event is determined on the basis of information obtained from the sensor for determining movement of the subject and on the basis of the level of the audio signal exceeding a threshold level after the sleep apnea event is determined.

14. The system of any preceding claim, comprising a conditioning unit (1004) capable of generating one or more impulses in the nervous system of the subject.

15. The system of claim 14, wherein the impulses have an increasing power and/or interval until a desired response is measured from the subject.

16. The system of any preceding claim, wherein ambient microphones (406a, 406b) are arranged in both ends of the collar, a phase difference is determined between the audio signals from the ambient microphones and interference that is present only on the left or right lateral side of the subject is determined on the basis of the phase difference and the determined interference is suppressed.

17. The system of any preceding claim, wherein certainty of the determined event is evaluated on the basis of movement data obtained from the subject and the certainty is displayed together with the determined event on a display device.

18. A system according to any preceding claim, wherein:

the central sleep apnea is determined for the subject, if movement of the thoracic diaphragm and the chest are not determined and the audio signal indicates that the respiratory air flow of the subject is reduced or there is no respiratory air flow; or

the obstructive sleep apnea is determined for the subject, if the thoracic diaphragm moves and the chest does not move and the audio signal indicates that the respiratory air flow of the subject is reduced or there is no respiratory air flow.

19. A system according to claim 18, wherein:

it is determined that the subject does not have the central sleep apnea or the obstructive sleep apnea, if the chest of the subject moves and the thoracic diaphragm moves.

20. A system (1410) to determine a sleep apnea, comprising: a microphone (1412) configured to obtain audio signals representing an amount of respiratory air flow via a trachea of a subject; and a processing unit (1414) and a memory (1418) comprising computer program code (1416) executable by the processing unit (1414), wherein the execution of the computer program code (1416) causes:

determining inhales (I) and exhales (E) from the audio signals based on an analysis of frequencies (F) of the audio signals; and

if a time period (1504) between successive exhale (1500) and inhale (1502) exceeds a predetermined time threshold, determining (1510) a central sleep apnea for the subject; or

if a time period (1604) between successive exhale (1600) and inhale (1602) includes one or more partial inhale attempts (1606, 1608), determining (1610) an obstructive sleep apnea for the subject.