Classifications

• • G—PHYSICS
  • G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
  • G16Z—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS, NOT OTHERWISE PROVIDED FOR
  • G16Z99/00—Subject matter not provided for in other main groups of this subclass
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/08—Measuring devices for evaluating the respiratory organs
  • A61B5/087—Measuring breath flow
• • A—HUMAN NECESSITIES
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  • A61B5/08—Measuring devices for evaluating the respiratory organs
  • A61B5/087—Measuring breath flow
  • A61B5/0873—Measuring breath flow using optical means
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
  • A61B5/0075—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
  • A61B5/0077—Devices for viewing the surface of the body, e.g. camera, magnifying lens
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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  • A61B5/08—Measuring devices for evaluating the respiratory organs
  • A61B5/087—Measuring breath flow
  • A61B5/0876—Measuring breath flow using means deflected by the fluid stream, e.g. flaps
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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  • A61B5/08—Measuring devices for evaluating the respiratory organs
  • A61B5/091—Measuring volume of inspired or expired gases, e.g. to determine lung capacity
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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  • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb
  • A61B5/1126—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb using a particular sensing technique
  • A61B5/1127—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb using a particular sensing technique using markers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
  • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
  • A61B5/6813—Specially adapted to be attached to a specific body part
  • A61B5/6814—Head
  • A61B5/6819—Nose
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
  • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
  • A61B5/6813—Specially adapted to be attached to a specific body part
  • A61B5/6814—Head
  • A61B5/682—Mouth, e.g., oral cavity; tongue; Lips; Teeth
• • A—HUMAN NECESSITIES
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  • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
  • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
  • A61B5/683—Means for maintaining contact with the body
  • A61B5/6832—Means for maintaining contact with the body using adhesives
  • A61B5/6833—Adhesive patches
• • A—HUMAN NECESSITIES
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  • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
  • A61B5/7271—Specific aspects of physiological measurement analysis
  • A61B5/7278—Artificial waveform generation or derivation, e.g. synthesizing signals from measured signals
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
  • A61B90/39—Markers, e.g. radio-opaque or breast lesions markers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
  • A61B90/39—Markers, e.g. radio-opaque or breast lesions markers
  • A61B2090/3937—Visible markers
  • A61B2090/3945—Active visible markers, e.g. light emitting diodes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
  • A61B90/39—Markers, e.g. radio-opaque or breast lesions markers
  • A61B2090/397—Markers, e.g. radio-opaque or breast lesions markers electromagnetic other than visible, e.g. microwave
  • A61B2090/3975—Markers, e.g. radio-opaque or breast lesions markers electromagnetic other than visible, e.g. microwave active
  • A61B2090/3979—Markers, e.g. radio-opaque or breast lesions markers electromagnetic other than visible, e.g. microwave active infrared
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
  • A61B90/39—Markers, e.g. radio-opaque or breast lesions markers
  • A61B2090/3991—Markers, e.g. radio-opaque or breast lesions markers having specific anchoring means to fixate the marker to the tissue, e.g. hooks
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/103—Measuring devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor or mobility of a limb
  • A61B5/1113—Local tracking of patients, e.g. in a hospital or private home
  • A61B5/1114—Tracking parts of the body

Definitions

• the present invention relates to a system and method for determining vital sign information of a subject, in particular to optical measurement for remotely determining vital signs of an observed subject.
• Vital signs of a subject for example the heart rate (HR), the respiration rate (RR) or the body temperature serve as indicators of the current health status of a person and as powerful predictors of serious medical events. For this reason, vital signs are extensively monitored in in-patient and out-patient care settings, at home or in further health, leisure and fitness settings.
• HR heart rate
• RR respiration rate
• body temperature serve as indicators of the current health status of a person and as powerful predictors of serious medical events. For this reason, vital signs are extensively monitored in in-patient and out-patient care settings, at home or in further health, leisure and fitness settings.
• US 2009/0204100 Al discloses a body cover comprising a temperature sensing element.
• the temperature sensing element senses the temperature of proximate skin and converts the locally sensed temperature into a visual and/or electrical signal.
• the body cover may include a local display for converting electrical signals that are output by temperature sensing elements into a visual signal such that a wearer or a camera can read the state of the skin from the body cover.
• US 4,945,919 discloses a rhino logical diagnostic device comprising a thermochromic liquid crystal layer for displaying a temperature distribution of expired air in a thermochromic pattern for diagnosing an abnormality in the nasal cavity.
• US 2012/0289850 Al discloses monitoring respiration of a subject with a thermal imaging system set to a temperature range of a facial region.
• a thermal camera operating in the infrared wavelength range of 7,500 nm to 14,000 nm captures a thermal image video sequence.
• Temperatures of extremities of the head and face are used to locate facial features in the captured thermal images, i.e., nose and mouth, which are associated with respiration. Since the temperature of the exhaled air typically has a higher temperature than the inhaled air, a temporal variation of the nose and mouth region can be evaluated to determine the respiration rate. In an alternative embodiment, the respiration rate is determined by the motion of the nostrils, lips or chest.
• US 2012/0052469 Al discloses a nasal flow controller device. An air flow during sniffmg-in cools a region about the nose and air- flow during sniffing out warms a region about the nose. A pad can be attached to the subject's nose which responds sufficiently fast to temperature variations. A camera again
• a disadvantage of such systems is that a thermal measurement only works if there is a significant temperature difference between environmental temperature and exhaled air temperature.
• a further disadvantage is that thermal cameras are expensive.
• additional measurement modalities are needed to measure additional vital signs like the heart rate or oxygen saturation in parallel.
• US 6,110,123 A discloses motion-based respiration measurement.
• respiration correlated movements must be visible for the camera system.
• a movement of the chest is observed since respiratory movements are usually not visible in the face.
• a chest movement does not guarantee a gas flow into the lungs.
• a motion-based respiration measurement is susceptible to motion artifacts.
• a system for determining vital sign information of a subject that comprises
• a marker for application to the subject wherein the marker is configured to change an optical property due to a mechanical manipulation of the marker caused by a physiological process of the subject
• a detection unit for detecting radiation from the marker
• an analysis unit for determining the vital sign information of the subject from the detected radiation.
• a marker for use in the aforementioned system wherein the marker is configured for application to the subject, and wherein the marker is configured to change an optical property due to a mechanical manipulation of the marker caused by a physiological process of the subject.
• a method for determining vital sign information of the subject comprises the steps of
• the marker is applied to the subject, and wherein the marker is configured to change an optical property due to a mechanical manipulation of the marker (10, 10', 10", 40) caused by a physiological process of the subject, and
• the term 'vital sign' as used in the context of the present invention refers to a physiological parameter of the subject and derivative parameters.
• the term 'vital sign' comprises heart rate (HR) (sometimes also called pulse rate), heart rate variability (pulse rate variability), pulsatility strength, perfusion, perfusion indicator, perfusion variability, Traube Hering Mayer waves, respiratory rate (RR), body temperature, blood pressure, a concentration of substance in blood and/or tissue and/or sweat, such as an oxygen saturation or a glucose level.
• HR heart rate
• RR respiratory rate
• body temperature blood pressure
• a concentration of substance in blood and/or tissue and/or sweat such as an oxygen saturation or a glucose level.
• a 'vital sign' can be descriptive of an underlying physiological process such as cardiac pulses or a respiratory activity.
• a physiological signal descriptive of the underlying physiological process can be measured and evaluated.
• the term 'vital sign information' as used in the context of the present invention comprises the one or more measured vital signs as defined above. Furthermore, the term 'vital sign information' comprises data referring to a physiological parameter, corresponding waveform traces or data referring to a physiological parameter over time that can serve for subsequent analysis.
• a major drawback of existing measurement devices for determining vital signs is that they are tailored for a specific application such that a plurality of different devices is required to cover the desired vital signs.
• US 2012/0289850 Al is used for determining the respiration rate, and an additional camera operating in a visible part of the spectrum is used for determining a heart rate by remote photo-plethysmography.
• Verkruysse et al. "Remote plethysmographic imaging using ambient light", Optics Express, 16 (26), 22 December 2008, pp. 21434-21445 demonstrate that photo- plethysmo graphic signals can be measured remotely using ambient light and a conventional consumer level video camera. Different devices are needed, since the desired underlying physical quantities cannot be observed by one single device.
• the present invention is based on the idea that a marker is applied to the subject wherein the marker is configured to change an optical property in response to a physiological process of the subject.
• the marker is used to convert vital sign information, which is invisible itself to the measurement modality, to be detectable by that measurement modality.
• the marker is configured to change an optical property, such as a color or brightness, in response to a respiratory gas volume flow.
• a detection unit such as a low-cost CCD camera detects radiation received from the marker.
• the analysis unit analyzes the detected radiation and determines the respiratory rate by evaluating a temporal change of the optical property of the marker.
• the term 'detection unit' refers to a device for detecting electromagnetic radiation. It is configured to detect radiation received from the marker.
• the detection unit is a camera with an image sensor such as a CCD or CMOS image sensor that comprises an array of light sensitive pixels.
• the output of the detection unit is referred to as radiation data.
• the radiation data is a series of images over time, thus a video stream.
• the camera can be a monochrome or color camera.
• the detection unit is a remote detection unit, wherein the detection unit is spatially separated from the observed subject.
• the detection unit is configured to detect light in a spectral range of about 420 to 1100 nm.
• the marker is configured to change an optical property due to one of a mechanical, physical or chemical manipulation of the marker caused by a physiological process of the subject.
• a mechanical manipulation the marker is configured to change an optical property in response to a gas volume flow due to respiration, or in response to stress introduced by a muscular activity or dilation of blood vessels.
• a physical manipulation the marker is configured to change an optical property in response to a temperature change, for example induced by respiration.
• a chemical manipulation the marker is configured to change an optical property in response to a gas concentration for example constituents of exhaled air like carbon dioxide or other reaction product, a chemical property of the skin surface, such as a pH value, humidity and the like.
• the changing optical property of the marker is a reflectivity and/or color.
• the term 'reflectivity' as used herein also refers to a reflection, in particular specular reflection, as well as brightness or absorption characteristics.
• the changing optical property also includes an apparent change of an optical property. For example, an orientation of a structural element of the marker may be altered in response to a physiological process. Thus, the color of the structural element of the marker does not actually change. However, the different orientation of the structural element of the marker provides the detection unit with a different optical impression.
• the marker is a patch, in particular a patch for application to a skin of the subject.
• a patch for application to a skin of the subject.
• the marker can be configured for direct application to the subject, in particular to the skin of the subject.
• the marker can be provided in form of a lipstick or unguent, cream or lotion.
• the marker can be configured for application to a tubus or other medical equipment in proximity to the patient which is affected by a physiological process of the subject, such as a respiratory flow of air.
• the marker is configured for application to a nasal and/or oral region of the subject.
• the regio oralis is particularly well suited for application since it is affected by a respiratory flow of air and is seldom covered by a blanket.
• a patch for fastening a tube for supplying the patient with oxygen can carry the marker in the supralabial region or in proximity to the philtrum.
• the filaments comprise a first surface having a first optical property and a second surface having a second optical property.
• the first surface and the second surface can have different colors, be black and white, have different reflection or scattering properties.
• the first and second surface provide a high contrast.
• the filaments have a first optical property and the surface of the marker from which the filaments are protruding from has a second optical property.
• information about an orientation of the filaments can be inferred. It should be noted that it is not mandatory to know the exact orientation of the filaments since it can be sufficient to analyze a relative change in the detected radiation from the marker.
• the first optical property and the second optical property provide a high contrast.
• the detection unit comprises an image sensor or camera.
• the image sensor is a standard CCD or CMOS image sensor that is available at low cost. This is a significant advantage compared to the solution proposed in US
• the detection unit is configured to detect non- visible radiation, in particular near infrared (IR) and/or near ultraviolet (UV).
• IR near infrared
• UV near ultraviolet
• An advantage of this embodiment is that vital sign measurements can be performed in darkness, thus without disturbing the patient at night.
• a marker wherein the color of the marker corresponds to the color of the skin of the subject in the visible range.
• the marker is configured to change an optical property in the non- visible part of the spectrum. Thereby, an aesthetic appearance is improved.
• Near infrared can be defined as a wavelength range of 750 nm to 1400 nm.
• Near ultra violet can be defined as a wavelength range of 300 nm to 400 nm.
• Visible light can be defined as a wavelength range from 400 nm to 750 nm.
• the detection unit can be configured to detect near infrared and/or near ultraviolet light in addition to visible light or in alternative to visible light.
• the analysis unit is configured to evaluate the detected radiation over time.
• an absolute value does not have to be known.
• the respiratory rate can be determined by evaluating a time series of the measured radiation data.
• long-term monitoring of a subject enables a comparison of measurement values of the subject at different points in time, thus a self-referencing system. Thereby, an improving or deteriorating condition can be determined.
• aging of the marker can be considered. For example, a marker that changes its optical property based on a mechanical manipulation or chemical manipulation may degrade over time such that its ability to change its optical property wears off.
• this aging of the marker can also be considered, for example by applying a correction function in the analysis unit.
• the marker is configured to change an optical property in response to a respiration of the subject
• the analysis unit is configured to derive information about the tidal volume.
• a relative change can be evaluated for example for indicating a decreasing tidal volume.
• the marker is further configured to visualize a physiological property of the subject by the optical property.
• a physiological property of the subject For example, an absolute value, such as a temperature or a concentration of a chemical substance, can be indicated by the optical property of the marker, wherein the optical property changes in response to a physiological process of the subject.
• the marker further comprises a reference area on the marker as a reference for determining the absolute value. This is particularly advantageous since the appearance of the optical property to the detection unit may depend upon and change with different lighting conditions.
• the marker comprises one or more additional optical features for detection by the detection unit of a group of features comprising an optical feature for tracking the marker, for reference, for measurement at night and for information coding.
• the marker can comprise a bar code or QR-code that comprises information about the patient that is to be measured and/or information about the
• the marker can comprise distinct optical features which enable tracking of the marker in the detected radiation.
• the system further comprises an image processing unit for identifying the marker in the detected radiation.
• Fig. 1 shows an exemplary embodiment of a system for determining vital sign information of a subject according to the present invention
• Fig. 2 shows a marker according to an aspect of the present invention applied to the subject
• Figs. 3A and 3B show an exemplary embodiment of a marker configured to change an optical property due to a mechanical manipulation of the marker
• Fig. 4 shows an alternative embodiment of a marker
• Fig. 5 shows a further embodiment of a marker
• Fig. 6 shows two markers applied to a face of the subject.
• Fig. 1 shows an exemplary embodiment of a system 1 for determining vital sign information 7 of a subject 100 according to an aspect of the present invention.
• the system 1 comprises a marker 10 for application to the subject 100, a detection unit 2 and an analysis unit 6 as the basic components.
• the system 1 for determining vital sign information 7 of the subject 100 is employed in a clinical setting, where the subject 100 lies in bed 200.
• the marker 10 is configured to change an optical property in response to a physiological process of the subject 100.
• the detection unit 2 is connected to an optional image processing unit 4.
• the detection unit 2 provides radiation data 3 that represents the detected radiation to the image processing unit 4 in form of a video stream.
• the image processing unit 4 identifies the marker 10 in the radiation data 3.
• the image processing unit 4 in turn is connected to the analysis unit 6.
• the image processing unit 4 provides pre-processed radiation data 5 to the analysis unit 6.
• the pre-processed radiation data 5 in this example comprises information about which region of the images of the video stream of the radiation data 3 depict the marker 10.
• the analysis unit 6 determines the vital sign information 7 of the subject 100 from the detected radiation.
• the image processing unit 4 for identifying the marker 10 can also be incorporated into the analysis unit 6.
• the radiation data 3 is directly provided to the analysis unit 6.
• the marker 10 can either be determined by manually selecting the marker 10 in the images of the video stream.
• the subject 100 with the marker 10 has to be located in a predetermined position within the field of view of the detection unit 2 such that the marker 10 is located at a predetermined position.
• an automated identification of the marker 10 in the radiation data 3 by the image processing unit 4 is preferred.
• the marker 10 is directly applied to the bare skin of the nasal/oral region 101 of the subject 100.
• An alternative marker 10' is located at the left forearm 102 of the subject 100.
• the size and shape of the marker 10, 10' can be adapted depending on the anatomic location.
• the system 1 for determining vital sign information 7 of the subject 100 can be further configured as a system for measuring vital signs by remote photo- plethysmography.
• Plethysmography historically refers to the measurement of volume changes of an organ or body part and in particular to the detection of volume changes due to a cardio-vascular pulse wave traveling through the body of the subject 100 with every heartbeat.
• Photo-plethysmography is an optical measurement technique that evaluates a time-variant change of light reflectance or transmission of an area or volume of interest.
• PPG for determining a heart rate is based on the principle that blood absorbs light more than surrounding tissue, so variations in blood volume with every heartbeat affect transmission or reflectance correspondingly.
• Every heartbeat causes small changes in the color of a face of the subject. These changes are not visible to the eye, but the detection unit 2 is configured to detect these "micro-blushes".
• the time-variant color change can be provided as a PPG waveform which is evaluated by the analysis unit 6 to measure the heart rate as the vital sign information 7.
• the PPG waveform can comprise information attributable to further physiological phenomena such as the respiration.
• the transmissivity and/or reflectivity at different wavelengths (typically red and infrared as mentioned before)
• the blood oxygen saturation can be determined.
• the prior art discloses using a thermal imager or alternatively evaluating body movements to determine a respiration rate.
• the present invention suggests to apply a marker to the subject, wherein the marker 10 is configured to change an optical property in response to a physiological process of the subject 100.
• vital sign information gets detectable by a detection unit 2, in particular a low-cost standard CCD sensor.
• the detection unit 2 can also be referred to as a vital signs camera.
• the scenery in Fig. 1 is illuminated by a source of radiation, such as sunlight 8a or an artificial light source 8b.
• the radiation source 8a, 8b directly or indirectly emits radiation 8d, 8e towards the subject 100.
• the system 1 can also comprise an optional system light source 8c that emits light 8f towards the subject 100.
• the use of the system light source 8c is particularly beneficial if the ambient light sources 8a, 8b do not provide sufficient light or if the spectrum of the ambient light sources 8a, 8b does not provide sufficient power in a desired spectral region.
• An optional control unit 9 is adapted to control the sensitivity of the detection unit 2 and/or to control the power of the system light source 8c. Because the dynamic range of detector or image sensor that is used as the detection unit 2 is limited, shutters and electronic offsets may have to be adjusted according to the lighting situation in the observed scene.
• the system light source 8c can be part of a control loop which sets an optimal operating point of the image sensor of the detection unit 2. Optimal in this context refers to an output signal without signal clipping, no saturation of individual detectors of the image sensor and a good signal-to-noise ratio at least for the detection area corresponding to the marker 10, 10'.
• the detection unit 2 comprises a standard image sensor for detecting radiation from the scenery with the marker 10, 10'.
• the detection unit is an off-the-shelf camera operating in a wavelength region between 300 nm to 1400 nm, preferably between 420 nm and 1100 nm, preferably between 420 nm and 750 nm, preferably in the visible range.
• the wavelength region of the detection unit preferably includes at least some near ultraviolet (UV) light and/or some near infrared (IR) light wavelengths.
• UV near ultraviolet
• IR near infrared
• An image sensor as used herein does explicitly not refer to a thermal imager operating in the mid to long infrared wavelength range of 7,500 nm to 14,000 nm.
• the system 1 with the detection unit 2, the analysis unit 6 and the marker 10 can be provided at much lower cost.
• the system light source 8c is configured to emit non-visible radiation 8f, in particular near infrared and/or near ultraviolet light. Thereby, the subject 100 can be monitored at night or darkness in terms of the visible wavelength spectrum, without disturbing the subject 100.
• the system light source 8c is configured to emit light with different spectral properties, for example red and infrared light or red and green light at the same and/or different times to enable a measurement of blood oxygen saturation, as for example disclosed by Wieringa et al. "Contactless Multiple Wavelength Photo- Plethysmographic Imaging: A First Step Towards "SP02 Camera” Technology", Annals of Biomedical Engineering, vol. 33, No. 8, 2005, pp. 1034-1041.
• the marker 10 is configured to change an optical property in response to a physiological process of the subject 100.
• Fig. 2 shows a close-up of the face of the subject 100, wherein the marker 10 is configured for application to a nasal and/or oral region 101 of the subject, in particular to a region underneath a nose 104 of the subject in the supralabial region, for example spanning across the philtrum.
• the marker 10 is configured to change an optical property due to a mechanical manipulation of the marker 10 caused by a physiological process of the subject 100.
• An exemplary embodiment of such a marker 10 is described with reference to Figs. 3 A and 3B.
• a surface 11 of the marker 10 comprises filaments 12 protruding from said surface 11.
• these filaments are flexible filaments, in particular textile fibers that are configured to move upon a stream of air passing by.
• Filaments are not limited to filaments of circular cross-section but also include shapes such as, for example, a lamella structure.
• the inset of Fig. 3 A illustrates an orientation of the filaments 12 during exhalation, wherein a flow of exhaled air 20 passes by the surface 11 of the marker during exhalation and bends the filaments 12 downwards.
• the filaments 12 comprise a first surface 12a having a first optical property and a second surface 12b having a second optical property.
• a first optical property For example as shown in Fig. 3 A, an upper surface 12a of the filament 12 is black, whereas a lower surface 12b is white.
• the first and second surface can have different color, different reflection or scattering properties.
• the first surface 12a and the second surface 12b have a high contrast. Thus, during exhalation, the detection unit 2 sees a darker color.
• Fig. 3B shows the marker 10 during inhalation, wherein a flow of air 21 passes by the marker surface 11 in an upward direction.
• the filaments 12a are oriented in an upward direction, such that the white side 12b of the filament 12 is visible to the detection unit 2.
• the detection unit 2 which captures a brighter image.
• the analysis unit 6 is configured to evaluate the detected radiation over time and can thus to analyze the change between a darker appearance of the marker 10 as shown in Fig. 3 A during exhalation and a brighter appearance of the marker 10 as shown in Fig. 3B during inhalation.
• vital sign information referring to the respiration of the subject, which is invisible itself to the visible optical spectrum, gets detectable by a potentially low-cost detection unit 2.
• a respiratory flow of air 22 does not orient all the filaments 12 of the surface 11 of the marker in the same direction but merely causes a re-orientation, wherein some filaments flex to a right and some filaments flex to a left side.
• absolute knowledge about an orientation of filaments is not mandatory, since a relative change can also be evaluated.
• the period times of a first optical property and a second optical property can be compared. For example, inspiration typically has a shorter duration than expiration. Moreover, expiration is often followed by a breathing pause.
• the analysis unit 6 is configured to derive information about a tidal volume of the subject 100 with a marker as shown in Figs. 3 A and 3B.
• the number of filaments that move with the airflow correlates to the breathing strength.
• the color change contains information about the breathing strength over time.
• An integral of the corresponding signal over time correlates to the tidal volume.
• each filament has a color/brightness scale gradient from top to the bottom. The stronger the breathing, the more of each single filament is visible to the detection unit 2. Thus, again the average color/brightness change would be indicative for the breathing strength over time.
• An integral of the corresponding signal over time again correlates with the tidal volume.
• the marker is directly applied to a skin of the subject 100.
• the marker is implemented in form of a colorimetric lipstick which is directly applied to the lips 13 of the subject.
• the lipstick is configured to change its color or other reflectance property, in general a substance configured to change an optical property, in response to a physiological process of the subject which, for example, causes a different temperature, gas concentration or humidity at the marker. Applying the marker directly on the lips has the advantage that a breathing of the subject 100 through the mouth can also be observed.
• the marker 10" is indirectly applied to the subject 100.
• the marker 10" is implemented as a part of a tubular system 30 of an intubated patient 100.
• the marker 10" is configured to change its color due to a chemical manipulation of the marker, i.e. in response to a different carbon dioxide concentration of inhaled and exhaled air.
• the color change is observed with the detection unit 2 for detecting radiation from the marker and the corresponding radiation data 3 is provided to the analysis unit 6 for determining the vital sign information 7 of the subject 100 from the detected radiation by evaluating the detected radiation over time.
• an actual value can be used as independent information.
• the system 1 for determining vital sign information as disclosed herein can be combined with colorimetric and/or fluorimetric optical measurements principles known from chemical analytic sensors, for example, to determine oxygen and carbon dioxide concentrations.
• chemical analytic sensors for example, to determine oxygen and carbon dioxide concentrations.
• oxygen concentration there are known principles of dynamic fluorescence quenching or sensors that use the fluorescence of a chemical complex in a sol-gel to measure the partial pressure of oxygen such as Joseph R. Lakowicz, "Principles of Fluorescence Spectroscopy", Third Edition, ISBN: 978-0-387-31278-1; Otto S.
• the optical information such as the actual color, may be sufficiently accurate for determining a carbon dioxide concentration of inhaled and exhaled air for certain applications.
• a delta value between an inspiration phase and an expiration phase or alternatively a trend thereof can be evaluated if an absolute accuracy is not sufficient.
• Exemplary parameters that can be determined include, but are not limited to exhaled carbon dioxide level, oxygen concentration (inspired and/or expired), oxygen consumption (delta between expired and inspired), oxygen uptake (efficiency indicator for lungs), temperature or temperature difference to ambient temperature, and humidity. This further includes a concentration of chemical substances, in particular chemical substances involved with certain diseases.
• the marker 10" shown in Fig. 5 can be part of the tubular system 30, wherein a color of the tubular system 30 can serve as a reference surface for calibrating the system 1 for determining vital sign information, in particular for calibrating the detection unit 2 to the available light intensity and spectrum.
• information can be encoded in the marker as shown in Fig. 6 in form of a barcode 41.
• the additional information can, for example, be used for calibrating the system 1, for configuring a measurement procedure or for automatically assigning the measured vital sign information to an electronic health record of the subject 100.
• a marker can be implemented as a forehead patch 40 configured for application to the forehead 103 of the subject 100.
• the forehead patch 40 is configured to change its color in response to a body temperature of the subject 100.
• the forehead patch 40 is skin-colored in the visible spectral range and changes its color at non-visible wavelengths, in particular near infrared and/or near ultraviolet.
• a plurality of markers 10, 40 can be applied to the subject 100.
• the markers can be configured for same or different vital signs to be measured.
• the detection unit 2 is configured correspondingly to detect radiation received from both markers. Furthermore, the detection unit can be configured to determine vital sign information of the subject by directly evaluating a time- variant change of the color of the skin of the subject 100.
• the system for determining vital sign information of a subject comprising a marker for application to the subject, wherein the marker is configured to change an optical property in response to a physiological process of the subject, a detection unit for detecting radiation from the marker, and an analysis unit for determining the vital sign information of the subject from the detected radiation successfully provides a system for unobtrusive monitoring of vital signs at low system cost.

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• 2014
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