WO2008111002A2

WO2008111002A2 - Device and a method for monitoring vital body signs

Info

Publication number: WO2008111002A2
Application number: PCT/IB2008/050912
Authority: WO
Inventors: Alexander Padiy; Cristian Presura
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-03-14
Filing date: 2008-03-13
Publication date: 2008-09-18
Also published as: WO2008111002A3

Abstract

A sensor for monitoring vital body signs of a living body resting on a structure, the structure being connected to the living body is disclosed. The sensor comprises one or more monitoring units arranged to measure microscopic displacements of the structure using laser self-mixing. The sensor (200) is useful for sensing motion related vital body signs such as heartbeat. The sensor (200) can be used in combination with a baby monitoring system (900) such as a baby phone to generate a signal indicative of the baby condition.

Description

Device and a method for monitoring vital body signs

Field of the invention

The subject matter relates to a device for monitoring vital body signs of a person at rest, and more specifically, to a device for monitoring the heart rate of a person at rest.

Background of the invention

Patent document WO97/14357 discloses a device for measuring heart rate of a person by attaching one or more sensors to the person's body. A disadvantage of the device is that it causes discomfort to the person since the device is attached to the person's body.

It is therefore an object of the invention to provide a device that measures vital body signs of the person without causing discomfort to the person. It is a further object of the invention to provide a method for measuring vital body signs of the person without causing discomfort to the person.

Summary of the invention

The object of the invention is realized by providing a sensor for monitoring vital body signs of a living body resting on a structure, the structure being connected to the living body. The sensor comprises one or more monitoring units arranged to measure microscopic displacements of the structure using laser self-mixing.

When a living body is at rest, the vital organs of the living body perform certain essential functions in order to keep the living body alive. Generally, the vital body signs (associated with the vital organs) of the living body cause microscopic displacements of the structure on which the living body is resting. The condition of the living body at rest can be monitored by measuring these microscopic displacements of the structure.

The disclosed sensor uses the technique of laser self-mixing to measure these microscopic displacements. A laser beam generated by a laser source is focused onto a surface of the structure and the light returning from the surface of the structure is optically mixed with the laser beam generated by the laser source. Optical mixing of the returning light and the laser beam generated by the laser source results in variations (fluctuations) in the laser power at a frequency proportional to the speed of the movement of the structure relative to the ground surface. The laser power fluctuations are measured with the help of a photo-detector that measures the power emitted by the laser. The photo-detector (e.g. photo- diode) can be situated in the structure on which the laser is built or can be situated next to the laser. In the later case an additional optical component may be needed that splits the laser light, such that a part goes on to the photo-detector. The laser self-mixing technique allows measurement of displacements that are approximately less than 0.1 micrometers.

The disclosed sensor is physically attached to the structure supporting the living body and not directly to the living body. Hence the disclosed sensor is able to monitor the condition of the living body without causing discomfort to the living body.

In an embodiment, regular heart rate of the living body is monitored.

Generally, the heart rate of a living body is regular under normal conditions and any sudden change in the heart rate relates to abnormalities in the living body. Hence, it is advantageous to monitor heart rate since it is a good indicator of the condition of the living body. In some embodiments, the breathing rhythm might be monitored additionally with the help of the same sensor.

In a further embodiment, each of the one or more monitoring units include an optical unit. The optical unit is arranged to use the laser self-mixing in combination with Doppler shift effect to detect heart rate of the living body at rest. The detection of the heart rate is performed by time-averaging the signal energy obtained from the microscopic displacements of the structure supporting the living body, wherein the microscopic displacements are within a frequency band that corresponds to the regular heart rate. This is advantageous since the optical unit allows measurement of sub-micrometer movements of the structure (supporting the living body) caused by the heartbeat. The movement of the structure towards or away from a laser source (caused by the heartbeat) results in Doppler shift in frequency of the returning light that can be used to find the speed at which the structure moves. The velocity of the structure with respect to the ground translates directly to the Doppler shift frequency. In some embodiments, the detection of the heart rate is performed without time-averaging the signal energy obtained from the microscopic displacements of the structure supporting the living body, in case the signal-to-noise ratio of the signal is high enough.

In an embodiment the optical unit includes: i) a flexible casing ii) a mirror iii) a laser module which includes a laser source and an optical detector. The detector is arranged to detect the reflected laser beam returning from the mirror for measuring Doppler shift due to at least one of vertical and lateral movement of the structure (supporting the living body). This is an advantageous embodiment since a small and relatively simple optical unit can be used to monitor the heart rate thereby reducing the complexity and allowing a cost effective solution.

In a still further embodiment, the sensor is an accelerometer. This is advantageous since it can detect the heart rate from a baby bed acceleration employing a laser self-mixing Doppler sensor in a non-rigid casing that can be fixed to the baby bed. It is also possible to have special elastic pads placed under the bedposts in order to control stiffness of the construction. Further, the elasticity of the pads can be tuned (either manually or automatically controlled by the main device) for achieving the best sensing performance.

In a still further embodiment, exemplary structures supporting the living body is one of a bed, a chair, a stroller, a wheel chair, a neonatal incubator, a patient bed, a ballistocardiographic chair and a ballistocardiographic bed. This is advantageous since the condition of the living body can be monitored in a variety of environments when the sensor is used in conjuction with such exemplary structures.

In a still further embodiment, the sensor can be placed under one of the bedposts. The sensor can measure at least one of vertical and lateral movements of the bedpost for detecting heart rate of the living body resting on the bed. This is advantageous since the sensor can be a stand-alone device or it can be used in combination with a bed thereby allowing easy monitoring of the condition of the living body. Additionally, there are no physical attachments on the living body and hence increases the comfort level of the living body.

In a still further embodiment, the disclosed sensor can be used in a baby monitoring system. The sensor can be disposed under the bedposts of a baby cot. The baby monitoring system can be configured to receive the monitored signals from the sensor and monitor the condition of the baby. The condition of the baby can be monitored without the physical presence of parents, which can relieve the parents of the worries of knowing for sure whether the baby is alive and well.

In an embodiment of the baby monitoring system, an alarm unit is arranged to generate an alarm indicative of the baby condition based on the detected regular heart rate. This is advantageous since the vital body sign of the baby can be monitored. Brief description of the drawings

These and other aspects, features and advantages will be further explained by the following description, by way of example only, with reference to the accompanying drawings in which same reference numerals indicate same or similar parts, and in which:

Fig.' s Ia - Id schematically illustrate exemplary structures supporting a living body;

Fig. 2 schematically illustrate a block diagram of the device used to monitor the condition of the living body according to the present subject matter;

Fig. 3 schematically illustrate detection of heartbeat according to an embodiment of the present subject matter;

Fig. 4a and Fig. 4b schematically illustrate a block diagram of an exemplary optical unit;

Fig. 5a and Fig. 5b schematically illustrate an embodiment of the device shown in Fig. 2 used to measure micrometer range displacements of the structure supporting the living body;

Fig. 6a and Fig. 6b schematically illustrate an other embodiment of the device shown in Fig. 2 used to measure micrometer range displacements of the structure supporting the living body;

Fig. 7a and Fig. 7b schematically illustrate an other embodiment of the device shown in Fig. 2 used to measure micrometer range displacements of the structure supporting the living body;

Fig. 8 illustrate the device shown in Fig. 2 disposed under the bedposts according to an embodiment of the present subject matter for monitoring the heart rate; and

Fig. 9 schematically illustrate a block diagram of an exemplary baby monitoring system that uses the device shown in Fig. 2.

The term "living body" here refers to the entire living organism, such as a human being (a person or a baby or an animal).

Referring now to Fig. Ia, a baby bed is a structure that provides a place for the baby to sleep. The structure comprises a bed 100 that is supported generally by four bed posts 102. Fig. Ib shows a chair which includes a seat 104 for a person with a support for the back 106 that allows a person to sit on the chair and take rest. The chair generally is supported by four legs 108 and fixed to the floor 504. Fig. Ic shows a stroller (baby carriage) which is generally a small vehicle designed to support and stroll a baby (child). Fig. Id shows a wheel chair which is a movable chair mounted on wheels 120 for invalids or those who are handicapped. The wheel chair is generally propelled by the occupant. Baby bed, chair, wheel chair and stroller are few examples of structures that are used by human beings to take rest. Further, the structure could include support structures used in the professional medical setting such as neonatal incubators and patient beds (both for adults and babies). Furthermore, the structure could be a ballistocardiographic (BCG) chair/bed that is meant for measuring not only the heart rate, but also finer features of blood pumping by the heart (i.e. sense dynamics of blood pulsation by means of ballistic measurements). The term "rest" here means that the human being is not moving and is in a resting position. In other words, the human being is taking a break from the normal activities in order to relax or the human being is not in action (i.e. the human being is not moving or the human being is not in motion).

It is important for the parents/caretakers to know the condition of the human being at rest, since it relieves the parents/caretakers from anxiety. There are devices in the market that monitor the condition of the human being. These devices are generally physically attached to the human being. Based on the movements (of the human being), the condition of the human being is monitored. Since these devices have to be physically attached to the human being, these devices can cause inconvenience/discomfort to the human being and can give an uncomfortable feeling.

Hence, it is an object of the invention to provide a device that monitors the condition of the human being without physically attaching the device to the human being.

Detailed description of the embodiments

Accordingly, a sensor (200) for monitoring vital body signs of a living body resting on a structure, the structure being connected to the living body is disclosed. The sensor comprises one or more monitoring units arranged to measure microscopic displacements of the structure using laser self-mixing.

When a human being is at rest, the vital organs of the human being perform certain essential functions in order to keep the human being alive. Generally, the vital body signs (associated with the vital organs) of the human being cause microscopic displacements of the structure on which the human being is resting. The condition of the human being at rest can be monitored by measuring these microscopic displacements of the structure.

The disclosed sensor 200 (Cf. Fig. 2) uses the technique of laser self-mixing to measure these microscopic displacements. A laser beam generated by a laser source is focused onto a surface of the structure and the light returning from the surface of the structure is optically mixed with the laser beam generated by the laser source. Optical mixing of the returning light and the laser beam generated by the laser source results in variations (fluctuations) in the laser power at a frequency proportional to the speed of the movement of the structure relative to the ground surface. The laser power fluctuations are measured with the help of a photo-detector that measures the power emitted by the laser. The photo-detector (e.g. photo-diode) can be situated in the structure on which the laser is built or can be situated next to the laser. In the later case an additional optical component may be needed that splits the laser light, such that a part goes on to the photo-detector. The laser self-mixing technique allows measurement of displacements that are approximately less than 0.1 micrometers.

The disclosed sensor 200 (Cf. Fig. 2) is physically attached to the structure supporting the human being and not directly to the human being. Hence the disclosed sensor 200 is able to monitor the condition of the human being without causing discomfort to the human being.

In an embodiment, regular heart rate of the human being is monitored. Generally, the heart rate of a living human being is regular under normal conditions and any sudden change in the heart rate relates to abnormalities in the human being. Hence, it is advantageous to monitor heart rate since it is a good indicator of the condition of the human being. In some embodiments, the breathing rhythm might be monitored additionally with the help of the same sensor.

In a further embodiment, each of the one or more monitoring units 202, 204 (Cf. Fig. 2) include an optical unit 250 (Cf. Fig. X). The optical unit 250 is arranged to use the laser self-mixing in combination with Doppler shift effect to detect heart rate of the living body at rest. The detection of the heart rate is performed by time-averaging the signal energy obtained from the microscopic displacements of the structure supporting the human being, wherein the microscopic displacements are within a frequency band that corresponds to the regular heart rate. This is advantageous since the optical unit 250 allows measurement of sub-micrometer movements of the structure (supporting the human being) caused by the heartbeat. The movement of the structure towards or away from a laser source (caused by the heartbeat) results in Doppler shift in frequency of the returning light that can be used to find the speed at which the structure moves. The velocity of the structure with respect to the ground translates directly to the Doppler shift frequency. In some embodiments, the detection of the heart rate is performed without time-averaging the signal energy obtained from the microscopic displacements of the structure supporting the human being, in case the signal-to-noise ratio of the signal is high enough. Referring to Fig. 3, the graph shows the average energy of the signal in the band 500Hz - 2KHz as a function of time. It is noted here that the spikes correspond to the heartbeat as verified by reference heart beat measurement.

Referring to Fig. 4A, in an embodiment the optical unit 250 includes: i) a flexible casing 260 ii) a mirror 270 iii) a laser module 280 which includes a laser source 280a and an optical detector

280b.

The detector 280b is arranged to detect the reflected laser beam returning from the mirror for measuring Doppler shift due to at least one of vertical and lateral movement of the structure (supporting the human being). This is an advantageous embodiment since a small and relatively simple optical unit 250 can be used to monitor the heart rate thereby reducing the complexity and allowing a cost effective solution.

In some embodiments, the laser module 280 (which includes the laser source 280a and the optical detector 280b) and the mirror 270 reflecting the laser beam are not placed in a single casing but are linked together by some sort of support structure as shown in Fig. 4b. Referring now to Fig. 4b, the laser module 280 is disposed under the mattress and the mirror 270 is disposed on a rigid rod placed on the floor.

Referring now to Fig. 5a, the vertical displacements of the structure supporting the human being can be measured using the arrangement shown in Fig. 5a. The optical unit 250 includes a flexible casing 260 attached to the structure 502 (on which the human being is resting). The laser module 280 is disposed on the floor 504. The term "floor" here refers to a horizontal surface of a room or a hallway. The laser module 280 includes a laser source 280a and an optical detector 280b. The mirror 270 is disposed on the flexible casing opposite to the laser module 280. The laser beam generated by the laser source 280a is focused onto the mirror 270 and the light returning from the mirror 270 is optically mixed with the laser beam generated by the laser source 280a. The Doppler shift due to vertical movement of the mirror (i.e. upper surface of the flexible casing attached to the structure 502) with respect to the floor 504 can be measured. Alternately, the mirror 270 can be disposed on the floor 504 and the laser module 280 on the upper surface of the flexible casing attached to the structure.

Referring now to Fig. 5b, the horizontal (i.e. lateral) displacements of the structure supporting the human being can be measured using the arrangement shown in Fig. 5b. The optical unit 250 includes a flexible casing 260 attached to the structure 502 (on which the human being is resting). The laser module 280 is disposed vertically (i.e. upright position) on the floor 504. The laser module 280 includes a laser source 280a and an optical detector 280b. The mirror 270 is disposed on the flexible casing opposite to the laser module 280. The laser beam generated by the laser source 280a is focused onto the mirror 270 and the light returning from the mirror 270 is optically mixed with the laser beam generated by the laser source 280a. The Doppler shift due to horizontal (i.e. lateral) movement of the mirror attached to the structure 502 with respect to the floor 504 can be measured.

Referring now to Fig. 6a and Fig. 6b, the sensor 200 (Cf. Fig. 2) can be adapted to measure the bed velocity in different directions by using the laser self-mixing in combination with Doppler shift effect. To achieve this, the optical unit 250 includes i) a source unit 620 having a plurality of laser modules 280A, 280B and 280C, each laser module including a laser source (280al, 280a2, 280a3) and an optical detector (280bl, 280b2, 280b3) ii) a target unit 630 having a plurality of mirrors 270a, 270b and 270c disposed on the first end of a right rod 602, the second end of the rigid rod being fixed to the floor 504. The source unit 620 can be disposed below the bed as shown in Fig. 6a. The target unit 630 can be disposed on the floor 504. The laser beam generated by the laser source (280al, 280a2, 280a3) is focused on to the respective mirrors (270a, 270b, 270c) and the light returning from the mirror(s) is optically mixed with the laser beam generated by the laser source. The arrangement shown in Fig. 6a can measure the bed velocity in different directions by using the laser self-mixing in combination with Doppler shift effect. Alternately, as shown in Fig. 6b, the source unit 620 can be disposed on the floor 504 and the target unit 630 can be disposed under the bed. In these arrangements, stiffness of the construction and thus the velocity range cannot be controlled by the device manufacturer as the stiffness is fully determined by the mechanical properties of the bed.

Referring now to Fig. 7a and Fig. 7b, a set of reflective structures or a set of slanted mirrors can be used instead of the rod (Cf. Fig. 6a, Fig. 6b). The optical unit 250 includes i) a source unit 620 having a plurality of laser modules 280A, 280B and 280C, each laser module including a laser source (280al, 280a2, 280a3) and an optical detector (280bl, 280b2, 280b3) ii) a target unit 630 having a plurality of reflective structures 290a, 290b, and

290c disposed under the bed. The source unit 620 can be disposed on the floor 504 as shown in Fig. 7a. The target unit 630 can be disposed under the bed. The laser beam generated by the laser source (280al, 280a2, 280a3) is focused on to the respective mirrors (290a, 290b, 290c) and the light returning from the mirror is optically mixed with the laser beam generated by the laser source. The arrangement shown in Fig. 7a can measure the bed velocity in different directions by using the laser self-mixing in combination with Doppler shift effect. Alternately, as shown in Fig. 7b, the source unit 620 can be disposed under the bed and the target unit 630 can be disposed on the floor 504. In these arrangements, stiffness of the construction and thus the velocity range cannot be controlled by the device manufacturer as the stiffness is fully determined by the mechanical properties of the bed.

The arrangements shown in Fig 6a, Fig. 6b, Fig. 7a and Fig. 7b generally use a kind of far- field optical mouse for measuring the movements of the bed with respect to the floor (uni-directional, bi-directional or 3 -directional) and extracting the heart rate (i.e. vital body signs) from these movements. A special reflective structure may be used in combination with the optical sensor. Alternatively, the natural bed surface might give sufficient reflection in some cases.

In a still further embodiment, the sensor 200 is an accelerometer. This is advantageous since it can detect the heart rate from the baby bed acceleration employing a laser self-mixing Doppler sensor in a non-rigid casing that can be fixed to the baby bed. It is also possible to have special elastic pads placed under the bedposts in order to control stiffness of the construction. Further, the elasticity of the pads can be tuned (either manually or automatically controlled by the main device) for achieving the best sensing performance.

In a still further embodiment, exemplary structures supporting the human being include a bed, a chair, a stroller, a wheel chair, a neonatal incubator, a patient bed, a ballistocardiographic chair and a ballistocardiographic bed. This is advantageous since the condition of the human being can be monitored in a variety of environments when the device is used in conjunction with such exemplary structures. It is noted that the wheel chair and the stroller are stationery (i.e. not moving) and the human being is resting on them.

In a still further embodiment, the sensor 200 shown in Fig. 2 can be placed under one of the bedposts 102 (Cf. Fig. 8). The sensor 200 can measure at least one of vertical and lateral movements of the bedpost 102 for detecting heart rate of the human being resting on the bed. This is advantageous since the sensor 200 can be a stand-alone device or it can be used in combination with a bed thereby allowing easy monitoring of the condition of the human being. Additionally, there are no physical attachments on the human being and hence increases the comfort level of the human being. Furthermore, the condition of the human being at rest can be monitored without the knowledge of the human being resting on the bed. It is noted here that only for illustrative purposes a baby cot and a (baby) bed 100 are shown in Fig. 8, but the device can generally be disposed below any structure on which the human being rests.

In a still further embodiment, the disclosed sensor 200 can be used in a baby monitoring system 900 as shown in Fig. 9. The sensor 200 (Cf. Fig.2) can be disposed under the bedposts of a baby cot. The baby monitoring system 900 includes: i) an alarm unit 902 ii) a weight sensor 904 iii) Logic circuit 906.

The baby monitoring system 900 is configured to receive the monitored signals from the sensor 200 and monitor the condition of the baby. The condition of the baby can be monitored without the physical presence of parents, which can relieve the parents of the worries of knowing for sure whether the baby is alive and well.

In an embodiment of the baby monitoring system 900, the alarm unit 902 is arranged to generate an alarm indicative of the baby condition based on the detected regular heart rate. This is advantageous since the vital body sign of the baby can be monitored. Additionally, a signal can be provided to the parent that is indicative of the condition of the baby thereby relieving the parents of the anxiety. Furthermore, in some embodiments the signal can provide relevant information about the patient to the caregivers.

In a further embodiment of the baby monitoring system 900, the optical unit 250 is adapted to also detect the presence of the baby (or patient) in the structure. The self- mixing laser sensor itself can be used as a kind of weight sensor/presence detector, as leaving the bed can be seen as the characteristic velocity pattern in the sensor signal, and the displacement due to weight change can be computed by integrating the velocity as measured by the sensor (the absolute accuracy of the weight measurement may be poor, but sufficient for presence detection). Furthermore, the logic circuit 906 is arranged to switch on/off the alarm unit based on detecting the presence of the baby in the bed and the detected regular heart rate. This is advantageous since robust automatic detection of the baby presence in the bed can be implemented. Additionally, the alarm unit can be automatically deactivated when the heartbeat suddenly disappear due to the baby taken out of the bed (i.e. the event of taking the baby out of the bed can be detected by observing a characteristic drop in the bed weight coinciding in time with the loss of the heartbeat signal). Alternatively, a separate weight sensor 904 can be used to detect the presence of the baby (or patient) in the bed.

In summary, a sensor for monitoring vital body signs of a living body resting on a structure, the structure being connected to the living body is disclosed. The sensor comprises one or more monitoring units arranged to measure microscopic displacements of the structure using laser self-mixing. The sensor is useful for sensing motion related vital body signs such as heartbeat. The sensor can be used in combination with a baby monitoring system such as a baby phone to generate a signal indicative of the baby condition.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the subject matter is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject matter, from a study of the drawings, the disclosure, and the appended claims. The use of the verb "comprise" does not exclude the presence of elements other than those listed in a claim or in the description. The use of the indefinite article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Claims

CLAIMS:

1. A sensor (200) for monitoring vital body signs of a living body resting on a structure, the structure being connected to the living body, the sensor comprising: one or more monitoring units (202, 204) arranged to measure microscopic displacements of the structure using laser self-mixing.

2. The sensor as claimed in claim 1, wherein the vital body sign is the heart rate.

3. The sensor as claimed in claim 1, wherein each of the one or more monitoring units (202,204) comprises: an optical unit (250) arranged to use the laser-self mixing in combination with Doppler shift to detect heart rate of the living body at rest by time-averaging a signal energy obtained from the microscopic displacements of the structure, wherein the microscopic displacements are within a frequency band that corresponds to the regular heart rate.

4. The sensor as claimed in claim 3, wherein the optical unit comprises: a flexible casing (260) that can be attached to the structure; a mirror (270) attached to the flexible casing; and a laser module (280) comprising: a laser source (280a) arranged to generate a laser beam; and an optical detector (280b) arranged to detect the reflected laser beam returning from the mirror for measuring Doppler shift due to at least one of vertical and lateral movement of the structure.

5. The sensor as claimed in claim 1, wherein the sensor is an accelerometer.

6. The sensor as claimed in any one of the claims 1 - 5, wherein the structure is one of a bed, a chair, a stroller, a wheel chair, a neonatal incubator, a patient bed, a ballistocardiographic chair and a ballistocardiographic bed.

7. The sensor as claimed in any one of the claims 1 - 5, wherein the sensor is disposed under at least one of the bedposts (102) to measure at least one of vertical and lateral movements of the bedpost for detecting the heart rate.

8. A baby monitoring system (900) comprising the sensor as claimed in any one of the claims 1 - 5.

9. The baby monitoring system as claimed in 8, further comprising: an alarm unit (902) arranged to generate an alarm indicative of the baby condition based on the detected heart rate.

10. The baby monitoring system (900) as claimed in claim 9, wherein the optical unit (250) is arranged to detect the presence of the baby in the bed.

11. The baby monitoring system (900) as claimed in claim 9, further comprising: a weight sensor (904) arranged to detect the presence of the baby in the bed; and a logic circuit (906) arranged to switch on/off the alarm unit based on detecting the presence of the baby in the bed and the detected regular heart rate.

12. A method for monitoring vital body sings of a living body resting on a structure, the structure being connected to the living body, the method comprising: using one or more monitoring units to measure microscopic displacements of the structure using laser self-mixing.

13. The method as claimed in claim 12, wherein, in monitoring, the vital body sign is the heart rate.

14. The method as claimed in claim 13, further comprising: using the laser self-mixing in combination with Doppler shift effect to detect the heart rate of the living body at rest by time-averaging a signal energy obtained from microscopic displacements of the structure, wherein the microscopic displacements are within a frequency band that corresponds to the regular heart rate.

15. The method as claimed in claim 14, further comprising: detecting the presence of the living body in the structure; and switching on/off an alarm indicative of the living body condition based on the detected presence of the living body in the structure and the detected regular heart rate.