A device for monitoring the pulmonary system of a subject

Abstract

An apparatus, system and method for monitoring a pulmonary system of a subject. An optical member for transmitting a light signal through a cavity of a pulmonary system of a subject. The optical member and a detector unit are configured to be positioned so that a detected light signal is transmitted from the optical member through the cavity. The control unit is configured to evaluate the detected light signal to determine a physiological state of the pulmonary system of the subject.

Description

Background of the Invention Field of the Invention

[0001] The present disclosure relates to the use of optical devices to examine air-filled cavities in the human body. In particular, the present disclosure relates to a device for monitoring the pulmonary system.

[0002] Description of the Prior Art

[0003] This transition of the lungs from the intrauterine environment to normal postnatal air breathing may result in lung diseases, which are becoming increasingly common with decreasing gestational age of the newborn. As survival rates of extremely preterm infants improve, the number of infants requiring respiratory support in neonatal care units will increase. Abnormalities of lung ventilation are common in postnatal lung diseases, such as respiratory distress syndrome due to surfactant deficiency and pulmonary bronchial hypoplasia. Despite modern methods of respiratory support and minimally invasive surfactant therapy, there is still a risk of life-threatening complications, such as pneumothorax.

[0004] Currently, lung ventilation problems are partly diagnosed through lung X-rays, which unfortunately only provide a snapshot of the current condition and can lead to harmful radiation loads when repeated, increasing the risk of malignancy later in life.

[0005] Another method is positive transillumination, in which, in a dark room, the doctor shines a strong light through the affected side of the newborn's chest. This procedure is performed to show the free air in the area surrounding the lungs (pleural cavity). Positive transillumination is a visual analysis and is not used to continuously monitor the pulmonary system.

[0006] Therefore, there is a clear clinical need to be able to monitor lung gas content and improve the detection of pulmonary complications while avoiding ionizing radiation as much as possible. It may also be an advantage if the method can include rapid detection of life-threatening complications such as pneumothorax and bronchial obstruction causing varying degrees of atelectasis.

[0007] Therefore, new and improved devices and methods for monitoring the pulmonary system, and particularly for detecting pulmonary ventilation problems, would be advantageous.

[0008] Summary of the Disclosure

[0009] Therefore, embodiments of the present disclosure preferably seek to mitigate, alleviate or eliminate one or more deficiencies, shortcomings or problems in the art by providing an apparatus, system or method, such as described above, alone or in any combination, for measuring free air in a cavity (e.g., lungs). The apparatus, system or method is suitable for monitoring the pulmonary system and detecting the state of the pulmonary system, such as detecting ventilation problems, such as pulmonary ventilation problems and / or pulmonary complications, and more specifically diagnosing pneumothorax and / or atelectasis.

[0010] According to a first aspect, a device for monitoring a pulmonary system of a subject is disclosed. The device may include an optical component for emitting a light signal through a cavity of the pulmonary system of the subject, such as a lung. The light signal may include at least one wavelength. The device may also include a detector unit. The optical component and the detector unit may be configured to be positioned so that the light signal can be transmitted from the optical component through the cavity to be detected by the detector. The device may also include a control unit for evaluating the detected light signal to determine a physiological state of the pulmonary system of the subject. The physiological state can be determined by evaluating the change in the intensity of the light signal detected by transmitting through the cavity over time.

[0011] The determined state of the pulmonary system (e.g., lungs) can be used as feedback to a medical ventilator, for example, to change settings of the medical ventilator.

[0012] In some examples, the determined status may relate to detection of pulmonary complications and / or ventilation problems in the subject.

[0013] In some examples, the detected optical signals may be associated with the same wavelength over time.For example, at least one wavelength of the emitted optical signal is a single wavelength.

[0014] The term "single wavelength" refers to the fact that the light source is locked to one wavelength rather than swept. The term should be interpreted as the central wavelength of the light emitted from the source and encompasses the fact that the emitted light has a linewidth.

[0015] In some examples, the wavelength of the optical signal may be unrelated to the absorption band of the free gas in the cavity (eg, lungs).

[0016] In some examples, changes in the intensity of a detection signal transmitted through a cavity over time can be correlated to changes in the volume of the cavity.

[0017] In some examples, the change in volume can be a qualitative measure. For example, an increase or decrease in the intensity signal can be correlated to an increase or decrease in the cavity volume. As another example, the volume change can be detected by obtaining a first transmission signal transmitted through a first cavity (e.g., a first lung) and a second transmission signal transmitted through a second cavity (e.g., a lung). The first and second transmission signals are then compared to each other to detect a volume change of one cavity relative to another cavity.

[0018] In some examples, the emitted light signal may have a wavelength associated with an optical window of the tissue. When the determination of the state of the pulmonary system is based on an evaluation of the strength of the transmitted signal, the wavelength may be any wavelength capable of transmitting through the tissue surrounding the cavity of the pulmonary system being examined (e.g., a lung).

[0019] In some examples, the emitted light signal may have a wavelength associated with an absorption band of free gas in the pulmonary system cavity.

[0020] In some examples of the disclosed devices, the optical member can be adapted to be inserted internally into a subject using an introduction member.

[0021] In some examples, the optical member may be adapted to be disposed on a surface of the skin of a subject for emitting an optical signal into the cavity.

[0022] In some examples of the disclosed apparatus, a detector can be configured to be positioned on a skin surface for detecting an optical signal transmitted through a cavity of a subject.

[0023] In some examples of the disclosed apparatus, the control unit can be configured to determine the state of the pulmonary system by evaluating the intensity over time of the detected light signal transmitted through the cavity.

[0024] In some examples of the disclosed apparatus, the control unit can be configured to determine the state of the pulmonary system by obtaining the concentration and / or distribution of free gas from the detected light signal transmitted through the cavity and evaluating the concentration over time.

[0025] In some examples of the disclosed apparatus, the control unit can be configured to determine the state of the pulmonary system by correlating the intensity of the detected optical signal passing through the cavity with the concentration and / or distribution of the free gas obtained over time. In this example, the emitted light used to evaluate the transmitted intensity can have the same wavelength as the emitted light used to obtain the concentration and / or distribution of the free gas in the cavity, such as a wavelength associated with an absorption band of the free gas. Alternatively, the emitted light used to evaluate the transmitted intensity can have a different wavelength from the emitted light used to obtain the concentration and / or distribution of the free gas in the cavity. For example, the emitted light used for intensity evaluation can be any wavelength within the optical window of the tissue, and the emitted light used to obtain the concentration and / or distribution of the free gas can be associated with an absorption band of the free gas.

[0026] In some examples of the disclosed apparatus, when obtaining the concentration and / or distribution of free gas in the cavity, the emitted light can include at least two different wavelengths. For example, in some examples, at least one of the wavelengths can be associated with an absorption band of a reference gas.

[0027] In some examples of the disclosed apparatus, the free gas may be a physiological gas or gas mixture, such as any of oxygen, nitric oxide (NO), carbon dioxide, an anesthetic gas, and water vapor.

[0028] In some examples of the disclosed apparatus, the control unit can be configured to control a medical ventilator in response to a determined state of the pulmonary system, such as a detected pulmonary complication and / or ventilation problem.

[0029] It should be emphasized that the term "include / comprises" used in this specification is used to illustrate the existence of the features, integers, steps or components, but does not exclude the existence or addition of one or more other features, integers, steps, components or groups thereof.

[0030] Brief Description of the Figures

[0031] These and other aspects, features and advantages that examples of the present disclosure can have will become apparent and elucidated from the following description of examples of the present disclosure, with reference to the accompanying drawings, in which:

[0032] Figure 1 Examples of the disclosed devices and systems are shown;

[0033] FIG. 2A to FIG. 2D An example of the arrangement of a light source in the trachea for measuring lung function is shown;

[0034] Figure 3 is a diagram showing still another example of a light source configuration for measuring lung function using a bronchoscope;

[0035] Figure 4A and 4B Another example of an arrangement in which a light source is inserted through the esophagus is shown;

[0036] Figure 5 Temporal evolution of the O2 absorption signal and corresponding light transmission for induced atelectasis in four piglets; and

[0037] Figure 6 The temporal evolution of the O2 absorption signal and the corresponding light transmission of induced pneumothorax in four piglets is shown.

[0038] Example

[0039] Specific examples of the present disclosure will now be described with reference to the accompanying drawings. However, the present disclosure may be embodied in many different forms and should not be construed as limited to the examples set forth herein; on the contrary, these examples are provided to make the present disclosure thorough and complete and will fully convey the scope of the present disclosure to those skilled in the art.

[0040] The following disclosure focuses on examples of the present disclosure applicable to monitoring a subject's pulmonary system, for example by arranging a light source or optical component in a cavity, such as in the trachea, or in the digestive system, such as in the esophagus or intestines, such as a portion of the digestive tract, and using a detector, such as one or more detectors disposed outside the human body, to detect transmitted light.

[0041] This is advantageous, for example, for detecting weak signals resulting from the long path that light travels through the tissue surrounding the cavity.

[0042] Alternatively, both the detector and the light source may be arranged on the skin. The light source is then configured to transmit light to the cavity, and the detector is configured to detect light that has passed through the cavity at least once and scattered back. Such an arrangement is described in EP1871221, which is incorporated herein by reference.

[0043] Optical signals associated with free gas, such as absorption spectra, can be used to monitor the lung system to determine the state of the lung system, such as the physiological state of the lung system. The physiological problem can be, for example, a ventilation problem and / or a pulmonary complication, such as a pulmonary ventilation problem, more specifically diagnosed as pneumothorax and / or atelectasis.

[0044] In some examples of the present disclosure, the light source is arranged to transmit light to the tissue with the lowest possible loss, and then the light is detected on the skin surface. By arranging the light source or optical components internally to reduce the attenuation factor of the light transmitted to the tissue, thereby measuring the free gas in the cavity, the total attenuation factor can be reduced to about 0.001, which is about 1000 times greater than the attenuation factor previously achieved.

[0045] In some examples, free gas or gas mixtures in the pulmonary system cavity can be monitored to determine the state of the pulmonary system, such as the physiological state of the pulmonary system. In order to obtain the concentration and / or distribution of free gas, GASMAS technology can be applied.

[0046] When the light source is disposed internally, the disclosed devices, systems, and methods utilize a means for injecting the light source into tissue, such as a bronchoscope, nasogastric feeding tube, endoscope, endotracheal tube, colonoscope, or similar introduction means.

[0047] One group of patients that is considered relevant for monitoring the pulmonary system is premature infants. These infants often experience respiratory complications, such as respiratory distress syndrome, difficulty breathing, and lung function problems. Therefore, premature infants are often connected to medical ventilators to help them move air in and out of their lungs. When connected to a medical ventilator, premature infants are intubated with an endotracheal tube. In one example of the present specification, it is described how a fiber optic device for transmitting light to a cavity (e.g., the lungs) is combined with an endotracheal tube (e.g., an endotracheal tube) while detecting the transmitted light at the skin surface.

[0048] In another example of the present specification, it is described how a fiber optic device for delivering light to a cavity, such as the lungs, is used in conjunction with a nasogastric feeding tube inserted into the esophagus, while detection of the transmitted light is performed at the skin surface.

[0049] Furthermore, in another example, light from the fiber optic device is distributed over a larger distance or area by a light diffusing material.

[0050] Additionally, and / or alternatively, the transmitted light is detected at the skin surface by one or more detectors located at the skin above a cavity, such as a lung. The detectors can be configured to be arranged at the skin surface or other devices, such as optical fibers, can be used to collect light at the skin surface and direct the collected light to the detectors. In one example, multiple detectors can be used in parallel or sequentially to detect gas or gas distribution or gas concentration in different parts of the patient's bronchial tree or lungs.

[0051] In this way, the results of changes in settings on a medical ventilator or medication can be directly observed, and the information gained from the observations can be used to optimize the treatment of the patient through the use of a feedback system.

[0052] In some examples, the detection is frequency sensitive and / or phase sensitive. The light from the light source, such as a laser, can be wavelength modulated at a selected frequency, and when modulated around the gas absorption wavelength, synchronized intensity changes can be detected. When the modulation is performed near the gas absorption wavelength, as described in S. Svanberg, Gas in Scattering Media Absorption Spectroscopy-from Basic Studies to Biomedical Applications, Lasers and Photonics Reviews 7, 779 (2013), the intensity of the detected light will change rapidly with small changes in wavelength, which is incorporated herein by reference.

[0053] Alternatively, in some examples, the skin area can be detected by an imaging sensor (e.g., a digital camera) with high intensity dynamics at an absorption wavelength and a nearby non-absorption wavelength. The two images can then be compared, such as by division or subtraction, so that the area affected by the gas can be visualized.

[0054] When using GASMAS technology, the determination of gas concentration is affected by the path length in the gas-filled cavity that the light interacting with the gas must pass through. Due to multiple scattering, the path length in the tissue is unknown. Therefore, light that propagates longer distances and shorter distances through the tissue can be detected simultaneously. The Beer-Lambert relationship commonly used when analyzing gases gives that the intensity of the absorption signal is determined by the product of gas concentration and path length (see S. Svanberg, Atomic and Molecular Spectroscopy-Basic Aspects and Practical Applications, 4th Edition, Springer, Berlin, Heidelberg 2004, which is incorporated herein by reference). When the path length is known, that is, when measuring in a non-scattering material, the gas concentration can be directly calculated.

[0055] When using the GSMAS technique to measure gas concentration, the path length through the gas is unknown; this needs to be taken into account when making gas concentration measurements. Different methods can be used to deal with the problem of unknown path length, which are discussed in, for example, L. Mei, G. Somesfalean and S. Svanberg, Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy, Sensors 14, 3871 (2014), which is incorporated herein by reference.

[0056] One of the most accurate methods is to use distribution changes in absorption spectra, such as water vapor absorption lines. The changes in water vapor lines depend on the oxygen concentration, see P. Lundin, L. Mei, S. Andersson-Engels and S. Svanberg, Laser Spectroscopic Gas Concentration Measurements in Situations with Unknown Optical Path Length Enabled by Absorption Line Shape Analysis, Appl. Phys. Lett. 103, 034105 (2013), which is incorporated herein by reference. This method requires a good signal-to-noise ratio because the effect of oxygen on water vapor lines is very weak.

[0057] Another option is to perform GSMAS measurements on the gas concentrations and water vapor to be determined. It can be assumed that the water vapor concentration is saturated in the tissue, and the concentration is determined by the known temperature, see AL Buck, Buck Research Manuals; Updated Equation from (1981), which is incorporated herein by reference, and New Equation for Computing Vapor Pressure and Enhancement Factor. J. Appl. Meteorol. 20, 1527 (1996), which is incorporated herein by introduction. Based on the measured water vapor signal, the effective path length of the wavelength used can be calculated. As long as the difference between the wavelengths used is small, the path length obtained may be roughly the same as the path length of light transmitted through the gas of unknown concentration to be determined (such as oxygen, nitric oxide (NO) or carbon dioxide). Then the approximate path length can be used to directly calculate the gas concentration, such as the concentration of oxygen, nitric oxide (NO) and carbon dioxide. This method works best when the light absorption and light scattering in the tissues of the two measurements are the same, that is, when the wavelengths used for measurement are close. For example, oxygen is often monitored around some sharp component of the A band of oxygen molecules at about 760nm. Water vapor has strong absorption around 935nm, but due to the different optical properties of different wavelengths, it may be necessary to correct for the wavelength difference compared to oxygen. Therefore, a weaker absorption wavelength for water vapor around 820nm may be a better choice.

[0058] In a preferred example, the devices, systems and methods described herein utilize tunable diode laser absorption spectroscopy (TDLAS) to detect gas through multiple light scattering in tissue, where the absorbed free gas is dispersed in a cavity surrounded by a medium. In TDLAS, the wavelength of the light source is swept across an absorption peak or absorption band. The scan, where each step can be reduced to a sub-nanometer scale.

[0059] Figure 1 An example of an embodiment is shown in . The patient 1 in this example is a premature infant. The infant is connected to a medical ventilator 2 due to respiratory distress syndrome (RDS), a common medical condition.

[0060] A medical ventilator 2 is connected to an intubated patient 1 via, for example, an endotracheal tube 3 inserted into the trachea 4. In this example, two light sources 5, 6 are used to measure gases, for example oxygen at about 760nm, and water vapor at about 820nm. Other wavelengths may be used depending on the gas measured. In some examples, other gases than water vapor may be used as reference gases. The requirement is only that the gas concentration can be calculated without using the path length that the detected light has traveled.

[0061] Alternatively, in other examples, only one light source may be used. In some other examples, more than two light sources may be used to detect additional gases, gas distributions, or gas concentrations.

[0062] Alternatively, other configurations of light sources are possible when using other methods associated with GASMAS previously described herein.

[0063] The light source may be a semiconductor laser, such as a distributed feedback laser (DFBL), a vertical cavity surface emitting laser (VCSEL) or other types of available lasers. The power of the emitted light is preferably in the range of 1 mW to 3000 mW.

[0064] The laser can be driven by a current and temperature regulation unit comprised in a drive unit 7. The drive unit 7 can be controlled by a control unit 8, for example a computer. The control unit 8 can be used for signal processing and evaluation of the measurement data.

[0065] All determinations or calculations described herein may be performed by a control unit or a data processing device (not shown).

[0066] The control unit or data processing device may be implemented by dedicated software (or firmware) running on one or more general or special computing devices. In this context, it should be understood that each "element" or "means" of such a computing device refers to the conceptual equivalent of a method step; there is not always a one-to-one correspondence between an element / means and a specific hardware or software routine. A piece of hardware sometimes includes different means / elements. For example, a processing unit acts as one element / means when executing one instruction and another element / means when executing another instruction. In addition, an element / means may be implemented by one instruction in some cases, but may be implemented by multiple instructions in some other cases. Such a software-controlled computing device may include one or more processing units, such as a CPU ("central processing unit"), a DSP ("digital signal processor"), an ASIC ("application-specific integrated circuit"), discrete analog and / or digital components, or some other programmable logic device, such as an FPGA ("field programmable gate array"). The data processing device 10 may also include a system memory and a system bus that couples various system components including the system memory to the processing unit. The system bus may be any of a variety of types of bus structures, including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. The system memory may include computer storage media in the form of volatile and / or non-volatile memory, such as read-only memory (ROM), random access memory (RAM), and flash memory. The application-specific software may be stored in the system memory, or on other removable / non-removable volatile / non-volatile computer storage media contained in or accessible to the computing device, such as magnetic media, optical media, flash memory cards, digital tapes, solid-state RAM, solid-state ROM, etc. The data processing device 10 may include one or more communication interfaces, such as serial interfaces, parallel interfaces, USB interfaces, wireless interfaces, network adapters, etc., and one or more data acquisition devices, such as A / D converters. The application-specific software may be provided to the control unit or data processing device on any suitable computer-readable medium, including recording media and read-only memory.

[0067] Additionally, in some examples, the control unit 8 may be connected to a controller 9 of the medical ventilator 2 to control settings of the medical ventilator 2 .

[0068] Additionally, and / or alternatively, the controller 9 may also be used to control the dispensing of medication to the patient 1 .

[0069] Furthermore, in some examples, the laser can be wavelength modulated by modulating the drive current at two separate frequencies. The frequencies can typically be in the region of about 10 kHz to allow for phase-sensitive detection (lock-in detection) with reduced noise.

[0070] By using separate modulation frequencies, different gases, such as oxygen, nitric oxide (NO) and carbon dioxide, and water vapor can be separated even though light injection can be done through the same optical fiber 11. Light from individual optical fibers connected to a light source 12 such as a semiconductor laser 5, 6 can be connected to a single injection fiber 11.

[0071] In addition, in some examples, a small portion of the light to be injected can be optically diverted, for example, by optical fiber 5 to the calibration unit 13. The calibration unit 13 can be a gas chamber including the gas to be detected, such as oxygen, nitric oxide (NO) and carbon dioxide. The gas has a known concentration and the gas chamber has a predetermined length. The calibration unit 13 can also include a water droplet and a temperature measurement unit. All parts of the calibration unit 13 can have a common detector unit.

[0072] Alternatively, in some examples, a compact diffuse reflective multi-pass chamber made of a porous material such as ceramic can be used. The porous material can be packaged in a compact gas cell, see T. Svensson, E. Adolfsson, M. Lewis, CT Xu and S. Svanberg, Disordered, Strongly Scattering Porous Materials as Miniature Multi-pass Gas Cells, Phys. Rev. Lett. 107, 143901 (2011), which is incorporated herein by reference.

[0073] The main part of the light of the individual frequency markers is guided through the optical fiber 11 down through, in this example used, the endotracheal tube 3.

[0074] exist Figures 2B to 2D In the example shown, the fiber 11 ends in a diffuser. The diffuser can be a structure on the surface of the fiber or a separate component made of light scattering material. The diffuser is used to distribute the light over a larger tissue surface to achieve a reduced intensity. The lower intensity may help avoid increased tissue temperature. Another advantage is eye safety if the test is performed outside the human body.

[0075] In some examples, the injected light transmitted from the end of the optical fiber 11 can be transmitted to the tissue without passing through any air in the trachea, such as through a diffuser. If the light passes through the air, the air may give some background signal in the light detected by the detector 14.

[0076] In one example, an inflatable cuff or balloon made of an optically scattering material and having a reflective material on the inner wall may be used so that as much light as possible is transmitted directly into the tissue, such as Figure 2A As seen in.

[0077] Figure 2A The example shown in gives good positioning of the fiber for monitoring the upper lungs. By using a bronchoscope and a diffuse fiber tip, light can be injected deeper into the bronchial tree, such as Figure 3 shown.

[0078] Alternatively or additionally, in some examples, more than one (e.g., at least two) positions are used for light injection. When multiple positions are used for measurement, measurements at different positions need to be performed sequentially. Alternatively, more than one controllable standard optical fiber may be used.

[0079] Diffuse optical tomography can be used when multiple positions are used for light injection and to obtain a better 3D gas distribution analysis, as described in the article by J. Swartling, J. Axelsson, S. Svanberg, S. Andersson-Engels, K. Svanberg, G. Ahlgren, KM and S. Nilsson, System for Interstitial Photodynamic Therapy with On-line Dosimetry-First Clinical Experiences of Prostate Cancer, J. Biomed. Optics 15, 058003 (2010), which is incorporated herein by reference; and T. Durduran, R. Choe, WB Baker and AG Yodh, Diffuse Optics for Tissue Monitoring and Tomography, Rep. Progr. Phys. 73, 076701 (2010), which is incorporated herein by reference.

[0080] One or more detectors 14 are suitably placed in close proximity to the skin. The surface size of the detector should be such that it can detect light that has passed through the tissue, for example within 0.25 cm 2 Up to 5cm 2 Within the range, for example 1cm 2 The detectors can be made of different materials, such as germanium.

[0081] The detected light is transmitted as an electrical signal to the control unit 8. The signals can be evaluated sequentially or in parallel using a digital lock-in technique, as described in the article L. Mei, and S. Svanberg, Wavelength Modulation Spectroscopy-Digital detection of Gas Absorption Harmonics based on Fourier Analysis, Applied Optics 54, 2254 (2015), which is incorporated herein by reference.

[0082] Alternatively, in some examples, an analog lock-in amplifier may be used. The analog lock-in amplifier may be connected to the control unit 8.

[0083] Furthermore, in some examples, a threshold value may be selected. When the measured value has reached or exceeded the selected threshold value, an alarm 15 may be activated for the healthcare personnel. The alarm 15 may be an acoustic alarm and / or an electronic alarm to the monitoring center.

[0084] Figures 2A to 2D Different examples of how to use a tracheal tube, such as an endotracheal tube, are shown.

[0085] Figure 3 An example of using the working channel of a bronchoscope to inject diffuse light is shown.

[0086] It can be observed that the same device can be used with some modifications to inject light from the outside into the human body through the esophagus without the use of a medical ventilator or bronchoscope with an endotracheal tube, such as through a feeding tube. In these cases, the light can be expanded and diffused by a scattering medium with a sufficiently large surface (e.g., several square centimeters) and in contact with the skin. This arrangement can avoid local increases in tissue temperature and achieve eye safety.

[0087] Figure 1 An exemplary configuration of the disclosed apparatus and system is illustrated.A patient 1 is connected to a medical ventilator 2 via an introduction member 3 connected to a trachea 4, such as a bronchoscope, a tracheal tube or an endotracheal tube.

[0088] In some other examples, the introducing member 3 may be, for example, a nasogastric feeding tube.

[0089] The light sources 5, 6 are, for example, lasers, having wavelengths associated with the free gases of interest (eg, oxygen, nitric oxide (NO) and carbon dioxide) and a reference gas (eg, water vapor).

[0090] In some examples, gases other than water vapor may be used as reference gases. The requirement is only that the gas concentration can be calculated without using the path length that the detected light has traveled.

[0091] Alternatively, in other examples, only one light source may be used. In some other examples, more than two light sources may be used to detect additional gases, gas distributions, or gas concentrations.

[0092] Alternatively, other configurations of light sources are possible when using other methods associated with GASMAS previously described herein.

[0093] The light source is connected to a drive unit 7 which is controlled by a control unit 8 .

[0094] In some examples, measurements of free gas in the lungs may be used to influence controller 9 to control settings of medical ventilator 2 .

[0095] Alternatively and / or additionally, in some examples, the measured values ​​of the control unit 8 may be used for administration of the drug 10 .

[0096] The light is emitted to the tissue via the optical fiber 11. To the single optical fiber 11, light from separate optical fibers 12 connected to light sources 5, 6, such as semiconductor lasers, may be connected.

[0097] Additionally, in some examples, a small portion of the light to be injected may be optically diverted, for example via an optical fiber, to the calibration unit 13 .

[0098] The detector 14 is configured to be positioned at a skin position on the patient's chest for detecting the transmitted diffuse light. The detected light carries information about the concentration of gases in the lungs or the distribution of gases in lung tissue, such as oxygen, nitric oxide (NO) and carbon dioxide concentration or distribution.

[0099] Additionally, in some examples, alarm 15 may be activated when a measurement reaches or exceeds a selected threshold.

[0100] Figures 2A to 2D Different examples of coupling light from an optical fiber into tissue for measuring lung function are illustrated.

[0101] Figure 2A An example of a tracheal tube 3 is shown, such as an endotracheal tube, having an inflatable balloon or cuff 16 to prevent air leakage around the tracheal tube 3, the tracheal tube 3 including an optical fiber 11 for transmitting light down into the trachea.

[0102] Figure 2B An example of an optical fiber 11 is shown, which descends from a tracheal tube, such as an endotracheal tube, to its end. A light diffuser 17 is arranged as the end of the optical fiber 11.

[0103] Figure 2CAn example is shown of how light in an optical fiber 11 may be connected to the end 18 of a tracheal tube, such as an endotracheal tube. The tip portion is made of a material that does not absorb but strongly scatters light.

[0104] Figure 2D An example of how light from an optical fiber 11 can be coupled to a balloon or cuff 16 is shown. The balloon or cuff can be made of a non-absorbing but light-scattering material. In some examples, the inner wall is coated 19 with a light-reflecting material.

[0105] In one example, the laser light source is applied through the esophagus rather than the trachea. In this example, the laser light source can be combined with a nasogastric tube used by most infants in neonatal intensive care. Using a nasogastric tube in the light application is advantageous because most infants already require such a device to be inserted, so no additional equipment needs to be introduced. This is also advantageous because the esophageal environment is less susceptible to infection. This is also advantageous because the esophagus is usually mostly collapsed, so an inflated cuff may not be required to create good optical contact between the light source and the tissue. In addition, the lower part of the lungs can also be more easily reached.

[0106] The light source should be located at a point in the esophagus that represents a location close to the lungs. In one example, the optical fiber that guides the laser is integrated with the nasogastric feeding tube so that the optical fiber is routed along the tube to the appropriate location along the tube. The nasogastric feeding tube has markings on it that indicate how deep the tube is inserted, and these markings can be used to determine the location of the light source in the esophagus.

[0107] In a preferred embodiment, an optical fiber that guides the laser is embedded into the tube wall during the manufacturing process of the nasogastric feeding tube, so that the nasogastric feeding tube and the laser light guide are one device.

[0108] In one example, the distal end of the optical fiber is terminated with a light diffuser that distributes the light over a larger area than that provided by the optical fiber tip alone. In a preferred example, when the optical fiber is embedded in the tube wall as described above, the diffuser is implemented by designing the tube wall in front of the optical fiber tip to have light scattering properties so that the light is scattered along the tube to an area corresponding to the desired diffuser properties. In an alternative example, the diffuser is manufactured as a separate component embedded in the tube wall similar to the optical fiber.

[0109] In an alternative example, the diffuser may be formed as part of an inflatable cuff similar to the diffuser described above in connection with the trachea.

[0110] The optical fiber can also be positioned in the nasogastric tube in such a way that it can be moved sequentially to different positions along the tube to facilitate the use of multiple detectors 14 to achieve, for example, a complete tomographic view of gas distributions, such as oxygen, nitric oxide (NO), and carbon dioxide distribution.

[0111] Alternatively, multiple optical fibers may be used in parallel at different locations to facilitate the use of multiple detectors 14 to achieve, for example, a complete tomographic view of gas distributions, such as oxygen, nitric oxide (NO), and carbon dioxide distributions.

[0112] In an alternative example, the light source on the nasogastric feeding tube is implemented by placing one or more laser diodes directly where the light source should be and having wires for driving the laser diodes along the nasogastric feeding tube. This implementation can also be applied in the case of endotracheal intubation.

[0113] Figure 4A An optical fiber 41 is shown in combination with a nasogastric feeding tube 46 inserted into the esophagus 42. Also shown is the relationship to the trachea 43 and lungs 44. At the distal end of the optical fiber 41, there may be a light diffuser 45. The upper portion of the stomach 47 is also shown.

[0114] Figure 4B A close-up of an optical fiber 41 embedded in the wall of a nasogastric feeding tube 46 is shown. The nasogastric feeding tube is inserted into the esophagus 42. In this example, the optical fiber has a diffuser 45 at the distal end of the optical fiber 41. In other examples, the optical fiber 41 may not have a diffuser.

[0115] Alternatively, gas concentrations can be assessed non-invasively using light transmitted from outside the body, such as toward the skin over a cavity containing free gas (e.g., the lungs). Light that penetrates enough tissue to reach the cavity is scattered and transmitted to a detector placed against the skin. For example, the detector is typically located a few centimeters from the light source. This allows for a non-invasive measurement procedure.

[0116] The same arrangement can be used when only transmission signals are detected and evaluated for determining the state of the pulmonary system, or when correlating transmission and gas concentration and / or distribution measurements, wherein the light source is arranged on the skin.

[0117] In the above examples, the light source or optical member is described as a fiber optic arrangement connected to a light source (eg a laser), but other arrangements are equally possible. For example, the light source or optical member may be a waveguide, or an LED arranged directly in the introduction member.

[0118] When the optical probe is arranged on the skin surface (ie the skin), a fiber arrangement connected to a light source may be used, but in some examples the light source may be adapted to be arranged directly on the skin surface, such as LEDs, lasers and waveguides.

[0119] The detector unit may be a photodiode, a photomultiplier tube, an avalanche photodiode, a charge coupled device, a CCD or a CMOS photosensitive device. As described herein, the detector may be a single detector or may be a plurality of detectors.

[0120] Different ways of measuring free air in the cavity have been described above, which can be used to monitor the pulmonary system and determine the state of the pulmonary system, such as detecting ventilation problems and / or pulmonary complications, such as pulmonary ventilation problems, more particularly diagnosing pneumothorax and / or atelectasis.

[0121] The same techniques described for introducing an optical signal into a cavity of a pulmonary system and detecting the transmitted light to observe the concentration and / or distribution of free gas in the cavity can be used to measure and evaluate the intensity of the transmitted light. Determination of the state of the pulmonary system can be performed by evaluating changes in the intensity of the transmitted light, such as changes over time, or by evaluating changes in the shape of the intensity curve over time.

[0122] When evaluating the transmitted light to determine the state of the pulmonary system, for example to detect ventilation problems and / or pulmonary complications, such as pulmonary ventilation problems, more particularly to diagnose pneumothorax and / or atelectasis, the wavelength can be any wavelength that can penetrate the tissue surrounding the cavity but can still be detected. Preferably, the wavelength is within the optical window of the tissue that will give a greater penetration depth. In addition, in some examples, the signal is associated with the same wavelength over time. This means that the wavelength is not scanned but remains constant. For example, by locking the light source to a single wavelength. This wavelength, which is used only when evaluating the intensity signal, may not be related to the absorption band of the free gas. When the wavelength used needs to be associated with the absorption of at least one gas, this is different from measuring the concentration or distribution of at least one gas. The term "single wavelength" should be interpreted as the central wavelength of the light emitted by the light source, including that the emitted light has a line width.

[0123] The change in intensity of the detected light signal transmitted through the cavity over time can be correlated to the change in volume of the cavity. This is related to the fact that the intensity of the detected signal may vary depending on the distance the light travels through the cavity. This can be used as a qualitative measure of the ventilation of the cavity, such as the lungs. For example, by monitoring or observing the change in the intensity of the light signal transmitted through the cavity over time, an increase and / or decrease in intensity can be correlated to an increase and / or decrease in the volume of the cavity.

[0124] The volumes of different cavities can also be compared, for example by obtaining a first transmission signal of a first cavity, such as a first lung, and a second transmission signal of a second cavity, such as a second lung. The first and second transmission signals can then be compared to detect changes in the volume of one cavity relative to another cavity.

[0125] Detecting or monitoring changes in the transmitted signal due to volume changes can be used to detect problems with lung ventilation. For example, a change in volume may mean that a tube used for aeration is not positioned correctly or has become blocked. Changes in the transmitted signal due to volume changes can be used to detect overpressure in at least one lung or collapse, such as a partial collapse, of at least one lung. It can also be used to detect lung inflammation or sepsis. Detection of volume changes can also be used to detect problems with increased mucus in the lungs.

[0126] Determination of the status of the pulmonary system can be accomplished by continuously monitoring a signal transmitted through a cavity of the pulmonary system (e.g., a lung). Determination of the status, such as detecting a ventilation problem and / or a pulmonary complication, can be accomplished by evaluating a detected optical signal transmitted through the lungs. Pulmonary complications and / or ventilation problems can be detected by observing changes in the detected optical signal, such as an increase or decrease in the signal over time, or a change in the intensity curve of the optical signal transmitted through the cavity.

[0127] One option can be to obtain the concentration and / or distribution of free gas based on the detected light signal transmitted through the lung system cavity. The light should preferably have a wavelength associated with the absorption band of the free gas to be detected. The concentration and / or distribution can be obtained by using the above system. In addition, the GASMAS technology can also be applied. The free gas can be a physiological gas or a gas mixture, such as any one of oxygen, nitric oxide (NO), carbon dioxide, anesthetic gas and water vapor.

[0128] The state of the pulmonary system, such as pulmonary complications and / or ventilation problems, can be detected by observing changes in the free gas concentration and / or distribution, such as an increase or decrease in concentration over time, or a change in the shape of the concentration curve. The concentration of the free gas can be obtained as an absorption signal of the free gas. The absorption signal can have dimensions [%m] and is the product of the relative gas concentration [%] and the absorption path length [m].

[0129] A further option may be to monitor the pulmonary system by correlating the detected light transmitted through the cavity of the pulmonary system (e.g., lungs) with the concentration / distribution signal of the free gas. The emitted light used to evaluate the transmitted intensity may have the same wavelength as the emitted light used to obtain the concentration and / or distribution of the free gas in the cavity, such as a wavelength associated with an absorption band of the free gas. Alternatively, the emitted light used to evaluate the transmitted intensity may have a different wavelength than the emitted light used to obtain the concentration and / or distribution of the free gas in the cavity. For example, the emitted light used for intensity evaluation may be any wavelength within the optical window of the tissue, and the emitted light used to obtain the concentration and / or distribution of the free gas may be associated with an absorption band of the free gas.

[0130] In order to show that it is possible to monitor the lung system to detect ventilation problems and / or lung complications (e.g. pulmonary ventilation problems), measurements were performed on four piglets. For the measurements, the GASMAS system was used to measure the gas absorption at two wavelengths, 764 nm for oxygen absorption and 820 nm for water vapor absorption.

[0131] The relative humidity within the lungs is approximately 100%, and combined with knowledge of tissue temperature and air pressure, the water vapour gas concentration can theoretically be calculated. Therefore, the water vapour gas absorption measured in [%m] for light at 820nm provides the absorption path length in [m]. Assuming that 764nm light travels the same average distance in the tissue, the measured oxygen absorption [%m] then provides the oxygen concentration in [%.

[0132] The emission from two diode lasers providing 764nm and 820nm light is focused into the optical fiber. The diode lasers and light combining optics are enclosed in a nitrogen-filled box to eliminate offsets in the absorption signal.

[0133] The gas absorption signal was obtained by sequentially scanning the wavelength of the laser at a rate of 1 kHz over one of the absorption lines of oxygen molecules (O2) at 764 nm and water vapor (H2O) at 820 nm. The two gases were measured sequentially before switching, and the measurement time was 100 s.

[0134] An optical fiber was inserted into the piglet for transesophageal light management, and the end of the fiber was configured to diffuse the light.

[0135] After propagating through the tissue, the transmitted light is detected by a photodiode incorporated into the detector probe attached to the skin. The detector probe area is covered with a layer of ultrasound gel to reduce the offset of the absorption signal. The detected absorption signal is intensity normalized and frequency filtered by an electronic platform to obtain the absorption amplitude.

[0136] By inserting a 4Fr balloon-tipped embolectomy catheter ( A tracheal intubation (100 μl) was inserted into the right main bronchus to simulate partial atelectasis. Partial airway obstruction was confirmed when the end-tidal CO2 decreased by 50% immediately after inflation of the balloon. The balloon was deflated after approximately 1.5 minutes or if the piglet became circulatory unstable. The oxygen signal was measured continuously during the process, which was repeated 3 times.

[0137] After the piglet's atelectasis was recovered, a small thoracostomy was made in the right axillary line, 1 cm below the dermal detector probe, and a drainage tube was placed and sutured. The piglet was ventilated with 100% oxygen, while 150 ml of atmospheric air (21% oxygen) was infused into the pleural cavity through the tube. The oxygen signal was continuously measured during the pneumothorax stage. Approximately 2 minutes after induction, air was withdrawn from the pleural cavity, followed by lung recruitment. This process was repeated 3 times.

[0138] Atelectasis was induced in four piglets while oxygen absorption and light transmission were continuously monitored using an internal light source. Figure 5, which shows the time evolution of the O2 absorption signal and the corresponding light transmission upon induction of atelectasis. A decrease in oxygen absorption and light transmission can be seen at the onset of atelectasis. The dashed line represents the transmission signal in %, the solid line the absorption in %m. When the balloon was deflated within the bronchus, it was observed that the absorption and light transmission returned in most cases to their initial values ​​before atelectasis. For pneumothorax measurements, see Figure 6 , where the time evolution of the O2 absorption signal and the corresponding light transmission of an induced pneumothorax is shown, the pneumothorax was induced by instilling air into the pleural cavity with the FiO2 set to 1.0. When the pneumothorax started, the continuously monitored oxygen absorption decreased. At the same time, an increase in light transmission was detected. The dashed line represents the transmission signal in percent, the solid line represents the absorption in %m.

[0139] In order to improve the detection of optical signals detected having passed through the cavity of the pulmonary system, such as the lungs, different methods can be applied. In some examples, a filter with transmission at the wavelength of the emitted optical signal can be arranged in front of the detector unit. The filter can pass only long wavelengths (long-pass), only short wavelengths (short-pass), or block a wavelength band of longer and shorter wavelengths (bandpass), or the filter can be a combination of them. The passband can be narrower or wider; the transition between maximum and minimum transmission can be sharp or gradual. Filters with more complex transmission characteristics can be used, for example with two peaks instead of a single band.

[0140] Additionally and / or alternatively, in some examples, the emitted light signal may be a pulse with gated detection. The gated detection may, for example, be time-gated, whereby the pulsed light source is pulsed at a frequency, such as a user-defined frequency. For a period of time after the light pulse (called the "gate delay"), the camera is insensitive. The camera then becomes sensitive for a period of time (called the "gate width").

[0141] Additionally and / or alternatively, in some examples, the emitted light signal may be amplitude modulated. The modulation may be seen in the detected signal, and by performing a frequency analysis on the detected signal, the amplitude at the modulation frequency will be a transmission measure that is less susceptible to noise and background signals. Furthermore, to further suppress the possibility of noise and background, the frequency of the amplitude modulation may also be varied, such as by amplitude modulating the emitted light signal with a varying modulation frequency, and analyzing the spectrum of the detected signal at the varying modulation frequency.

[0142] In some examples, the determined state of the lung system can be used as a feedback signal to a medical ventilator. For example, settings of the medical ventilator can be changed in response to the detected state, such as automatically. This can be achieved by having the control unit send a signal to the medical ventilator or by having the control unit as an integrated part of the medical ventilator.

[0143] A medical ventilator can be, for example, invasive ventilation (conventional), high frequency oscillatory ventilation (HFOV) or continuous positive airway pressure (CPAP). However, a medical ventilator can also mean passive respiratory support, such as a high flow nasal cannula (HFNC).

[0144] One setting that can be changed is pressure. For example, the control unit can be configured to send a signal to the medical ventilator to increase pressure when atelectasis is detected, and / or to decrease pressure when atelectasis decreases.

[0145] The present invention has been described above with reference to specific examples. However, within the scope of the present disclosure, other examples than those described above are equally possible. Method steps different from those described above may be provided within the scope of the present invention, the method being performed by hardware or software. The different features and steps of the present invention may be combined in ways different from those described. The scope of the present disclosure is limited only by the appended patent claims.

[0146] The indefinite articles "a" and "an" used in the specification and claims should be understood to mean "at least one" unless explicitly stated to the contrary. The phrase "and / or" used in the specification and claims should be understood to mean "one or both" of the elements so conjoined, i.e., elements that are present in conjunction in some cases and separate in other cases.

Claims

1. A device for monitoring the pulmonary system of a subject, the device comprising: an optical member for transmitting an optical signal through a cavity of the pulmonary system of the subject, wherein the optical signal comprises at least one wavelength, wherein the at least one wavelength is within an optical window of tissue; a detector unit configured to be positioned on a skin surface for detecting the optical signal transmitted through the cavity of the subject; wherein the optical member and the detector unit are configured to be positioned such that the light signal is transmitted from the optical member through the cavity to be detected by the detector; and a control unit for evaluating the detected light signal for determining a physiological state of the pulmonary system of the subject by evaluating a change in the intensity of the detected light signal transmitted through the cavity over time, the control unit being further configured to correlate the change in the intensity of the detected light signal transmitted through the cavity over time with a change in the volume of the cavity; Wherein the physiological state relates to detecting lung complications and / or ventilation problems.

2. The device according to claim 1, wherein: The detected optical signals are associated with the same wavelength over time such that the at least one wavelength of the emitted optical signals is a single wavelength.

3. The device according to any one of claims 1 or 2, wherein: The wavelengths are not associated with absorption bands of free gases.

4. The device according to claim 1, wherein: The change in the volume is a qualitative measure.

5. The device according to claim 1, wherein: The change in volume is detected by obtaining a first transmission signal transmitted through the first cavity and a second transmission signal transmitted through the second cavity; and then comparing the first transmission signal and the second transmission signal to detect a change in volume of one of the cavities relative to the other.

6. The device of claim 5, wherein the first cavity is a first lung and the second cavity is a second lung.

7. The device of claim 1, wherein: The at least one wavelength of the emitted light signal is associated with an absorption band of free gas in the lung system.

8. The device of claim 1, wherein: The optical member is adapted to be inserted internally into a subject using an introducing member.

9. The device of claim 1, wherein: The optical member is adapted to be arranged on a skin surface of the subject for transmitting the optical signal to the cavity.

10. The device according to claim 7, wherein: The control unit is configured to further detect the physiological state of the lung system by obtaining the concentration and / or distribution of the free gas from the detected light signal transmitted through the cavity and evaluating changes in the concentration and / or distribution over time.

11. The device of claim 10, wherein: The detected optical signal is provided using tunable diode laser absorption spectroscopy.

12. The device of claim 10, wherein: The control unit is configured to detect the physiological state of the pulmonary system by correlating the intensity of the detected light signal transmitted through the cavity with the concentration and / or distribution of the free gas over time.

13. The device of claim 10, wherein: The optical signal emitted by the optical component includes at least two different wavelengths.

14. The device of claim 13, wherein: At least one of the wavelengths is associated with an absorption band of a reference gas.

15. The device of claim 7, wherein: The free gas is a physiological gas or a gas mixture.

16. The device of claim 15, wherein: The free gas is any one of oxygen, nitric oxide, carbon dioxide, anesthetic gas and water vapor.

17. The device of claim 1, wherein: The control unit is configured to control a medical ventilator based on the detected physiological state of the pulmonary system.

18. The device of claim 17, wherein: The control unit is configured to send a signal to increase the pressure of the medical ventilator when atelectasis is detected.

19. The device as claimed in claim 18, wherein: The control unit is configured to send a signal to reduce the pressure of the medical ventilator when the atelectasis decreases.

20. The device according to claim 1, in, An optical filter having a transmittance at said wavelength of said emitted optical signal is arranged in front of said detector unit; and / or wherein the optical signal emitted is pulsed with a gated detection pulse; and / or wherein the emitted optical signal is amplitude modulated with a modulation frequency and the spectrum of the detected optical signal is analyzed at the modulation frequency; and / or The emitted optical signal is amplitude modulated at a varying modulation frequency, and the spectrum of the detected optical signal is analyzed at the varying modulation frequency.

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