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Title:
TEXTILE PRODUCT AND SYSTEM AND METHOD FOR MONITORING VITAL SIGNS
Document Type and Number:
WIPO Patent Application WO/2017/194669
Kind Code:
A1
Abstract:
The present invention relates to a textile product having a first area (14) and at least one second area (13), the first area (14) having a first transmittance for radiation in a predetermined wavelength range, the at least one second area (13) having a second transmittance for radiation in the predetermined wavelength range, wherein the second transmittance is higher than the first transmittance by at least 50%. The present invention relates further to a system (3) and method for monitoring vital signs of a human subject (1) and to the use of the disclosed textile product.

Inventors:
MEFTAH, Mohammed (High Tech Campus 5, 5656 AE Eindhoven, 5656 AE, NL)
DE HAAN, Gerard (High Tech Campus 5, 5656 AE Eindhoven, 5656 AE, NL)
VERKRUIJSSE, Willem (High Tech Campus 5, 5656 AE Eindhoven, 5656 AE, NL)
Application Number:
EP2017/061312
Publication Date:
November 16, 2017
Filing Date:
May 11, 2017
Export Citation:
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Assignee:
KONINKLIJKE PHILIPS N.V. (High Tech Campus 5, 5656 AE Eindhoven, 5656 AE, NL)
International Classes:
A61B5/024; A41D13/12; A61B5/1455; A61M16/06; A61B5/0205
Attorney, Agent or Firm:
DE HAAN, Poul, Erik (Philips International B.V, Intellectual Property & StandardsHigh Tech Campus 5, 5656 AE Eindhoven, 5656 AE, NL)
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Claims:
CLAIMS:

1. Textile product having a first area (14) and at least one second area (13), the first area (14) having a first transmittance for radiation in a predetermined wavelength range, the at least one second area (13) having a second transmittance for radiation in the predetermined wavelength range, wherein the second transmittance is higher than the first transmittance by at least 50%, and

wherein the textile product contains one or more of: one or more second areas (13) woven less loosely than the first area (14), pigments and/or dye which are reflective or absorptive for radiation in the predetermined wavelength range, integrated fibers and/or yarns which are dyed in pigments being reflective/absorptive for radiation in the predetermined wavelength range.

2. Textile product according to claim 1, wherein the radiation in the

predetermined wavelength range is visible radiation in the range of 380 to 640 nm, and/or radiation invisible to the human eye, in particular in the near infrared wavelength range, in particular in the wavelength range of 640 to 1200 nm.

3. Textile product according to claim 1 or 2, wherein the textile product has an absorption at the predetermined wavelength range which is significantly different from the absorption of human skin, in particular higher by at least 15%.

4. Textile product according to claim 1, wherein the textile product has a reflectivity spectrum in the predetermined wavelength range or a sub-range thereof, which is significantly different, in particular higher or lower, from the reflectivity spectrum of human skin in the predetermined wavelength range or the sub-range thereof, in particular higher by at least 15%.

5. Textile product according to claim 1, wherein the textile product is at least part of a bedding, a blanket, a duvet, clothes, underwear, nightwear, a medical device, a continuous positive airway pressure cap, a medical material, a bandage, a diaper or a cast.

6. Textile product according to claim 1, wherein the second area (13) is formed as a plurality of separate areas arranged in a patterned fashion, in particular in lines, stripes or grids, or distributed at random, at least partially over the first area (14).

7. System (3) for monitoring vital signs of a human subject (1) comprising:

a detection unit (6) for detection of radiation in a predetermined wavelength range from a scene including at least part of the human subject (1),

a classifier (9) for classifying one or more regions of interest of said scene as skin region or as non-skin region of the human subject (1) based on the strength and/or color of the light detected from the respective region of interest, and

a cover (7) covering the human subject (1) to be monitored at least partially, the cover (7) being at least partially a textile product according to claim 1. 8. System (3) according to claim 7, wherein the second area (13) of the textile product is provided at the feet and/or the hands and/or the arms and/or the neck of the covered human subject (1).

9. System (3) according to claim 7, wherein the textile product of the cover (7) is covered by an overlay at least in the at least one second area (13) of the textile product, the overlay being transparent or semi-transparent for radiation in the predetermined wavelength range.

10. System (3) according to claim 7, wherein the cover (7) is a continuous positive airway pressure cap, the cap having a second area (13) covering the forehead of the human subject (1), the second area (13) being transparent or semi-transparent for radiation in the chosen wavelength range.

11. Method for skin detection of a human subject, said method comprising:

- detecting radiation in a predetermined wavelength range from a scene including at least part of the human subject (1),

classifying one or more regions of interest of said scene as skin region of a living being or as non-skin region based on the strength and/or the color of the light detected from the respective region of interest, wherein the human subject is supported and/or partially covered by a textile product as claimed in claim 1.

12. Use of a textile product according to claim 1 for at least partially covering a human subject (1) while performing monitoring of vital signs of the human subject (1) by a system (3) as claimed in claim 7.

Description:
Textile product and system and method for monitoring vital

FIELD OF THE INVENTION

The present invention relates to a textile product, in particular for use in a healthcare setting for covering a human subject which is to be monitored with respect to his/her vital signs like heart rate, respiration rate, Sp02 saturation, etc. The present invention relates further to a system and method for monitoring vital signs and to the use of such a textile product.

BACKGROUND OF THE INVENTION

Health monitoring is traditionally present in the hospital, particularly the ICU and includes the monitoring of vital signs like EEG, ECG, pulse-rate, respiratory rate, blood- oxygenation level, blood pressure, etc. Also sleep laboratories acquire information about sleeping subjects using actigraphy and electromyography, additionally to some of the other vital signs. These application areas often involve multiple sensors attached to the body of the patient, some of which may be wireless and others wired, restricting the freedom to move or the quality of sleep of the patient, in addition to causing discomfort and possible skin- damage.

Video Health Monitoring is recently emerging as a promising unobtrusive alternative for an increasing number of the above health indicators, not the least driven by the strong wish to reduce the burden caused by current techniques to (pre-term) neonates and patients with extensive skin damage, e.g. due to burns.

Clearly, Video Health Monitoring, due to its unobtrusive character, adds to patient comfort even in cases where no real damage is done by the current technology.

However, also new application fields emerge in the consumer domain, as simpler derived methods may run on consumer platforms like laptops, tablets and mobile phones, or on embedded platforms inside equipment used for exercise in the gym.

Video Health Monitoring is also emerging for use in analyzing the human skin, in particular with relevance for cosmetic industry (e.g. moisturizers advice) and dermatology (e.g. melanoma detection). Various diseases may be diagnosed from motion in video sequences, like Periodic Leg Movements, Delirium, while video analysis may reveal information about body posture with relevance in baby monitors to prevent Sudden Infant Death. Such motions that can be analyzed in order to extract the health condition of a patient are also understood as vital signs.

Consequently, there is a very broad application domain for Video Health Monitoring ranging from beauty product, the gym, consumer home -healthcare including baby-monitoring, sleep-center, the General Ward, the Intensive Care Unit, to the highly specialized Neonatal Intensive Care Unit and burn-center.

US 2008/0194906 Al discloses a non-intrusive physiological data measurement system and method, as well as an optically induced treatment system. The measurement system includes a monitoring mechanism that includes light emitter modules capable of emitting light at at least two wavelengths. The light emitted from the light emitter modules is transmitted through a subject and to a light receiving mechanism, such as an optical sensor. Physiological data is taken from the received light. The system also can ascertain movement of the subject by obtaining an initial outline of the subject and comparing that outline with a subsequently obtained outline. A therapeutic optic system includes a non-adhering light emitting mechanism for providing light at therapeutic wavelengths.

The aforementioned system comprises a rather complicated structure to expose the patient to radiation which is transmitted through the whole body of the patient. In addition, the photobiological safety (both for skin and eyes) has to be taken into account to prevent damage to the respective parts of the patient under monitoring. The patient has to be arranged between the source of radiation and a detector. The application is mainly suitable for neonates or premature neonates which are lying in an incubator. For adults, the application becomes less reliable due to the higher degree of absorption of radiation in the adult body.

US 9,237,869 B l describes a lapel adaptor for use with a physiologic sensor pod having a housing and a pair of electrodes spaced apart from one another on a bottom surface of the housing. The lapel adaptor includes a first portion comprising an elastic ring including an opening having an inner circumference slightly smaller than an outer circumference of a groove extending around the peripheral surface of the sensor pod housing. The lapel adaptor also includes a second portion having a pair of magnets spaced apart from one another by substantially a same distance as a distance between the pair of electrodes on the bottom surface of the sensor pod housing. The lapel adaptor further includes a third portion that enables the first and second portions of the lapel adaptor to be folded toward one another.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a solution for a system and method for monitoring vital signs of a wide variety of persons, neonates as well as adults, in various environments which is simple and reliable and allows the patient to be covered by clothes or beddings for better comfort and privacy.

In a first aspect of the present invention a textile product is presented, the textile product having a first area and at least one second area, the first area having a first transmittance for radiation in a predetermined wavelength range, the at least one second area having a second transmittance for radiation in the predetermined wavelength range, wherein the second transmittance is higher than the first transmittance by at least 50%. The textile product contains one or more of: one or more second areas woven less loosely than the first area, pigments and/or dye which are reflective or absorptive for radiation in the

predetermined wavelength range, integrated fibers and/or yarns which are dyed in pigments being reflective/absorptive for radiation in the predetermined wavelength range.

The advantage of a textile product having different transmittances (i.e. where the transmittance of the second areas is relatively higher than the transmittance of the first areas) in a predetermined wavelength range is the possibility to arrange areas of higher transmittance in regions where monitoring can take place best, thus allowing to keep a human subject covered and in privacy and at the same time reliably detect regions of interest for monitoring. This makes monitoring safe and easy for the medical staff and comfortable for the human subject. Both areas could e.g. have the same distinctive fiber woven in (in about equal concentration) but with a distinctive different pattern (e.g. clockwise vs.

counterclockwise patterns, symbols, such as letters, or other asymmetric pattern, etc.). Any of the mentioned features are suitable to enhance transmittance of the fabric in order to allow detection of skin regions for monitoring vital signs.

In a further aspect of the present invention a system for monitoring vital signs of a human subject is presented, the system comprising a detection unit for detection of radiation in a predetermined wavelength range from a scene including at least part of the human subject, a classifier for classifying one or more regions of interest of said scene as skin region or as non-skin region of the human subject based on the strength and/or color of the light detected from the respective region of interest, and a cover covering the human subject to be monitored at least partially, the cover being at least partially a textile product as disclosed herein.

Due to the features of the proposed textile product the detection and classification of suitable skin regions for monitoring of vital signs can be achieved in a very reliable fashion without the need of tactile sensing systems fixed to the human subject which are prone to failure due to unintentional loss of the sensors, entangling in connecting lines during sleep, etc. In particular, the first areas show a substantial contrast compared to the second areas of the textile product, which can be easily evaluated to detect potential regions of skin, which are likely to be arranged under the second areas.

In yet a further aspect of the present invention the use of a textile product for at least partially covering a human subject while performing monitoring of vital signs of the human subject by a monitoring system is presented.

Preferred embodiments of the invention are defined in the dependent claims. It shall be understood that the claimed method, system and use have similar and/or identical preferred embodiments as the claimed device and as defined in the dependent claims.

Advantageously, the radiation in the predetermined wavelength range is visible radiation in the wavelength range of 380 to 640 nm, and/or radiation invisible to the human eye, in particular in the near infrared wavelength range, e.g. the wavelength range of 640 to 1200 nm. The NIR wavelength range is on the one hand easy to detect with a variety of detection units and on the other hand unobtrusive thus not disturbing the human subject to be monitored. The visible wavelength range, especially of green light, is particularly useful for obtaining vital signs, in particular Sp02.

The textile product preferably has an absorption at the predetermined wavelength range which is significantly different from the absorption of human skin, in particular higher by at least 15%. This makes it possible to reliably detect regions of skin which are suitable for monitoring vital signs.

The textile product may have a reflectivity spectrum in the predetermined wavelength range or a sub-range thereof, which is significantly different, in particular higher or lower, from the reflectivity spectrum of human skin in the predetermined wavelength range or the sub-range thereof, in particular higher by at least 15%. This also helps to determine suitable areas of skin for monitoring vital signs and ensures a good contrast between skin and textile in the respective wavelength range and a higher accuracy of measurements. Hereby, reflectivity differences (leading to differences in contrast between the first and second areas) may be sufficient to distinguish the first and second areas and, thus, to detect skin areas.

According to preferred embodiments of the invention, the textile product is at least part of one of: a bedding, a blanket, a duvet, clothes, underwear, nightwear, a medical device, a continuous positive airway pressure cap, a medical material, a bandage, a diaper or a cast. This allows providing the human subject with a wide variety of clothing and beddings to enhance comfort and privacy without restricting the possibilities of monitoring vital signs.

According to an advantageous embodiment, the second area is formed as a plurality of separate areas arranged in a patterned fashion, in particular in lines, stripes or grids or other patterns, or distributed at random, at least partially over the first area. Thus, the areas of enhanced transmittance can be arranged at suitable locations making monitoring easy and simultaneously providing maximum comfort for the human subject.

Preferably, the second area of the textile product is provided at the feet and/or the hands and/or the arms and/or the neck of the covered human subject. These body parts/limbs are highly perfused and thus suitable for monitoring. Besides, they will most probably be uncovered by further clothing, thus being well accessible for incident radiation.

Advantageously, the textile product of the cover can be covered by an overlay at least in the at least one second area of the textile product, the overlay being transparent or semi-transparent for radiation in the chosen wavelength range. This can help to enhance detectability of suitable skin regions and provide comfort and warmth for the human subject.

According to an embodiment, the cover can be a continuous positive airway pressure (CPAP) cap, the cap having a second area covering the forehead of the human subject, the second area being transparent or semi-transparent for radiation in the chosen wavelength range. Since the forehead is the most suitable location for measurement of oxygen saturation due to the possibility of good calibration, it is advisable to keep this region accessible for monitoring.

The monitoring device can further comprise a control unit, a processor for processing the detected signals and/or a display for displaying values.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. In the following drawings: Fig. 1 shows a schematic diagram of a system and textile product according to the invention, and

Fig. 2 shows a perspective view of a neonate wearing a continuous positive airway pressure (CPAP) cap using a textile product according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Monitoring of vital signs is essential in many healthcare settings like in hospitals, for example for neonates and especially for premature neonates, for intensive care wards, but also for general wards, nursing or elderly homes or in a home environment e.g. for sleep monitoring of adults due to sleep apnoea. Often monitoring is carried out by use of different sensing systems being in direct contact to the skin of a human subject. This can be very uncomfortable due to connecting lines of the sensors to a monitoring device. Besides, the use of connected sensors is unreliable since the sensor might unintentionally fall off during sleep by movement of the human subject or the human subject might entangle in the connecting lines thus leading to failure of the monitoring device.

In camera based monitoring of vital signs e.g. during sleep, on the other hand the visibility of a large enough skin-region of the human subject to be monitored is difficult, as often much of the human subject's skin is covered by bedding and/or clothes.

The present invention seeks to solve this problem using special fabrics used for bedding or clothes having areas of enhanced transparency for certain wavelengths ranges used by monitoring systems that allow for skin visibility while keeping the subject comfortable. The solution is amongst others applicable e.g. in an incubator for neonates, kangaroo-care and for adult sleep monitoring applications, and can be used along with non- obtrusive illumination for example in near infra-red (NIR) wavelength ranges so as to not disturb the human subject and avoid privacy concerns.

Fig. 1 shows a schematic diagram of a first embodiment of a system 3 according to the present invention illustrating an exemplary use scenario of the present invention. In this use scenario, a human subject 1, e.g. a patient or elderly person, is lying in a bed 2, e.g. in a hospital or similar healthcare setting, in a nursing home or at home. The human subject 1 is under monitoring of his/her vital signs like heart rate, respiration rate, Sp02 and/or other values which are determined by way of the system 3.

In most environments it will be more comfortable and give more privacy for the human subject 1 to wear clothes, for example a pyjama or a dressing gown, and/or being covered by a duvet or blanket. Further, the subject 1 may be equipped with a medical device or material, like bandages, diapers or casts. It is proposed according to the present invention to adapt the respective piece of clothing, bedding or medical devices or materials, in the following generally denoted as "cover 7", to allow identification and use of skin areas which are suitable and large enough for detection of the respective vital signs. Solutions to provide enough skin area to determine the desired vital signs are described in detail hereinafter.

The monitoring system 3 according to the first embodiment comprises a detection unit 6 for detection of light reflected from or transmitted through a body part of the subject 1. The detection unit 6 may include a camera (also referred to as camera-based or remote PPG sensor, in the following also denoted as camera 6) for acquiring an image data (also called images, which shall be understood as an image in the wavelength range of visible light and infrared light) of the scene, in particular for acquiring a sequence of image frames of the subject 1 over time, preferably including skin areas of the subject 1 from which PPG signals can be derived.

The image frames captured by the detection unit 6 in this embodiment may particularly correspond to a video sequence captured by means of an analog or digital photosensor, e.g. in a (digital) camera 6. Such a camera 6 usually includes a photosensor, such as a CMOS or CCD sensor, which may also operate in a specific spectral range (visible, NIR) or provide information for different spectral ranges, particularly enabling the extraction of PPG signals. The camera 6 may provide an analog or digital signal. The image frames include a plurality of image pixels having associated pixel values. Particularly, the image frames include pixels representing light intensity values captured with different

photosensitive elements of a photosensor. These photosensitive elements may be sensitive in a specific spectral range (i.e. representing a specific color). The image frames include at least some image pixels being representative of a skin portion of the person. Thereby, an image pixel may correspond to one photosensitive element of a photo -detector and its (analog or digital) output or may be determined based on a combination (e.g. through binning) of a plurality of the photosensitive elements.

Optionally, the monitoring system 3 further contains an illumination source 5 (also called illumination source or light source or electromagnetic radiator), such as a lamp or LED, for emitting radiation in a predetermined wavelength range for illuminating/irradiating a region of interest with light, for instance in a predetermined wavelength range or ranges (e.g. in the infrared and, optional red and/or green wavelength range(s)). The light reflected from said region of interest in response to said illumination is detected by the detection unit 6. In another embodiment no dedicated light source is provided, but ambient light is used for illumination of the subject 1. From the reflected light only light in a desired wavelength ranges (e.g. infrared light, or light in a sufficiently large wavelength range covering at least two wavelength channels) may be detected and/or evaluated.

The system 3 comprises further a classifier 9 for classifying one or more regions of interest of said scene as skin region of a living being or as non-skin region based on the strength and/or the color of the light detected from the respective region of interest. The classifier 9 may e.g. be a processor or computer that processes the detected NIR light, i.e. the output (e.g. electronic detection signals) of the detection unit 6.

The illumination source 5 and the detection unit 6 may be controlled by a control unit 8. The device 4, e.g. a processor or computer including the classifier 9 and the control unit 8, may further be connected to an interface 10 for displaying the determined information and/or for providing medical personnel with an interface to change settings of the device 4, the camera 6, the illumination unit 5 and/or any other parameter of the system 3. Such an interface 10 may comprise different displays, buttons, touchscreens, keyboards or other human machine interface means, e.g. for displaying the obtained vital signs or other values of interest to the medical staff.

A system 3 as illustrated in Fig. 1 may, e.g., be located in a hospital, healthcare facility, elderly care facility or the like. Apart from the monitoring of patients, the present invention may also be applied in other fields such as neonate monitoring, general surveillance applications, security monitoring or so-called Lifestyle environments, such as fitness equipment, a wearable, a handheld device like a smartphone, or the like. The uni- or bidirectional communication between the device 4, the camera 6 and the interface 10 may work via a wireless or wired communication interface. Other embodiments of the present invention may include a device 4, which is not provided stand-alone, but integrated into the camera 6 or the interface 10.

The radiation emitted by the illumination source 5 might preferably be not visible to the human eye, most preferable in a wavelength range correlating to near infra-red (NIR) radiation. This wavelength range is unobtrusive, thus e.g. not disturbing the sleep or daily life of the human subject 1 to be monitored. Preferably, a wavelength or wavelength range in the wavelength range of 760 to 1200 nm is used. As mentioned before, also visible light might be used due to e.g. the advantages for PPG sensing.

The human subject 1 is at least partly covered/wrapped by the cover 7, thus covering most of the bare skin of the human subject 1. To allow the respective radiation to reach the skin of the human subject 1, thus enabling to classify the regions of interest for monitoring to be classified, the cover 7 is at least partially transparent for the radiation in the chosen wavelength range, especially in regions of interest for measurements of vital signs. These regions will be preferably body parts with high perfusion, like the head, neck, hands, arms, feet, etc. To give the radiation access to the suitable skin regions, the cover 7 comprises one or more (second) areas 13 with higher transparency or transmittance as compared to the rest of the cover 7 for the chosen wavelength range. In the following, the main part of the cover 7 with substantially lower (or even substantially no) transmittance is denoted by reference sign 14 and is called "first area", whereas the part(s) with increased transmittance are referred to as second areas 13.

In a simple embodiment, the second area(s) 13 can be shaped in the form of one or more apertures in the cover 7 through which the bare skin of the human subject 1 is visible respectively detectable as suitable skin area by the detection device 6. For example, a single layer blanket can be used with apertures at places where skin can be expected. For instance, in an incubator where the infant is not wearing further clothes, the apertures can be relatively small and placed at regular intervals or in patterns, while the bedding preferably has a skin contrasting reflection in the light spectrum registered by the detection unit 6. For adult sleep monitoring where the subject may be wearing pyjamas, an advantageous arrangement of the apertures could be where the feet, the hands, the arms or other suitable skin regions of the human subject 1 are expected. This embodiment may be most suitable for relatively warm environments.

In another embodiment, more suitable for colder environments, the apertures mentioned above may be replaced by a material that is semi-transparent or transparent for the wavelengths in the chosen range registered by the vital signs detection unit 6. In case of a transparent material, it is important that some light can pass, but it is acceptable that attenuation occurs. It could further be imagined that the apertures are replaced by very loosely woven fabric with a high absorption of the wavelengths used by the vital signs detection unit 6. This would allow some light onto the skin which is reflected towards the detection unit 6 without spoiling the contrast, as would happen with a material that has a high reflection.

In yet another embodiment, the invention may take the form of a duvet with apertures covered by a transparent duvet casing or overlay. The overlay has to be transparent only in the range of wavelengths used by the vital signs detection unit 6, i.e. for example in the NIR-range mentioned above. Again this may be achieved with an at least locally loosely woven fabric with a high absorption. Generally, the second areas 13 of enhanced transparency can be distributed randomly or in patterns over the cover 7. Possible patterns can comprise lines, stripes, grids or any other suitable, even ornamental patterns. Care should only be observed to arrange the apertures according to the area of highest probability of detecting skin underneath. It is e.g. not productive to arrange the areas 13 on the edges of a blanket when the body of the human subject 1 is covered by the middle part of the blanket.

To achieve optimized results for the monitoring of the vital signs of the human subject 1, the cover 7 may fulfil one or more the following criteria:

the second areas 13 may be at least partially transparent to radiation in a predetermined wavelength range;

he cover 7 may have a relatively high absorption in the wavelength range used by the vital signs monitoring system 3 to enable easy detection of skin;

the contrast between the absorption of the cover 7 and the skin or the reflectivity of the cover 7 and the skin may be significant, i.e., the absorption and/or the reflectivity of the cover should be significantly higher or lower than the respective absorption and/or reflectivity of the skin; and

the second areas 13 may be arranged where skin usable for monitoring of vital signs can be expected, especially body parts/limbs with high perfusion.

A cover 7 fulfilling the criteria mentioned above may be fabricated at least partially by a textile product which has one or more apertures forming one or more second areasl3, one or more second areas 13 woven less loosely than the first area 14, pigments and/or dye which are reflective or absorptive for radiation in the predetermined wavelength range, integrated fibers and/or yarns which are dyed in pigments being reflective/absorptive for radiation in the predetermined wavelength range.

Fig. 2 shows a perspective view of a neonate wearing a continuous positive airway pressure (CPAP) cap using a textile product according to the present invention. In this embodiment, the invention is applied to a cover 7 in form of a medical object (in this example a therapeutic object) in the form of a CPAP cap used for premature neonates, especially in an incubator. As the forehead is an important measurement site for camera- based Sp02 because of the possibility of a reliable calibration it is one of the most preferred spots for monitoring of oxygen saturation. The problem that the forehead is largely covered by the CPAP cap is solved by an aperture in the cap or a semi-transparent or transparent material integrated in the cap in the area of the forehead that does not influence the wavelengths of interest, or a material that blocks visible light but allows NIR radiation to pass through.

Generally, according to the present invention the first areas 14 have a first transmittance for radiation in a predetermined wavelength range and the second areas 13 have a second transmittance for radiation in the predetermined wavelength range, wherein the second transmittance is higher (in relative terms) than the first transmittance by at least 50%, in particular significantly higher. It should be noted that there is generally no upper boundary for the ratio of first and second transmittance. The second transmittance can e.g. be 1000 % or even 10000% higher than the first transmittance, or the first transmittance can e.g. be (substantially) zero and the second transmittance can be at a level that significantly allows light in the desired wavelength range to pass. In an embodiment the ratio of the first and second transmittance may mainly depends on the material used for the textile.

Detection of skin can then be tuned by enhancing the contrast by further means, e.g. by adapting the reflectivity ratio in the predetermined wavelength range.

Accordingly, the textile product may have a reflectivity spectrum in the predetermined wavelength range or a sub-range thereof, which is significantly different, in particular higher or lower (in relative terms), from the reflectivity spectrum of human skin in the

predetermined wavelength range or the sub-range thereof, in particular higher by at least 15% (or even a much higher percentage).

Effectively, the light traveling through the second areas of the textile, reflected by the skin (having a reflectivity of approximately 60%), traveling back through the second areas of the textile is (much) more intensive than the light that is directly reflected from the textile at the first areas or the second areas, which allows easily distinguishing the first and second areas due to the substantially different contrast. The reason is that most of the light reflected from this area is then actually modulated by the pulse (i.e. reflected from skin). In other words, it roughly holds that 0.6*T2*T2 > R2, or T2>SQRT(R2/0.6), preferably T2»SQRT(R2/0.6), where T2 is the transmittance of the textile at the second areas and R2 is the reflectance of the textile at the second areas.

Furthermore, it is preferred that the light reflected from the first areas is significantly different (higher or lower) than the light that is traveling through the second areas of the textile, reflected by the skin and traveling back through the second areas of the textile, so that the first and second areas can be distinguished easily. This makes it easy to find the spots where PPG can be measured due to the substantially different contrast between the first and second areas. For instance, in case of T2=100%, then Rl (the reflectivity at the first areas) may be higher than e.g. 80% or lower than e.g. 30%.

The contrast may not only stem from absolute difference with skin but also from spectral difference (on average), i.e. it could have the same absorption but trending the opposite direction with wavelength as compared to skin.

The present invention may be applied for camera-based measurement of pulse rate, respiration and Sp02 in patient monitoring. The contactless monitoring with a camera 6 is assumed to be highly relevant for premature babies with very sensitive skin in NICUs.

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 invention 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 invention, from a study of the drawings, the disclosure, and the appended claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Any reference signs in the claims should not be construed as limiting the scope.